Note: Large images and tables on this page may necessitate printing in landscape mode.

Copyright © The McGraw-Hill Companies. All rights reserved.

Harrison's Online > Chapter 237. Valvular Heart Disease >

Valvular Heart Disease: Introduction

The role of the physical examination in the evaluation of patients with valvular heart disease is also considered in Chaps. e13 and 227; of electrocardiography (ECG) in Chap. 228; of echocardiography and other noninvasive imaging techniques in Chap. 229; and of cardiac catheterization and angiography in Chap. 230.

Mitral Stenosis

Etiology and Pathology

Rheumatic fever is the leading cause of mitral stenosis (MS) (Table 237-1). Other less common etiologies of obstruction to left atrial outflow include congenital mitral valve stenosis, cor triatriatum, mitral annular calcification with extension onto the leaflets, systemic lupus erythematosus, rheumatoid arthritis, left atrial myxoma, and infective endocarditis with large vegetations. Pure or predominant MS occurs in approximately 40% of all patients with rheumatic heart disease and a history of rheumatic fever (Chap. 322). In other patients with rheumatic heart disease, lesser degrees of MS may accompany mitral regurgitation (MR) and aortic valve disease. With reductions in the incidence of acute rheumatic fever, particularly in temperate climates and developed countries, the incidence of MS has declined considerably over the past few decades. However, it remains a major problem in developing nations, especially in tropical and semitropical climates (see p. 1949).

Table 237-1 Major Causes of Valvular Heart Diseases

Valve LesionEtiologiesMitral stenosis

Rheumatic fever

Congenital

Severe mitral annular calcification

SLE, RA

Mitral regurgitation

Acute

EndocarditisPapillary muscle rupture (post-MI)TraumaChordal rupture/leaflet flail (MVP, IE)

Chronic

Myxomatous (MVP)Rheumatic feverEndocarditis (healed)Mitral annular calcificationCongenital (cleft, AV canal)HOCM with SAMIschemic (LV remodeling)Dilated cardiomyopathyRadiation

Aortic stenosis

Congenital (bicuspid, unicuspid)

Degenerative calcificRheumatic feverRadiation

Aortic regurgitation

Valvular

Congenital (bicuspid)EndocarditisRheumatic feverMyxomatous (prolapse)TraumaticSyphilisAnkylosing spondylitis

Root disease

Aortic dissectionCystic medial degenerationMarfan's syndromeBicuspid aortic valveNonsyndromic familial aneurysmAortitisHypertension

Tricuspid stenosis

Rheumatic

Congenital

Tricuspid regurgitation

Primary

RheumaticEndocarditisMyxomatous (TVP)CarcinoidRadiationCongenital (Ebstein's)TraumaPapillary muscle injury (post-MI)

Secondary

RV and tricuspid annular dilatationMultiple causes of RV enlargement (e.g., long-standing pulmonary HTN)Chronic RV apical pacing

Pulmonic stenosis

Congenital

Carcinoid

Pulmonic regurgitation

Valve disease

CongenitalPostvalvotomyEndocarditis

Annular enlargement

Pulmonary hypertensionIdiopathic dilationMarfan's syndrome

Abbreviations: AV, atrioventricular; HOCM, hypertrophic obstructive cardiomyopathy; HTN, hypertension; IE, infective endocarditis; LV, left ventricular; MI, myocardial infarction; MVP, mitral valve prolapse; RA, rheumatoid arthritis; RV, right ventricular; SAM, systolic anterior motion of the anterior mitral valve leaflet; SLE, systemic lupus erythematosus; TVP, tricuspid valve prolapse.

In rheumatic MS, the valve leaflets are diffusely thickened by fibrous tissue and/or calcific deposits. The mitral commissures fuse, the chordae tendineae fuse and shorten, the valvular cusps become rigid, and these changes, in turn, lead to narrowing at the apex of the funnel-shaped ("fish-mouth") valve. Although the initial insult to the mitral valve is rheumatic, the later changes may be a nonspecific process resulting from trauma to the valve caused by altered flow patterns due to the initial deformity. Calcification of the stenotic mitral valve immobilizes the leaflets and narrows the orifice further. Thrombus formation and arterial embolization may arise from the calcific valve itself, but in patients with atrial fibrillation (AF), thrombi arise more frequently from the dilated left atrium (LA), particularly from within the left atrial appendage.

Pathophysiology

In normal adults, the area of the mitral valve orifice is 4–6 cm2. In the presence of significant obstruction, i.e., when the orifice area is reduced to < ∼2 cm2, blood can flow from the LA to the left ventricle (LV) only if propelled by an abnormally elevated left atrioventricular pressure gradient, the hemodynamic hallmark of MS. When the mitral valve opening is reduced to <1 cm2, often referred to as "severe" MS, a LA pressure of ∼25 mmHg is required to maintain a normal cardiac output (CO). The elevated pulmonary venous and pulmonary arterial (PA) wedge pressures reduce pulmonary compliance, contributing to exertional dyspnea. The first bouts of dyspnea are usually precipitated by clinical events that increase the rate of blood flow across the mitral orifice, resulting in further elevation of the LA pressure (see below).

To assess the severity of obstruction hemodynamically, both the transvalvular pressure gradient and the flow rate must be measured (Chap. 230). The latter depends not only on the CO but on the heart rate, as well. An increase in heart rate shortens diastole proportionately more than systole and diminishes the time available for flow across the mitral valve. Therefore, at any given level of CO, tachycardia, including that associated with rapid AF, augments the transvalvular pressure gradient and elevates further the LA pressure. Similar considerations apply to the pathophysiology of tricuspid stenosis.

The LV diastolic pressure and ejection fraction (EF) are normal in isolated MS. In MS and sinus rhythm, the elevated LA and PA wedge pressures exhibit a prominent atrial contraction pattern (a wave) and a gradual pressure decline after the v wave and mitral valve opening (y descent). In severe MS and whenever pulmonary vascular resistance is significantly increased, the pulmonary arterial pressure (PAP) is elevated at rest and rises further during exercise, often causing secondary elevations of right ventricular (RV) end-diastolic pressure and volume.

Cardiac Output

In patients with moderate MS (mitral valve orifice 1 cm2–1.5 cm2), the CO is normal or almost so at rest, but rises subnormally during exertion. In patients with severe MS (valve area <1 cm2), particularly those in whom pulmonary vascular resistance is markedly elevated, the CO is subnormal at rest and may fail to rise or may even decline during activity.

Pulmonary Hypertension

The clinical and hemodynamic features of MS are influenced importantly by the level of the PAP. Pulmonary hypertension results from: (1) passive backward transmission of the elevated LA pressure; (2) pulmonary arteriolar constriction (the so-called "second stenosis"), which presumably is triggered by LA and pulmonary venous hypertension (reactive pulmonary hypertension); (3) interstitial edema in the walls of the small pulmonary vessels; and (4) at end stage, organic obliterative changes in the pulmonary vascular bed. Severe pulmonary hypertension results in RV enlargement, secondary tricuspid regurgitation (TR) and pulmonic regurgitation (PR), as well as right-sided heart failure.

Symptoms

In temperate climates, the latent period between the initial attack of rheumatic carditis (in the increasingly rare circumstances in which a history of one can be elicited) and the development of symptoms due to MS is generally about two decades; most patients begin to experience disability in the fourth decade of life. Studies carried out before the development of mitral valvotomy revealed that once a patient with MS became seriously symptomatic, the disease progressed continuously to death within 2–5 years.

In patients whose mitral orifices are large enough to accommodate a normal blood flow with only mild elevations of LA pressure, marked elevations of this pressure leading to dyspnea and cough may be precipitated by sudden changes in the heart rate, volume status, or CO, as, for example, with severe exertion, excitement, fever, severe anemia, paroxysmal AF and other tachycardias, sexual intercourse, pregnancy, and thyrotoxicosis. As MS progresses, lesser degrees of stress precipitate dyspnea, the patient becomes limited in daily activities, and orthopnea and paroxysmal nocturnal dyspnea develop. The development of permanent AF often marks a turning point in the patient's course and is generally associated with acceleration of the rate at which symptoms progress.

Hemoptysis (Chap. 34) results from rupture of pulmonary-bronchial venous connections secondary to pulmonary venous hypertension. It occurs most frequently in patients who have elevated LA pressures without markedly elevated pulmonary vascular resistances and is rarely fatal. Recurrent pulmonary emboli (Chap. 262), sometimes with infarction, are an important cause of morbidity and mortality rates late in the course of MS. Pulmonary infections, i.e., bronchitis, bronchopneumonia, and lobar pneumonia, commonly complicate untreated MS, especially during the winter months.

Pulmonary Changes

In addition to the aforementioned changes in the pulmonary vascular bed, fibrous thickening of the walls of the alveoli and pulmonary capillaries occurs commonly in MS. The vital capacity, total lung capacity, maximal breathing capacity, and oxygen uptake per unit of ventilation are reduced (Chap. 252). Pulmonary compliance falls further as pulmonary capillary pressure rises during exercise.

Thrombi and Emboli

Thrombi may form in the left atria, particularly within the enlarged atrial appendages of patients with MS. Systemic embolization, the incidence of which is 10–20%, occurs more frequently in patients with AF, in patients >65 years of age, and in those with a reduced CO. However, systemic embolization may be the presenting feature in otherwise asymptomatic patients with only mild MS.

Physical Findings

(See also Chaps. e13 and 227)

Inspection and Palpation

In patients with severe MS, there may be a malar flush with pinched and blue facies. In patients with sinus rhythm and severe pulmonary hypertension or associated tricuspid stenosis (TS), the jugular venous pulse reveals prominent a waves due to vigorous right atrial systole. The systemic arterial pressure is usually normal or slightly low. An RV tap along the left sternal border signifies an enlarged RV. A diastolic thrill may rarely be present at the cardiac apex, with the patient in the left lateral recumbent position.

Auscultation

The first heart sound (S1) is usually accentuated and slightly delayed. The pulmonic component of the second heart sound (P2) also is often accentuated, and the two components of the second heart sound (S2) are closely split. The opening snap (OS) of the mitral valve is most readily audible in expiration at, or just medial to, the cardiac apex. This sound generally follows the sound of aortic valve closure (A2) by 0.05–0.12 s. The time interval between A2 and OS varies inversely with the severity of the MS. The OS is followed by a low-pitched, rumbling, diastolic murmur, heard best at the apex with the patient in the left lateral recumbent position (see Fig. 227-5); it is accentuated by mild exercise (e.g., a few rapid sit-ups) carried out just before auscultation. In general, the duration of this murmur correlates with the severity of the stenosis in patients with preserved CO. In patients with sinus rhythm, the murmur often reappears or becomes louder during atrial systole (presystolic accentuation). Soft, grade I or II/VI systolic murmurs are commonly heard at the apex or along the left sternal border in patients with pure MS and do not necessarily signify the presence of MR. Hepatomegaly, ankle edema, ascites, and pleural effusion, particularly in the right pleural cavity, may occur in patients with MS and RV failure.

Associated Lesions

With severe pulmonary hypertension, a pansystolic murmur produced by functional TR may be audible along the left sternal border. This murmur is usually louder during inspiration and diminishes during forced expiration (Carvallo's sign). When the CO is markedly reduced in MS, the typical auscultatory findings, including the diastolic rumbling murmur, may not be detectable (silent MS), but they may reappear as compensation is restored. The Graham Steell murmur of PR, a high-pitched, diastolic, decrescendo blowing murmur along the left sternal border, results from dilation of the pulmonary valve ring and occurs in patients with mitral valve disease and severe pulmonary hypertension. This murmur may be indistinguishable from the more common murmur produced by aortic regurgitation (AR), although it may increase in intensity with inspiration and is accompanied by a loud and often palpable P2.

Laboratory Examination

ECG

In MS and sinus rhythm, the P wave usually suggests LA enlargement (see Fig. 228-8). It may become tall and peaked in lead II and upright in lead V1 when severe pulmonary hypertension or TS complicates MS and right atrial (RA) enlargement occurs. The QRS complex is usually normal. However, with severe pulmonary hypertension, right-axis deviation and RV hypertrophy are often present.

Echocardiogram

(See also Chap. 229) Transthoracic echocardiography (TTE) with color flow and spectral Doppler imaging provides critical information, including measurements of mitral inflow velocity during early (E wave) and late (A wave in patients in sinus rhythm) diastolic filling, estimates of the transvalvular peak and mean gradients and of the mitral orifice area, the presence and severity of any associated MR, the extent of leaflet calcification and restriction, the degree of distortion of the subvalvular apparatus, and the anatomic suitability for percutaneous mitral balloon valvotomy [percutaneous mitral balloon valvuloplasty (PMBV); see below]. In addition, TTE provides an assessment of LV and RV function, chamber sizes, an estimation of the pulmonary artery pressure (PAP) based on the tricuspid regurgitant jet velocity, and an indication of the presence and severity of any associated valvular lesions. Transesophageal echocardiography (TEE) provides superior images and should be employed when TTE is inadequate for guiding management decisions. TEE is especially indicated to exclude the presence of left atrial thrombus prior to PMBV.

Chest X-Ray

The earliest changes are straightening of the upper left border of the cardiac silhouette, prominence of the main pulmonary arteries, dilation of the upper lobe pulmonary veins, and posterior displacement of the esophagus by an enlarged LA. Kerley B lines are fine, dense, opaque, horizontal lines that are most prominent in the lower and mid-lung fields and that result from distention of interlobular septae and lymphatics with edema when the resting mean LA pressure exceeds approximately 20 mmHg.

