Clinical Features of Valvular Disease

Mitral Stenosis

Stenosis of the mitral valve is always the aftereffect of acute rheumatic fever. It affects primarily women (60–75 percent of all cases). It takes years for the gradual scarring process following the initial lesions of rheumatic fever to produce mitral stenosis. The interval between the attack (usually in childhood) and the development of symptoms varies widely. One factor is the severity of the attack of rheumatic fever. Furthermore, recurrent attacks lead to more-rapid

scarring of the valve. On average, mitral stenosis can first be detected 10 years after the initial attack; significant symptoms may not develop for another 10 to 30 years.

As described in chapter 1, the mitral valve consists of two leaflets separated by two commissures. The initial, rather minor damage to the valve during acute rheumatic fever consists of small lesions located usually at the edges of the leaflet. The healing and scarring process leads to the formation of adhesions between the leaflets, sealing the outer parts of the commissures, so that only the center part of the valve can open during diastole (see fig. 31, p. 129). The normal opening of the mitral orifice during diastole measures 4–6 cm² . Only when the sealing process reduces the size of the orifice to less than 2 cm² does the first effect of stenosis develop: the smooth flow of blood through the orifice becomes turbulent, giving rise to a murmur, which the examining physician can detect as evidence of mitral stenosis. However, at this point there is not enough resistance to flow to produce any effect on the circulation. Only further progression of the sealing process leads to the damming up of the orifice, raising the pressure in the left atrium. Usually when the opening is reduced to about 1.5 cm² , the patient begins to experience shortness of breath with activity. At this stage (mild mitral stenosis) disability may be minimal, merely requiring the patient to curtail strenuous activities. Sometimes postrheumatic progression stops before symptoms develop, and the patient may go through life without any serious consequences of the disease, in some cases even remaining unaware of its existence. Further progression of mitral stenosis, leaving an orifice of 1 cm² (moderate mitral stenosis), may produce more-pronounced symptoms and disability; furthermore, complications often develop. Severe mitral stenosis (with an orifice of 0.5–0.7 cm² ) produces serious disability—congestive heart failure and, in some patients, severe pulmonary hypertension.

Mitral stenosis differs from the other valvular diseases in that the mechanical obstacle to flow occurs before the blood enters the left ventricle; hence that important cardiac chamber is spared increased workload. Yet the blood dammed in the left atrium produces an effect on the pulmonary circulation similar to failure of the left ventricle. Consequently, shortness of breath resulting in disability develops early, as soon as mitral stenosis becomes mild or moderate, whereas in the other diseases dyspnea develops late, only

when the hypertrophied left ventricle can no longer cope with the overload.

The health of patients with mitral stenosis is frequently affected by complications, which may produce new disabilities or aggravate existing ones:

Atrial fibrillation . Elevated pressure in the left atrium resulting in its dilatation is a powerful contributing factor to atrial fibrillation, present in the majority of patients older than 50 years of age. The onset of atrial fibrillation, as a rule associated with a fast heart rate, is likely to produce disabling dyspnea or heart failure. However, response to treatment is usually satisfactory: as soon as the heart rate is slowed, the patient's symptoms abate or disappear.

Left atrial thrombi with emboli . Atrial fibrillation in the presence of a dilated left atrium facilitates the formation of thrombi attached to the atrial wall. Some portions of the clot may break loose and travel in the bloodstream as emboli, the most serious consequence of which is stroke—a relatively common complication of mitral stenosis. Embolic strokes are often reversible; that is, muscle paralysis and speech disturbance may only be temporary. Some patients, however, may suffer permanently disabling or even fatal strokes in the course of mitral stenosis.

Respiratory infection . Mitral stenosis affects blood flow through the lungs. The resulting congestion facilitates upper respiratory infections. Mild infections are inconsequential, but more-severe infections may greatly increase disability and precipitate heart failure.

Pulmonary hemorrhage . Spitting up of blood occurs commonly in mitral stenosis and is of no significance. Serious hemorrhaging from the lungs, requiring blood transfusion, is rare.

