CHAPTER 16

Serge C. Harb
Brian P. Griffin

Mitral Valve Disease

I.Introduction

A.The mitral valvular apparatus consists of the anterior and posterior leaflets, the mitral annulus, the chordae tendineae, and the papillary muscles (PMs) (Fig. 16.1).

1.Normal function of the apparatus brings both leaflets together in systole, creating the coaptation zone.

2.The anterior portion of the mitral annulus is in continuity with the fibrous skeleton of the heart, making it less prone to dilation than the posterior annulus.

3.The coaptation line of the anterior and posterior leaflets is located in the posterior one-third of the valve orifice.

4.The middle scallop of the posterior leaflet is designated P₂, with the lateral scallop designated P₁ and medial scallop designated P₃. The corresponding areas of the anterior leaflet are designated A₁, A₂, and A₃.

5.The mitral valve leaflets are attached via the chordae tendineae to the PMs, which are part of the left ventricle.

B.Mitral regurgitation (MR) can occur as a result of malfunction of any of these components.

C.Mitral valve prolapse (MVP) exists when one or both mitral leaflets extend beyond the plane of the mitral valve annulus into the left atrium during systole.

D.Mitral stenosis (MS) is usually valvular and is caused more rarely by the fusion of subvalvular components.

II.Mitral Regurgitation

A.Clinical presentation

1.Signs and symptoms

a.With acute, severe de novo MR, an abrupt rise in pulmonary capillary wedge pressure (PCWP) causes pulmonary edema. The symptoms include rest dyspnea, orthopnea, and possibly signs of diminished forward flow, including cardiogenic shock.

b.Chronic MR is usually asymptomatic for years. The most common presentation is an asymptomatic murmur. When symptoms develop, exercise intolerance and exertional dyspnea usually occur first. Orthopnea and paroxysmal nocturnal dyspnea may develop as MR progresses. Fatigue is caused by diminished forward cardiac output. With the development of left ventricular (LV) dysfunction, further symptoms of congestive heart failure (CHF) are manifest. Long-standing severe MR may cause pulmonary hypertension, with symptoms of right ventricular (RV) failure. Atrial fibrillation commonly occurs as a consequence of left atrial (LA) dilation.

2.Physical findings

a.Inspection and palpation. When LV function is preserved, carotid upstrokes are sharp, and the cardiac apical impulse is brisk and hyperdynamic. An early diastolic LV filling wave may be palpable because of the large volume of blood traversing from the left atrium to the left ventricle. A late systolic thrust may be present in the parasternal location because of systolic expansion of the left atrium (which may be difficult to differentiate from an RV lift). With the development of LV dilation, the apical impulse is displaced laterally. An RV heave and a palpable P₂ are present if pulmonary hypertension has developed. An elevated jugular venous pressure, hepatomegaly, ascites, and peripheral edema indicate secondary RV dysfunction.

b.Auscultation. The main auscultatory findings are shown in Figure 16.2. A loud S₄ (not illustrated) can be heard sometimes, particularly with acute MR.

FIGURE 16.1 Anatomy of the mitral valve apparatus. (Copyright © Cleveland Clinic Foundation. Reprinted with permission, Cleveland Clinic Center for Medical Art & Photography © 2011-2018. All Rights Reserved.)

FIGURE 16.2 Auscultatory findings in mitral regurgitation. MR, mitral regurgitation.

In acute, severe MR, the systolic driving pressure across the mitral valve is reduced due to a high LA pressure and, as a result, the murmur is short and relatively soft. If the LA pressure is markedly elevated, the murmur of acute MR may be inaudible. With decompensated systolic heart failure, fine inspiratory pulmonary crackles may be evident.

3.The differential diagnosis of holosystolic murmurs includes MR, tricuspid regurgitation, and ventricular septal defect (VSD). All are high pitched, but the murmur of a VSD is often harsh in quality, unlike the blowing murmurs of MR and tricuspid regurgitation.

a.The murmur of MR is best heard in the apical position and often radiates to the axilla (although possibly to the base with anteriorly directed jets); those of tricuspid regurgitation and VSD typically do not. The murmur of posteriorly directed MR radiates to the back.

b.Tricuspid regurgitation is best heard at the left lower sternal border and radiates to the right of the sternum and left midclavicular line. Like all right-sided murmurs, tricuspid regurgitation is accentuated by inspiration.

c.A VSD murmur is heard at the left sternal border and often radiates throughout the precordium.

B.Etiology and pathophysiology. MR is more commonly myxomatous or ischemic, rather than rheumatic, in etiology. The causes of MR are summarized in Table 16.1.

TABLE 16.1 Causes of Mitral Regurgitation

Leaflet Abnormalities

Myxomatous degeneration of leaflets with excessive motion (most common)

Rheumatic disease: scarring and contraction lead to the loss of leaflet tissue

Endocarditis: can cause leaflet perforations and retraction in the healing phase

Aneurysms: usually from aortic valve endocarditis; aortic insufficiency produces jet lesion on the mitral valve

Congenital:

Cleft mitral valve: isolated or with ostium primum atrial septal defect

Double-orifice mitral valve

Hypertrophic cardiomyopathy: systolic anterior motion of the mitral valve

Mitral Annular Abnormalities

Annular dilation

From left ventricular dilation: dilated cardiomyopathy, ischemic disease, hypertension

Normal 10 cm in circumference

With sufficient dilation, loss of adequate leaflet coaptation

Tethering of leaflet and chordae can occur and produce relative restriction of leaflet motion

Mitral annular calcification

Degenerative disorder, most commonly seen in the elderly

Accelerated by hypertension or diabetes

Also seen in renal failure with dystrophic calcification

Also seen with rheumatic heart disease

Marfan syndrome and Hurler syndrome

MR results from immobility of the annulus and loss of sphincter activity

Chordal Abnormalities

Chordal rupture (most severe form is flail leaflet) results in loss of leaflet support usually with myxomatous degeneration

Rheumatic heart disease (chordal fibrosis and calcification)

Papillary Muscle Abnormalities

Rupture with myocardial infarction

Complete rupture typically not survived

Partial rupture more typically encountered

Dysfunctional papillary muscle

Ischemia

Posteromedial papillary muscle, single blood supply through posterior descending artery

Anterolateral papillary muscle, supplied by left anterior descending artery and left circumflex artery

Infiltrative processes: amyloid and sarcoid

Congenital: malposition, parachute mitral valve

MR, mitral regurgitation.

1.In acute MR, the regurgitant volume that returns from the left atrium causes a sudden increase in LV end-diastolic volume. The left ventricle compensates for this by means of the Frank–Starling mechanism: Increased sarcomere length (preload) enhances LV contraction (inotropy). This occurs at the cost of increasing LV filling pressure and may cause symptoms of pulmonary congestion. LV wall stress (afterload) is reduced because blood is ejected into the lower pressure left atrium as well as into the systemic circulation. Increased inotropy and reduced afterload cause more complete LV emptying and hyperdynamic function. Forward cardiac output declines, however, because much of the flow is directed to the left atrium. If the acute hemodynamic insult is tolerated, the patient’s condition may progress to a chronic compensated state.

2.In chronic compensated MR, there is dilation of the left ventricle with eccentric hypertrophy.

a.Wall stress is normalized with the development of hypertrophy. Afterload reduction by the low-resistance left atrium is not as significant as it is in the acute phase. Preload remains elevated by the same mechanism as in acute MR. LA dilation helps to accommodate the increased preload at lower filling pressures. LV function is not as hyperdynamic as in the acute state but is in the high-normal range.

b.Patients may stay in this asymptomatic or minimally symptomatic phase for years; however, contractile dysfunction may develop insidiously during this phase. Increased preload, normal or decreased afterload, and increased sympathetically mediated contractility all continue to augment the ejection fraction (EF). However, because the regurgitant volume ejected back into the left atrium diminishes the actual forward stroke volume (SV), the EF may overrepresent true cardiac function. Thus, in severe MR, normal left ventricular ejection fraction (LVEF) is considered to be at least 60% and values below that are thought to represent contractile impairment.

3.In chronic decompensated MR, there is LV dysfunction along with progressive enlargement of the LV chamber with increased wall stress. LV dysfunction and enlargement increase the severity of MR, further contributing to the cycle of deterioration. Irreversible LV contractile dysfunction may be present by the time overt symptoms develop and this confers higher rates of postoperative heart failure and increased mortality.

C.Laboratory examination

1.The electrocardiographic findings are nonspecific. The principal features are LA enlargement and atrial fibrillation. LV hypertrophy and RV hypertrophy may also be seen in patients with severe MR.

2.Chest radiography. Cardiomegaly with LA and LV enlargement may be seen in chronic MR. Interstitial edema, manifest as Kerley B lines, followed by alveolar edema may develop in acute cases or with progressive LV failure. Calcification of the mitral annulus may be visualized as a C-shaped opacity in the lateral projection.

D.Diagnostic testing

1.Echocardiography plays a pivotal role in the evaluation of MR. It is useful in diagnosing MR and in determining its severity and cause. MR severity is graded semiquantitatively as follows: 1+ for mild, 2+ for moderate, 3+ for moderately severe, and 4+ for severe regurgitation. Increasingly, MR is quantified where feasible. This is accomplished most often using the proximal convergence method (see Section II D.d). Quantification provides prognostically powerful information that is less affected by the ongoing loading conditions.

The American College of Cardiology/American Heart Association (ACC/AHA) class I recommendation is for the use of Doppler echocardiography to determine the mechanism and severity of MR, to assess the LA and LV size and function over time, to assess the pulmonary artery (PA) pressures, and to reevaluate periodically if more than mild, and after mitral valve surgery. The current ACC/AHA classification of MR severity by Doppler echocardiography is summarized in Table 16.2.