Differential Diagnosis

Like MS, significant MR may also be associated with a prominent diastolic murmur at the apex due to increased antegrade transmitral flow, but in patients with isolated MR, this diastolic murmur commences slightly later than in patients with MS, and there is often clear-cut evidence of LV enlargement. An opening snap and increased P2are absent, and S1 is soft or absent. An apical pansystolic murmur of at least grade III/VI intensity as well as an S3 suggest significant MR. Similarly, the apical mid-diastolic murmur associated with severe AR (Austin Flint murmur) may be mistaken for MS but can be differentiated from it because it is not intensified in presystole and becomes softer with administration of amyl nitrite. TS, which occurs rarely in the absence of MS, may mask many of the clinical features of MS or be clinically silent; when present, the diastolic murmur of TS increases with inspiration.

Atrial septal defect (Chap. 236) may be mistaken for MS; in both conditions there is often clinical, ECG, and chest x-ray evidence of RV enlargement and accentuation of pulmonary vascularity. However, the absence of LA enlargement and of Kerley B lines and the demonstration of fixed splitting of S2 with a grade 2 or 3 mid-systolic murmur at the mid to upper left sternal border all favor atrial septal defect over MS. Atrial septal defects with large left-to-right shunts may result in functional TS because of the enhanced diastolic flow.

Left atrial myxoma (Chap. 240) may obstruct LA emptying, causing dyspnea, a diastolic murmur, and hemodynamic changes resembling those of MS. However, patients with an LA myxoma often have features suggestive of a systemic disease, such as weight loss, fever, anemia, systemic emboli, and elevated serum IgG and interleukin 6 (IL-6) concentrations. The auscultatory findings may change markedly with body position. The diagnosis can be established by the demonstration of a characteristic echo-producing mass in the LA with TTE.

Cardiac Catheterization

Left and right heart catheterization is useful when there is a discrepancy between the clinical and TTE findings that cannot be resolved with either TEE or cardiac magnetic resonance (CMR) imaging. The growing experience with CMR for the assessment of patients with valvular heart disease may decrease the need for invasive catheterization. Catheterization is helpful in assessing associated lesions, such as aortic stenosis (AS) and AR. Catheterization and coronary angiography are not usually necessary to aid in decision-making about surgery in patients younger than 65 years of age, with typical findings of severe mitral obstruction on physical examination and TTE. In men older than 40 years of age, women older than 45 years of age, and younger patients with coronary risk factors, especially those with positive noninvasive stress tests for myocardial ischemia, coronary angiography is advisable preoperatively to identify patients with critical coronary obstructions that should be bypassed at the time of operation. Computed tomographic coronary angiography (CTCA) (Chap. 229) is now often used to screen preoperatively for the presence of coronary artery disease (CAD) in patients with valvular heart disease and low pretest likelihood of CAD. Catheterization and left ventriculography are indicated in most patients who have undergone PMBV or previous mitral valve surgery, and who have redeveloped limiting symptoms, especially if questions regarding the severity of the valve lesion(s) remain after echocardiography.

Treatment: Mitral Stenosis

(See Fig. 237-1) Penicillin prophylaxis of group A -hemolytic streptococcal infections (Chap. 322) for secondary prevention of rheumatic fever is important for at-risk patients with rheumatic MS (Table 237-2). Recommendations for infective endocarditis prophylaxis have recently changed. In symptomatic patients, some improvement usually occurs with restriction of sodium intake and small doses of oral diuretics. Beta blockers, nondihydropyridine calcium channel blockers (e.g., verapamil or diltiazem), and digitalis glycosides are useful in slowing the ventricular rate of patients with AF. Warfarin to an international normalized ratio (INR) of 2–3 should be administered indefinitely to patients with MS, who have AF or a history of thromboembolism. The routine use of warfarin in patients in sinus rhythm with LA enlargement (maximal dimension >5.5 cm) with or without spontaneous echo contrast is more controversial.

Figure 237-1

Management Strategy for Patients with Mitral Stenosis (MS) and Mild Symptoms. There is controversy as to whether patients with severe MS (MVA <1 cm2) and severe pulmonary hypertension (PH) (PASP >60 mmHg) should undergo percutaneous mitral balloon valvotomy (PMBV) or mitral valve replacement (MVR) to prevent right ventricular failure. CXR, chest x-ray; ECG, electrocardiogram; echo, echocardiography; LA, left atrial; MR, mitral regurgitation; MVA, mitral valve area; MVG, mean mitral valve pressure gradient; NYHA, New York Heart Association; PASP, pulmonary artery systolic pressure; PAWP, pulmonary artery wedge pressure; 2D, 2-dimensional. (From RO Bonow et al: J Am Coll Cardiol 48:e1, 2006; with permission.)

Table 237-2 Medical Therapy of Valvular Heart Disease

LesionSymptom ControlNatural HistoryMitral stenosis

Beta blockers, nondihydropyridine calcium channel blockers, or digoxin for rate control of AF; cardioversion for new-onset AF and HF; diuretics for HF

Warfarin for AF or thromboembolism; PCN for RF prophylaxis

Mitral regurgitation

Diuretics for HF

Warfarin for AF or thromboembolism

Vasodilators for acute MR

Vasodilators for HTN

Aortic stenosis

Diuretics for HF

No proven therapy

Aortic regurgitation

Diuretics and vasodilators for HF

Vasodilators for HTN

Note: Antibiotic prophylaxis is recommended according to current American Heart Association guidelines. For patients with these forms of valvular heart disease, prophylaxis is indicated for a prior history of endocarditis. HF is an indication for surgical or percutaneous treatment, and the recommendations here pertain to short-term therapy prior to definitive correction of the valve lesion. For patients whose comorbidities prohibit surgery, the medical therapies listed can be continued according to available guidelines for the management of HF. See text.

Abbreviations: AF, atrial fibrillation; HF, heart failure; HTN, systemic hypertension; PCN, penicillin; RF, rheumatic fever.

Source: Adapted from NA Boon, P Bloomfield: Heart 87:395, 2002, with permission.

If AF is of relatively recent onset in a patient whose MS is not severe enough to warrant PMBV or surgical commissurotomy, reversion to sinus rhythm pharmacologically or by means of electrical countershock is indicated. Usually, cardioversion should be undertaken after the patient has had at least 3 consecutive weeks of anticoagulant treatment to a therapeutic INR. If cardioversion is indicated more urgently, then intravenous heparin should be provided and TEE performed to exclude the presence of left atrial thrombus before the procedure. Conversion to sinus rhythm is rarely successful or sustained in patients with severe MS, particularly those in whom the LA is especially enlarged or in whom AF has been present for more than 1 year.

Mitral Valvotomy

Unless there is a contraindication, mitral valvotomy is indicated in symptomatic [New York Heart Association (NYHA) Functional Class II–IV] patients with isolated MS, whose effective orifice (valve area) is < ∼1 cm2/m2 body surface area, or <1.5 cm2 in normal-sized adults. Mitral valvotomy can be carried out by two techniques: PMBV and surgical valvotomy. In PMBV (Figs. 237-2 and 237-3), a catheter is directed into the LA after transseptal puncture, and a single balloon is directed across the valve and inflated in the valvular orifice. Ideal patients have relatively pliable leaflets with little or no commissural calcium. In addition, the subvalvular structures should not be significantly scarred or thickened, and there should be no left atrial thrombus. The short- and long-term results of this procedure in appropriate patients are similar to those of surgical valvotomy, but with less morbidity and a lower periprocedural mortality rate. Event-free survival in younger (<45 years) patients with pliable valves is excellent, with rates as high as 80–90% over 3–7 years. Therefore, PMBV has become the procedure of choice for such patients when it can be performed by a skilled operator in a high-volume center.

Figure 237-2

Inoue Balloon Technique for Percutaneous Mitral Balloon Valvotomy.A. After transseptal puncture, the deflated balloon catheter is advanced across the interatrial septum, then across the mitral valve and into the left ventricle. B.-D. The balloon is inflated stepwise within the mitral orifice.

Figure 237-3

Simultaneous Left Atrial (LA) and Left Ventricular (LV) Pressure before and after percutaneous mitral balloon valvuloplasty (PMBV) in a patient with severe mitral stenosis. (Courtesy of Raymond G. McKay, MD; with permission.)

Transthoracic echocardiography is helpful in identifying patients for the percutaneous procedure, and TEE is performed routinely to exclude left atrial thrombus at the time of the scheduled procedure. An "echo score" has been developed to help guide decision-making. The score accounts for the degree of leaflet thickening, calcification, and mobility, and for the extent of subvalvular thickening. A lower score predicts a higher likelihood of successful PMBV.

In patients in whom PMBV is not possible or unsuccessful, or in many patients with restenosis, an "open" valvotomy using cardiopulmonary bypass is necessary. In addition to opening the valve commissures, it is important to loosen any subvalvular fusion of papillary muscles and chordae tendineae and to remove large deposits of calcium, thereby improving valvular function, as well as to remove atrial thrombi. The perioperative mortality rate is ∼2%.

Successful valvotomy is defined by a 50% reduction in the mean mitral valve gradient and a doubling of the mitral valve area. Successful valvotomy, whether balloon or surgical, usually results in striking symptomatic and hemodynamic improvement and prolongs survival. However, there is no evidence that the procedure improves the prognosis of patients with slight or no functional impairment. Therefore, unless recurrent systemic embolization or severe pulmonary hypertension has occurred (PA systolic pressures >50 mmHg at rest or >60 mmHg with exercise), valvotomy is not recommended for patients who are entirely asymptomatic and/or who have mild stenosis (mitral valve area >1.5 cm2). When there is little symptomatic improvement after valvotomy, it is likely that the procedure was ineffective, that it induced MR, or that associated valvular or myocardial disease was present. About half of all patients undergoing surgical mitral valvotomy require reoperation by 10 years. In the pregnant patient with MS, valvotomy should be carried out if pulmonary congestion occurs despite intensive medical treatment. PMBV is the preferred strategy in this setting and is performed with TEE and no or minimal x-ray exposure.

Mitral valve replacement (MVR) is necessary in patients with MS and significant associated MR, those in whom the valve has been severely distorted by previous transcatheter or operative manipulation, or those in whom the surgeon does not find it possible to improve valve function significantly with valvotomy. MVR is now routinely performed with preservation of the chordal attachments to optimize LV functional recovery. Perioperative mortality rates with MVR vary with age, LV function, the presence of CAD, and associated comorbidities. They average 5% overall but are lower in young patients and may be twice as high in patients >65 years of age with comorbidity rates (Table 237-3). Since there are also long-term complications of valve replacement (p. 1949), patients in whom preoperative evaluation suggests the possibility that MVR may be required should be operated on only if they have severe MS—i.e., an orifice area ≤1 cm2—and are in NYHA Class III, i.e., symptomatic with ordinary activity despite optimal medical therapy. The overall 10-year survival of surgical survivors is ∼70%. Long-term prognosis is worse in patients >65 years of age and those with marked disability and marked depression of the CO preoperatively. Pulmonary hypertension and RV dysfunction are additional risk factors for poor outcome.

Table 237-3 Mortality Rates After Valve Surgery*

OperationNumberUnadjusted Operative Mortality (%)AVR (isolated)

20,168

3.2

MVR (isolated)

4,616

5.0

AVR + CAB

16,678

5.0

MVR + CAB

2,479

8.8

AVR + MVR

1,239

9.0

MVP

5,617

1.8

MVP + CAB

4,932

4.8

TV surgery

6,235

9.2

PV surgery

480

6.0

*Data are for calendar year 2008, in which 912 sites reported a total of 276,308 procedures. Data are available from the Society of Thoracic Surgeons at http://www.sts.org/documents/pdf/ndb/2ndHarvestExecutiveSummary_2009.pdf.

Abbreviations: AVR, aortic valve replacement; CAB, coronary artery bypass; MVR, mitral valve replacement; MVP, mitral valve repair; TV surgery, tricuspid valve repair and replacement; PV surgery, pulmonic valve repair and replacement.

Mitral Regurgitation

Etiology

MR may result from an abnormality or disease process that affects any one or more of the five functional components of the mitral valve apparatus (leaflets, annulus, chordae tendineae, papillary muscles, and subjacent myocardium) (Table 237-1). Acute MR can occur in the setting of acute myocardial infarction (MI) with papillary muscle rupture (Chap. 245), following blunt chest wall trauma, or during the course of infective endocarditis. With acute MI, the posteromedial papillary muscle is involved much more frequently than the anterolateral papillary muscle because of its singular blood supply. Transient, acute MR can occur during periods of active ischemia and bouts of angina pectoris. Rupture of chordae tendineae can result in "acute-on-chronic MR" in patients with myxomatous degeneration of the valve apparatus.

Chronic MR can result from rheumatic disease, mitral valve prolapse (MVP), extensive mitral annular calcification, congenital valve defects, hypertrophic obstructive cardiomyopathy (HOCM), and dilated cardiomyopathy (Chap. 238). The rheumatic process produces rigidity, deformity, and retraction of the valve cusps and commissural fusion, as well as shortening, contraction, and fusion of the chordae tendineae. The MR associated with both MVP and HOCM is usually dynamic in nature. MR in HOCM occurs as a consequence of anterior papillary muscle displacement and systolic anterior motion of the anterior mitral valve leaflet into the narrowed LV outflow tract. Annular calcification is especially prevalent among patients with advanced renal disease and is commonly observed in women >65 years of age with hypertension and diabetes. MR may occur as a congenital anomaly (Chap. 236), most commonly as a defect of the endocardial cushions (atrioventricular cushion defects). A cleft anterior mitral valve leaflet accompanies primum atrial septal defect. Chronic MR is frequently secondary to ischemia and may occur as a consequence of ventricular remodeling, papillary muscle displacement, and leaflet tethering, or with fibrosis of a papillary muscle, in patients with healed myocardial infarction(s) and ischemic cardiomyopathy. Similar mechanisms of annular dilation and ventricular remodeling contribute to the MR that occurs among patients with nonischemic forms of dilated cardiomyopathy once the left ventricular end-diastolic dimension reaches 6 cm.