Pulmonary edema . Some patients with mitral stenosis are prone to pulmonary edema, particularly after eating salty food. Though potentially dangerous, pulmonary edema is easily treated, and recurrences can be prevented by restricting dietary salt or administering diuretics.

Severe pulmonary hypertension . In most cases of mitral stenosis elevation of pulmonary arterial pressure is only moderate. But in some patients small pulmonary vessels may react abnormally to

elevated pressure in the left atrium by developing severe pulmonary hypertension. This condition seriously compounds disability and may cause intractable heart failure.

Mitral stenosis can generally be diagnosed by performing a physical examination, though evaluation of its severity requires further tests. Among noninvasive tests, electrocardiographic changes and the size and shape of the cardiac shadow in a chest X ray are usually the first indicators in the diagnostic evaluation; an echocardiogram provides further data for estimating the severity of the stenosis and its effect on the circulation. The size of the stenotic mitral orifice can be calculated by means of cardiac catheterization, usually combined with angiography. These two invasive tests are typically performed when surgical treatment is being considered, in which case the extent of pulmonary hypertension and the presence or absence of mitral regurgitation and, in older patients, coronary-artery disease need to be determined.

Surgical repair or replacement of a stenotic mitral valve can not only restore adequate blood flow but also reverse all the secondary effects of mitral stenosis, even in the late stages of the disease. However, several cautionary factors must be considered before deciding on surgery. First, none of the available interventions is capable of restoring fully normal valvular function. Second, early disability in mitral stenosis may be amenable to effective nonsurgical treatment. Third, mitral stenosis often remains stable for years or even permanently, and moderate disability can be controlled by adjustments in life-style. Thus the consensus is that prime candidates for surgery are patients in congestive heart failure or otherwise seriously disabled who are unresponsive to intensive medical treatment.

Several kinds of medical (nonsurgical) treatment are available to patients with mitral stenosis. Diuretics, reinforced by restrictions on salt in the diet, can control fluid retention and the early stages of heart failure. Atrial fibrillation can be treated either by reducing the excessive ventricular rate or by restoring sinus rhythm. To inhibit clot formation, anticoagulants may be administered to certain patients, particularly those experiencing atrial fibrillation. Modification of physical activities may also be recommended.

Surgical treatment of mitral stenosis includes various approaches. In closed mitral valvotomy (without the use of the heart-lung machine)

the surgeon introduces a finger (or sometimes a special instrument) into the left atrium of a beating heart to break the adhesions between the two leaflets. This method, the first used in treating mitral stenosis, was the only one available until pump-oxygenators were developed. Open mitral valvotomy (with the use of the heart-lung machine) permits other techniques for separating the leaflets under direct vision. Mitral valvotomy has the advantage of preserving the natal mitral valve and is particularly successful in younger patients in whom the leaflets have not yet stiffened or calcified. A third alternative is replacement of the natal valve with a prosthetic valve or transplanted biological valve. A recent development, invasive but nonsurgical dilatation of the mitral valve (percutaneous balloon mitral valvuloplasty), has been shown to produce satisfactory results in some patients. The long-term effects of this procedure are not yet known.

The dramatic decrease in the incidence of rheumatic fever since the 1940s has greatly reduced the number of cases of mitral stenosis in the Western countries. Most persons in the United States treated for mitral stenosis are over the age of 50; many return for treatment because of the recurrence of stenosis following mitral valvotomy in the distant past or because of malfunction of prosthetic valves. Younger patients with mitral stenosis are mainly immigrants from less-developed countries.

Aortic Stenosis

Stenosis of the aortic orifice is now the commonest valvular disease; it is seen predominantly among the elderly. The term "valvular aortic stenosis" denotes stenosis caused by a stiffened valve and is distinguished from narrowing below or above the aortic valve, occasionally seen as a variety of congenital heart disease.

There are two principal ways in which the aortic valve may become stenotic—fusion of the three valve leaflets, due to adhesion among them, or stiffening and calcification of the leaflets, which may keep the valve from fully opening, leaving a greatly reduced orifice during systole (see fig. 32, p. 130). In addition, aortic stenosis may be present since birth, as a congenital defect in which the three leaflets have grown together, leaving open a small central orifice that can still function normally during diastole.