TABLE 16.2 Assessment of Severity of Mitral Regurgitation
	Mild	Moderate	Severea
Qualitative
Angiographic grade	1+	2+	3–4+
Color Doppler jet area	Small, central jet (<4 cm2 or <20% LA area)	Signs of MR > mild present, but no criteria for severe MR	Vena contracta width > 0.7 cm with large central MR jet (area > 40% of LA area) or with a wall-impinging jet of any size
Doppler vena contracta width (cm)	<0.3	0.3–0.69	≥0.70
Quantitative (Echo)
Regurgitant volume (mL/beat)	<30	30–59	≥60
Regurgitant fraction (%)	<30	30–49	≥50
Regurgitant orifice area (cm2)	<0.20	0.2–0.39	≥0.40

MR, mitral regurgitation; LA, left atrium; LV, left ventricle.

^aIn severe MR, evidence of LA and LV dilation is essential.

a.Color Doppler echocardiography allows the diagnosis of MR by means of visualization of the regurgitant jet or jets entering the left atrium and allows the assessment of severity.

(1)Jet length and area are used in this assessment. These measurements are reliable with central jets, but underestimation of MR may occur with eccentric jets. Because a jet directed against the atrial wall appears smaller than a free jet of the same regurgitant volume (Coanda effect), it is common practice to upgrade the estimated severity of MR by at least one grade in this situation. The direction of the MR jet can also aid in assessing the cause of MR (Table 16.3). Regurgitation caused by prolapse or flail (excessive leaflet motion) results in a jet direction opposite to the affected leaflet (i.e., posterior jet with anterior leaflet prolapse). MR caused by leaflet restriction (rheumatic and ischemic) is directed toward the affected leaflet.

TABLE 16.3 Mechanisms, Direction of Color Jet, and Surgical Management of Mitral Regurgitation
Jet Direction	Leaflet Motion	Likely Cause	Surgical Method
Anterior	Excessive	Posterior leaflet prolapse	Quadrilateral resection Annuloplasty Chordal shortening Shortening of papillary muscle
	Restricted	Anterior leaflet restriction	Debridement
Posterior	Excessive	Anterior leaflet prolapse	Chordal transfer or shortening
			Synthetic chords
	Restricted	Posterior leaflet restriction	Debridement, annuloplasty
	Normal	Ventricular dilation	Annuloplasty
Central	Excessive	Bileaflet prolapse	Resection, chordal transfer, synthetic chords
	Restricted	Bileaflet restriction	Debridement
	Normal	Ventricular dilation	Annuloplasty
Commissural	Papillary muscle dysfunction		Reattach or fold papillary muscle
	Eccentric	Perforation or cleft	Pericardial patch
Reprinted with permission from Stewart WJ. Adapted from Intraoperative echocardiography. In: Topol EJ, ed. Textbook of Cardiovascular Medicine. Philadelphia, PA: Lippincott–Raven Publishers; 1998.

(a)Caveats

i.MR is often assessed with transesophageal echocardiography (TEE). Patients often receive sedation before TEE, and the sedation may reduce systemic blood pressure (afterload). This could make the MR appear less severe than it is under normal physiologic circumstances. This effect of sedation may be mitigated to some extent by increasing the afterload by handgrip or by the cautious administration of phenylephrine.

ii.In the evaluation of MR in the intraoperative setting, there may be fluctuations in afterload and preload.

(b)Multiple factors, such as hemodynamic considerations, geometric factors (constraint imposed by the LA wall), and instrumentation, may affect color Doppler measurements. This has led to the development of other measurements to quantify MR.

(2)The width of the vena contracta, which is the narrowest portion of the proximal regurgitant jet downstream from the orifice, is a reliable indicator of the severity of MR. A width ≥0.70 cm suggests severe MR. High-resolution and zoom images must be used for an accurate assessment of the vena contracta or else TEE may be needed. There is some tendency for overestimation of the width of the vena contracta because of limited lateral resolution.

b.Pulsed-wave Doppler echocardiography of pulmonary venous flow may be useful in the assessment of the severity of MR (Fig. 16.3).

FIGURE 16.3 Pulmonary venous flow changes with increasing mitral regurgitation severity.

Sampling of the pulmonary veins results in three distinct waves: a systolic antegrade wave, a smaller diastolic antegrade wave, and a small negative wave (not shown in Fig. 16.3) that represents atrial reversal during atrial contraction. With increasing MR, there is a progressive decrease in the systolic wave of pulmonary inflow with eventual reversal. Blunting of the systolic component of pulmonary venous flow in the presence of normal LV function suggests at least moderately severe MR. Systolic flow reversal suggests severe MR. Blunted pulmonary venous flow is a less reliable indicator of substantial MR in the setting of atrial fibrillation or severe LV dysfunction, because these conditions can also cause systolic blunting.

c.Pulsed-wave Doppler echocardiography of mitral inflow. SV across the regurgitant mitral valve can be estimated and compared with the SV derived from pulsed-wave Doppler imaging across a competent valve (such as the aortic or pulmonary valve). The excess flow at the mitral valve over that derived at the aortic valve is the regurgitant volume. These methods are both tedious and technically difficult.

d.The proximal isovelocity surface area (PISA) or flow convergence method provides a quantitative assessment of MR (Fig. 16.4). With PISA, the flow on the upstream (proximal) side of the valve is the same as that going through the actual regurgitant orifice at the valve itself. Flow is the product of area and velocity. If we can measure flow going into the valve and the velocity at the regurgitant orifice itself, we can derive the area of the regurgitant orifice. PISA utilizes the quality of color Doppler flow leaking through the valve that sets up a series of concentric hemispheres. All the flow at the hemisphere where the color changes from blue to red is at the aliasing velocity (Va) which can be read off the machine. The cross-sectional area of a hemisphere is 2πr² where r is the radius of the hemisphere which may be measured directly. The velocity baseline can be manipulated to maximize the size of the radius and make it easier to measure.

FIGURE 16.4 Flow convergence method. PISA, proximal isovelocity surface area; Regurg, regurgitant; Va, aliasing velocity.

Peak mitral flow rate (QFC) is derived as follows:

QFC = 2πr²Va

where r is the radius of the hemisphere and Va is the aliasing velocity at that hemisphere. Regurgitant orifice area (ROA), a relatively load-independent measure of regurgitation, is derived from peak flow rate by dividing this by peak flow velocity (maximal MR continuous-wave velocity, Vmr):

ROA = 2πr²Va/Vmr

The regurgitant volume (RV) may be further calculated by the equation ROA × VTImr, where VTImr is the velocity–time integral of the regurgitant jet.

If the forward SV is known, then the regurgitant fraction (RF%) may be derived as follows:

RF = RV/RV + SV

SV may be estimated in the LV outflow tract as area × VTI, as performed in the continuity equation.

ROA has been shown to be prognostically powerful in MR of ischemic or degenerative origin. An ROA of 0.4 cm2 or greater is consistent with severe MR and is associated with poor long-term outcomes if the valve is not repaired or replaced. In ischemic MR (IMR), ROA of ≥ 0.2 cm2 is indicative of poorer long-term outcomes.

(1)Simplified proximal convergence method. The preceding calculation may be simplified to allow the ROA to be estimated with only one measurement. Using this method, MR velocity is assumed to be 5 m/s and the aliasing velocity is set at 40 cm/s. The ROA may be calculated as r²/2. Higher ROA indicates an increased severity of MR.

(2)Inaccuracies in using proximal convergence method occur when the orifice is nonspherical, multiple jets are present, or the flow convergence zone is constrained as occurs with eccentric jets. The latter situation occurs with a flail leaflet, as regurgitant flow and ROA are typically overestimated by the use of the PISA method; accuracy may be improved by the use of angle-correction formulas.

2.Cardiac catheterization

a.The amplitude of the v-waves on hemodynamic tracings (which are a reflection of LA filling from the pulmonary veins during ventricular systole) can provide clues to the severity of MR, particularly in acute MR.

(1)Amplitudes of v-waves more than two to three times mean LA pressure suggest severe MR. However, in slowly developing MR, an abnormal v-wave may not be seen. The v-waves are also diminished by afterload reduction. The absence of v-waves does not exclude severe MR.

(2)Other conditions that may produce prominent v-waves are LV dysfunction with a dilated noncompliant left atrium, postinfarction VSD, and other situations in which there is increased pulmonary blood flow.

b.Left ventriculography allows the visual assessment of the severity of MR. It is affected by multiple factors such as the adequacy of the contrast injection to fill the ventricle, the placement of the catheter, and ventricular arrhythmia during injection. The grading system is as follows:

(1)1+ (mild): clears with each beat; entire left atrium is never opacified

(2)2+ (moderate): does not clear with a single beat; may faintly opacify the entire left atrium

(3)3+ (moderate to severe): fills entire left atrium over 2 or 3 beats; complete opacification of the left atrium, equal in intensity to the left ventricle

(4)4+ (severe): complete opacification of the left atrium in 1 beat; contrast material refluxes into the pulmonary veins

c.Coronary angiography is useful to detect concomitant coronary artery disease (CAD) in these patients. Those being considered for surgery to correct MR undergo coronary angiography, even in the absence of symptoms, if they are older than 50 years or have multiple risk factors.

E.Therapy. An understanding of the pathophysiologic mechanism of MR is essential to management.