Irrespective of cause, chronic severe MR is often progressive, since enlargement of the LA places tension on the posterior mitral leaflet, pulling it away from the mitral orifice and thereby aggravating the valvular dysfunction. Similarly, LV dilation increases the regurgitation, which, in turn, enlarges the LA and LV further, causing chordal rupture and resulting in a vicious circle; hence the aphorism, "mitral regurgitation begets mitral regurgitation."

Pathophysiology

The resistance to LV emptying (LV afterload) is reduced in patients with MR. As a consequence, the LV is decompressed into the LA during ejection, and with the reduction in LV size during systole, there is a rapid decline in LV tension. The initial compensation to MR is more complete LV emptying. However, LV volume increases progressively with time as the severity of the regurgitation increases and as LV contractile function deteriorates. This increase in LV volume is often accompanied by a reduced forward CO, although LV compliance is often increased and, thus, LV diastolic pressure does not increase until late in the course. The regurgitant volume varies directly with the LV systolic pressure and the size of the regurgitant orifice; as mentioned above, the latter, in turn, is influenced by the extent of LV and mitral annular dilation. Since ejection fraction (EF) rises in severe MR in the presence of normal LV function, even a modest reduction in this parameter (<60%) reflects significant dysfunction.

During early diastole, as the distended LA empties, there is a particularly rapid y descent in the absence of accompanying MS. A brief, early diastolic LA-LV pressure gradient [often generating a rapid filling sound (S3) and mid-diastolic murmur masquerading as MS] may occur in patients with pure MR as a result of the very rapid flow of blood across a normal-sized mitral orifice.

Semi-quantitative estimates of left ventricular ejection fraction (LVEF), CO, PA systolic pressure, regurgitant volume, regurgitant fraction (RF), and the effective regurgitant orifice area can be obtained during a careful Doppler echocardiographic examination. These measurements can also be obtained with CMR. Left and right heart catheterization with contrast ventriculography is used less frequently. Severe, nonischemic MR is defined by a regurgitant volume 60 mL/beat, regurgitant fraction (RF) 50%, and effective regurgitant orifice area 0.40 cm2. Severe ischemic MR is usually associated with an effective regurgitant orifice area of >0.3 cm2.

La Compliance

In acute severe MR, the regurgitant volume is delivered into a normal-sized LA having normal or reduced compliance. As a result, LA pressures rise markedly for any increase in LA volume. The v wave in the LA pressure pulse is usually prominent, LA and pulmonary venous pressures are markedly elevated, and pulmonary edema is common. Because of the rapid rise in LA pressures during ventricular systole, the murmur of acute MR is early in timing and decrescendo in configuration ending well before S2, as a reflection of the progressive diminution in the LV-LA pressure gradient. LV systolic function in acute MR may be normal, hyperdynamic, or reduced, depending on the clinical context.

Patients with chronic severe MR, on the other hand, develop marked LA enlargement and increased LA compliance with little if any increase in LA and pulmonary venous pressures for any increase in LA volume. The LA v wave is relatively less prominent. The murmur of chronic MR is classically holosystolic in timing and plateau in configuration, as a reflection of the near-constant LV-LA pressure gradient. These patients usually complain of severe fatigue and exhaustion secondary to a low forward CO, while symptoms resulting from pulmonary congestion are less prominent initially; AF is almost invariably present once the LA dilates significantly.

Symptoms

Patients with chronic mild-to-moderate isolated MR are usually asymptomatic. This form of LV volume overload is well tolerated. Fatigue, exertional dyspnea, and orthopnea are the most prominent complaints in patients with chronic severe MR. Palpitations are common and may signify the onset of AF. Right-sided heart failure, with painful hepatic congestion, ankle edema, distended neck veins, ascites, and secondary TR, occurs in patients with MR who have associated pulmonary vascular disease and marked pulmonary hypertension. Conversely, acute pulmonary edema is common in patients with acute severe MR.

Physical Findings

In patients with chronic severe MR, the arterial pressure is usually normal, although the carotid arterial pulse may show a sharp upstroke owing to the reduced forward cardiac output. A systolic thrill is often palpable at the cardiac apex, the LV is hyperdynamic with a brisk systolic impulse and a palpable rapid-filling wave (S3), and the apex beat is often displaced laterally.

In patients with acute severe MR, the arterial pressure may be reduced with a narrow pulse pressure, the jugular venous pressure and wave forms may be normal or increased and exaggerated, the apical impulse is not displaced, and signs of pulmonary congestion are prominent.

Auscultation

S1 is generally absent, soft, or buried in the holosystolic murmur of chronic MR. In patients with severe MR, the aortic valve may close prematurely, resulting in wide but physiologic splitting of S2. A low-pitched S3 occurring 0.12–0.17 s after the aortic valve closure sound, i.e., at the completion of the rapid-filling phase of the LV, is believed to be caused by the sudden tensing of the papillary muscles, chordae tendineae, and valve leaflets. It may be followed by a short, rumbling, mid-diastolic murmur, even in the absence of structural MS. A fourth heart sound is often audible in patients with acute severe MR who are in sinus rhythm. A presystolic murmur is not ordinarily heard with isolated MR.

A systolic murmur of at least grade III/VI intensity is the most characteristic auscultatory finding in chronic severe MR. It is usually holosystolic (see Fig. 227-5A), but as previously noted it is decrescendo and ceases in mid- to late systole in patients with acute severe MR. The systolic murmur of chronic MR is usually most prominent at the apex and radiates to the axilla. However, in patients with ruptured chordae tendineae or primary involvement of the posterior mitral leaflet with prolapse or flail, the regurgitant jet is eccentric, directed anteriorly, and strikes the LA wall adjacent to the aortic root. In this situation, the systolic murmur is transmitted to the base of the heart and, therefore, may be confused with the murmur of AS. In patients with ruptured chordae tendineae, the systolic murmur may have a cooing or "sea gull" quality, while a flail leaflet may produce a murmur with a musical quality. The systolic murmur of chronic MR not due to MVP is intensified by isometric exercise (handgrip) but is reduced during the strain phase of the Valsalva maneuver because of the associated decrease in LV preload.

Laboratory Examination

ECG

In patients with sinus rhythm, there is evidence of LA enlargement, but RA enlargement also may be present when pulmonary hypertension is severe. Chronic severe MR is generally associated with AF. In many patients, there is no clear-cut ECG evidence of enlargement of either ventricle. In others, the signs of eccentric LV hypertrophy are present.

Echocardiogram

TTE is indicated to assess the mechanism of the MR and its hemodynamic severity. LV function can be assessed from LV end-diastolic and end-systolic volumes and EF. Observations can be made regarding leaflet structure and function, chordal integrity, LA and LV size, annular calcification, and regional and global LV systolic function. Doppler imaging should demonstrate the width or area of the color flow MR jet within the LA, the intensity of the continuous wave Doppler signal, the pulmonary venous flow contour, the early peak mitral inflow velocity, and the quantitative measures of regurgitant volume, RF, and effective regurgitant orifice area. In addition, the PA pressures can be estimated from the TR jet velocity. TTE is also indicated to follow the course of patients with chronic MR and to provide rapid assessment for any clinical change. The echocardiogram in patients with MVP is described in the next section. TEE provides greater detail than TTE (see Fig. 229-5).

Chest X-Ray

The LA and LV are the dominant chambers in chronic MR. Late in the course of the disease, the LA may be massively enlarged and forms the right border of the cardiac silhouette. Pulmonary venous congestion, interstitial edema, and Kerley B lines are sometimes noted. Marked calcification of the mitral leaflets occurs commonly in patients with longstanding, combined rheumatic MR and MS. Calcification of the mitral annulus may be visualized, particularly on the lateral view of the chest. Patients with acute severe MR may have asymmetric pulmonary edema if the regurgitant jet is directed predominantly to the orifice of an upper lobe pulmonary vein.

Treatment: Mitral Regurgitation

Medical Treatment

(See Fig. 237-4 and Table 237-2) The management of chronic severe MR depends to some degree on its cause. Warfarin should be provided once AF intervenes with a target INR of 2–3. Cardioversion should be considered depending on the clinical context and left atrial size. In contrast to the acute setting, there are no large, long-term prospective studies to substantiate the use of vasodilators for the treatment of chronic, isolated severe MR with preserved LV systolic function in the absence of systemic hypertension. The severity of MR in the setting of an ischemic or nonischemic dilated cardiomyopathy may diminish with aggressive, evidence-based treatment of heart failure, including the use of diuretics, beta blockers, angiotensin-converting enzyme (ACE) inhibitors, digitalis, and biventricular pacing (cardiac resynchronization therapy [CRT]). Asymptomatic patients with severe MR in sinus rhythm with normal LV size and systolic function should avoid isometric forms of exercise.

Figure 237-4

Management Strategy for Patients with Chronic Severe Nonischemic Mitral Regurgitation. *Mitral valve (MV) repair may be performed in asymptomatic patients with normal left ventricular (LV) function if performed by an experienced surgical team and if the likelihood of successful MV repair is >90%. AF, atrial fibrillation; Echo, echocardiography; EF, ejection fraction; ESD, end-systolic dimension; eval, evaluation; HT, hypertension; MVR, mitral valve replacement. (From RO Bonow et al: J Am Coll Cardiol 48:e1, 2006; with permission.)

Patients with acute severe MR require urgent stabilization and preparation for surgery. Diuretics, intravenous vasodilators (particularly sodium nitroprusside), and even intraaortic balloon counterpulsation may be needed for patients with post-MI papillary muscle rupture or other forms of acute severe MR.

Surgical Treatment

In the selection of patients with chronic, nonischemic, severe MR for surgical treatment, the often slowly progressive nature of the condition must be balanced against the immediate and long-term risks associated with operation. These risks are significantly lower for primary valve repair than for valve replacement (Table 237-3). Repair usually consists of valve reconstruction using a variety of valvuloplasty techniques and insertion of an annuloplasty ring. Repair spares the patient the long-term adverse consequences of valve replacement, i.e., thromboembolic and hemorrhagic complications in the case of mechanical prostheses and late valve failure necessitating repeat valve replacement in the case of bioprostheses (p. 1949). In addition, by preserving the integrity of the papillary muscles, subvalvular apparatus, and chordae tendineae, mitral repair and valvuloplasty maintain LV function to a relatively greater degree.

Surgery for chronic, nonischemic, severe MR is indicated once symptoms occur, especially if valve repair is feasible (Fig. 237-4). Other indications for early consideration of mitral valve repair include recent-onset AF and pulmonary hypertension, defined as a PA pressure 50 mmHg at rest or 60 mmHg with exercise. Surgical treatment of chronic, nonischemic severe MR is indicated for asymptomatic patients when LV dysfunction is progressive, with LVEF falling below 60% and/or end-systolic dimension increasing beyond 40 mm. These aggressive recommendations for surgery are predicated on the outstanding results achieved with mitral valve repair, particularly when applied to patients with myxomatous disease, such as that associated with prolapse or flail leaflet. Indeed, primary valvuloplasty repair of patients younger than 75 years with normal LV systolic function and no CAD can now be performed by experienced surgeons with <1% perioperative mortality risk. Repair is feasible in up to 95% of patients with myxomatous disease. Long-term durability is excellent; the incidence of reoperative surgery for failed primary repair is ∼1% per year for 10 years after surgery. For patients with AF, left or bi-atrial Maze surgery or radiofrequency isolation of the pulmonary veins is often performed to reduce the risk of recurrent, postoperative AF.

The surgical management of patients with ischemic MR is more complicated and almost always involves simultaneous coronary artery revascularization. Although current surgical practice includes annuloplasty repair with an undersized ring for patients with moderate or greater degrees of MR at the time of coronary artery bypass surgery, the efficacy of this approach has not been established in prospective, randomized trials. There is also uncertainty as to whether or not valve repair or replacement is the preferred strategy, given the higher incidence of residual or recurrent MR after repair in this context compared with outcomes in patients with organic (myxomatous) disease. In patients with significantly impaired LV function (EF <30%), the risk of surgery increases, the recovery of LV performance is incomplete, and the long-term survival is reduced. However, conservative management has little to offer these patients, so operative treatment may be indicated, and the clinical and hemodynamic improvement that follows surgical treatment of patients with advanced disease is occasionally dramatic, especially when severe CAD is present and bypass grafting can be performed. The routine performance of valve repair in patients with significant MR in the setting of severe, dilated cardiomyopathy has not been shown to improve long-term survival. Patients with acute severe MR can often be stabilized temporarily with appropriate medical therapy, but surgical correction will be necessary, emergently in the case of papillary muscle rupture and within days to weeks in most other settings.

When surgical treatment is contemplated, left and right heart catheterization and left ventriculography may be helpful in confirming the presence of severe MR in patients in whom there is a discrepancy between the clinical and TTE findings that cannot be resolved with TEE or CMR. Coronary angiography identifies patients who require concomitant coronary revascularization.

Percutaneous Mitral Valve Repair

A transcatheter approach to the treatment of either organic or functional MR may be feasible in selected patients with appropriate anatomy, although the proper role of current techniques remains under active investigation. One approach involves the deployment of a clip delivered via transeptal puncture that grasps the leading edges of the mitral leaflets in their mid-portion (anterior scallop 2–posterior scallop 2 or A2-P2, Fig. 237-5). The length and width of the gap between these leading edges have dictated patient eligibility in the trials reported to date. Preliminary results with this technically demanding technique have been favorable. A second approach involves the deployment of a device within the coronary sinus that can be adjusted to reduce its circumference, thus secondarily decreasing the circumference of the mitral annulus and the effective orifice area of the valve, much like a surgically implanted ring. Variations in the anatomic relationship of the coronary sinus to the mitral annulus and circumflex coronary artery have limited the applicability of this technique. Attempts to reduce the septal-lateral dimension of a dilated annulus using adjustable cords placed across the LV in a subvalvular location have also been investigated.

