Management of Valvular Heart Disease
Richard R. Liberthson
Ignacio Inglessis
As a result of increased physician awareness and improvements in noninvasive diagnostic techniques, the diagnosis of valvular heart disease is being made earlier in the course of illness. Outpatient evaluation and management has become commonplace because symptoms are frequently absent or mild at the time the condition is discovered. Although consultation with a cardiologist is usually obtained, the responsibility for long-term care often falls on the primary physician. Proper management requires that the primary physician is familiar with the natural history of valvular disease, the early warning signs of hemodynamic deterioration, and the indications for medical and surgical therapies. Skill in the application of anticoagulation (see Chapter 83) and antibiotic prophylaxis (see Chapter 16) is essential, as is the ability to manage the early phases of heart failure (see Chapter 32) and atrial fibrillation (see Chapter 28). Of major importance is the proper timing of referral for consideration of valve repair.
Mitral Stenosis
Most cases of mitral stenosis are rheumatic in origin, even though as many as 50% of patients cannot give a history of rheumatic fever. In the elderly, there is an increasing incidence of mitral stenosis secondary to progressive annular calcification limiting leaflet mobility (see below). The symptom-free interval averages about 10 years (range, 3 to 25 years). In most instances, symptoms develop gradually over a decade, roughly paralleling the progression of stenosis; however, some people remain relatively free of complaints until stenosis becomes severe. Left atrial and pulmonary venous pressures increase substantially as the valve area falls to less than 1.5 cm2, and at this point, patients typically experience dyspnea on exertion. Any stimulus that rapidly increases blood flow or decreases the time available for diastolic filling can precipitate a sudden increase in pulmonary congestion and result in an acute shortness of breath. Strenuous activity, fever, emotion, and the onset of atrial fibrillation are often responsible for acute dyspnea.
Progressive narrowing of the valve orifice is accompanied by worsening exercise tolerance and increasing dyspnea. In patients with tight stenosis (valve area of <1.0 cm2), the period from the onset of symptoms to incapacity averages 7 years, but the decline can be precipitous with the onset of atrial fibrillation or pneumonia. A chronic marked increase in pulmonary venous pressure often leads to pulmonary hypertension, with progressive vascular remodeling and a potentially irreversible elevation of pulmonary vascular resistance occurring in approximately 20% of patients. Cardiac output usually falls with the onset of severe pulmonary hypertension, and fatigue may become a prominent symptom. The right ventricle hypertrophies in response to the rise in pulmonary artery pressure, and right-sided heart failure, tricuspid valve insufficiency, and death ensue unless intervention occurs; deterioration may be rapid at this stage.
Atrial fibrillation complicates 40% to 50% of cases of symptomatic mitral stenosis. The correlation between the development of atrial fibrillation and the severity of stenosis is slight and is not due solely to the degree of left atrial enlargement. The loss of atrial systole and the increase in heart rate that characterize atrial fibrillation markedly reduce flow across the mitral valve and boost the left atrial pressure. Premature atrial contractions and paroxysmal atrial fibrillation often precede sustained atrial fibrillation due to mitral stenosis.
Systemic embolization occurs in 10% to 20% of patients with mitral stenosis. Age and the presence of atrial fibrillation are the major determinants of risk; the severity of stenosis is not a determinant. Embolization may be a presenting symptom of mitral stenosis.
In sum, there is typically a symptom-free period of about 10 years. Patients then begin to note dyspnea on exertion over the next 10 years, which progresses in many instances in the following decade. Once symptoms are present on minimal exertion, survival becomes markedly reduced. Patients with New York Heart Association class IV disease (symptoms at rest) have been found to have a 5-year mortality rate of 85%. Some patients have disease that may remain stable for many years; symptoms may not develop until late in the illness.
Mitral Regurgitation
Rheumatic Mitral Regurgitation
Rheumatic mitral regurgitation can remain asymptomatic for many years because the left ventricle (LV) dilates and adjusts well to the increase in volume load. Onset of dyspnea and fatigue may not occur for decades. Symptoms take an average of 10 years to progress to the point of disability and need for surgery. It is not until very late in the course of the disease
that myocardial reserve falters. Once the LV fails, patients note progressive dyspnea and fatigue; symptoms become present at rest (functional class IV disease). If pulmonary hypertension develops, signs of right-sided heart failure ensue. Prognosis is poor at this stage.
that myocardial reserve falters. Once the LV fails, patients note progressive dyspnea and fatigue; symptoms become present at rest (functional class IV disease). If pulmonary hypertension develops, signs of right-sided heart failure ensue. Prognosis is poor at this stage.