1.Acute MR

a.Medical therapy. If there is adequate mean arterial pressure, pharmacologic therapy with afterload reducing agents may reduce the acute MR. Intravenous nitroprusside and nitroglycerin may reduce pulmonary pressures and maximize forward flow. If surgery is not immediately indicated, a switch to oral agents may be made. Angiotensin-converting enzyme (ACE) inhibitors (ACE-I) and direct-acting vasodilators (such as hydralazine) help maximize forward output and reduce regurgitant fraction.

b.Percutaneous therapy. The large sudden volume overload on a left ventricle that is not dilated or hypertrophied causes symptoms of pulmonary congestion and even cardiogenic shock. For such patients with acute hemodynamically significant MR, especially from postinfarction PM rupture, placement of an intra-aortic balloon pump (IABP) may serve as a temporary stabilizing measure until surgical repair can be undertaken.

c.Surgical therapy. Patients with acute, severe MR usually require urgent surgical intervention.

2.Chronic MR

a.Choosing the appropriate therapy (see Table 16.4 for a summary of the current ACC/AHA guidelines)

TABLE 16.4 Indications for Mitral Valve Surgery in Mitral Regurgitation

Class I

a.MV surgery is recommended for the symptomatic patient with acute severe MR

b.MV surgery is of benefit for symptomatic patients with chronic severe MR in the absence of severe LV dysfunction (defined as EF <30%)

c.MV surgery is of benefit for asymptomatic patients with chronic severe MR and mild to moderate LV dysfunction (EF 30% to 60%, and/or end-systolic dimension ≥ 40 mm)

d.MV repair is indicated over MV replacement in most patients with severe chronic MR who require surgery, and patients should be referred to surgical centers experienced in MV repair

Class IIa

a.MV repair is reasonable in experienced surgical centers (Heart Valve Center of Excellence) for asymptomatic patients with chronic severe MR and preserved LV function in whom the likelihood of successful repair is >95%

b.MV surgery is reasonable for asymptomatic patients with chronic severe MR, preserved LV function, and new-onset atrial fibrillation.

c.MV surgery is reasonable for asymptomatic patients with chronic severe MR, preserved LV function, and pulmonary hypertension (PASP > 50 mm Hg)

Class IIb

a.MV surgery is reasonable for symptomatic patients with chronic severe MR because of a primary abnormality of the mitral apparatus severe LV dysfunction (EF < 30%) in whom MV repair is highly likely

b.MV repair may be considered for patients with chronic severe secondary MR because of severe LV dysfunction (EF < 30%) who have persistent symptoms despite optimal therapy for heart failure, including biventricular pacing

c.Transcatheter MV repair may be considered in symptomatic patients with chronic severe primary MR who are deemed nonsurgical candidates because of severe comorbidities

Class III

a.MV surgery is not indicated for asymptomatic patients with MR and preserved LV function (EF > 60%) in whom significant doubt about the feasibility of repair exists

b.Isolated MV surgery is not indicated for patients with mild or moderate MR

EF, ejection fraction; MR, mitral regurgitation; MV, mitral valve; LV, left ventricular; PASP, pulmonary artery systolic pressure.

Adapted from 2014 Valve Disease ACC/AHA Valve Disease Guidelines. Reprinted with permission from Nishimura RA, Otto CM, Bonow RO et al. 2014 AHA/ACC guideline for the management of patients with valvular heart disease: executive summary. Circulation. 2014;129(23):2440–2492. Copyright © 2014 American Heart Association, Inc.

(1)Most patients who have moderately severe to severe MR and are symptomatic should be considered for elective surgical treatment. Decisions need to be individualized based on the age of the patient, the likelihood of valve repair, comorbidities, LV function, and the likelihood that surgical intervention will improve symptoms and/or survival. Generally, intervention for symptoms is indicated for severe MR if the cause of the MR is primary to the valve (i.e., prolapse, rheumatic, or congenital in origin). When the valve lesion is secondary to ventricular dysfunction, either from ischemic heart disease or from dilated cardiomyopathy, aggressive medical management of heart failure (see subsequent text) is indicated first.

(2)In severe MR because of dilated cardiomyopathy associated with severe symptoms and refractory to medical management and cardiac resynchronization therapy (CRT) where indicated, mitral valve repair may lead to symptomatic improvement, but a survival benefit has not yet been demonstrated.

(3)Management of patients with minimal or no symptoms but severe MR is more complex. The key is to identify patients before contractile dysfunction of the left ventricle becomes irreversible. Watchful waiting until serious symptoms develop carries a risk for the development of severe LV dysfunction and a poor prognosis. The feasibility of mitral valve repair with improved postoperative survival and EF (see later) has been another incentive in the push for earlier surgical intervention. If the valve repair is not feasible, one may choose to wait longer before proceeding to surgical treatment. The 2014 valve guidelines consider it reasonable to perform mitral valve repair in asymptomatic patients with severe MR when repair is performed in an experienced center where the likelihood of repair exceeds 95% with an expected mortality <1% (Heart Valve Center for Excellence; Table 16.4).

b.Timing of surgery. A variety of clinical, echocardiographic, and invasively derived values appear to be predictive of the development of postoperative LV dysfunction, decompensated heart failure, and death among patients with significant but asymptomatic MR. The timing of mitral valve surgery is a decision that must be individualized and depends on several variables, including clinical signs and symptoms, echocardiographic findings, catheterization data, hemodynamic data, operative risk, and repairability of the mitral valve. Generally, the variables to be considered in patients whose MR is asymptomatic are (a) LV size and function; (b) exercise capacity and LV size and function at peak exercise; (c) repairability of the valve; (d) severity of MR, including the presence of flail leaflet; (e) PA pressures; (f) atrial fibrillation; and (g) age and other comorbidities.

(1)LV size and function. As noted previously, contractile impairment is often occult in severe MR when conventional indices of LV function are used. Elastance measured at the time of cardiac catheterization is the best load-independent measure of true contractile function in MR. However, because it requires the construction of a series of pressure–volume loops for its calculation, it is rarely performed outside research laboratories. Fortunately, conventional indices of LV size and function do provide useful information in MR. Newer noninvasive techniques, such as two-dimensional (2D) strain imaging, are of interest because of their ability to detect subtle changes in LV function that precede reductions in EF. In severe primary MR with preserved contractile function, LVEF should be in the high-normal range. Studies have indicated that once the LVEF is <60%, the likelihood of impaired survival and permanent LV dysfunction postoperatively is high. Therefore, consideration should be given to surgical intervention before the LVEF drops to below 60%. Increased LV size and volume in end systole (more load-independent than end diastole) is also an indicator of increased likelihood of impaired survival and LV dysfunction postoperatively. When LV end-systolic diameter is >4.0 cm, surgical intervention should be considered.

(2)We have found that exercise echocardiography is very helpful in determining the likelihood of latent LV contractile dysfunction. The ability of the left ventricle to cope with exercise is an indication of its contractile reserve. In addition, poor functional capacity may indicate an adaptive response to MR (the patient was not truly asymptomatic) and may influence the decision to proceed with surgical treatment. We have found that a failure to increase LVEF, or for end-systolic volume to decrease with stress, is predictive of postoperative LV dysfunction and is a superior predictor of this eventuality than resting LVEF. In patients with severe asymptomatic MR, we perform stress echocardiography at 6-month intervals and recommend mitral valve surgery once end-systolic volume fails to decrease significantly at peak exercise or if LVEF fails to increase. This is particularly helpful in patients who wish to postpone surgical intervention as long as possible. We have also recently shown that mitral valve surgery can be safely postponed in patients with significant myxomatous MR as long as they achieve >100% predicted metabolic equivalents.

(3)The feasibility of repair depends on the cause of MR. This can be determined during the preoperative evaluation by echocardiography. Repair in an experienced center is usually likely in MVP unless chordae to both leaflets are severed, severe damage from endocarditis has occurred, or there is extensive leaflet calcification. Repair is usually feasible for a cleft valve and in less extreme forms of endocarditis such as leaflet perforation without chordal disruption, as well as in many cases of secondary MR (ischemic or dilated cardiomyopathy). Repair is more difficult to achieve in rheumatic involvement and when the valve leaflets or chordae are severely disrupted from any cause. The threshold to intervene surgically is lower if repair appears feasible because of the lower surgical and long-term mortality and morbidity associated with repair compared with replacement.

(4)The more severe the MR, the greater the volume load on the left ventricle usually, and the more likely that LV dysfunction will develop. One caveat here is that MR is not always holosystolic. Occasionally, apparently severe MR is seen without evidence of significant LV enlargement because the MR is occurring only in the latter part of the systole.

The threshold to intervene surgically is lower as MR severity increases. In situations where MR severity is in doubt, a TEE should be performed and the quantitative assessment used as described previously. A flail leaflet usually (but not always) implies severe MR. A retrospective study suggested that earlier surgical intervention was associated with better long-term survival in patients with a flail leaflet, even if the condition was asymptomatic, with flail being considered a surrogate for severe MR. More recent quantitative studies suggest that once ROA is ≥0.4 cm², survival is better in those treated surgically, even in the absence of symptoms.

(5)Pulmonary hypertension (pulmonary artery systolic pressures [PASP] > 50 mm Hg) in the absence of another likely cause is an indication of severe MR and impaired survival and is considered ACC/AHA class IIa indications for surgical intervention. It can be assessed noninvasively from the tricuspid regurgitant velocity.

(6)The occurrence of atrial fibrillation in the setting of severe MR is considered an indication (IIa) for surgical intervention. A concomitant maze or more usually now a modified maze procedure (pulmonary vein and great vein isolation) may be performed with mitral valve repair, especially if atrial fibrillation has become persistent or frequent.