Figure 237-5

Clip Used to Grasp the Free Edges of the Anterior and Posterior Leaflets in Their Mid-Sections during Percutaneous Repair of Selected Patients with Mitral Regurgitation.(Courtesy of Abbott Vascular. © 2010 Abbott Laboratories. All rights reserved.)

Mitral Valve Prolapse

MVP, also variously termed the systolic click-murmur syndrome, Barlow's syndrome, floppy-valve syndrome, and billowing mitral leaflet syndrome, is a relatively common but highly variable clinical syndrome resulting from diverse pathologic mechanisms of the mitral valve apparatus. Among these are excessive or redundant mitral leaflet tissue, which is commonly associated with myxomatous degeneration and greatly increased concentrations of certain glycosaminoglycans.

In most patients with MVP, the cause is unknown, but in some it appears to be a genetically determined collagen disorder. A reduction in the production of type III collagen has been incriminated, and electron microscopy has revealed fragmentation of collagen fibrils.

MVP is a frequent finding in patients with heritable disorders of connective tissue, including Marfan's syndrome (Chap. 363), osteogenesis imperfecta, and Ehlers-Danlos syndrome. MVP may be associated with thoracic skeletal deformities similar to but not as severe as those in Marfan's syndrome, such as a high-arched palate and alterations of the chest and thoracic spine, including the so-called straight back syndrome.

In most patients with MVP, myxomatous degeneration is confined to the mitral valve, although the tricuspid and aortic valves may also be affected. The posterior mitral leaflet is usually more affected than the anterior, and the mitral valve annulus is often dilated. In many patients, elongated, redundant, or ruptured chordae tendineae cause or contribute to the regurgitation.

MVP also may occur rarely as a sequel to acute rheumatic fever, in ischemic heart disease, and in various cardiomyopathies, as well as in 20% of patients with ostium secundum atrial septal defect.

MVP may lead to excessive stress on the papillary muscles, which, in turn, leads to dysfunction and ischemia of the papillary muscles and the subjacent ventricular myocardium. Rupture of chordae tendineae and progressive annular dilation and calcification contribute to valvular regurgitation, which then places more stress on the diseased mitral valve apparatus, thereby creating a vicious circle. The ECG changes (see below) and ventricular arrhythmias appear to result from regional ventricular dysfunction related to the increased stress placed on the papillary muscles.

Clinical Features

MVP is more common in women and occurs most frequently between the ages of 15 and 30 years; the clinical course is most often benign. MVP may also be observed in older (>50 years) patients, often men, in whom MR is often more severe and requires surgical treatment. There is an increased familial incidence for some patients, suggesting an autosomal dominant form of inheritance with incomplete penetrance. MVP varies in its clinical expression, ranging from only a systolic click and murmur with mild prolapse of the posterior leaflet to severe MR due to chordal rupture and leaflet flail. The degree of myxomatous change of the leaflets can also vary widely. In many patients, the condition progresses over years or decades; in others it worsens rapidly as a result of chordal rupture or endocarditis.

Most patients are asymptomatic and remain so for their entire lives. However, in North America, MVP is now the most common cause of isolated severe MR requiring surgical treatment. Arrhythmias, most commonly ventricular premature contractions and paroxysmal supraventricular and ventricular tachycardia, as well as AF, have been reported and may cause palpitations, light-headedness, and syncope. Sudden death is a very rare complication and occurs most often in patients with severe MR and depressed LV systolic function. There may be an excess risk of sudden death among patients with a flail leaflet. Many patients have chest pain that is difficult to evaluate; it is often substernal, prolonged, and not related to exertion, but may rarely resemble angina pectoris. Transient cerebral ischemic attacks secondary to emboli from the mitral valve due to endothelial disruption have been reported. Infective endocarditis may occur in patients with MR and/or leaflet thickening.

Auscultation

The most important finding is the mid- or late (nonejection) systolic click, which occurs 0.14 s or more after S1 and is thought to be generated by the sudden tensing of slack, elongated chordae tendineae or by the prolapsing mitral leaflet when it reaches its maximum excursion. Systolic clicks may be multiple and may be followed by a high-pitched, late systolic crescendo-decrescendo murmur, which occasionally is "whooping" or "honking" and is heard best at the apex. The click and murmur occur earlier with standing, during the strain phase of the Valsalva maneuver, and with any intervention that decreases LV volume, exaggerating the propensity of mitral leaflet prolapse. Conversely, squatting and isometric exercises, which increase LV volume, diminish MVP; the click-murmur complex is delayed, moves away from S1, and may even disappear. Some patients have a mid-systolic click without a murmur; others have a murmur without a click. Still others have both sounds at different times.

Laboratory Examination

The ECG most commonly is normal but may show biphasic or inverted T waves in leads II, III, and aVF, and occasionally supraventricular or ventricular premature beats. TTE is particularly effective in identifying the abnormal position and prolapse of the mitral valve leaflets. A useful echocardiographic definition of MVP is systolic displacement (in the parasternal long axis view) of the mitral valve leaflets by at least 2 mm into the LA superior to the plane of the mitral annulus. Color flow and continuous wave Doppler imaging is helpful to evaluate the associated MR and provide semiquantitative estimates of severity. The jet lesion of MR due to MVP is most often eccentric, and assessment of RF and effective regurgitant orifice area can be difficult. TEE is indicated when more accurate information is required and is performed routinely for intraoperative guidance for valve repair. Invasive left ventriculography is rarely necessary but can also show prolapse of the posterior and sometimes of both mitral valve leaflets.

Treatment: Mitral Valve Prolapse

Infective endocarditis prophylaxis is indicated only for patients with a prior history of endocarditis. Beta blockers sometimes relieve chest pain and control palpitations. If the patient is symptomatic from severe MR, mitral valve repair (or rarely, replacement) is indicated (Fig. 237-4). Antiplatelet agents, such as aspirin, should be given to patients with transient ischemic attacks, and if these are not effective, anticoagulants, such as warfarin, should be considered. Warfarin is also indicated once AF intervenes.

Aortic Stenosis

AS occurs in about one-fourth of all patients with chronic valvular heart disease; approximately 80% of adult patients with symptomatic valvular AS are male.

Etiology and Pathogenesis

(Table 237-1)

AS in adults is due to degenerative calcification of the aortic cusps and occurs most commonly on a substrate of congenital disease (bicuspid aortic valve [BAV]), chronic (tri-)leaflet deterioration, or previous rheumatic inflammation. A recent pathologic study of specimens removed at the time of aortic valve replacement for AS showed that 53% were bicuspid and 4% unicuspid. Contrary to previous teachings, the process of aortic valve deterioration and calcification is not a passive one, but rather one that shares many features with vascular atherosclerosis, including endothelial dysfunction, lipid accumulation, inflammatory cell activation, cytokine release, and upregulation of several signaling pathways (Fig. 237-6). Eventually, valvular myofibroblasts differentiate phenotypically into osteoblasts and actively produce bone matrix proteins that allow for the deposition of calcium hydroxyapatite crystals. Genetic polymorphisms involving the vitamin D receptor, the estrogen receptor in postmenopausal women, interleukin 10, and apolipoprotein E4 have been linked to the development of calcific AS, and a strong familial clustering of cases has been reported from western France. Several traditional atherosclerotic risk factors have also been associated with the development and progression of calcific AS, including low-density lipoprotein (LDL)-cholesterol, lipoprotein a [Lp(a)], diabetes mellitus, smoking, chronic kidney disease, and the metabolic syndrome. The presence of aortic valve sclerosis (focal thickening and calcification of the leaflets not severe enough to cause obstruction) is associated with an excess risk of cardiovascular death and MI among persons older than age 65. Approximately 30% of persons older than 65 years exhibit aortic valve sclerosis, whereas 2% exhibit frank stenosis.

Figure 237-6

Pathogenesis of Calcific Aortic Stenosis. Inflammatory cells infiltrate across the endothelial barrier and release cytokines that act on fibroblasts to promote cellular proliferation and matrix remodeling. LDL is oxidatively modified and taken up by macrophage scavengers to become foam cells. Angiotensin-converting enzyme colocalizes with Apo-B. A subset of myofibroblasts differentiate into an osteoblast phenotype capable of promoting bone formation. ACE, angiotensin-converting enzyme; ApoB, apolipoprotein B; LDL, low-density lipoprotein; IL, interleukin; MMP, matrix metalloproteinase; TGF, transforming growth factor. (From RV Freeman, CM Otto: Circulation 111:3316, 2005; with permission.)

Rheumatic disease of the aortic leaflets produces commissural fusion, sometimes resulting in a bicuspid-appearing valve. This condition, in turn, makes the leaflets more susceptible to trauma and ultimately leads to fibrosis, calcification, and further narrowing. By the time the obstruction to LV outflow causes serious clinical disability, the valve is usually a rigid calcified mass, and careful examination may make it difficult or even impossible to determine the etiology of the underlying process. Rheumatic AS is almost always associated with involvement of the mitral valve and with AR. Mediastinal radiation can also result in late scarring, fibrosis, and calcification of the leaflets with AS.

Bicuspid Aortic Valve Disease

A bicuspid aortic valve (BAV) is the most common congenital heart valve defect and occurs in 0.5–1.4% of the population with a 2–4:1 male to female predominance. The inheritance pattern appears to be autosomal dominant with incomplete penetrance, although some have questioned an X-linked component as suggested by the prevalence of BAV disease among patients with Turner's syndrome. The prevalence of BAV disease among first-degree relatives of an affected individual is approximately 10%. A single gene defect to explain the majority of cases has not been identified, although a mutation in the NOTCH1 gene has been described in some families. Abnormalities in endothelial nitric oxide synthase and NKX2.5 have been implicated, as well. Aortic coarctation or medial degeneration with ascending aortic aneurysm formation occurs commonly among patients with BAV disease. Patients with BAV disease have larger aortas than patients with comparable tricuspid aortic valve disease. The aortopathy develops independent of the hemodynamic severity of the valve lesion and is a risk factor for dissection. A BAV can be a component of more complex congenital heart disease with or without other left heart obstructing lesions.

Other Forms of Obstruction to Left Ventricular Outflow

In addition to valvular AS, three other lesions may be responsible for obstruction to LV outflow: hypertrophic obstructive cardiomyopathy (Chap. 238), discrete fibromuscular/membranous subaortic stenosis, and supravalvular AS (Chap. 236). The causes of left ventricular outflow obstruction can be differentiated on the basis of the cardiac examination and Doppler echocardiographic findings.

Pathophysiology

The obstruction to LV outflow produces a systolic pressure gradient between the LV and aorta. When severe obstruction is suddenly produced experimentally, the LV responds by dilation and reduction of stroke volume. However, in some patients, the obstruction may be present at birth and/or increase gradually over the course of many years, and LV contractile performance is maintained by the presence of concentric LV hypertrophy. Initially, this serves as an adaptive mechanism because it reduces toward normal the systolic stress developed by the myocardium, as predicted by the Laplace relation (S = Pr/h, where S = systolic wall stress, P = pressure, r = radius, and h = wall thickness). A large transaortic valve pressure gradient may exist for many years without a reduction in CO or LV dilation; ultimately, however, excessive hypertrophy becomes maladaptive, LV systolic function declines, abnormalities of diastolic function progress, and irreversible myocardial fibrosis develops.

A mean systolic pressure gradient >40 mmHg with a normal CO or an effective aortic orifice area <∼1 cm2 (or ∼<0.6 cm2/m2 body surface area in a normal-sized adult)—i.e., less than approximately one-third of the normal orifice area—is generally considered to represent severe obstruction to LV outflow. The elevated LV end-diastolic pressure observed in many patients with severe AS and preserved EF signifies the presence of diminished compliance of the hypertrophied LV. Although the CO at rest is within normal limits in most patients with severe AS, it usually fails to rise normally during exercise. Loss of an appropriately timed, vigorous atrial contraction, as occurs in AF or atrioventricular dissociation, may cause rapid progression of symptoms. Late in the course, contractile function deteriorates because of afterload excess, the CO and LV–aortic pressure gradient decline, and the mean LA, PA, and RV pressures rise. LV performance can be further compromised by superimposed CAD.

The hypertrophied LV causes an increase in myocardial oxygen requirements. In addition, even in the absence of obstructive CAD, coronary blood flow is impaired to the extent that ischemia can be precipitated under conditions of excess demand. Capillary density is reduced relative to wall thickness, compressive forces are increased, and the elevated LV end-diastolic pressure reduces the coronary driving pressure. The subendocardium is especially vulnerable to ischemia by this mechanism.

Symptoms

AS is rarely of clinical importance until the valve orifice has narrowed to approximately 1 cm2. Even severe AS may exist for many years without producing any symptoms because of the ability of the hypertrophied LV to generate the elevated intraventricular pressures required to maintain a normal stroke volume. Once symptoms occur, valve replacement is indicated.

Most patients with pure or predominant AS have gradually increasing obstruction over years, but do not become symptomatic until the sixth to eighth decades. Adult patients with BAV disease, however, develop significant valve dysfunction and symptoms one to two decades sooner. Exertional dyspnea, angina pectoris, and syncope are the three cardinal symptoms. Often, there is a history of insidious progression of fatigue and dyspnea associated with gradual curtailment of activities. Dyspnea results primarily from elevation of the pulmonary capillary pressure caused by elevations of LV diastolic pressures secondary to reduced left ventricular compliance and impaired relaxation. Angina pectoris usually develops somewhat later and reflects an imbalance between the augmented myocardial oxygen requirements and reduced oxygen availability. CAD may or may not be present, although its coexistence is common among AS patients older than age 65. Exertional syncope may result from a decline in arterial pressure caused by vasodilation in the exercising muscles and inadequate vasoconstriction in nonexercising muscles in the face of a fixed CO, or from a sudden fall in CO produced by an arrhythmia.