Atrial fibrillation is found in more than 75% of cases, but the abrupt episodes of pulmonary congestion that typify mitral stenosis complicated by atrial fibrillation are less frequent in mitral regurgitation, although rupture of one of the chordae tendineae can result in sudden deterioration.
Chronic Nonrheumatic Mitral Regurgitation
Chronic nonrheumatic mitral regurgitation is commonly encountered in the outpatient setting. In the Western world, the most common causes of chronic mitral regurgitation are ischemic heart disease and mitral valve prolapse (MVP) secondary to myxomatous degeneration of the valve. Other etiologies include papillary muscle dysfunction and mitral annulus dilation secondary to cardiomyopathy, calcified mitral valve annulus, congenital disease, and drug-induced valve injury.
Mitral Valve Prolapse.
MVP is one of the most common valvular disorders, with a community prevalence of 2.5%. The condition is due to degenerative myxomatous proliferation of the spongiosa and elongation of the chordae. It is defined echocardiographically as systolic atrial displacement of the mitral valve extending above the annulus by a minimum of 2 mm. Only patients with truly redundant and thickened mitral leaflets and chordal elongation on two-dimensional cardiac ultrasound should be considered to have MVP; they almost always have a classic clinical examination that includes a mid- to late systolic regurgitant murmur. Many patients with normal mitral valve leaflets that appear as bowed or saddle shaped on certain echocardiographic views have been mistakenly labeled as having MVP and approached as if they have its attendant risks. The condition is more prevalent and less severe in women than in men.
Although patients with true MVP are at increased risk for valvular incompetence, endocarditis, systemic embolization, and dysrhythmias, the prognosis for most is excellent, and most are entirely asymptomatic and at only minimal risk. Many MVP patients do not experience hemodynamically significant regurgitation or an increase in regurgitant flow with time, but there is a subset that do, particularly those with an initial left ventricular diastolic dimension greater than 60 mm. The associated valvular insufficiency can cause chronic volume overload, leading to left ventricular dysfunction and necessitating mitral valve repair or replacement. The initial phases of left ventricular decline may not be accompanied by symptoms or a major fall in ejection fraction, making early detection for timely intervention clinically problematic (see later discussion). Patients with severe disease are at risk for the elongated chordae rupturing, with resultant worsen of regurgitation. There is a slight increase in risk of bacterial endocarditis, especially in patients with clinically evident valvular incompetence (regurgitant murmur evident on examination) or a markedly redundant and thickened valve on echocardiogram. Although endocarditis prophylaxis has been recommended for patients with MVP who have evidence of mitral insufficiency, recent guidelines question its utility. Patients with normal variants have little or no increase in risk of endocarditis and do not require antibiotic prophylaxis (see Chapter 16).
Stroke risk is also much lower than previously estimated, due to stricter criteria and better precision in the diagnosis of MVP. Among younger persons with embolic stroke, there is no increase in the prevalence of MVP, suggesting that the risk is minimal in the absence of other embolic risk factors. A very small group of MVP patients have malignant ventricular arrhythmias; the overall risk of sudden death is extremely low in most patients with MVP but is heightened in those with a history of syncope, prior ventricular tachyarrhythmias, or a family history of sudden death. Risk appears related to the degree of myxomatous changes but not to the degree of valve incompetence or left ventricular dysfunction.
Some have raised the question of a relation between panic disorder and MVP because of panic-like symptoms occurring in a small percentage of patients with MVP. Indeed, a small percentage of MVP patients do suffer from autonomic dysfunction and complain of palpitations, atypical chest pain, orthostatic dizziness, near-syncope, cold extremities, throbbing headaches, and neurasthenia and manifest tachyarrhythmias, orthostatic hypotension, and peripheral vasoconstriction. However, careful studies have found no causal link between MVP and autonomic dysfunction or panic disorder.
Papillary Muscle Dysfunction.