Acquired fusion of the leaflets by adhesions among them is almost always the result of rheumatic fever and, as in mitral stenosis, takes decades to develop. Rheumatic aortic stenosis, however, is now relatively uncommon. Today most cases are considered a type of "calcific aortic stenosis," a gradual fibrotic thickening of the leaflets in which the deposition of calcium can eventually make the valve leaflets as hard as bone. Normal leaflets, paper-thin, open wide in systole, permitting easy flow of blood through the aortic orifice. The slightest deviation from the norm may alter the flow patterns through the valve and in time cause minor damage to the valve. This damage may then produce fibrosis and eventually the deposition of calcium. A common cause of calcific aortic stenosis is a minor congenital malformation, namely an aortic valve consisting of two rather than three leaflets. Such a valve functions normally, and its presence is seldom recognized. But any minor change in the shape of the orifice may initiate the process that can produce aortic stenosis after a period of sixty to seventy years.

Thus aortic stenosis is a disease of old age, with most patients in their sixties, seventies, or eighties. This process progresses slowly, so that many years usually elapse from the time aortic stenosis is first detected until it becomes severe enough to cause symptoms. The normal aortic orifice during systole measures 3–5 cm.² When it reaches about one-half of its normal size, turbulent flow produces a heart murmur. However, the overload on the left ventricle does not develop until the orifice is reduced to less than 1.5 cm.² In moderate aortic stenosis the orifice has narrowed to 0.7–1.0 cm² ; in severe aortic stenosis the orifice may be as small as 0.4 cm.² The degree of hypertrophy of the left ventricle depends on the severity of stenosis; hence the first manifestation of left ventricular failure may become apparent only once the stenosis is severe. The patient then is likely to become aware of shortness of breath during exercise. Before the onset of left ventricular failure, however, some patients develop symptoms unique to aortic stenosis, related to the extreme pressure in the left ventricle and the slow ejection of blood through the stenotic aortic orifice. Certain reflexes originating in the left ventricle may interfere with the regulation of blood pressure and produce sudden loss of consciousness (syncope); furthermore, blood flow through the coronary arteries may be affected by aortic stenosis, producing anginalike chest pain unrelated to coronary

disease. Children with congenital aortic stenosis usually tolerate it well, although sometimes unusually severe aortic stenosis may bring about emergencies in infancy.

Aortic stenosis can be detected on physical examination by the characteristic heart murmur and a peculiarity of the pulse. The electrocardiogram will disclose left ventricular hypertrophy, which, though a nonspecific finding, usually indicates that aortic stenosis is at least of moderate severity. In older patients a chest X ray may show calcification of the aortic valve. An echocardiogram can display more directly the narrowing of the aortic orifice, the severity of which can be estimated by the Doppler technique. The size of the aortic orifice can be calculated more accurately from data obtained through cardiac catheterization, which reveals the magnitude of the pressure gradient between the left ventricle and the aorta and the volume of blood flow. In older patients cardiac catheterization is usually combined with coronary angiography. Chest pain, if present, may be caused in these patients by aortic stenosis alone or by coexisting coronary-artery disease—an important distinction when deciding on the proper medical or surgical management of the patient.

In contrast to mitral stenosis, where complications play a major role in its course, there are relatively few complications in aortic stenosis. Atrial and ventricular arrhythmias occasionally develop but are relatively rare. Patients with mitral stenosis are susceptible to infective endocarditis, and preventive measures should be taken. Those with advanced aortic stenosis are at higher risk of sudden cardiac death than those with other valvular diseases.