Because the CO at rest is usually well maintained until late in the course, marked fatigability, weakness, peripheral cyanosis, cachexia, and other clinical manifestations of a low CO are usually not prominent until this stage is reached. Orthopnea, paroxysmal nocturnal dyspnea, and pulmonary edema, i.e., symptoms of LV failure, also occur only in the advanced stages of the disease. Severe pulmonary hypertension leading to RV failure and systemic venous hypertension, hepatomegaly, AF, and TR are usually late findings in patients with isolated severe AS.

When AS and MS coexist, the reduction in CO induced by MS lowers the pressure gradient across the aortic valve and, thereby, masks many of the clinical findings produced by AS.

Physical Findings

The rhythm is generally regular until late in the course; at other times, AF should suggest the possibility of associated mitral valve disease. The systemic arterial pressure is usually within normal limits. In the late stages, however, when stroke volume declines, the systolic pressure may fall and the pulse pressure narrow. The peripheral arterial pulse rises slowly to a delayed peak (pulsus parvus et tardus. A thrill or anacrotic "shudder" may be palpable over the carotid arteries, more commonly the left. In the elderly, the stiffening of the arterial wall may mask this important physical sign. In many patients, the a wave in the jugular venous pulse is accentuated. This results from the diminished distensibility of the RV cavity caused by the bulging, hypertrophied interventricular septum.

The LV impulse is usually displaced laterally. A double apical impulse (with a palpable S4) may be recognized, particularly with the patient in the left lateral recumbent position. A systolic thrill may be present at the base of the heart to the right of the sternum when leaning forward or in the suprasternal notch.

Auscultation

An early systolic ejection sound is frequently audible in children, adolescents, and young adults with congenital BAV disease. This sound usually disappears when the valve becomes calcified and rigid. As AS increases in severity, LV systole may become prolonged so that the aortic valve closure sound no longer precedes the pulmonic valve closure sound, and the two components may become synchronous, or aortic valve closure may even follow pulmonic valve closure, causing paradoxical splitting of S2 (Chap. 227). The sound of aortic valve closure can be heard most frequently in patients with AS who have pliable valves, and calcification diminishes the intensity of this sound. Frequently, an S4 is audible at the apex and reflects the presence of LV hypertrophy and an elevated LV end-diastolic pressure; an S3 generally occurs late in the course, when the LV dilates and its systolic function becomes severely compromised.

The murmur of AS is characteristically an ejection (mid) systolic murmur that commences shortly after the S1, increases in intensity to reach a peak toward the middle of ejection, and ends just before aortic valve closure. It is characteristically low-pitched, rough and rasping in character, and loudest at the base of the heart, most commonly in the second right intercostal space. It is transmitted upward along the carotid arteries. Occasionally it is transmitted downward and to the apex, where it may be confused with the systolic murmur of MR (Gallavardin effect). In almost all patients with severe obstruction and preserved CO, the murmur is at least grade III/VI. In patients with mild degrees of obstruction or in those with severe stenosis with heart failure and low CO in whom the stroke volume and, therefore, the transvalvular flow rate are reduced, the murmur may be relatively soft and brief.

Laboratory Examination

ECG

In most patients with severe AS there is LV hypertrophy. In advanced cases, ST-segment depression and T-wave inversion (LV "strain") in standard leads I and aVL and in the left precordial leads are evident. However, there is no close correlation between the ECG and the hemodynamic severity of obstruction, and the absence of ECG signs of LV hypertrophy does not exclude severe obstruction. Many patients with AS have systemic hypertension, which can also contribute to the development of hypertrophy.

Echocardiogram

The key findings on TTE are thickening, calcification, and reduced systolic opening of the valve leaflets and LV hypertrophy. Eccentric closure of the aortic valve cusps is characteristic of congenitally bicuspid valves. TEE imaging usually displays the obstructed orifice extremely well, but it is not routinely required for accurate characterization. The valve gradient and aortic valve area can be estimated by Doppler measurement of the transaortic velocity. Severe AS is defined by a valve area <1 cm2, whereas moderate AS is defined by a valve area of 1–1.5 cm2 and mild AS by a valve area of 1.5–2 cm2. Aortic valve sclerosis, conversely, is accompanied by a jet velocity of less than 2.5 meters/s (peak gradient <25 mmHg). LV dilation and reduced systolic shortening reflect impairment of LV function. There is increasing experience with the use of longitudinal strain and strain rate to characterize earlier changes in LV systolic function, well before a decline in EF can be appreciated. Doppler indices of impaired diastolic function are frequently seen.

Echocardiography is useful for identifying coexisting valvular abnormalities; for differentiating valvular AS from other forms of LV outflow obstruction; and for measurement of the aortic root and proximal ascending aortic dimension. These aortic measurements are particularly important for patients with BAV disease. Dobutamine stress echocardiography is useful for the evaluation of patients with AS and severe LV systolic dysfunction (EF <0.35), in whom the severity of the AS can often be difficult to judge.

Chest X-Ray

The chest x-ray may show no or little overall cardiac enlargement for many years. Hypertrophy without dilation may produce some rounding of the cardiac apex in the frontal projection and slight backward displacement in the lateral view. A dilated proximal ascending aorta may be seen along the upper right heart border in the frontal view. Aortic valve calcification may be discernible in the lateral view, but is usually readily apparent on fluoroscopic examination or by echocardiography; the absence of valvular calcification in an adult suggests that severe valvular AS is not present. In later stages of the disease, as the LV dilates there is increasing roentgenographic evidence of LV enlargement, pulmonary congestion, and enlargement of the LA, PA, and right heart chambers.

Catheterization

Right and left heart catheterization for invasive assessment of AS is now performed infrequently but can be useful when there is a discrepancy between the clinical and Doppler echocardiographic findings. Appropriate concerns have been raised that attempts to cross the aortic valve for measurement of left ventricular pressures are associated with a risk of cerebral embolization. Catheterization is also useful in three distinct categories of patients: (1) patients with multivalvular disease, in whom the role played by each valvular deformity should be defined to aid in the planning of operative treatment; (2) young, asymptomatic patients with noncalcific congenital AS, to define the severity of obstruction to LV outflow, since operation or percutaneous aortic balloon valvoplasty (PABV) may be indicated in these patients if severe AS is present, even in the absence of symptoms; balloon valvotomy may follow left heart catheterization in the same sitting; and (3) patients in whom it is suspected that the obstruction to LV outflow may not be at the level of the aortic valve but rather at the sub- or supravalvular level.

Coronary angiography is indicated to detect or exclude CAD in appropriate patients with severe AS who are being considered for surgery. The incidence of significant CAD for which bypass grafting is indicated at the time of aortic valve replacement (AVR) exceeds 50% among adult patients.

Natural History

Death in patients with severe AS occurs most commonly in the seventh and eighth decades. Based on data obtained at postmortem examination in patients before surgical treatment became widely available, the average time to death after the onset of various symptoms was as follows: angina pectoris, 3 years; syncope, 3 years; dyspnea, 2 years; congestive heart failure, 1.5–2 years. Moreover, in >80% of patients who died with AS, symptoms had existed for <4 years. Among adults dying with valvular AS, sudden death, which presumably resulted from an arrhythmia, occurred in 10–20%; however, most sudden deaths occurred in patients who had previously been symptomatic. Sudden death as the first manifestation of severe AS is very uncommon (<1% per year) in asymptomatic adult patients. Calcific AS is a progressive disease, with an annual reduction in valve area averaging 0.1 cm2 and annual increases in the peak jet velocity and mean valve gradient averaging 0.3 meters/s and 7 mmHg, respectively (Table 237-2, Fig. 237-7).

Figure 237-7

Management Strategy for Patients with Severe Aortic Stenosis. Preoperative coronary angiography should be performed routinely as determined by age, symptoms, and coronary risk factors. Cardiac catheterization and angiography may also be helpful when there is a discrepancy between clinical findings and echocardiography. AVA, aortic valve area; BP, blood pressure; CABG, coronary artery bypass graft surgery; echo, echocardiography; LV, left ventricle; Vmax, maximal velocity across aortic valve by Doppler echocardiography. (From Bonow et al. Modified from CM Otto: J Am Coll Cardiol 47:2141, 2006.)

Treatment: Aortic Stenosis

Medical Treatment

In patients with severe AS (valve area <1 cm2), strenuous physical activity and competitive sports should be avoided, even in the asymptomatic stage. Care must be taken to avoid dehydration and hypovolemia to protect against a significant reduction in CO. Medications used for the treatment of hypertension or CAD, including beta blockers and ACE inhibitors, are generally safe for asymptomatic patients with preserved left ventricular systolic function. Nitroglycerin is helpful in relieving angina pectoris in patients with CAD. Retrospective studies have shown that patients with degenerative calcific AS who receive HMG-CoA reductase inhibitors ("statins") exhibit slower progression of leaflet calcification and aortic valve area reduction than those who do not. However, randomized prospective studies with either high-dose atorvastatin or combination simvastatin/ezetimibe have failed to show a measurable effect on valve-related outcomes. The use of statin medications should continue to be driven by considerations regarding primary and secondary prevention of CAD. ACE inhibitors have not been studied prospectively for AS-related outcomes. The need for endocarditis prophylaxis is restricted to AS patients with a prior history of endocarditis.

Surgical Treatment

Asymptomatic patients with calcific AS and severe obstruction should be followed carefully for the development of symptoms and by serial echocardiograms for evidence of deteriorating LV function. Operation is indicated in patients with severe AS (valve area <1 cm2 or 0.6 cm2/m2 body surface area) who are symptomatic, those who exhibit LV dysfunction (EF <50%), as well as those with BAV disease and an aneurysmal or expanding aortic root (maximal dimension >4.5 cm or annual increase in size >0.5 cm/year), even if they are asymptomatic. Patients with asymptomatic moderate or severe AS who are referred for CABG surgery should also have AVR. In patients without heart failure, the operative risk of AVR is approximately 3% (Table 237-3) but increases as a function of age and the need for concomitant coronary revascularization with bypass grafting. The indications for AVR in the asymptomatic patient have been the subject of intense debate over the past 5 years, as surgical outcomes in selected patients have continued to improve. Relative indications for which surgery can be considered include an abnormal response to treadmill exercise; rapid progression of AS, especially when urgent access to medical care might be compromised; very severe AS defined by a valve area <0.6 cm2; and severe LV hypertrophy suggested by a wall thickness of >15 mm. Exercise testing can be safely performed in the asymptomatic patient, as many as one-third of whom will show signs of functional impairment.

Operation should be carried out within 3–4 months of symptom onset and certainly well before frank LV failure develops; at this late stage, the aortic valve pressure gradient declines in parallel with the CO and stroke volume (low gradient, low output AS). In such patients, the perioperative mortality risk is high (15–20%), and evidence of myocardial disease may persist even when the operation is technically successful. Long-term postoperative survival correlates with preoperative LV function. Nonetheless, in view of the even worse prognosis of such patients when they are treated medically, there is usually little choice but to advise surgical treatment, especially in patients in whom contractile reserve can be demonstrated by dobutamine echocardiography (defined by a 20% in stroke volume after dobutamine challenge). In patients in whom severe AS and CAD coexist, relief of the AS and revascularization may sometimes result in striking clinical and hemodynamic improvement (Table 237-3).

Because many patients with calcific AS are elderly, particular attention must be directed to the adequacy of hepatic, renal, and pulmonary function before AVR is recommended. Age alone is not a contraindication to AVR for AS. The mortality rate depends to a substantial extent on the patient's preoperative clinical and hemodynamic state. The 10-year survival rate of patients with AVR is approximately 60%. Approximately 30% of bioprosthetic valves evidence primary valve failure in 10 years, requiring re-replacement, and an approximately equal percentage of patients with mechanical prostheses develop significant hemorrhagic complications as a consequence of treatment with anticoagulants (p. 1949). Homograft AVR is usually reserved for patients with aortic valve endocarditis.

The Ross procedure involves replacement of the diseased aortic valve with the autologous pulmonic valve and implantation of a homograft in the native pulmonic position. Its use has declined considerably in the United States because of the technical complexity of the procedure and the incidence of late postoperative aortic root dilation and autograft failure with AR. There is also a low incidence of homograft stenosis.

Percutaneous Balloon Aortic Valvuloplasty

This procedure is preferable to operation in many children and young adults with congenital, noncalcific AS (Chap. 236). It is not commonly used in adults with severe calcific AS because of a very high restenosis rate (80% within 1 year) and the risk of procedural complications, but on occasion it has been used successfully as a "bridge to operation" in patients with severe LV dysfunction and shock who are too ill to tolerate surgery.

Percutaneous Aortic Valve Replacement

Transcatheter aortic valve implantation (TAVI) for treatment of AS has been performed in more than 20,000 high-risk (Society for Thoracic Surgery mortality risk >10%) adult patients worldwide using one of two available systems, a balloon-expandable valve and a self-expanding valve, both of which incorporate a pericardial prosthesis (Fig. 237-8). The aorto-iliofemoral anatomy must allow for passage of large-bore catheters; a direct, trans-LV apical approach under surgical guidance is an alternative means of delivering the valve. There are also several reports of the successful use of axillary or subclavian artery access with construction of a vascular surgical sleeve. Aortic balloon valvuloplasty is performed as a first step to create an orifice sufficient for the prosthesis. Procedural success rates now exceed 90%, and intermediate-term prosthetic function is excellent. A mild degree of paravalvular AR is common with TAVI; postprocedural heart block is observed more frequently with the self-expanding valve. Preliminary results with TAVI have been very favorable (Fig. 237-9), and it is anticipated that this technology, now clinically available in Canada and Europe, will gain regulatory approval in the United States for the treatment of patients with severe AS considered too high risk for surgical AVR. For elderly patients with symptomatic, severe AS who are deemed too high risk for surgery, TAVI has been shown in a randomized prospective trial to prolong life and improve functionality. The use of these devices for the treatment of prosthetic valve failure not due to paravalvular regurgitation ("valve-in-valve"), as an alternative to reoperative valve replacement, is also under active study.