Papillary muscle dysfunction is responsible for as many as 10% of mitral regurgitation cases found clinically. Causes include ischemic injury, left ventricular dilation, and cardiomyopathy. Ischemic heart disease is the most frequent etiology, with 40% of posterior infarcts and 20% of anterior infarcts accompanied by the development of papillary muscle dysfunction. The amount of regurgitant flow is highly variable. Severe mitral regurgitation and marked pulmonary congestion can occur even in the context of only a minimal reduction in left ventricular ejection fraction. However, prognosis does depend on left ventricular systolic performance.
Calcification of the Mitral Annulus.
Calcification of the mitral annulus occurs in older people, often in conjunction with calcification of the aortic valve. The mitral lesion is usually not of hemodynamic significance, but heart block can develop if calcification extends into the ventricular septum.
Congenital Mitral Insufficiency.
Congenital mitral insufficiency develops secondary to the formation of mitral valve clefts and is associated with primum atrial septal defects. Varying degrees of insufficiency ensue.
Drug-Induced Disease.
Use of the appetite suppressants dexfenfluramine and the combination phentermine/fenfluramine (“phen-fen”) was popular in the mid- to late 1990s (see Chapter 234) before reports of new onset of valvular heart disease appeared. Aortic regurgitation was the most frequently noted problem (see later discussion), but mitral valve involvement was also seen. Risk appeared limited to use that exceeded 3 months. The precise magnitude of valve damage and the relative and absolute risks are somewhat less than originally feared (see subsection on nonrheumatic causes of aortic regurgitation).
Concern has arisen about the association between acquired valvular insufficiency and the use of ergot-derived dopamine agonists (e.g., pergolide and cabergoline), which are used in patients with Parkinson disease, restless leg syndrome, and prolactinoma. Mitral leaflet thickening and “tenting” have been observed, leading to significant regurgitant flow. A frequency of nearly 25% and a relative risk of greater than 6.0 have been recorded in case-control study. At least 6 months of exposure were required for the changes to be seen and were greatest in those with higher daily doses (>3 mg of pergolide or cabergoline).
Mixed Mitral Disease
Mortality is increased when significant stenosis and regurgitation occur simultaneously. In one large series of patients managed medically, the 10-year survival rate from the time of diagnosis was 33%.
Aortic Stenosis
Because of the marked ability of the LV to undergo hypertrophy and compensate for the pressure load, patients with aortic stenosis can remain symptom-free for many years, even with tight stenosis (valve area of <0.7 cm2). This is especially true in young patients. However, it must be remembered that sudden death can occur in previously asymptomatic individuals with critical aortic stenosis. The onset of angina and effort syncope suggests a hemodynamically critical lesion that is limiting cardiac output, although in as many as 30% to 60% of aortic stenosis patients with angina, there coexists a significant occlusion of a coronary vessel. Survival averages 3 years from the onset of angina or effort syncope. The development of congestive failure is an ominous sign because it signals the inability of the myocardium to continue tolerating the severe pressure load; survival averages 2 years from the time that failure is first noted. More than half of patients with aortic stenosis die of congestive failure. Sudden death accounts for another 20%. The mean age of death for patients dying suddenly is 60 years; the mechanism of death in these cases is believed to be a dysrhythmia triggered by myocardial ischemia, although debate continues. The rate of stenosis is unpredictable, and stenosis can progress rapidly over a few years, especially as patients enter their 60s. Figures for survival are only averages; the range is wide, and many patients die soon after the onset of symptoms.
Congenital Aortic Stenosis: Bicuspid Valve
Age at clinical onset of aortic stenosis depends partly on the underlying etiology. Significant aortic stenosis appearing in a patient younger than 30 years of age is congenital in origin, due most often to a bicuspid valve. Patients presenting with aortic stenosis between ages 30 and 70 years have either a bicuspid valve or a valve damaged by rheumatic fever.
Congenital bicuspid valve may be associated with aortic stenosis (in about 25%) and/or incompetence (in about 60%) as well as coarctation, dilation, and aneurysmal formation of the ascending aorta. In approximately 15% of patients, obstruction is caused by a discrete subaortic membrane. In community-based study, the risk of developing an aneurysm was 84.9 per 10,000 patient-years, but the risk of developing aortic dissection was very low (3.1 per 10,000 patient-years), though significantly increased (relative risk 8.4).
Bicuspid valves may calcify, worsening the degree of stenosis; affected patients may present in their early 60s with evidence of significant calcification and outflow tract obstruction.