Treatment of aortic stenosis is almost entirely surgical. Relief of the condition represents one of the most spectacular accomplishments of cardiac surgery and is usually effective even in the most advanced cases. There are several approaches, depending on the type of aortic stenosis. Aortic commissurotomy , surgical separation of adherent leaflets through open-heart surgery, is mainly performed on children and adolescents with congenital aortic stenosis. The results are moderately satisfactory, although secondary changes may develop later in life requiring reoperation. Aortic-valve replacement is the standard treatment of aortic stenosis. It is the second most frequently performed cardiac operation (after coronary bypass surgery), and its successes are often brilliant: function of the left

ventricle, if impaired, returns to normal, and hypertrophy of the left ventricle may regress. Percutaneous aortic balloon valvuloplasty has been available only since the mid-1980s; hence its long-range success is uncertain. The advantages of dilating the aortic orifice without surgery are obvious. However, in elderly patients with heavily calcified aortic valves the successful widening of the orifice may not last long, for restenosis is very common. Consequently, this procedure is performed mostly on patients who are poor candidates for open-heart surgery.

The prevailing view is that patients with symptoms clearly related to aortic stenosis should undergo surgery. In the case of an aortic stenosis, even severe, that permits the patient a symptom-free, active life, surgery is usually postponed. Following valve replacement most patients can lead a normal, unrestricted life. Further treatment consists of preventive measures against endocarditis and, in patients with nonbiological valves, anticoagulant therapy. Successful operations are being performed on patients even in their eighties or nineties.

Mitral Regurgitation

The mitral valve is subjected to the highest stresses of the four cardiac valves: it is exposed to the systolic pressure in the left ventricle, at least 120 mm Hg. Its competence is contingent not only on the state and function of its two leaflets but also on the function of the reinforcing auxiliary parts of the mitral-valve apparatus—the chordae tendineae and the papillary muscles of the left ventricle. Consequently, mitral regurgitation may be caused by a variety of mechanisms:

Scarring after rheumatic fever may produce shrinking of the leaflet.

Infective endocarditis may create a hole in a leaflet.

The chordae may stretch, preventing tight closure of the leaflets.

One or more chordae may rupture.

The left ventricular papillary muscle may malfunction and be unable to tighten the chordae.

When the left ventricle dilates, the orifice may become too large for the leaflets to cover it.

The valve may be congenitally deformed.

Mitral regurgitation often develops as a complication of other cardiac diseases. A mild degree of incompetence of this valve has no significant effect on the circulation. Significant mitral regurgitation may also appear as the principal cardiac disease.

Rheumatic mitral regurgitation is most often seen in combination with mitral stenosis, with the latter being the predominant disease. Alone, mitral regurgitation is in some ways similar to mitral stenosis. Although regurgitation in children may be an immediate consequence of rheumatic fever, it is more likely to develop a long time after the attack. Disability tends to appear only in middle age or later. Complications include atrial fibrillation, although embolic episodes are less common than in mitral stenosis. Surgical treatment frequently involves valve replacement, but in some cases the deformed mitral valve can be successfully repaired. In developing countries, where severe recurrent rheumatic fever is prevalent, mitral regurgitation may evolve rapidly, requiring valvular surgery at a young age.

Prolapse of the mitral valve was first identified in the 1960s. Its unique feature is that the volume of blood returning to the left atrium is small and does not increase the workload of the left ventricle. Nevertheless, mitral-valve prolapse has become one of the most widely debated topics in cardiology. The potential complications of this lesion are graver than its direct effect. Mitral-valve prolapse may be associated with the following sequelae:

arrhythmias, both atrial and ventricular

infective endocarditis

embolic stroke (slight but definite risk)

atypical chest pain, which may be mistaken for coronary disease

rupture of some chordae, which can change trivial mitral regurgitation into acute severe mitral regurgitation requiring emergency intervention

In mitral-valve prolapse the leaflets may be larger than normal and stretch the chordae, producing valvular incompetence. Prolapse of the valve means that one leaflet overlaps the other, the most important cause of which is an abnormal structure of the leaflets called mucoid degeneration. This condition is often genetic. Such valves may become progressively larger, with redundant

tissues flapping in the mitral orifice like a parachute. Hereditary degeneration of the mitral valve occurs in young patients, is more common in women than in men, and has a relatively high rate of complications. Yet it accounts for only a small fraction of the cases of prolapse. In general, mitral-valve prolapse is a benign condition most frequently discovered on routine examination and having an excellent prognosis.