Figure 237-8.

A. Balloon-expandable and B and self-expanding valves for percutaneous aortic valve replacement. B, inflated balloon; N, nose cone; V, valve. (Part A, courtesy of Edwards Lifesciences, Irvine, CA; with permission. RetroFlex 3 is a trademark of Edwards Lifesciences Corporation. Part B, © Medtronic, Inc. 2010. Medtronic CoreValve Transcatheter Aortic Valve. CoreValve is a registered trademark of Medtronic, Inc.)

Figure 237-9

Twelve-Month Outcomes Following Percutaneous Aortic Valve Replacement.(Adapted from JG Webb et al: Circulation 116:755, 2007; with permission.)

Aortic Regurgitation

Etiology

(Table 237-1) AR may be caused by primary valve disease or by primary aortic root disease.

Primary Valve Disease

Rheumatic disease results in thickening, deformity, and shortening of the individual aortic valve cusps, changes that prevent their proper opening during systole and closure during diastole. A rheumatic origin is much less common in patients with isolated AR who do not have associated rheumatic mitral valve disease. Patients with congenital BAV disease may develop predominant AR, and approximately 20% of patients will require aortic valve surgery between 10 and 40 years of age. Congenital fenestrations of the aortic valve occasionally produce mild AR. Membranous subaortic stenosis often leads to thickening and scarring of the aortic valve leaflets with secondary AR. Prolapse of an aortic cusp, resulting in progressive chronic AR, occurs in approximately 15% of patients with ventricular septal defect (Chap. 236) but may also occur as an isolated phenomenon or as a consequence of myxomatous degeneration sometimes associated with mitral (p. 1937) and/or tricuspid valve involvement.

AR may result from infective endocarditis, which can develop on a valve previously affected by rheumatic disease, a congenitally deformed valve, or on a normal aortic valve, and may lead to perforation or erosion of one or more leaflets. The aortic valve leaflets may become scarred and retracted during the course of syphilis or ankylosing spondylitis and contribute further to the AR that derives primarily from the associated root disease. Although traumatic rupture or avulsion of the aortic valve is an uncommon cause of acute AR, it does represent the most frequent serious lesion in patients surviving nonpenetrating cardiac injuries. The coexistence of hemodynamically significant AS with AR usually excludes all the rarer forms of AR because it occurs almost exclusively in patients with rheumatic or congenital AR. In patients with AR due to primary valvular disease, dilation of the aortic annulus may occur secondarily and lead to worsening regurgitation.

Primary Aortic Root Disease

AR may also be due entirely to marked aortic dilation, i.e., aortic root disease, without primary involvement of the valve leaflets; widening of the aortic annulus and separation of the aortic leaflets are responsible for the AR (Chap. 248). Cystic medial degeneration of the ascending aorta, which may or may not be associated with other manifestations of Marfan's syndrome; idiopathic dilation of the aorta; annuloaortic ectasia; osteogenesis imperfecta; and severe hypertension may all widen the aortic annulus and lead to progressive AR. Occasionally AR is caused by retrograde dissection of the aorta involving the aortic annulus. Syphilis and ankylosing spondylitis, both of which may affect aortic valves, may also be associated with cellular infiltration and scarring of the media of the thoracic aorta, leading to aortic dilation, aneurysm formation, and severe regurgitation. In syphilis of the aorta (Chap. 169), now a very rare condition, the involvement of the intima may narrow the coronary ostia, which in turn may be responsible for myocardial ischemia.

Pathophysiology

The total stroke volume ejected by the LV (i.e., the sum of the effective forward stroke volume and the volume of blood that regurgitates back into the LV) is increased in patients with AR. In patients with severe AR, the volume of regurgitant flow may equal the effective forward stroke volume. In contrast to MR, in which a portion of the LV stroke volume is delivered into the low-pressure LA, in AR the entire LV stroke volume is ejected into a high-pressure zone, the aorta. An increase in the LV end-diastolic volume (increased preload) constitutes the major hemodynamic compensation for AR. The dilation and eccentric hypertrophy of the LV allow this chamber to eject a larger stroke volume without requiring any increase in the relative shortening of each myofibril. Therefore, severe AR may occur with a normal effective forward stroke volume and a normal left ventricular EF [total (forward plus regurgitant) stroke volume/end-diastolic volume], together with an elevated LV end-diastolic pressure and volume. However, through the operation of Laplace's law, LV dilation increases the LV systolic tension required to develop any given level of systolic pressure. Chronic AR is, thus, a state in which LV preload and afterload are both increased. Ultimately, these adaptive measures fail. As LV function deteriorates, the end-diastolic volume rises further and the forward stroke volume and EF decline. Deterioration of LV function often precedes the development of symptoms. Considerable thickening of the LV wall also occurs with chronic AR, and at autopsy the hearts of these patients may be among the largest encountered, sometimes weighing >1000 g.

The reverse pressure gradient from aorta to LV, which drives the AR flow, falls progressively during diastole, accounting for the decrescendo nature of the diastolic murmur. Equilibration between aortic and LV pressures may occur toward the end of diastole in patients with chronic severe AR, particularly when the heart rate is slow. In patients with acute severe AR, the LV is unprepared for the regurgitant volume load. LV compliance is normal or reduced, and LV diastolic pressures rise rapidly, occasionally to levels >40 mmHg. The LV pressure may exceed the LA pressure toward the end of diastole, and this reversed pressure gradient closes the mitral valve prematurely.

In patients with chronic severe AR, the effective forward CO usually is normal or only slightly reduced at rest, but often it fails to rise normally during exertion. An early sign of LV dysfunction is a reduction in the EF. In advanced stages there may be considerable elevation of the LA, PA wedge, PA, and RV pressures and lowering of the forward CO at rest.

Myocardial ischemia may occur in patients with AR because myocardial oxygen requirements are elevated by LV dilation, hypertrophy, and elevated LV systolic tension, and coronary blood flow may be compromised. A large fraction of coronary blood flow occurs during diastole, when arterial pressure is low, thereby reducing coronary perfusion or driving pressure. This combination of increased oxygen demand and reduced supply may cause myocardial ischemia, particularly of the subendocardium, even in the absence of concomitant CAD.

History

Approximately three-fourths of patients with pure or predominant valvular AR are men; women predominate among patients with primary valvular AR who have associated rheumatic mitral valve disease. A history compatible with infective endocarditis may sometimes be elicited from patients with rheumatic or congenital involvement of the aortic valve, and the infection often precipitates or seriously aggravates preexisting symptoms.

In patients with acute severe AR, as may occur in infective endocarditis, aortic dissection, or trauma, the LV cannot dilate sufficiently to maintain stroke volume, and LV diastolic pressure rises rapidly with associated marked elevations of LA and PA wedge pressures. Pulmonary edema and/or cardiogenic shock may develop rapidly.

Chronic severe AR may have a long latent period, and patients may remain relatively asymptomatic for as long as 10–15 years. However, uncomfortable awareness of the heartbeat, especially on lying down, may be an early complaint. Sinus tachycardia, during exertion or with emotion, or premature ventricular contractions may produce particularly uncomfortable palpitations as well as head pounding. These complaints may persist for many years before the development of exertional dyspnea, usually the first symptom of diminished cardiac reserve. The dyspnea is followed by orthopnea, paroxysmal nocturnal dyspnea, and excessive diaphoresis. Anginal chest pain even in the absence of CAD may occur in patients with severe AR, even in younger patients. Anginal pain may develop at rest as well as during exertion. Nocturnal angina may be a particularly troublesome symptom, and it may be accompanied by marked diaphoresis. The anginal episodes can be prolonged and often do not respond satisfactorily to sublingual nitroglycerin. Systemic fluid accumulation, including congestive hepatomegaly and ankle edema, may develop late in the course of the disease.

Physical Findings

In chronic severe AR, the jarring of the entire body and the bobbing motion of the head with each systole can be appreciated, and the abrupt distention and collapse of the larger arteries are easily visible. The examination should be directed toward the detection of conditions predisposing to AR, such as bicuspid valve, endocarditis, Marfan's syndrome, and ankylosing spondylitis.

Arterial Pulse

A rapidly rising "water-hammer" pulse, which collapses suddenly as arterial pressure falls rapidly during late systole and diastole (Corrigan's pulse), and capillary pulsations, an alternate flushing and paling of the skin at the root of the nail while pressure is applied to the tip of the nail (Quincke's pulse), are characteristic of chronic severe AR. A booming "pistol-shot" sound can be heard over the femoral arteries (Traube's sign), and a to-and-fro murmur (Duroziez's sign) is audible if the femoral artery is lightly compressed with a stethoscope.

The arterial pulse pressure is widened as a result of both systolic hypertension and a lowering of the diastolic pressure. The measurement of arterial diastolic pressure with a sphygmomanometer may be complicated by the fact that systolic sounds are frequently heard with the cuff completely deflated. However, the level of cuff pressure at the time of muffling of the Korotkoff sounds (phase IV) generally corresponds fairly closely to the true intraarterial diastolic pressure. As the disease progresses and the LV end-diastolic pressure rises, the arterial diastolic pressure may actually rise as well, because the aortic diastolic pressure cannot fall below the LV end-diastolic pressure. For the same reason, acute severe AR may also be accompanied by only a slight widening of the pulse pressure. Such patients are invariably tachycardic as the heart rate increases in an attempt to preserve the CO.

Palpation

In patients with chronic severe AR, the LV impulse is heaving and displaced laterally and inferiorly. The systolic expansion and diastolic retraction of the apex are prominent. A diastolic thrill may be palpable along the left sternal border in thin-chested individuals, and a prominent systolic thrill may be palpable in the suprasternal notch and transmitted upward along the carotid arteries. This systolic thrill and the accompanying murmur do not necessarily signify the coexistence of AS. In many patients with pure AR or with combined AS and AR, the carotid arterial pulse is bisferiens, i.e., with two systolic waves separated by a trough (see Fig. 227-2D).

Auscultation

In patients with severe AR, the aortic valve closure sound (A2) is usually absent. A systolic ejection sound is audible in patients with BAV disease, and occasionally an S4 also may be heard. The murmur of chronic AR is typically a high-pitched, blowing, decrescendo diastolic murmur, heard best in the third intercostal space along the left sternal border (see Fig. 227-5B). In patients with mild AR, this murmur is brief, but as the severity increases, it generally becomes louder and longer, indeed holodiastolic. When the murmur is soft, it can be heard best with the diaphragm of the stethoscope and with the patient sitting up, leaning forward, and with the breath held in forced expiration. In patients in whom the AR is caused by primary valvular disease, the diastolic murmur is usually louder along the left than the right sternal border. However, when the murmur is heard best along the right sternal border, it suggests that the AR is caused by aneurysmal dilation of the aortic root. "Cooing" or musical diastolic murmurs suggest eversion of an aortic cusp vibrating in the regurgitant stream.

A mid-systolic ejection murmur is frequently audible in isolated AR. It is generally heard best at the base of the heart and is transmitted along the carotid arteries. This murmur may be quite loud without signifying aortic obstruction. A third murmur sometimes heard in patients with severe AR is the Austin Flint murmur, a soft, low-pitched, rumbling mid-to-late diastolic murmur. It is probably produced by the diastolic displacement of the anterior leaflet of the mitral valve by the AR stream and is not associated with hemodynamically significant mitral obstruction. The auscultatory features of AR are intensified by strenuous and sustained handgrip, which augments systemic vascular resistance.

In acute severe AR, the elevation of LV end-diastolic pressure may lead to early closure of the mitral valve, a soft S1, a pulse pressure that is not particularly wide, and a soft, short, early diastolic murmur of AR.

Laboratory Examination

ECG

In patients with chronic severe AR, the ECG signs of LV hypertrophy become manifest (Chap. 228). In addition, these patients frequently exhibit ST-segment depression and T-wave inversion in leads I, aVL, V5, and V6 ("LV strain"). Left-axis deviation and/or QRS prolongation denote diffuse myocardial disease, generally associated with patchy fibrosis, and usually signify a poor prognosis.

Echocardiogram

LV size is increased in chronic AR and systolic function is normal or even supernormal until myocardial contractility declines, as signaled by a decrease in ejection or increase in the end-systolic dimension. A rapid, high-frequency diastolic fluttering of the anterior mitral leaflet produced by the impact of the regurgitant jet is a characteristic finding. The echocardiogram is also useful in determining the cause of AR, by detecting dilation of the aortic annulus and root, aortic dissection (see Fig. 229-5), or primary leaflet pathology. With severe AR, the central jet width assessed by color flow Doppler imaging exceeds 65% of the left ventricular outflow tract, the regurgitant volume is 60 mL/beat, the regurgitant fraction is 50%, and there is diastolic flow reversal in the proximal descending thoracic aorta. The continuous wave Doppler profile shows a rapid deceleration time in patients with acute severe AR, due to the rapid increase in LV diastolic pressure. Surveillance transthoracic echocardiography forms the cornerstone of longitudinal follow-up and allows for the early detection of changes in LV size and/or function. For patients in whom echocardiography is limited by poor acoustical windows or inadequate semiquantitative assessment, gated cardiac MR imaging can be performed. This modality also allows for accurate assessment of aortic size and contour.