Rheumatic Aortic Stenosis
Patients who present with significant aortic stenosis caused by rheumatic fever are on average 10 to 15 years older than patients who present with rheumatic mitral stenosis, due to the more gradual progression of the illness when it involves the aortic valve. Nevertheless, the course can be one of rapid deterioration.
Calcific Aortic Sclerosis and Aortic Stenosis
Aortic sclerosis in the elderly represents valve calcification and fibrosis in the absence of hemodynamically significant stenosis. By age 65 years, about 25% of the population has an audible systolic ejection murmur due to calcific aortic sclerosis, with 1% to 2% already having hemodynamically significant stenosis. By age 80 years, almost half of the population manifests evidence of valve calcification. Previously viewed as a degenerative condition of the aging heart, calcific aortic disease in the elderly is now recognized as having atherosclerotic-like risk factors (e.g., lipoprotein(a) locus gene mutation) and pathology (e.g., deposition of low-density lipoprotein, an inflammatory cell infiltrate, and eventual fibrosis and calcification). Even without significant stenosis, the condition is associated with a 50% increase in morbidity and mortality from coronary artery disease, underscoring the probable pathophysiologic link and serving as a marker for atherosclerotic disease.
Unlike the aortic stenosis of rheumatic disease, with its fusion of valve commissures, calcific disease aortic stenosis results in thickening of the valve leaflets and resultant loss of mobility and ability to open during systole. The degree of calcification and severity of stenosis may progress. The severity of stenosis parallels the contractile state of the LV and the degree of calcification. The weaker the LV contraction, the less will the valve open and the greater is the outflow obstruction. A failing LV may cause a rapid downhill course. The degree of calcification is an independent determinant of prognosis. Persons with severe calcification have a less than 20% chance of 4-year event-free survival.
Once symptoms develop (angina, syncope, heart failure), the 2-year survival rate falls to less than 50%. Whereas symptoms are an important indicator of prognosis, they may be absent in persons who harbor hemodynamically significant obstruction to left ventricular outflow. Besides valve calcification, other echocardiographic features that help to refine the prognosis in asymptomatic persons include degree of valve calcification, aortic-jet velocity, and valve area. The presence of a high-velocity jet (>4.0 m/s) or a rapid rate of increase in velocity (>0.3 m/s/y) in a person with marked calcification reduces the 2-year probability of survival or surgery to 20%. A valve area of less than 1.0 cm2 identifies severe stenosis in persons with calcific disease. Despite the poor prognosis of persons with severe stenosis, the risk of sudden death remains low (<1%/year) in truly asymptomatic persons; however, once even mild symptoms develop, risk rises substantially.
Aortic Regurgitation
Rheumatic Fever
Most patients with severe aortic regurgitation live for decades with little incapacity because the LV dilates to accommodate the extra volume load. The latent period from occurrence of rheumatic fever to the onset of clinical manifestations is about 10 years. During the next decade, symptoms appear and progress. The onset of symptoms is typically gradual, with palpitations being among the earliest changes noted by the patient, followed by dyspnea on exertion and fatigability. The appearance of left ventricular hypertrophy with strain and progressive left ventricular dilation are associated with a markedly increased risk of heart failure and death within 5 years. If exertional dyspnea worsens, other manifestations of congestive failure are likely to follow and signal the beginning of a rapidly declining phase of the disease due to left ventricular decompensation. At this stage, deterioration is rapid, with death occurring within 1 to 2 years of the onset of congestive failure. Angina is common, reported by almost 30% of patients; unlike the angina of aortic stenosis, it typically takes place at rest rather than on exertion. Angina becomes more frequent when there is worsening heart failure. Sudden death may also occur in patients with severe aortic regurgitation.