(7)Age and other comorbidities. Patients >75 years, those with concomitant CAD, or those with renal dysfunction have worse outcomes after surgical treatment. Patients with IMR have a worse prognosis than those with regurgitation from other causes.

c.Medical therapy

(1)The role of medical therapy for asymptomatic, chronic MR caused by primary valve disease is not well established. There is no evidence that pharmacologic agents delay progression of the disease or prevent ventricular dysfunction. Patients with severe MR should be evaluated semiannually with echocardiography and stress echocardiography, if indicated. Patients with moderate MR should be evaluated annually.

(a)The success of afterload reducers in acute MR has led to trials of vasodilators, such as ACE-I and hydralazine, in chronic MR. However, existing small trials have been largely negative. As a result, the ACC/AHA and European Society of Cardiology guidelines do not recommend the use of pharmacologic vasodilatation in chronic MR with preserved EF, although this is not necessarily reflected in common practice.

(b)Sympathetic overstimulation appears to be a key element of progression to LV failure in MR, and there is limited evidence for the experimental use of β-blockers in MR but no clinical evidence of utility of postponement of surgical intervention.

(c)MR secondary to LV dysfunction is managed with standard heart failure therapy, including ACE-I and β-blockers.

(d)Diuretics and nitrates have a role in the management of pulmonary congestion.

(e)Ventricular rate-controlling agents and antiarrhythmics are used for atrial fibrillation. Digitalis and βa-blockers are the mainstay of therapy for rate control. In severe MR with atrial fibrillation, maintenance of sinus rhythm is unlikely if the regurgitation remains uncorrected.

(2)In accordance with recent AHA guidelines, endocarditis prophylaxis is not routinely indicated in patients with MR. These new guidelines recommend that prophylaxis be used only in patients with underlying cardiac conditions associated with the highest adverse outcome from infective endocarditis, including prosthetic heart valves or prior repair surgery, previous infective endocarditis, certain classes of congenital heart disease, and in valvulopathy occurring post cardiac transplantation.

d.Surgical therapy

(1)Mitral valve replacement with transection of the subvalvular apparatus was once the only approach used in the surgical management of MR. Postoperative reduction of LV function and decompensated heart failure were common sequelae. Chordal preservation by leaving the subvalvular structures intact has been shown to reduce LV volumes and wall stress postoperatively and is now the technique of choice.

(2)The increasing success of mitral valve repair has greatly reduced the morbidity and mortality associated with severe MR. Mitral valve repair almost always involves placement of an undersized annuloplasty ring, which reduces annular diameter, improves leaflet coaptation, and significantly decreases MR. Additional components may include a pericardial patch at the site of leaflet perforation, chordal shortening or transposition, leaflet resection, and sliding valvuloplasty of the posterior leaflet to reposition the coaptation line. Artificial chordae are increasingly used in the repair of anterior leaflet prolapse.

(3)Although no randomized trials have compared repair with replacement, comparative data suggest better postoperative LV function and survival with repair (which in part reflects the selection of patients who are able to undergo repair). Long-term risk of thromboembolism and endocarditis is reduced with repair versus replacement, and the need for reoperation is similar. Excellent 20-year outcomes following repair have been reported from multiple large volume centers, with the estimated risk of reoperation approximating 10% at 20 years.

(4)Minimally invasive video-assisted approaches employing hemi-lower sternotomy and right thoracotomy incisions may be options in experienced centers and selected patients. In the latter, cardiopulmonary bypass is usually achieved via femoral artery and vein cannulation. These approaches have the benefit of smaller incisions, resulting in more rapid postoperative recovery but require considerable expertise. Introduction of robotic surgical instrumentation and high-definition three-dimensional (3D) imaging allows mitral valve repair through portlike incisions, with further reduction in procedural invasiveness. Robotically assisted valve repair has shown good results in a few centers, although there are currently no data for superior outcomes. Complex surgeries, particularly if they require concomitant coronary artery bypass grafting (CABG) or multivalvular repair, are performed with a standard sternotomy.

(5)Mitral valve replacement is indicated when repair is not technically possible. The choice of mechanical or bioprosthetic valve replacement depends on weighing the risk of chronic anticoagulation required with mechanical valves, against the reduced longevity of the bioprosthetic valves. Structural degeneration of bioprosthetic mitral valves typically affects 20% to 40% patients at 10 years and over 60% at 15 years but is highly related to patient age at the time of surgery. In older patients, a bioprosthesis will last longer and this is the valve of choice in those over age 70.

(6)Intraoperative echocardiography helps in the assessment of complications of valve repair or replacement.

(a)Residual MR is the most common problem after a pump run. If further repair is feasible, a second pump run should be considered to correct residual MR (if 1+ or greater). If further repair is not possible, valve replacement may be needed. A second pump run does not appear to increase in-hospital mortality.

(b)Dynamic LV outflow obstruction is an important potential complication of mitral valve repair. This is now uncommon in experienced centers. It is caused by anterior displacement of mitral leaflet coaptation point when the posterior leaflet is redundant (typically >1.5 cm in height). The result is systolic motion of the mitral leaflet into the outflow tract, creating a pressure gradient across the outflow tract and the development of MR. This may be apparent immediately after surgery in the operating room, with intraoperative echo or later in the course. It is exacerbated by increased inotropy and small LV size. Many instances resolve with cessation of the use of sympathomimetic agents and volume repletion. In the operating room, if these efforts fail to correct the condition, more surgery to reduce the height of the posterior mitral leaflet (sliding annuloplasty) or, rarely, mitral valve replacement may be necessary. In the postoperative patient, volume repletion and judicious use of β-blockade are often all that is necessary, although occasionally surgical revision of the repair is needed. The development of a new apical systolic murmur in a patient who has undergone mitral valve repair should prompt an echocardiogram to exclude this complication.

e.Postsurgical follow-up care

(1)Baseline echocardiography should be performed postoperatively. This is ideally scheduled 4 to 6 weeks after the operation, but for the sake of convenience, it is often done before hospital discharge (within 3 to 4 days).

(2)MR can recur because of failure of the repair or because of progression of the disease that caused MR. Patients should undergo clinical evaluations at least once a year. Yearly echocardiography after the operation to assess for MR and LV function is reasonable.

f.Resynchronization therapy. LV wall motion abnormalities are often the major pathology in secondary (functional) MR, and CRT has demonstrated symptomatic benefit in carefully selected patients.

g.Percutaneous mitral valve repair and replacement. Percutaneous mitral valve repair is a developing catheter-based treatment option in which improved coaptation of the mitral leaflets is attempted using an implantable device. Current techniques emulate the existing surgical procedures, with the devices currently under investigation being classified into two functional approaches.

(1)A clip can be used to approximate the center of the mitral valve leaflets, thus giving a double-orifice valve in an approach that models the surgical Alfieri edge-to-edge repair. To date, this is the best studied percutaneous option and the only US Food and Drug Administration–approved device for percutaneous mitral valve repair. The Endovascular Valve Edge-to-Edge Repair Study II randomized 279 patients with 3 to 4+ MR to MitraClip (Abbott Vascular, Menlo Park, CA) versus surgical mitral valve repair/replacement. The primary composite end point for efficacy was freedom from death, from mitral valve surgery, and from 3 or 4+ MR at 12 months. About 55% of subjects in the percutaneous repair group met the end point at 1 year compared with 73% in the surgery group. All-cause mortality was equivalent in the percutaneous and surgical groups. There were significantly fewer adverse events in the percutaneous group, although significance was lost when blood transfusion was excluded as a complication. At 4-year follow-up, the overall rates of mortality and of 3+ or 4+ MR remained similar in both groups However, the need for mitral valve surgery for valvular dysfunction was higher in the percutaneous group.

(2)A flexible ring can be deployed and tightened in the coronary sinus (CS) in order to effectively reduce the mitral annulus area. Concerns regarding this procedure include the variable relationship between the CS and mitral annulus, as well as the proximity to the circumflex artery. Investigational devices include two stents deployed into the CS, with the connecting coil bridge being tightened over time called the Monarc (Edwards Lifesciences, Irvine, CA); a fixed length, double-anchor CS device called the Carillon Mitral Contour System (Cardiac Dimensions, Kirkland, WA); and a CS anchor that is attached to the interatrial septum via a cord under tension called the Percutaneous Septal Shortening System (Ample Medical, Foster City, CA).

The clip may be more appropriate for repair of MVP, whereas annular remodeling is felt to be better suited for the repair of functional regurgitation.

Percutaneous mitral valve replacement is under investigation. None of the various devices have received approval for clinical use as yet. In patients with a very calcified mitral annulus or who have had a prior mitral valve ring placed, a stented prosthesis has been successfully deployed at the mitral position similar to that at the aortic position.

III.ISCHEMIC MITRAL REGURGITATION

A.Clinical presentation. IMR may present either acutely in the setting of active ischemia or infarction or chronically with long-standing CAD. Among patients with CAD, the presence of MR portends a worse prognosis. Acute severe IMR presents with cardiogenic shock and hemodynamic instability, with symptoms and signs consistent with those previously described for acute MR. The clinical presentation of chronic IMR also parallels that of other etiologies of chronic MR; in addition, a history of known CAD or cardiovascular risk factors should be sought.