Chest X-Ray

In chronic severe AR, the apex is displaced downward and to the left in the frontal projection. In the left anterior oblique and lateral projections, the LV is displaced posteriorly and encroaches on the spine. When AR is caused by primary disease of the aortic root, aneurysmal dilation of the aorta may be noted, and the aorta may fill the retrosternal space in the lateral view. Echocardiography, cardiac MR, and CT angiography are more sensitive than the chest x-ray for the detection of aortic root enlargement.

Cardiac Catheterization and Angiography

When needed, right and left heart catheterization with contrast aortography can provide confirmation of the magnitude of regurgitation and the status of LV function. Coronary angiography is performed routinely in appropriate patients prior to surgery.

Treatment: Aortic Regurgitation

Acute Aortic Regurgitation

(See Fig. 237-10) Patients with acute severe AR may respond to intravenous diuretics and vasodilators (such as sodium nitroprusside), but stabilization is usually short-lived and operation is indicated urgently. Intraaortic balloon counterpulsation is contraindicated. Beta blockers are also best avoided so as not to reduce the CO further or slow the heart rate. Surgery is the treatment of choice and is usually necessary within 24 hours of diagnosis.

Figure 237-10

Management Strategy for Patients with Chronic Severe Aortic Regurgitation. Preoperative coronary angiography should be performed routinely, as determined by age, symptoms, and coronary risk factors. Cardiac catheterization and angiography may also be helpful when there is a discrepancy between clinical and echocardiographic findings. "Stable" refers to stable echocardiographic measurements. In some centers, serial follow-up may be performed with radionuclide ventriculography (RVG) or magnetic resonance imaging (MRI) rather than echocardiography (echo) to assess left ventricular (LV) volume and systolic function. AVR, aortic valve replacement; DD, end-diastolic dimension; EF, ejection fraction; eval, evaluation; SD, end-systolic dimension. (Modified from Bonow et al.)

Chronic Aortic Regurgitation

Early symptoms of dyspnea and effort intolerance respond to treatment with diuretics; vasodilators (ACE inhibitors, dihydropyridine calcium channel blockers, or hydralazine) may be useful as well. Surgery can then be performed in a more controlled setting. The use of vasodilators to extend the compensated phase of chronic severe AR before the onset of symptoms or the development of LV dysfunction is more controversial. Expert consensus is strong regarding the need to control systolic blood pressure (goal <140 mmHg) in patients with chronic AR, and vasodilators are an excellent first choice as antihypertensive agents. It is often difficult to achieve adequate control because of the increased stroke volume that accompanies severe AR. Cardiac arrhythmias and systemic infections are poorly tolerated in patients with severe AR and must be treated promptly and vigorously. Although nitroglycerin and long-acting nitrates are not as helpful in relieving anginal pain as they are in patients with ischemic heart disease, they are worth a trial. Patients with syphilitic aortitis should receive a full course of penicillin therapy (Chap. 169). Beta blockers and the angiotensin receptor blocker, losartan, may be useful to retard the rate of aortic root enlargement in young patients with Marfan's syndrome and aortic root dilation. Early reports of the efficacy of losartan in patients with Marfan's syndrome have led to its use in other populations of patients, including those with BAV disease and aortopathy. The use of beta blockers in patients with valvular AR was previously felt to be relatively contraindicated due to concerns that the resulting slowing of the heart rate would allow more time for diastolic regurgitation. More recent observational reports, however, suggest that beta blockers may provide functional benefit in patients with chronic AR. Beta blockers can sometimes provide incremental blood pressure lowering in patients with chronic AR and hypertension. Patients with severe AR, particularly those with an associated aortopathy, should avoid isometric exercises.

Surgical Treatment

In deciding on the advisability and proper timing of surgical treatment, two points should be kept in mind: (1) patients with chronic severe AR usually do not become symptomatic until after the development of myocardial dysfunction; and (2) when delayed too long (defined as >1 year from onset of symptoms or LV dysfunction), surgical treatment often does not restore normal LV function. Therefore, in patients with chronic severe AR, careful clinical follow-up and noninvasive testing with echocardiography at approximately 6-month intervals are necessary if operation is to be undertaken at the optimal time, i.e., after the onset of LV dysfunction but prior to the development of severe symptoms. Operation can be deferred as long as the patient both remains asymptomatic and retains normal LV function without severe chamber dilation (end-diastolic dimension >75 mm).

AVR is indicated for the treatment of severe AR in symptomatic patients irrespective of LV function. In general, the operation should be carried out in asymptomatic patients with severe AR and progressive LV dysfunction defined by an LVEF <50%, an LV end-systolic dimension >55 mm or end-systolic volume >55 mL/m2, or an LV diastolic dimension >75 mm. Smaller dimensions may be appropriate thresholds in individuals of smaller stature. Patients with severe AR without indications for operation should be followed by clinical and echocardiographic examination every 3–12 months.

Surgical options for management of aortic valve and root disease have expanded considerably over the past decade. AVR with a suitable mechanical or tissue prosthesis is generally necessary in patients with rheumatic AR and in many patients with other forms of regurgitation. Rarely, when a leaflet has been perforated during infective endocarditis or torn from its attachments to the aortic annulus by thoracic trauma, primary surgical repair may be possible. When AR is due to aneurysmal dilation of the root, or proximal ascending aorta, rather than to primary valve involvement, it may be possible to reduce or eliminate the regurgitation by narrowing the annulus or by excising a portion of the aortic root without replacing the valve. Elective, valve-sparing aortic root reconstruction generally involves reimplantation of the valve in a contoured graft with reattachment of the coronary artery buttons into the side of the graft and is best undertaken in specialized surgical centers (Fig. 237-11). Resuspension of the native aortic valve leaflets is possible in approximately 50% of patients with acute AR in the setting of type A aortic dissection. In other conditions, however, regurgitation can be effectively eliminated only by replacing the aortic valve, the dilated or aneurysmal ascending aorta responsible for the regurgitation, and implanting a composite valve-graft conduit. This formidable procedure entails a higher risk than isolated AVR.

Figure 237-11

Valve-Sparing Aortic Root Reconstruction (David Procedure). (From P Steltzer et al (eds): Valvular Heart Disease: A Companion to Braunwald's Heart Disease, 3rd ed, Fig 12-27, p. 200.)

As in patients with other valvular abnormalities, both the operative risk and the late mortality rate are largely dependent on the stage of the disease and myocardial function at the time of operation. The overall operative mortality rate for isolated AVR is approximately 3% (Table 237-3). However, patients with marked cardiac enlargement and prolonged LV dysfunction experience an operative mortality rate of approximately 10% and a late mortality rate of approximately 5% per year due to LV failure despite a technically satisfactory operation. Nonetheless, because of the very poor prognosis with medical management, even patients with LV systolic failure should be considered for operation.

Patients with acute severe AR require prompt surgical treatment, which may be lifesaving.

Tricuspid Stenosis

TS, which is much less prevalent than MS in North America and Western Europe, is generally rheumatic in origin and more common in women than men. It does not occur as an isolated lesion and is usually associated with MS. Hemodynamically significant TS occurs in 5–10% of patients with severe MS; rheumatic TS is commonly associated with some degree of TR. Nonrheumatic causes of TS are rare.

Pathophysiology

A diastolic pressure gradient between the RA and RV defines TS. It is augmented when the transvalvular blood flow increases during inspiration and declines during expiration. A mean diastolic pressure gradient of 4 mmHg is usually sufficient to elevate the mean RA pressure to levels that result in systemic venous congestion. Unless sodium intake has been restricted and diuretics administered, this venous congestion is associated with hepatomegaly, ascites, and edema, sometimes severe. In patients with sinus rhythm, the RA a wave may be extremely tall and may even approach the level of the RV systolic pressure. The y descent is prolonged. The CO at rest is usually depressed, and it fails to rise during exercise. The low CO is responsible for the normal or only slightly elevated LA, PA, and RV systolic pressures despite the presence of MS. Thus, the presence of TS can mask the hemodynamic and clinical features of any associated MS.

Symptoms

Because the development of MS generally precedes that of TS, many patients initially have symptoms of pulmonary congestion and fatigue. Characteristically, patients with severe TS complain of relatively little dyspnea for the degree of hepatomegaly, ascites, and edema that they have. However, fatigue secondary to a low CO and discomfort due to refractory edema, ascites, and marked hepatomegaly are common in patients with TS and/or TR. In some patients, TS may be suspected for the first time when symptoms of right-sided failure persist after an adequate mitral valvotomy.

Physical Findings

Because TS usually occurs in the presence of other obvious valvular disease, the diagnosis may be missed unless it is considered. Severe TS is associated with marked hepatic congestion, often resulting in cirrhosis, jaundice, serious malnutrition, anasarca, and ascites. Congestive hepatomegaly and, in cases of severe tricuspid valve disease, splenomegaly are present. The jugular veins are distended, and in patients with sinus rhythm there may be giant a waves. The v waves are less conspicuous, and because tricuspid obstruction impedes RA emptying during diastole, there is a slow y descent. In patients with sinus rhythm there may be prominent presystolic pulsations of the enlarged liver as well.

On auscultation, an OS of the tricuspid valve may rarely be heard approximately 0.06 s after pulmonic valve closure. The diastolic murmur of TS has many of the qualities of the diastolic murmur of MS, and because TS almost always occurs in the presence of MS, it may be missed. However, the tricuspid murmur is generally heard best along the left lower sternal border and over the xiphoid process, and is most prominent during presystole in patients with sinus rhythm. The murmur of TS is augmented during inspiration, and it is reduced during expiration and particularly during the strain phase of the Valsalva maneuver, when tricuspid transvalvular flow is reduced.

Laboratory Examination

The ECG features of RA enlargement (see Fig. 228-8) include tall, peaked P waves in lead II, as well as prominent, upright P waves in lead V1. The absence of ECG evidence of right ventricular hypertrophy (RVH) in a patient with right-sided heart failure who is believed to have MS should suggest associated tricuspid valve disease. The chest x-ray in patients with combined TS and MS shows particular prominence of the RA and superior vena cava without much enlargement of the PA and with less evidence of pulmonary vascular congestion than occurs in patients with isolated MS. On echocardiographic examination, the tricuspid valve is usually thickened and domes in diastole; the transvalvular gradient can be estimated routinely by continuous wave Doppler echocardiography. TTE provides additional information regarding mitral valve structure and function, LV and RV size and function, and PA pressure.

Treatment: Tricuspid Stenosis

Patients with TS generally exhibit marked systemic venous congestion; intensive salt restriction, bed rest, and diuretic therapy are required during the preoperative period. Such a preparatory period may diminish hepatic congestion and thereby improve hepatic function sufficiently so that the risks of operation, particularly bleeding, are diminished. Surgical relief of the TS should be carried out, preferably at the time of surgical mitral valvotomy or MVR, in patients with moderate or severe TS who have mean diastolic pressure gradients exceeding ∼4 mmHg and tricuspid orifice areas <1.5–2 cm2. TS is almost always accompanied by significant TR. Operative repair may permit substantial improvement of tricuspid valve function. If repair cannot be accomplished, the tricuspid valve may have to be replaced with a prosthesis, preferably a large bioprosthetic valve. Mechanical valves in the tricuspid position are more prone to thromboembolic complications than in other positions.

Tricuspid Regurgitation

Most commonly, TR is secondary to marked dilation of the tricuspid annulus from RV enlargement due to PA hypertension. Functional TR may complicate RV enlargement of any cause, including an inferior MI that involves the RV. It is commonly seen in the late stages of heart failure due to rheumatic or congenital heart disease with severe PA hypertension (pulmonary artery systolic pressure >55 mmHg), as well as in ischemic and idiopathic dilated cardiomyopathies. It is reversible in part if PA hypertension can be relieved. Rheumatic fever may produce organic (primary) TR, often associated with TS. Infarction of RV papillary muscles, tricuspid valve prolapse, carcinoid heart disease, endomyocardial fibrosis, radiation, infective endocarditis, and trauma all may produce TR. Less commonly, TR results from congenitally deformed tricuspid valves, and it occurs with defects of the atrioventricular canal, as well as with Ebstein's malformation of the tricuspid valve (Chap. 236). TR also develops eventually in patients with chronic RV apical pacing.

As is the case for TS, the clinical features of TR result primarily from systemic venous congestion and reduction of CO. With the onset of TR in patients with PA hypertension, symptoms of pulmonary congestion diminish, but the clinical manifestations of right-sided heart failure become intensified. The neck veins are distended with prominent v waves and rapid y descents, marked hepatomegaly, ascites, pleural effusions, edema, systolic pulsations of the liver, and a positive hepatojugular reflex. A prominent RV pulsation along the left parasternal region and a blowing holosystolic murmur along the lower left sternal margin, which may be intensified during inspiration and reduced during expiration or the strain of the Valsalva maneuver, are characteristic findings; AF is usually present.

The ECG may show changes characteristic of the lesion responsible for the enlargement of the RV that leads to TR, e.g., an inferior Q-wave MI or RVH. Echocardiography may be helpful by demonstrating RV dilation and prolapsing, flail, scarred, or displaced tricuspid leaflets; the diagnosis and assessment of TR can be made by color flow Doppler imaging (see Fig. 229-8). Severe TR is accompanied by hepatic vein systolic flow reversal. Continuous wave Doppler of the TR velocity profile is useful in estimating PA systolic pressure. Roentgenographic examination usually reveals enlargement of both the RA and RV.

In patients with severe TR, the CO is usually markedly reduced, and the RA pressure pulse may exhibit no x descent during early systole but a prominent c-v wave with a rapid y descent. The mean RA and the RV end-diastolic pressures are often elevated.