Nonrheumatic Causes
In the Western world, most cases of aortic insufficiency are nonrheumatic in origin. About 5% of persons with a bicuspid aortic valve also have aortic regurgitation. Other causes of aortic regurgitation include syphilis, myxomatous degeneration, bacterial endocarditis, and connective tissue disease. Aortic regurgitation secondary to untreated syphilis appears about 15 to 25 years after the initial infection and often has a more rapid downhill course than aortic regurgitation caused by rheumatic
fever. Myxomatous degeneration has been found in 10% to 15% of cases of aortic regurgitation studied pathologically. The process is progressive and becomes clinically evident between the ages of 30 and 60 years. Patients with Marfan syndrome may have significant dilation of the ascending aorta and effacing of the sinus of Valsalva impeding closure of the aortic valve leaflets. Severe, progressive valvular insufficiency may ensue. Although bacterial endocarditis can damage a tricuspid aortic valve, particularly one that is fibrotic or calcific, it is far more likely to occur with a bicuspid valve. Uncommon anomalies associated with aortic regurgitation include ventricular septal defect and discrete subaortic membrane and quadricuspid aortic valve.
fever. Myxomatous degeneration has been found in 10% to 15% of cases of aortic regurgitation studied pathologically. The process is progressive and becomes clinically evident between the ages of 30 and 60 years. Patients with Marfan syndrome may have significant dilation of the ascending aorta and effacing of the sinus of Valsalva impeding closure of the aortic valve leaflets. Severe, progressive valvular insufficiency may ensue. Although bacterial endocarditis can damage a tricuspid aortic valve, particularly one that is fibrotic or calcific, it is far more likely to occur with a bicuspid valve. Uncommon anomalies associated with aortic regurgitation include ventricular septal defect and discrete subaortic membrane and quadricuspid aortic valve.
Ankylosing spondylitis is complicated by aortic regurgitation in about 3% of cases. The severity of the lesion is highly variable, and conduction defects are frequent. Aortic regurgitation may appear before the onset of other symptoms, but in most instances, it follows the appearance of arthritic symptoms by 10 to 20 years. The presence of severe aortic regurgitation shortens the otherwise normal life expectancy of patients with ankylosing spondylitis. Reiter syndrome is associated with the development of aortic regurgitation in 5% of cases, typically in those with florid manifestations of the disease such as iritis, mucocutaneous changes, and extensive sacroiliac inflammation. The onset of aortic regurgitation occurs an average of 15 years after the disease is first noted, often preceded by conduction disturbances. The severity and course of the aortic regurgitation are highly variable.
Use of the diet-pill combination phen-fen or dexfenfluramine alone was very popular (see Chapter 234) before it was linked to valvular injury in the late 1990s. Fibrosis leading to incompetence of the aortic valve was the most common lesion, but mitral and tricuspid injury was also noted. At surgery, the fibrosis of the endocardial surface resembled that seen in carcinoid syndrome, leading some to link the pill’s potent serotonergic effects with disturbance of valvular endocardial metabolism. Risk increased with dose and duration of treatment; a 1% to 5% risk was associated with a minimum of 3 months of use, rising to as high as 20% among those who took the pills for 18 months or more. With full cessation of use, stabilization and some improvement (particularly of aortic regurgitation) were noted, and the risk of new disease ceased. In most instances, the degree of valve incompetence was mild, and patients remained asymptomatic. Whether asymptomatic persons will eventually become symptomatic remains to be determined, but because valve injury appears to be largely mild, the risk of developing symptomatic disease is probably low.
Mixed Aortic Valve Disease and Combined Aortic and Mitral Disease
Mixed Aortic Valve Disease
Many patients with aortic stenosis have some degree of aortic regurgitation, and vice versa. Whenever the gradient across the aortic valve is greater than 25 mm Hg in the context of significant regurgitation, there begins to develop a substantial pressure load and an increased volume load on the LV. The clinical course is similar to that for isolated aortic stenosis of the same degree, although some clinicians believe that there is an earlier onset of symptoms. Connective tissue abnormalities in persons with a bicuspid aortic valve may result in clinically silent dilation of the ascending aorta and lead to dissection.
Combined Aortic and Mitral Disease
The etiology is mostly rheumatic; in fact, most cases of rheumatic fever produce some degree of multiple-valve damage, although disease of one valve often dominates the clinical picture. Mitral stenosis may be overlooked in the setting of concurrent heart failure, pneumonia, or aortic valvular disease. In a study of 152 patients with echocardiographically significant mitral stenosis, 15% of mitral stenosis cases were unrecognized before ultrasound examination, yet most had an audible murmur on reexamination. The most common combination is aortic regurgitation in conjunction with mitral disease. Atrial fibrillation and systemic embolization are more frequent than in isolated aortic regurgitation, as is the severity of pulmonary symptoms. Less common is the coexistence of aortic stenosis and mitral stenosis. Symptoms and signs of aortic stenosis are blunted by significant mitral stenosis, such that pulmonary symptoms, atrial fibrillation, and systemic embolization may dominate the presentation, but there may be more angina and syncope than expected from isolated mitral stenosis. Course is dictated by the severity of the individual lesions, but mitral stenosis can delay the appearance of some of the manifestations of advanced aortic stenosis.