B.Etiology and pathology

1.Ischemia or infarction may give rise to one or more of the following mechanisms of IMR. Those common in the acute setting include the following:

a.PM rupture or chordal avulsion

b.Altered LV geometry, causing PM displacement

c.Elongation of the infarcted PM and exaggerated contraction of the noninfarcted PM

2.Mechanisms common in the chronic IMR setting include (Fig. 16.5)

FIGURE 16.5 Larger view (L). As evident in the figure, there is distortion of the left ventricular geometry with resultant annular dilation and papillary muscle displacement causing tethering of the chordae and restricted leaflet closure. All these changes lead to ischemic mitral regurgitation.

a.PM necrosis and segmental dysfunction of inferoposterior wall causing leaflet tethering and poor coaptation

b.Decreased mitral valve closing forces because of LV systolic dysfunction

c.LV cavity dilation causing mitral valve annular dilation

3.The anterolateral PM receives its blood supply from the left anterior descending and circumflex circulations; the posteromedial PM is supplied by the right coronary or left circumflex artery depending on the coronary dominance.

4.Of note, acute IMR is more frequently a result of geometric changes because of regional LV dysfunction (especially of the inferolateral wall) that induce leaflet tethering and prolapse, rather than ischemia of the PM itself.

C.Laboratory examination and diagnostic testing

1.Echocardiography. The most important determinations are the assessment of valvular anatomy, quantification of regurgitation, and evaluation of LV structure and function. Echocardiography can often reveal the mechanism of IMR by evaluating for PM rupture, leaflet restriction, mitral valve tethering, and relevant regional wall motion abnormalities. As previously described, the degree of regurgitation is quantified using color flow and Doppler techniques. Urgent transthoracic echocardiography and/or TEE is the investigation of choice in a patient with acute pulmonary edema where IMR is being considered as an etiology.

2.Electrocardiogram (ECG). In acute IMR, ECG is key in evaluating for the presence of active ischemia or infarction. As described above, branches from the left or right coronary systems can supply the PMs. However, it is in the setting of inferior or inferolateral MIs that acute IMR is most commonly seen. In chronic IMR, LA abnormalities, atrial fibrillation, and nonspecific ST–T changes may be seen.

3.Chest radiography. In acute IMR, findings of pulmonary edema may be present. Cardiomegaly with LA and LV enlargement may be seen in chronic IMR.

4.Cardiac catheterization. Evaluation of the patient with IMR will include angiography to assess the location, extent, and revascularization options of the CAD. In some cases, invasive hemodynamics may provide useful additional data regarding MR severity.

D.Therapy

1.Intravenous afterload reduction with nitroprusside and nitroglycerin +/− IABP insertion is often required when managing cardiogenic shock secondary to acute IMR. This scenario is associated with a very poor prognosis, and surgical intervention with coronary artery bypass and valve repair or replacement is usually the only hope for survival.

2.The medical management of chronic IMR with preserved EF remains controversial, as described above. If LV dysfunction is present, the use of a heart failure medical regimen is essential.

3.Controversy exists regarding the need for concomitant mitral valve surgery in patients with significant IMR who require coronary artery bypass surgery (CABG). A recent randomized trial did not show a clinically meaningful advantage of adding mitral valve repair to CABG in patients with moderate IMR. Also, when repair was compared to replacement in severe IMR, randomized studies did not show a significant difference in LV remodeling or survival at 1 year and at 2 years; however, recurrent MR was more likely with repair.

IV.Mitral Valve Prolapse

A.Clinical presentation. Prolapse exists when either or both of the mitral leaflets protrude >2 mm beyond the annulus into the left atrium during systole, and the coaptation point of the leaflets lies superior to the plane of the annulus. A wide spectrum of pathologic changes and clinical symptoms have been observed, from mild degrees of prolapse diagnosed with echocardiography only to clinically evident severe MR. MVP is the most common cause of MR in the United States. It affects approximately 2% of the population. Recent studies have suggested an equal prevalence among males and females. Males and older patients (age > 45 years) are disproportionately more likely to require surgical intervention and to develop other major complications such as endocarditis.

1.Signs and symptoms

a.Most patients with MVP have no symptoms, and the diagnosis is made by means of routine examination or echocardiography performed for other indications.

b.Although in the past, many symptoms were attributed to MVP, including chest pain, panic attacks, and autonomic instability, more recent studies suggest that these occur no more frequently in patients with MVP than in control populations. Most symptoms associated with adverse prognostic implications occur when significant MR is present.

c.Both atrial and ventricular arrhythmias have been reported in patients with MVP. However, the prevalence of these arrhythmias seems related to the degree of MR rather than MVP itself. Previous reports have shown that in MVP patients without significant MR, the prevalence of arrhythmias is similar to the general population, and becomes more prevalent with development of significant MR.

d.Transient ischemic attack or stroke has been reported in MVP. However, more recent studies in this area suggest no excess risk of cerebrovascular events among young patients with MVP.

e.When prolapse causes MR, symptoms referable to the valvular insufficiency may be present.

2.Physical findings

a.Inspection. There is a higher than expected incidence of pectus excavatum among patients with MVP. Straight back and scoliosis are also found. Patients often have low body weight and relative hypotension.

b.The main auscultatory findings are shown in Figure 16.6. The midsystolic click is the classic finding in prolapse. A systolic murmur is heard if MR is present.

FIGURE 16.6 Auscultatory findings in mitral valve prolapse.

c.Dynamic changes are elicited by conditions that decrease LV size (decreased venous return, increased contractility, or decreased systemic volume), which lead to earlier occurrence of prolapse, an earlier click, and increased duration of the murmur. These conditions include standing, the Valsalva maneuver, dehydration, and exposure to amyl nitrite.

d.Maneuvers that increase LV size by increasing venous return, decreasing contractility, or increasing systemic volume move the click and murmur later into systole. Examples include squatting and infusion of phenylephrine. The presence of a click that responds to provocative maneuvers is sufficient for the diagnosis of prolapse, even if an echocardiogram is not diagnostic.

Systolic click occurs at least 0.14 s after S₁, after onset of carotid upstroke. Multiple clicks can be heard later in systole from snapping taut of chordae (heard best with diaphragm at lower sternal border).

e.The intensity of the murmur typically decreases with conditions that result in a later click and murmur. An exception is exposure to amyl nitrite, which also reduces LV systolic pressure and the gradient that drives regurgitant flow. As such, the murmur is of lower intensity, although it occurs earlier in systole.

f.Aortic and pulmonic ejection sounds can produce systolic clicks. These occur earlier in systole than the click of mitral prolapse and may be differentiated on the basis of timing in conjunction with the carotid upstroke. Other causes of midsystolic clicks include septal and free wall aneurysms and mobile tumors such as myxoma. Clicks produced by these conditions do not change with maneuvers that alter LV volume.

B.Etiology and pathology. Prolapse may exist as a result of valvular abnormalities, deemed primary prolapse, or occur in the setting of normal leaflets (secondary prolapse).

1.Primary prolapse results from myxomatous proliferation of the leaflets. Myxomatous mitral valve disease describes thickening of the leaflets and chordae tendineae because of abnormal accumulation of mucopolysaccharides, with prominence of the spongiosa layer of the leaflets. Impaired tensile strength is more marked in the chordae than in the leaflets. Chordal elongation results in prolapse and loss of leaflet coaptation and may cause MR. Thickening of the leaflets ≥5 mm is considered “classic” MVP and is associated with greater future complications.

a.Within the pathologic spectrum of myxomatous mitral valve disease, there are two subtypes of diseases. Barlow disease is seen in younger patients, shows greater annular dilation, and has more marked leaflet redundancy and prolapse that may involve multiple segments. Conversely, fibroelastic deficiency occurs in older patients, is typically confined to the posterior middle scallop (P₂), and is associated with thinning and rupture of chordae.

b.Primary prolapse appears to have a genetic predisposition. There is a higher prevalence of MVP among family members of those affected, and an autosomal dominant mode of inheritance with variable penetrance has been postulated. Three loci, on chromosomes 11, 13, and 16, have been identified in families with multiple affected members. In addition, MVP is commonly identified in patients with Marfan, Loeys–Dietz, Ehlers–Danlos, and osteogenesis imperfecta syndromes.

c.Most complications of prolapse, particularly severe MR, are associated with primary prolapse. Men in their sixth decade of life represent the most common demographic group with such a presentation.

2.In secondary prolapse, there is relatively normal valvular structure. A disproportion between leaflet size and LV cavity size produces mechanical forces that may lead to leaflet prolapse. This form of prolapse particularly affects younger women. It may also occur with atrial septal defect, hyperthyroidism, emphysema, and hypertrophic cardiomyopathy. Normalization of the relative disproportion between leaflet size and cavity size often occurs with ageing among women, so the incidence decreases with age. Secondary prolapse is usually of little clinical significance and is not usually associated with significant MR.

C.Laboratory examination and diagnostic testing

1.Echocardiography. M-mode demonstrates late or holosystolic bowing of the mitral valve leaflet 3 mm or more below the C–D line. In 2D echocardiography, prolapse is defined as >2-mm displacement of one or both mitral leaflets into the left atrium during systole in the parasternal or apical long-axis views. Caution must be used in making the diagnosis with the apical four-chamber view because normal valve leaflets may appear to prolapse in this view owing to the saddle shape of the mitral annulus. With primary causes of prolapse, increased leaflet thickness (≥5 mm) and redundant leaflets and chordae are seen. Doppler echocardiography is used to assess the presence and severity of MR. Annual echocardiography is advised for those patients with moderate to severe MR.

2.Electrocardiogram. If there is severe MR, the findings described earlier are present. Otherwise, the ECG usually is normal or has nonspecific ST–T changes.

3.Chest radiography. Pectus excavatum or scoliosis can be present in some cases. If severe MR is present, the typical findings described earlier are seen. Otherwise, the chest radiograph is usually normal.

D.Therapy. For most patients, MVP carries a benign prognosis, and periodic clinical follow-up examinations and reassurance are all that is needed.