Treatment: Tricuspid Regurgitation

Isolated TR, in the absence of PA hypertension, such as that occurring as a consequence of infective endocarditis or trauma, is usually well tolerated and does not require operation. Indeed, even total excision of an infected tricuspid valve may be well tolerated for several years if the PA pressure and resistance are normal. Treatment of the underlying cause of left heart failure usually reduces the severity of functional TR, by reducing the size of the tricuspid annulus. In patients with mitral valve disease and TR secondary to PA hypertension and RV enlargement, effective surgical correction of the mitral valve abnormality results in lowering of the PA pressures and a gradual reduction or disappearance of the TR without direct treatment of the tricuspid valve. However, recovery may be more rapid in patients with severe functional TR if, at the time of mitral valve surgery and especially when there is enlargement of the tricuspid valve annulus, tricuspid valve annuloplasty (generally with the insertion of a ring) or in the rare instance of severe organic tricuspid valve disease, tricuspid valve replacement, is performed (Table 237-3). Tricuspid valve annuloplasty or replacement may rarely be required for severe, primary TR.

Pulmonic Valve Disease

The pulmonic valve is affected by rheumatic fever far less frequently than are the other valves, and it is uncommonly a nidus for infective endocarditis. The most common acquired abnormality affecting the pulmonic valve is regurgitation secondary to dilation of the pulmonic valve ring as a consequence of severe PA hypertension. This dilation produces the Graham Steell murmur, a high-pitched, decrescendo, diastolic blowing murmur along the left sternal border, which is difficult to differentiate from the far more common murmur produced by AR. Pulmonic regurgitation is usually of little hemodynamic significance; indeed, surgical removal or destruction of the pulmonic valve by infective endocarditis does not produce heart failure unless significant PA hypertension is also present.

The carcinoid syndrome may cause pulmonic stenosis and/or regurgitation. Pulmonic regurgitation occurs universally among patients who have undergone childhood repair of tetralogy of Fallot with reconstruction of the RV outflow tract. Congenital pulmonic stenosis is discussed in Chap. 236.

Percutaneous pulmonic valve replacement has been successfully performed in many patients with severe PR after childhood repair of tetralogy of Fallot or pulmonic valve stenosis or atresia. This procedure was introduced clinically prior to percutaneous aortic valve replacement.

Multiple and Mixed Valvular Heart Disease

Many acquired and congenital cardiac lesions may result in stenosis and/or regurgitation of one or more heart valves. For example, rheumatic fever may present with mitral (MS, MR, MS and MR), aortic (AS, AR, AS and AR), and/or tricuspid (TS, TR, TS and TR) valve involvement. The common association of secondary TR with significant mitral valve disease has been discussed previously. Aortic valve infective endocarditis may secondarily involve the mitral apparatus. Mediastinal radiation may result in aortic, mitral, and even tricuspid valve disease, most often with mixed stenosis and regurgitation. Ergotamines, and the previously used combination of fenfluramine and phentermine, may result in mixed valve lesions, as are also seen in patients with carcinoid heart disease. Patients with Marfan's syndrome may have both AR from root dilation and MR due to MVP.

The clinical assessment of patients with multiple or mixed valve disease can be challenging, With combined mitral and aortic valve disease, the hemodynamic derangements associated with the mitral lesion(s) may mask the full expression of the aortic valve disease. For example, severe mitral stenosis may decrease LV preload to the extent that the severity of AS or AR can be underappreciated. Alternatively, the development of AF during the course of MS can lead to sudden worsening in a patient whose aortic valve disease was not previously felt to be significant. In patients with mixed MS/MR or AS/AR, the regurgitant lesion usually predominates, and can be followed primarily as the trigger for surgical or transcatheter intervention as appropriate. Nevertheless, there are frequent exceptions to the rules, and careful assessment is indicated. The LV in a patient with hypertrophy in the setting of both AS and AR may not be able to dilate in response to the volume load imposed by the regurgitant lesion and, thus, show signs or lead to the development of symptoms of compromise at a relatively earlier point in the natural history. Serial echocardiography can aid in decision-making.

Similar considerations pertain to the evaluation of patients with heart valve disease and other cardiac and systemic disorders that can contribute to impaired exercise tolerance, such as hypertension, coronary artery disease, obesity, sleep apnea, and skeletal muscle deconditioning.

Valve Replacement and Repair

The results of valve replacement surgery are dependent on (1) the patient's myocardial function and general medical condition at the time of operation; (2) the technical abilities of the operative team and the quality of the postoperative care; and (3) the durability, hemodynamic characteristics, and thrombogenicity of the prosthesis. Increased perioperative mortality rate is associated with advanced age and comorbidity rate (e.g., pulmonary or renal disease, the need for nonvalvular cardiovascular surgery, diabetes mellitus) as well as with greater levels of preoperative functional disability and PA hypertension. Late complications of valve replacement include thromboemboli, bleeding due to anticoagulants, mechanical valve thrombosis, pannus ingrowth, paravalvular leak, hemolysis, structural deterioration, infective endocarditis, and prosthesis-patient mismatch (functional prosthetic valve stenosis that occurs when the prosthesis is too small relative to the patient's anatomy).

The choice between a tissue and mechanical prosthesis is essentially a trade-off between the risk of structural valve deterioration and the possible need for reoperation with a tissue valve versus the obligate need for lifelong anticoagulation and its attendant risks with a mechanical valve. The incidence of structural valve deterioration varies inversely with patient age and may be accelerated further by pregnancy or end-stage renal disease. Failure of a tissue prosthesis results in the need for reoperation in up to 30% of patients by 10 years and in 50% by 15 years. Rates of structural valve deterioration are higher for mitral than for aortic bioprostheses. This phenomenon may be due in part to the greater closing pressure to which a mitral prosthesis is exposed.

Traditionally, a mechanical prosthesis was considered preferable for a patient younger than age 65 who could take anticoagulants reliably. Bioprostheses were recommended for older patients (>65 years) who did not otherwise have an indication for anticoagulation (e.g., AF). Recent surveys of cardiac surgery in the United States, as reflected in the Society of Thoracic Surgeons database, show a clear and progressive trend favoring the implantation of bioprosthetic valves in younger (<65 years) patients. Reasons for this development include improved durability of newer generation bioprostheses, decreased risk of death or major complication at time of reoperation, the hazards of long-term anticoagulation, and patient preference to avoid anticoagulation for lifestyle reasons. Patient preference must be factored into any decision regarding the type of valve replacement. A mechanical prosthesis is reasonable for aortic or mitral valve replacement in patients younger than 65 years without a contraindication to anticoagulation. A bioprosthesis is equally reasonable for aortic or mitral valve replacement in patients younger than 65 years who elect this strategy for lifestyle reasons with full knowledge of the likely need for reoperation over time.

Bioprostheses remain the preferred valve choice for patients older than 65 years, in both the aortic and mitral position. Bioprosthetic valves are also indicated for women who expect to become pregnant, as well as for others who refuse to take anticoagulation or for whom anticoagulation may be contraindicated. Types of bioprostheses include xenografts (e.g., porcine aortic valves; cryopreserved, mounted bovine pericardial valves), homograft (allograft) aortic valves obtained from cadavers, and pulmonary autografts transplanted into the aortic position (Ross procedure). Homograft replacement may be preferred for the management of complicated aortic valve infective endocarditis.

In patients without contraindications to anticoagulants, particularly those younger than 65 years, a mechanical prosthesis is reasonable. Many surgeons now select the St. Jude prosthesis, a double-disk tilting prosthesis, for replacement of both aortic and mitral valves because of favorable hemodynamic characteristics and possible association with lower thrombogenicity. A tissue valve is preferred for tricuspid replacement.

The decision to proceed with valve replacement should be finalized only after an experienced surgeon has agreed that valve repair is either not appropriate or not feasible. As noted previously, valve repair techniques have improved considerably over the past 10–15 years, for both mitral and aortic lesions. Primary repair is often associated with a lower risk of postoperative LV functional impairment, particularly for patients with MR, and avoids the long-term risks of a prosthesis.

Antibiotic prophylaxis prior to dental procedures that involve manipulation of gingival tissue or the periapical region of teeth or perforation of the oral mucosa is indicated for patients after valve replacement or ring annuloplasty. Prosthetic valve and ventricular function should be assessed with transthoracic echocardiography 3 months after surgery and a baseline complete blood count, reticulocyte count, and serum lactate dehydrogenase (LDH) test obtained to serve as a baseline set of values should the question of hemolysis arise in the future. The intensity of anticoagulation should follow recommended guidelines.

Global Burden of Valvular Heart Disease

Primary valvular heart disease ranks well below coronary heart disease, stroke, hypertension, obesity, and diabetes as major threats to the public health. Nevertheless, it is the source of significant morbidity and mortality rates. Rheumatic fever (Chap. 322) is the dominant cause of valvular heart disease in developing countries. Its prevalence has been estimated to range from as low as 1 per 100,000 school-age children in Costa Rica to as high as 150 per 100,000 in China. Rheumatic heart disease accounts for 12–65% of hospital admissions related to cardiovascular disease and 2–10% of hospital discharges in some developing countries. Prevalence and mortality rates vary among communities even within the same country as a function of crowding and the availability of medical resources and population-wide programs for detection and treatment of group A streptococcal pharyngitis. In economically deprived areas, tropical and subtropical climates (particularly on the Indian subcontinent), Central America, and the Middle East, rheumatic valvular disease progresses more rapidly than in more-developed nations and frequently causes serious symptoms in patients younger than 20 years of age. This accelerated natural history may be due to repeated infections with more virulent strains of rheumatogenic streptococci. Approximately 16 million people live with rheumatic heart disease worldwide. As of 2000, worldwide death rates for rheumatic heart disease approximated 5.5 per 100,000 population (n = 332,000), with the highest rates reported from Southeast Asia (7.6 per 100,000).

Although there have been recent reports of isolated outbreaks of streptococcal infection in North America, valve disease in developed countries is now dominated by degenerative or inflammatory processes that lead to valve thickening, calcification, and dysfunction. The prevalence of valvular heart disease increases with age. Important left-sided valve disease may affect as many as 12–13% of adults older than the age of 75. In the United States, there were 1.5 million hospital discharges with any diagnosis of valvular heart disease in 2005, and 94,000 of these were related to surgical procedures for heart valve disease (mostly involving the aortic and mitral valves).

The incidence of infective endocarditis (Chap. 124) has increased with the aging of the population, the more widespread prevalence of vascular grafts and intracardiac devices, the emergence of more virulent multidrug-resistant microorganisms, and the growing epidemic of diabetes. Infective endocarditis has become a more frequent cause of acute valvular regurgitation. Bicuspid aortic valve disease affects as many as 0.5–1.4% of the population, and an increasing number of childhood survivors of congenital heart disease present later in life with valvular dysfunction. The global burden of valvular heart disease is expected to progress.

As is true for other health conditions, disparities in access to and quality of care for patients with valvular heart disease have been well documented. Management decisions and outcome differences based on age, gender, and race require educational efforts across all levels of providers.

Further Readings

Bonow RO et al: ACC/AHA 2006 Guidelines for the management of patients with valvular heart disease: Executive summary. Circulation 114:450, 2006

Carabello BA, Paulus WJ: Aortic stenosis. Lancet 373:956, 2009[PMID: 19232707]

Coats L, Bonhoeffer P: New percutaneous treatments for valve disease. Heart 93:639, 2007[PMID: 17435075]

Enriquez-Sarano M, Tajik AJ: Aortic regurgitation. N Engl J Med 351:1539, 2004[PMID: 15470217]

Feldman T, Leon MB: Prospects for percutaneous valve therapies. Circulation 116:2866, 2007[PMID: 18071090]

Freeman RV, Otto CM. Spectrum of calcific aortic valve disease: Pathogenesis, disease progression, and treatment strategies. Circulation 111:3316, 2005[PMID: 15967862]

Grube E et al: Progress and current status of percutaneous aortic valve replacement: Results of three device generations of the CoreValve Revalving system. Circ Cardiovasc Interven 1:167, 2008[PMID: 20031675]

Nkomo VT et al: Burden of valvular heart diseases: A population-based study. Lancet 368:1005, 2006[PMID: 16980116]

Otto CM, Bonow RO (eds): Valvular Heart Disease. A Companion to Braunwald's Heart Disease, 3rd ed. Philadelphia, Saunders Elsevier, 2009

———: Valvular heart disease, in Braunwald's Heart Disease, 8th ed, P Libby et al (eds). Philadelphia, Saunders, 2008

Pellikka PA et al: Outcome of 622 adults with asymptomatic, hemodynamically significant aortic stenosis during prolonged follow-up. Circulation 111:3290, 2005[PMID: 15956131]

Rosenhek R et al: Outcome of watchful waiting in asymptomatic severe mitral regurgitation. Circulation 113:2238, 2006[PMID: 16651470]

Society of Thoracic Surgeons: STS Adult Cardiovascular National Surgery Database. Period Ending 03/31/2009 Executive Summary. http://www.sts.org/documents/pdf/ndb/2ndHarvestExecutiveSummary_2009.pdf

———: STS national database risk calculator. http://www.sts.org/sections/stsnationaldatabase/riskcalculator/

Tadros TM et al: Ascending aortic dilatation associated with bicuspid aortic valve: pathophysiology, molecular biology, and clinical implications. Circulation 119:880, 2009[PMID: 19221231]

Webb JG et al: Percutaneous transarterial aortic valve replacement in selected high risk patients with aortic stenosis. Circulation 116:755, 2007[PMID: 17646579]

Wilson W et al: Prevention of infective endocarditis. Guidelines from the American Heart Association Rheumatic Fever, Endocarditis, and Kawasaki Disease Committee, Council on Cardiovascular Disease in the Young, and the Council on Clinical Cardiology, Council on Cardiovascular Surgery and Anesthesia and the Quality of Care and Outcomes Research Interdisciplinary Working Group. April 2007, http://circ.ahajournals.org

World Health Organization: Rheumatic fever and rheumatic heart disease. World Health Organ Tech Rep Ser 923:1, 2004

Copyright © The McGraw-Hill Companies. All rights reserved.