Mitral Stenosis
Symptoms
Symptoms provide crude indications of the severity of stenosis. Dyspnea correlates with an increase in left atrial pressure and the development of pulmonary venous congestion, but the relationship between degree of stenosis and elevation of left atrial pressure is variable. Fatigue occurs most often in the context of pulmonary hypertension, but the nonspecific nature of the symptom lessens its utility in estimating severity. Hemoptysis is related to pulmonary venous hypertension but does not necessarily imply severe stenosis. Thus, history alone may fail to detect severe stenosis that is unaccompanied by marked pulmonary congestion; however, a worsening of dyspnea and a decline in exercise tolerance suggest hemodynamic deterioration and require further investigation.
Physical Examination
The interval between the second heart sound and the opening snap, referred to as the S2 to OS interval, and the duration and timing of the diastolic murmur provide additional clues of severity. The S2 to OS interval is a function of the elevation in left atrial pressure. The greater the pressure, the shorter is the interval. Unfortunately, the degree of mitral stenosis is not the only determinant of left atrial pressure; the interval can be affected by factors other than valve area, such as heart rate and left ventricular pressure. Moreover, the valve must be mobile to snap; in advanced disease, the valve may calcify, and the snap becomes inaudible. Nevertheless, the S2 to OS interval is useful because it can be determined at the bedside and does provide data that may help in judging severity when considered in the context of other findings. Perhaps the most precise use of the interval is in separating hemodynamically insignificant disease from moderate and severe mitral stenosis. An interval of greater than 0.11 second at rest with a heart rate of 70 to 80 beats/min argues against a significant lesion (although there are exceptions). Patients with moderate to tight stenosis usually demonstrate intervals of less than 0.08 second, which shorten with exercise. Proper estimation of the S2 to OS interval takes considerable practice.
The intensity of the diastolic murmur does not correlate with severity of stenosis, but its duration through diastole does. However, development of pulmonary hypertension may decrease cardiac output from the right side of the heart, result in
a diminution of flow across the mitral valve, and consequently shorten the duration of the murmur.
a diminution of flow across the mitral valve, and consequently shorten the duration of the murmur.
Laboratory Studies
A few simple, carefully selected, noninvasive laboratory studies can be very helpful.
Chest X-Ray.
Chest x-ray provides important evidence of severity. The earliest radiologic sign of mitral stenosis is dilation of the left atrium, which is best seen on a lateral view in conjunction with a barium swallow to outline the esophagus. Other signs include elevation of left-main-stem bronchus and a “double-shadow” right heart border. Overall, these findings are not very reliable manifestations of severity. A better sign is redistribution of the pulmonary venous blood flow, producing dilation of the upper-zone pulmonary veins. Upper-zone redistribution becomes prominent at a left atrial pressure of 25 mm Hg and parallels the severity of stenosis. This change in pulmonary venous flow is very sensitive to changes in left atrial pressure, but it is not unique to mitral stenosis. Radiologic evidence of pulmonary hypertension (dilation of the right pulmonary artery to 15 to 18 mm, rapid tapering of vessels, and right ventricular enlargement) strongly suggests advanced mitral stenosis, although again the findings are not specific for mitral stenosis. The presence of Kerley B lines, perihilar haze, and other manifestations of interstitial edema are seen in patients with severe dyspnea due to mitral stenosis; the absence of interstitial edema on chest film does not rule out tight mitral stenosis, but a patient with dyspnea at rest should always show these changes on chest x-ray; otherwise, one must question the etiology of the shortness of breath. In sum, no single radiologic finding is specific for severe mitral stenosis, but x-ray data can provide important supporting evidence.
Cardiac Ultrasound (Echocardiography).