A preliminary diagnosis of mitral-valve prolapse may be made simply by listening with the stethoscope (auscultation) for the characteristic heart murmur and an extra sound. The principal test used to establish a firm diagnosis of this disease is the echocardiogram, which shows one leaflet slipping over the other. The echocardiogram may in fact be too sensitive a diagnostic tool: normal mitral valves may have somewhat oversized leaflets, which on the echocardiogram may resemble abnormal prolapse. It is now generally recognized that echocardiographic criteria for diagnosing mitral-valve prolapse have to be critically evaluated to guard against ascribing this valvular disease to healthy young adults.

Patients with mitral-valve prolapse need to be reassured of the favorable prognosis. Some patients require endocarditic prophylaxis. Those with the more pronounced hereditary prolapse are sometimes treated for arrhythmias. In rare cases of severe mitral regurgitation valve replacement may become necessary.

Rupture of the chordae tendineae is one of the causes of acute severe mitral regurgitation. It usually develops as a complication of other cardiac diseases, such as mitral-valve prolapse or infective endocarditis, but may represent a primary mitral-valve disease. Spontaneous rupture of the chords occurs occasionally, especially in older male patients. Chordal rupture may also result from trauma, a nonpenetrating injury to the chest. Mild varieties of chordal rupture usually involve separation of a single chord; it may have a minimal hemodynamic effect and require no treatment. More often, however, rupture involves multiple chords and may create an emergency requiring early valve replacement or repair.

Ischemic mitral regurgitation is a complication of coronary-artery disease, most frequently during or after an acute myocardial infarction. It is caused by damage to one of the two papillary muscles in the left ventricle, which then can no longer pull the chordae

tendineae tight to help make the valve competent. There are two types. (1) Rupture of the papillary muscle or a part of it is a serious, often catastrophic complication of myocardial infarction and usually requires an emergency valvular operation. (2) Malfunction of a papillary muscle may also develop during the course of myocardial infarction but has less serious consequences. Occasionally mitral regurgitation may not be apparent until after recovery from myocardial infarction. The severity of mitral regurgitation due to damage of the papillary muscle varies; furthermore, regurgitation may become progressively more severe. Treatment may be medical or surgical, depending on the severity of the condition and the patient's response to drug therapy. Valve replacement performed because of heart failure produced by mitral regurgitation may be ineffective if serious postinfarction damage to the heart muscle has occurred.

Infective endocarditis may result in new damage to the mitral valve, causing regurgitation in a previously competent valve. This is sometimes the case in patients with mitral stenosis or when the infection develops on a valve with a minor abnormality not affecting its function, such as mitral-valve prolapse. If the infection is seated on an already incompetent valve, the amount of regurgitation may increase, particularly if infection produces perforation of the valve or disrupts the chordae tendineae. Acute mitral regurgitation caused by endocarditis, if severe, may lead to a cardiac emergency requiring immediate valvular surgery.

Rarer varieties of mitral regurgitation include congenital mitral valve clefts (division of one or both leaflets into two parts with a space between them), marked dilatation of the left ventricle in association with heart failure, and cardiac tumors (myxomas of the left atrium), which may interfere with the closure of the valve.

Aortic Regurgitation

There are several causes of incompetence of the aortic valve:

rheumatic damage to the leaflets

perforation of leaflets in infective endocarditis

disease of the aortic root (the initial portion of the aorta just above the valve)

congenital deformity (either combined with other malformations or as a sole lesion)

trauma producing detachment of a leaflet

Two basic mechanisms produce aortic regurgitation—abnormality of the leaflet and dilatation of the root of the aorta (the ring to which the valve is attached becomes widened and the orifice too large for healthy valves to cover it).

Given a comparable volume of blood regurgitating through an incompetent left-sided cardiac valve, aortic regurgitation imposes a greater overload on the left ventricle than does mitral regurgitation. Blood leaking through an incompetent mitral valve into the atrium raises the left ventricular workload mildly; blood returning to the left ventricle through an incompetent aortic valve has to be ejected again into the aorta, steeply increasing the workload. This difference results in a more pronounced hypertrophy of the left ventricle in aortic regurgitation. Furthermore, the large volume of blood handled by the left ventricle dilates it. The dilated, volume-overloaded left ventricle characteristic of aortic regurgitation works less efficiently than the nondilated, pressure-overloaded left ventricle in aortic stenosis.