1.Endocarditis prophylaxis is not routinely indicated in patients with MVP.

2.Approximately 10% to 15% of patients, particularly those with redundant and thickened leaflets, eventually develop progressive MR. Chordal rupture is a contributing factor among these patients. Management of MR is outlined in Section II.E. Patients with evidence of primary MVP should avoid situations that might increase the stress on the chordae, such as sudden heavy lifting.

3.For patients with a history of transient ischemic attacks, antiplatelet therapy with aspirin (80 to 325 mg/d) is indicated. The ACC/AHA guidelines also recommend aspirin for poststroke patients with MVP who have no evidence of MR, atrial fibrillation, LA thrombus, or echocardiographic evidence of thickening (≥5 mm) or redundancy of the valve leaflets. However, long-term anticoagulation therapy with warfarin is recommended if any of these higher risk features are present, and in MVP patients with recurrent transient ischemic attacks while taking aspirin (international normalized ratio: 2.0 to 3.0). Aspirin is sufficient for patients with MVP and atrial fibrillation who are <65 years, have no MR, and have no history of stroke, hypertension, or heart failure.

4.Patients who experience palpitations should be advised to abstain from caffeine, alcohol, and tobacco use. βa-Blockers are useful in the management of premature atrial or ventricular contractions and often alleviate symptoms. Ambulatory electrocardiographic monitoring is recommended for persistent palpitations. Ventricular tachycardia is an indication for electrophysiologic testing to assess the risk of sudden death and the possible need for implantation of a defibrillator device.

V.Mitral Stenosis. Although declining in incidence in the United States, rheumatic disease remains the predominant cause of MS. Other etiologic factors are listed in Table 16.5. In general, once symptoms begin to develop, there follows a period of about 10 years before they become debilitating. Once significant limiting symptoms develop, the 10-year survival rate is <15%.

TABLE 16.5 Causes of Mitral Stenosis

Rheumatic: most common cause

Congenital

Parachute mitral valve: single papillary muscle to which chordae to both leaflets attach; results in MS or MR

Supravalvular mitral ring

Systemic diseases: can cause valvular fibrosis

Carcinoid

Systemic lupus erythematosus

Rheumatoid arthritis

Mucopolysaccharidosis

Healed endocarditis

Prior anorectic drug use

Severe mitral annular calcification

MR, mitral regurgitation; MS, mitral stenosis.

A.Clinical presentation

1.Signs and symptoms

a.There is often a long asymptomatic course, consisting of a couple of decades.

b.When symptoms do develop, dyspnea is common. Predominant symptoms are exertional dyspnea initially, followed by paroxysmal nocturnal dyspnea and orthopnea, which reflect elevated pulmonary venous pressure.

c.Precipitating factors, such as exercise, emotional stress, pregnancy, infection, or atrial fibrillation with a rapid ventricular response, can produce or dramatically worsen symptoms by generating increased transvalvular gradients and LA pressure. Atrial fibrillation with rapid ventricular response is a classic exacerbating factor and may produce pulmonary edema, even in those with mild MS. The LA dilation is a predisposing factor for the development of atrial fibrillation.

d.Hemoptysis can occur and likely represents rupture of small bronchial veins from elevated LA pressure.

e.Hoarseness occurs when the dilated left atrium impinges on the recurrent laryngeal nerve (Ortner syndrome).

f.LA dilation and stasis, particularly in the context of atrial fibrillation (persistent or paroxysmal), may cause thrombus formation and embolic events. Cerebrovascular events, coronary embolization, and renal emboli and infarction are all possible sequelae. The malformed valve is predisposed to the development of endocarditis.

g.Fatigue is common because of reduced cardiac output.

h.With long-standing MS and elevated pulmonary pressure, symptoms of RV failure may develop.

i.Patients with elevated pulmonary pressures may have angina-like chest pain, as a reflection of increased RV oxygen demand.

2.Physical findings

a.Inspection and palpation. Patients may have a malar facial flush. The jugular venous pulse can demonstrate a prominent a-wave if there is elevated pulmonary vascular resistance and the patient is still in sinus rhythm. Jugular venous pressure is elevated with RV failure. In advanced cases with low cardiac output, peripheral cyanosis occurs. The carotid upstrokes are usually normal but are of low amplitude if there is diminished cardiac output. The apex beat is not displaced and the impulse can have a tapping quality because of a palpable first heart sound. An apical diastolic thrill may be felt in the lateral decubitus position and has a quality that simulates a purring cat. If there is pulmonary hypertension, a parasternal RV lift with a palpable P₂ is present.

b.Auscultation. The main auscultatory findings are shown in Figure 16.7.

FIGURE 16.7 Auscultatory findings in mitral stenosis (MS).

(1)The opening snap is the most characteristic auscultatory hallmark of MS. However, as the mitral valve becomes more calcified and immobile, the opening snap may be lost (just as S₁ becomes softer).

(2)The murmur of MS is typically a low-pitched rumbling mid-diastolic murmur, heard best with the bell of the stethoscope with the patient in the left lateral decubitus position. Presystolic accentuation can be present whether or not the patient is in sinus rhythm (exact mechanism is unknown). Auscultation after a brief period of exercise may accentuate the murmur of MS as the increased output and heart rate increase the transvalvular gradient. The length of the murmur correlates better with the severity of MS than the loudness. The longer the murmur and the shorter the time interval from S₂ to the opening snap, the more severe the MS.

(3)Concomitant conditions that result in decreased flow across the valve, such as CHF, pulmonary hypertension, and aortic stenosis, may reduce the diastolic murmur. The presence of a loud S₁ may be the only clue to the presence of MS in these cases, particularly if pulmonary hypertension exists.

(4)Auscultation of the lungs may reveal fine inspiratory crackles. However, it is remarkable that some patients with severe MS have clear lung fields, possibly because of lymphatic hyperfunction clearing the transudated alveolar fluid that would be expected from the elevated LA pressure.

(5)Other conditions that mimic the clinical presentation of MS include LA myxoma and cor triatriatum. The tumor plop of myxoma may be mistaken for an opening snap, and tumor obstruction of the valve leads to a diastolic murmur. However, in this condition, the physical findings will vary with changes in position and from examination to examination. Other conditions in which a diastolic rumble may be present include atrial septal defect or VSD, the Austin-Flint murmur of aortic regurgitation (the murmur lessens with decreased afterload and is preceded by an S₃, and the S₁ is normal), and tricuspid stenosis (the murmur is heard at the left sternal border and typically increases with inspiration, known as Carvallo sign).

B.Etiology (Table 16.5)

1.In rheumatic MS, up to 50% of patients are not aware of a history of rheumatic fever. Rheumatic fever is now rare in developed nations, although it is unclear whether this is due to improvements in living conditions or a change in the virulence or immunogenicity of Streptococcus pyogenes.

a.In acute rheumatic fever, MR often predominates. Stenosis usually develops anywhere from 2 to 20 years later, and symptoms may not develop for many years thereafter. Although the incidence of rheumatic fever is roughly equal between men and women, rheumatic MS develops two to three times more frequently in women.

b.Thickening of leaflets with fibrous obliteration is a characteristic finding. Commissural and chordal fusion and chordal shortening contribute to the development of stenosis. Calcium deposition occurs on leaflets, chordae, and annulus, further restricting valvular function. These changes collectively produce a funnel-shaped mitral valve with a fish-mouth orifice.

2.Nonrheumatic MS causes include congenital malformation, extensive annular calcification in the elderly, radiation heart disease, and restrictive mitral valve repair for MR.

C.Pathophysiology

1.The normal area of the mitral orifice is 4 to 6 cm². When the valve area is <2 cm², a pressure gradient between the left atrium and the left ventricle in diastole occurs. As orifice area declines, both the transmitral pressure gradient and the LA pressure increase, but these are also affected by the flow through the valve. Although the transmitral pressure is a useful indicator of MS severity, it is critically affected by the cardiac output at any moment. The cross-sectional area of the mitral valve orifice is, for the most part, independent of flow considerations and thus is a more robust measure of the severity of MS.

This is reflected in the 2014 ACC/AHA valve disease guidelines where severity of MS is determined based on the mitral valve area (MVA) and diastolic pressure half-time (P1/2, will be discussed in detail later) along with its hemodynamic effects on the LA (presence of LA enlargement) and pulmonary vasculature (presence of pulmonary hypertension). Because of the variability of the mean pressure gradient with heart rate and flow, it has not been included in the severity criteria. However, the gradient is usually >5 to 10 mm Hg in severe MS.

a.Very severe stenosis is defined by an MVA ≤1.0 cm² with a P1/2 ≥ 220 ms, accompanied by severe LA enlargement and pulmonary hypertension (PASP > 30 mm Hg).

b.Severe stenosis is defined by an MVA ≤ 1.5 cm² with a P1/2 ≥ 150 ms, also commonly accompanied by severe LA enlargement and pulmonary hypertension (PASP > 30 mm Hg).

c.Progressive MS (mild to moderate) is associated with an MVA > 1.5 cm² and a P1/2 < 150 ms. There is usually mild to moderate LA enlargement and the pulmonary pressures are typically normal at rest.

The severity of the stenosis needs to be assessed also in terms of symptomatology and exercise capacity. Mixed MS/MR is often associated with greater symptomatic impairment than might be predicted from the severity of either lesion alone.

2.The increased LA pressure is transmitted to the pulmonary vasculature, resulting in symptoms of pulmonary congestion. The passive increase in pulmonary venous pressure may elevate pulmonary vascular resistance (reactive pulmonary hypertension). This condition is usually reversible if the stenosis is relieved. However, in long-standing, severe MS, obliterative changes in pulmonary vasculature may occur. Severe pulmonary hypertension can in turn lead to right-heart failure.