Cardiac ultrasound (echocardiography) is the most sensitive noninvasive method for evaluating mitral stenosis. Two-dimensional (B-mode) echocardiography provides definitive assessment by allowing direct visualization of the entire valve and its supporting apparatus, measurement of the valve orifice, left atrial and left ventricular chamber dimensions, and assessment of abnormality of other cardiac valves. The addition of Doppler ultrasound techniques— including continuous-wave Doppler and color-flow study—to the ultrasound examination provides detailed delineation of valve anatomy, blood flow, and magnitude of obstruction. A scoring system based on ultrasound estimates of valve mobility, degree of thickening, calcification, and anatomy of the subvalvular apparatus helps to identify candidates suitable for transcatheter balloon dilation of the stenotic valve.
Transesophageal ultrasound is useful when there is concern about intracavitary thrombosis (as in atrial fibrillation; see Chapter 28) or valvular vegetations (as in endocarditis). Cardiac catheterization is indicated when symptoms are progressive and cardiac surgery or balloon valvuloplasty is being considered (see later discussion).
The Electrocardiogram.
The electrocardiogram (ECG) is of limited utility for the estimation of severity. The best ECG sign appears to be the QRS axis; a rightward shift to greater than +60 is associated with a valve area of less than 1.3 cm2 in more than 85% of cases. The absence of the rightward shift in axis means little. The greater the pulmonary artery pressure, the more likely it is that right ventricular hypertrophy will appear on the ECG.
Mitral Regurgitation
History and Physical Examination
A reasonable estimate of the severity of mitral insufficiency can be obtained by history and physical examination. Dyspnea on exertion and fatigability suggest hemodynamically significant regurgitation, although the absence of such symptoms does not rule out severe regurgitant disease (which can be asymptomatic until left ventricular decompensation begins to set in). On physical examination, severe mitral regurgitation produces left ventricular enlargement with a hyperdynamic, slightly diffuse, apical impulse displaced to the left but of normal timing and duration. In addition, there is a pansystolic murmur (its loudness does not correlate directly with severity), a loud third heart sound (S3), often a middiastolic rumble from increased flow across the mitral valve, and at times wide splitting of the second sound due to shortening of left ventricular systole and early aortic valve closure. In contrast to other forms of valvular disease, a third heart sound may sometimes be audible in a mitral regurgitation patient in the absence of other signs of severe mitral regurgitation and need not represent a failing LV.
Laboratory Studies
In patients with advanced disease, cardiomegaly and left atrial enlargement are pronounced on chest film. A normal heart on chest x-ray and the absence of an apical pansystolic murmur rule out significant mitral regurgitation. The ECG reflects both left atrial and left ventricular enlargement but is hardly specific for mitral regurgitation.
Transthoracic cardiac ultrasound with Doppler is the test of choice for both estimation of severity and prognosis. As noted, some patients with severe mitral regurgitation, such as those with isolated MVP, may remain asymptomatic despite severe regurgitation, making ultrasound evaluation essential for the timely identification and treatment of persons who may be at high risk. By the time symptoms develop, left ventricular decompensation may already be underway. The severity of disease can be ascertained with the help of color-flow Doppler mapping. Prognostically important data provided by ultrasound include qualitative estimate of regurgitant flow, left atrial and left ventricular dimensions, ejection fraction, and, more recently, quantitative determination of regurgitant severity (i.e., regurgitant orifice). Echocardiographic parameters predictive of impending irreversible left ventricular dysfunction and clinical deterioration have been established to help time surgical correction; these include falling ejection fraction (<50%), end-systolic left ventricular dimension (>40 to 45 mm), increasing estimated right ventricular pressure (>45 to 50 mm Hg), and effective regurgitant orifice (>40 mm2).
Cardiac catheterization is indicated in patients with progressive symptoms and rapidly increasing heart size who are being considered for surgery. One needs to estimate the degree of regurgitation, assess ventricular function, and check for the presence and severity of associated valvular and coronary disease.
Evaluation of Mitral Valve Prolapse
In patients with mitral regurgitation due to MVP, the severity of regurgitation increases with age, male gender, duration of the murmur, degree of valve leaflet thickening, and degree of posterior leaflet prolapse. Only patients with truly redundant and thickened mitral leaflets are at risk for complications from MVP (e.g., valvular incompetence, endocarditis, systemic embolization, and dysrhythmias). Those with mild bowing and normal leaflets should be considered to have a variant of the normal mitral valve and not true MVP. Those with true MVP and associated valvular insufficiency are at risk for chronic volume overload leading to left ventricular dysfunction; there may be no premonitory symptoms or fall in the ejection fraction.
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