In the past, chronic aortic regurgitation was caused frequently by rheumatic fever, with or without coexisting mitral stenosis. With the decline in the prevalence of rheumatic heart disease in the West, the commonest cause of chronic aortic regurgitation has become disease of the aortic root, a variety of aortitis affecting the portion of the aorta immediately above the aortic valve (see chap. 14). Syphilitic aortitis was once common, often affecting the aortic valve, but today it is a rarity. Nowadays aortitis may be associated with certain varieties of rheumatoid arthritis or may develop as a result of atherosclerotic disease of the aorta in the elderly.

On physical examination aortic regurgitation displays a characteristic heart murmur. The severity of the regurgitation can be estimated by abnormalities of the arterial pulse and unusually low diastolic blood pressure. Aortic insufficiency cannot be quantified, but a more accurate estimation of regurgitant volume is possible by echocardiography, using the Doppler principle. As a rule, cardiac catheterization contributes little to the diagnosis.

The consequences of aortic regurgitation depend on whether the

lesion develops gradually or abruptly. The increased workload acute aortic regurgitation imposes on a normal left ventricle, if severe, may produce life-threatening heart failure requiring emergency valvular surgery. Chronic aortic regurgitation, by contrast, permits adaptive hypertrophy of the ventricle and is generally well tolerated; patients with severe aortic regurgitation may lead an unrestricted active life for many years. Eventually the left ventricle reaches the limit of its adaptative capacity, leading to cardiac failure. But in aortic regurgitation, more than in other valvular diseases, the onset of the first symptoms (usually dyspnea produced by activity) may develop so late that relief of the overload by valve replacement may no longer restore good left ventricular function. To avert this problem, in aortic regurgitation early deterioration of left ventricular function is occasionally considered an indication for surgery even in asymptomatic patients. When symptoms suggestive of heart failure are present, surgery is mandatory.

The major complication of aortic regurgitation is infective endocarditis. Atrial fibrillation is rare; ventricular arrhythmias may appear during late stages. The prolonged asymptomatic course of aortic regurgitation usually makes medical treatment unnecessary except to prevent endocarditis.

Other Diseases of the Cardiac Valves

Pulmonary stenosis is almost always congenital. It will be discussed in chapter 10. Pulmonary regurgitation is rare. It occasionally develops in severe pulmonary hypertension, without intrinsic disease of the valve leaflets, when high pressure in the pulmonary artery makes the healthy pulmonary valve incompetent. Damage to the pulmonary valve may occur in infective endocarditis, found most frequently in intravenous drug abusers since bacteria introduced with intravenously administered drugs tend to infect right-sided cardiac valves.

Tricuspid stenosis is a rare complication of rheumatic fever. It almost always coexists with mitral-valve disease. Tricuspid regurgitation is a relatively common sequel to pulmonary hypertension. It commonly results in right ventricular failure, when the tricuspid orifice stretches, making the valve incompetent. Its presence merely aggravates the effect of right ventricular failure on the pressure

in the veins bringing blood to the right atrium. Tricuspid-valve repair or replacement is occasionally imperative, but physicians prefer to avoid it because operations on the tricuspid valve are not as effective as those performed on left-sided cardiac valves. Tricuspid-valve involvement may also occur in endocarditis among drug abusers.

Combined diseases of cardiac valves are a relatively common consequence of rheumatic fever involving the mitral and aortic valves. Aortic stenosis or regurgitation resulting from rheumatic fever is more frequent in combination with mitral-valve involvement (usually stenosis) than as the sole consequence of rheumatic fever. The course and prognosis of double valve disease usually follows the pattern of the predominant lesion.

Stenosis of the mitral or aortic valve may be associated with incompetence of the same valve. The consequences of combined stenosis and regurgitation of a left-sided cardiac valve usually differ little from those of pure stenosis; less commonly, however, they follow the pattern of pure regurgitation of the valve.