3.Up to 30% of patients have a depressed LVEF. This appears to result from decreased preload (decreased inflow into the left ventricle) or a rheumatic myocarditis. The former will normalize after a corrective mitral valve procedure; the latter will not.

4.In severe MS, there may be sufficiently low cardiac output to cause symptoms of poor perfusion. Chronically depressed cardiac output causes a reflex increase in systemic vascular resistance and increased afterload. This may further diminish LV performance.

D.Laboratory examination and diagnostic testing

1.Echocardiography has several critical roles in the evaluation of MS: initial diagnosis, determination of severity, evaluation of suitability for percutaneous balloon mitral valvuloplasty, and identification of concomitant valve lesions.

a.M-mode findings include dense echoes on the mitral valve and decreased excursion of the mitral valve. Poor leaflet separation in diastole, anterior motion of the posterior leaflet, and decreased E–F slope on the anterior leaflet are M-mode hallmarks of MS.

b.Two-dimensional findings include restricted motion and diastolic doming of leaflets (hockey stick sign) (Fig. 16.8). The leaflets and chordae are thickened and are often calcified in older patients.

FIGURE 16.8 Severe mitral stenosis—the parasternal long-axis view on the left shows the typical doming of the anterior mitral leaflet (with the so-called “hockey stick” appearance) with associated leaflet thickening. The parasternal short-axis view on the right shows the typical “fish-mouth” appearance with restricted mitral valve opening.

c.Doppler echocardiography is essential in the assessment of stenosis severity.

(1)A transmitral peak velocity > 1 m/s suggests MS. However, this is not specific because tachycardia, increased inotropy, MR, and VSD may cause increased flow in the absence of MS.

(2)The transvalvular mean gradient (assessed by means of tracing mitral inflow) is also helpful in estimating mitral valve severity; however, it is highly dependent on flow and filling time and will vary greatly with heart rate.

d.Echocardiography is used to estimate the MVA.

(1)Direct planimetry of the orifice can be performed in the parasternal short-axis view.

(a)Optimal positioning is done by first obtaining a parasternal long-axis view and placing the mitral valve orifice in the center of the scan plane. The transducer is then rotated 90° to obtain the short-axis view. Measurements are obtained at the tips of the mitral leaflets.

(b)Poor-quality 2D images and a thick, calcified subvalvular apparatus can make it difficult to obtain accurate measurements. Improper orientation of the scanning plane can produce oblique cuts across the valve and lead to overestimation of valve area. Scanning up and down until the typical fish-mouth appearance is seen helps in this regard. Dense fibrosis or calcification at the margins of the valve orifice can lead to underestimation of the valve area. Low-gain settings can cause dropout at the edges of the valve and overestimation of the valve area. High-gain settings can lead to underestimation. Planimetry is more difficult if commissurotomy has been performed, but remains the preferred method to assess the MVA by means of echocardiography. With the advent of 3D imaging via transthoracic echocardiography, more accurate orifice mapping for planimetry is now possible (see below).

(2)Pressure half-time method. Impedance to LA emptying prolongs the decline in transvalvular pressure gradient. This prolongs pressure half-time (time that it takes for pressure to fall to one-half the starting value, which equates with the time for the velocity to decrease to 70% of peak velocity). The mitral inflow E-wave is used in the calculation.

(a)Empiric pressure half-time has been shown to correlate with valve area:

Mitral valve area (in cm²) = 220/pressure half-time

(b)If a software package to perform the calculations is not available, pressure half-time can be calculated by multiplying the deceleration time by 0.29. If atrial fibrillation is present, 5 to 10 consecutive beats are obtained and averaged.

(c)It is important to have the Doppler beam parallel to the direction of blood flow.

(d)The pressure half-time method is inaccurate if there are rapid changes in LA hemodynamics, such as immediately after balloon valvuloplasty.

(e)Obtaining a pressure half-time may be very difficult if sinus tachycardia is present (E–A fusion). Severe aortic insufficiency also fills the left ventricle in diastole, decreases pressure half-time, and leads to overestimation of the MVA.

e.Stress echocardiography is useful in the evaluation of patients with symptoms when the resting study is discrepant with symptoms or clinical findings (ACC/AHA class I). Gradients can be assessed during (supine bicycle) or immediately after (treadmill) exercise. Measurement of tricuspid regurgitation velocity is used to estimate pulmonary pressures with stress.

f.TEE is indicated to exclude LA thrombus and assess MR prior to valvuloplasty, or if the TTE data are suboptimal (ACC/AHA class I), but is not indicated routinely if TTE data are adequate.

g.Three-dimensional echocardiography (3DE) can provide a 3D data set to determine the MVA. This method can avoid error in measurement related to correct alignment of the cut-plane with the level of the mitral valve tips and speeds up the time required for optimal planimetry. Using real-time 3D transesophageal technology, visualization of the mitral valve en face from the left atrium or left ventricle is possible at the time of percutaneous balloon mitral valvuloplasty. The main advantage of preoperative transesophageal 3DE is that it replicates the surgical view of the mitral valve that will be seen upon opening the left atrium.

2.Cardiac catheterization. Hemodynamic measurements obtained in a cardiac catheterization laboratory are used to assess the severity of stenosis. Simultaneous measurement of LV end-diastolic pressure, LA pressure (either directly or more commonly with PCWP as a surrogate), cardiac output (Fick method or thermodilution), heart rate, and diastolic filling period (seconds per beat) is required. LV pressure and PCWP (or LA pressure) tracings are made simultaneously (Fig. 16.9). A mean transmitral gradient is derived from the preceding measurements (planimeter area between the left ventricle and PCWPs during diastole; this area is multiplied by the scale factor of the tracing in millimeters of mercury per centimeter to obtain the gradient). The PCWP tracing ideally should be realigned by 50 to 70 ms to the left (with tracing paper) to account for the time delay in transmission of LA pressure to the pulmonary venous beds.

FIGURE 16.9 Simultaneous left ventricular and pulmonary capillary wedge pressure tracings used to measure mean gradient across mitral valve during diastole.

a.The Gorlin formula:

Gorlin derived the empirical constant of 37.7, which is the Gorlin constant (44.3) multiplied by 0.85 (the correction factor for the mitral valve).

b.A simplified version of the Gorlin formula proposed by Hakki et al. has been validated and provides a reasonable approximation of the valve area:

c.Pitfalls. PCWP cannot be used if the patient has pulmonary venous occlusive disease or cor triatriatum. The catheter must be properly wedged. In addition, thermodilution cardiac output is less accurate if there is severe tricuspid regurgitation or low cardiac output. Immediately after valvuloplasty MR or atrial septal defect, flow may lead to inaccurate estimations of mitral flow.

d.Cardiac catheterization is indicated in the evaluation of patients when echo-Doppler and clinical findings are discrepant or when echo findings are internally discordant or if pulmonary hypertension is disproportionate to MS severity as assessed by echo.

3.ECG. LA enlargement (P mitrale) is usually present when sinus rhythm persists. Signs of RV hypertrophy are seen with pulmonary hypertension. Atrial fibrillation is common and the fibrillatory waves are usually coarse.

4.Chest radiography. LA enlargement is apparent with a double density along the right-heart border. A convexity can be apparent below the PA, representing the LA appendage. Radiographic splaying of the carina with elevation of the left main bronchus and posterior displacement of the esophagus at barium swallow examination reflect LA enlargement. Kerley B lines may be present from increased pulmonary venous pressure. RV enlargement (decreased retrosternal air space on the lateral radiograph) may be present. Evidence of mitral valve calcification, or rarely LA calcification (McCallum patch), may be present.

E.Therapy. The overall management approach to the individual with MS should integrate symptomatic status, degree of stenosis, and suitability of the valve for percutaneous balloon mitral valvuloplasty.

1.Medical therapy

a.Patients without symptoms who have mild MS (valve area > 1.5 cm² and mean gradient < 5 mm Hg) need no specific treatment and, in accordance with current AHA guidelines, do not require endocarditis prophylaxis. In patients with rheumatic valve disease, guidelines for the prevention of rheumatic fever should be applied. Annual reevaluation is recommended, but a yearly echocardiogram is not indicated unless there is a change in clinical status.

b.Patients with only mild symptoms of exertional dyspnea can be treated with diuretics and salt restriction to lower LA pressure. β-blockers blunt the chronotropic response to exercise and may improve exercise capacity. Arterial vasodilators should be avoided.

c.Atrial fibrillation can clearly exacerbate symptoms, and cardioversion or rate control measures are important to maintain diastolic filling time. Embolism is a much feared complication of MS and occurs in up to 20% of patients; risk is increased with advancing age and atrial fibrillation.

(1)Digitalis and β-blockers are the preferred agents to achieve rate control.

(2)Anticoagulation with warfarin is imperative for patients with paroxysmal, persistent, or chronic atrial fibrillation and MS because they are at high risk for thromboembolism and this is also indicated in those with a history of prior embolism or known LA thrombus (ACC/AHA class I).

(3)Antiarrhythmic drug therapy may be used in an attempt to restore sinus rhythm, but long-term efficacy may depend on correction of the MS.

(4)Percutaneous balloon mitral valvuloplasty may be considered in asymptomatic patients with new-onset atrial fibrillation and severe MS who have a favorable valve morphology and no contraindications.

2.Percutaneous or surgical therapy (Table 16.6). If more than mild symptoms (New York Heart Association [NYHA] class II or greater) are present due to MS, the patient should be referred for surgical or percutaneous therapy. An asymptomatic patient, with severe (or very severe) MS and evidence of pulmonary hypertension at rest or with exercise, should also be referred for percutaneous therapy if the valve is suitable. Mortality increases substantially as symptoms progress. Results of natural history studies, conducted before valvotomy procedures were developed, indicate that young symptomatic patients have about 40% mortality at 10 years and almost 80% at 20 years. Elderly patients have 60% to 70% mortality at 10 years. Marked pulmonary hypertension (PASP > 60 mm Hg) is an indication for mechanical treatment, even in the absence of symptoms in severe (or very severe) MS. Rarely, for patients with asymptomatic MS who do not have pulmonary hypertension, surgical or balloon intervention may be warranted. Instances where this is indicated include women with severe MS contemplating becoming pregnant, those with severe MS who will need a major surgical procedure with massive fluid shifts, or those with repeated embolism despite anticoagulation. In the last instance, surgical intervention is usually indicated, and LA appendage ligation is performed simultaneously.

TABLE 16.6 ACC/AHA Indications for Percutaneous Mitral Balloon Valvotomy

Class I

1.PMV is effective for symptomatic patients (NYHA functional class II, III, or IV), with moderate or severe MS and valve morphology favorable for PMV in the absence of LA thrombus or moderate to severe MR

2.PMV is effective for asymptomatic patients with moderate or severe MS and valve morphology that is favorable for PMV, who have pulmonary hypertension (PASP > 50 mm Hg at rest or > 60 mm Hg with exercise) in the absence of LA thrombus or moderate to severe MR

Class IIa

•PMV is reasonable for patients with moderate or severe MS who have a nonpliable calcified valve, are in NYHA functional class III–IV, and are either not candidates for surgery or at high risk for surgery

Class IIb

1.PMV may be considered for asymptomatic patients with moderate or severe MS and valve morphology favorable for PMV who have new-onset atrial fibrillation in the absence of LA thrombus or moderate to severe MR

2.PMV may be considered for symptomatic patients (NYHA functional class II, III, or IV) with MV area > 1.5 cm² if there is evidence of hemodynamically significant MS based on PASP >60 mm Hg, pulmonary artery wedge pressure of 25 mm Hg or more, or mean MV gradient >15 mm Hg during exercise

3.PMV may be considered as an alternative to surgery for patients with moderate or severe MS who have a nonpliable calcified valve and are in NYHA class III–IV

Class III

1.PMV is not indicated for patients with mild MS

2.PMV should not be performed in patients with moderate to severe MR or LA thrombus

LA, left atrial; MR, mitral regurgitation; MS, mitral stenosis; MV, mitral valve; NYHA, New York Heart Association; PASP, pulmonary artery systolic pressure; PMV, percutaneous mitral valvotomy.

a.Percutaneous balloon mitral valvuloplasty is considered the treatment of choice for symptomatic patients with severe MS who have favorable valve morphology. The technique involves placement of a balloon-tipped catheter into the left atrium through a transseptal puncture and then across the mitral valve. The hourglass-shaped balloon (Inoue balloon) is inflated and deflated to increasingly larger diameters until the desired result is obtained.

(1)Typically, there is an increment in valve area of 1 cm², mainly as a result of splitting of the fused commissures. The mean valve area usually doubles with a 50% to 60% reduction in transmitral gradient.

(2)This procedure is generally contraindicated in patients with >3+ MR (the procedure normally increases MR by one grade) or in whom there is an LA or appendage thrombus (risk of procedural embolism). Severe tricuspid regurgitation (does not improve substantially) and severe pulmonary hypertension (if PA pressures do not fall, then substantial risk of right-to-left shunt across procedural atrial septal defect) are relative contraindications to the procedure.

(3)An echocardiographic score has been developed to help select patients who may be candidates for percutaneous valvuloplasty. There are four parts to the assessment (mobility, leaflet thickening, subvalvular thickening, and calcification) (Table 16.7). In general, extensive subvalvular disease results in a poorer outcome with valvuloplasty. Patients with extensive fluoroscopically visible mitral valve calcification also have a worse outcome after percutaneous therapy.

TABLE 16.7 Echo Score Assessment for Percutaneous Valvuloplasty in the Management of Mitral Stenosis

Mobility (grade 0–4, 0 being normal)

1.Highly mobile with only leaflet tips restricted

2.Mild leaflet restriction; base portions have normal mobility

3.Valve moves forward in diastole, mainly from base

4.No or minimal diastolic movement of valve

Subvalvular thickening (grade 0–4, 0 being normal)

1.Minimal thickening below leaflets

2.Chordal thickening up to one-third of chordal length

3.Thickening extending to distal one-third of chords

4.Extensive thickening to papillary muscles

Thickening of leaflets (grade 0–4, 0 being normal)

1.Near normal (4–5 mm)

2.Marginal thickening (5–8 mm) with normal thickness of midleaflets

3.Thickening of entire leaflet (5–8 mm)

4.Extensive thickening of all leaflet tissues (>8–10 mm)

Calcification (grade 0–4, 0 being normal)

1.Single area of echo brightness

2.Scattered areas of increased brightness along leaflet margins

3.Brightness extending to the midportion of leaflets

4.Extensive brightness throughout the leaflet tissue

Reproduced from Wilkins GT, Weyman AE, Abascal VM, et al. Percutaneous balloon dilatation of the mitral valve: an analysis of echocardiographic variables related to outcome and the mechanism of dilatation. Br Heart J. 1988;60(4):299–308, with permission from BMJ Publishing Group Ltd.

(a)A total echocardiographic score (adding the four components) higher than 11 is associated with a poorer outcome and a suboptimal increase in valve area, a higher incidence of heart failure and restenosis, and higher mortality. Patients with high scores should not undergo valvuloplasty unless surgical treatment is impossible.

(b)Echocardiographic scores of 9 to 11 represent a gray zone in which some patients have good results with valvuloplasty. Others have suboptimal results.

(c)Optimal results of balloon valvuloplasty are usually achieved when the echocardiographic score is 8 or less.

(4)TEE plays a critical role during valvuloplasty. The most immediate concern is to rule out LA and appendage thrombi. If thrombosis is present, anticoagulation for at least 1 month is undertaken with repeat TEE to confirm resolution before valvuloplasty. TEE can also help guide balloon positioning; after each inflation, the degree of MR and the gradient can be assessed. The degree of residual MS can be estimated with planimetry of the valve orifice before and after inflation. The pressure half-time method is unreliable until 24 to 48 hours after the procedure.

(5)Echocardiography is useful in the determination of immediate postprocedural complications (Table 16.8). Among these is MR with an incidence estimated at 3% to 8%, depending on the series. The echocardiographic score is less predictive of the severity of postprocedural MR.

TABLE 16.8 Complications of Balloon Valvuloplasty

Mitral regurgitation

Cardiac perforation: incidence as high as 2%–4%

Embolization: incidence 2% in the National Heart, Lung, and Blood Institute registry

Residual atrial septal defect: most close within 6 months; can persist long term among as many as 10% of patients; generally small and well tolerated

(6)The frequency of restenosis of the valve is variable, depending on the age of the patient and the immediate procedural increment in valve area. Data from the National Heart, Lung, and Blood Institute registry of all functional classes of patients show an 84% survival rate 4 years after treatment. Advanced age, high NYHA functional class, presence of atrial fibrillation, smaller initial MVA, higher pulmonary arterial pressure, and substantial tricuspid regurgitation are associated with poorer long-term results. These variables identify a population with more serious illness that frequently necessitates intervention and should not preclude valvuloplasty. More postprocedural MR and lower postprocedural MVA are associated with poorer long-term results.

b.Surgical treatment. Closed commissurotomy was the earliest surgical approach used. This was performed through a thoracotomy (without cardiopulmonary bypass) and atriotomy with a valve dilator. This procedure is rarely used in the United States since the development of the percutaneous approach and improvements in open-heart surgery. Open mitral valvotomy involves direct visualization of the mitral valve (with cardiopulmonary bypass), debridement of calcium, and splitting of fused commissures and chordae.

(1)Severe subvalvular disease or valvular calcification often leads to the choice of surgical intervention over valvuloplasty. Coexistent disease in other valves (e.g., aortic stenosis or aortic regurgitation) that necessitates treatment also favors surgical intervention.

(2)Mitral valve replacement. Valve replacement is often required, especially when there is extensive fibrosis and calcification or concomitant MR.

(3)Mitral valve repair is more difficult but can be performed in selected cases with commissurotomy when there is mixed MS/MR.

(4)For patients with long-standing atrial fibrillation, a combined maze procedure (either surgical or using an intraoperative ablation catheter) can be performed in conjunction with the valve operation. LA appendage ligation may also be added to reduce future cardioembolic risk.

c.Comparison of balloon valvuloplasty and open commissurotomy. Studies in ideal patients for balloon valvuloplasty and commissurotomy suggest equal improvement in valve area and symptoms immediately postprocedure and in medium-term follow-up.

d.Postprocedural follow-up care. Patients who have undergone balloon valvuloplasty or operations for MS should undergo baseline echocardiography, preferably >72 hours after the procedure. In patients with a history of atrial fibrillation, warfarin should be restarted 2 to 3 days after the procedure. Clinical follow-up examination should be performed at least once a year and more often if symptoms develop. It has become common practice at many centers for patients to undergo follow-up echocardiography on a once-a-year basis, although no firm guidelines have been developed for this.

ACKNOWLEDGMENTS: The authors wish to thank Amanda R. Vest, MD, Carmel Halley MD, and Maran Thamilarasan MD for their contribution to the earlier editions of this chapter.

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