AUTHOR AND EDITOR INFORMATION

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• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Multimedia
• References

INTRODUCTION

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Background

Mitral stenosis is an obstruction to left ventricular inflow at the mitral valve level due to the structural abnormality of the mitral valve apparatus. Rheumatic fever is a main cause of mitral stenosis. Other uncommon etiologies include congenital mitral stenosis, such as parachute mitral valve; marked mitral annular calcification of the mitral valve; and infective endocarditis with large vegetations (often fungal). Sometimes, conditions such as left atrial myxoma can mimic mitral stenosis by obstructing outflow.

Since acute rheumatic fever is mild in nature, only fewer than half of patients with mitral stenosis give a clear history of being affected by it. As no specific tests are available, acute rheumatic fever is often underdiagnosed.

Stenosis of the mitral valve typically occurs decades after the episode of acute rheumatic fever. Pathologically, multiple inflammatory foci (Aschoff bodies, ie, perivascular mononuclear infiltrate) develop in the endocardium and myocardium after the initial insult. Sometimes, this might lead to the acute development of small vegetations along the border of the valves.

Over time, progression of the disease leads to reaction and adhesion of commissures, thickening and shortening of chordae tendineae, thickening of the valve leaflets, and ultimately deposition of calcium in the valve leaflets and/or the subvalvular apparatus. Slowly, the valve apparatus starts to retract and becomes contracted and stenotic. Whether the progression of valve damage is due to hemodynamic injury of the already affected valve apparatus or to the chronic inflammatory nature of the rheumatic process is unclear.

Pathophysiology

The normal mitral valve orifice area is approximately 4-6 cm². As the orifice size decreases, pressure gradient across the mitral valve increases to maintain adequate flow (Bernoulli principle).

Patients will be asymptomatic until the valve area reaches 2 cm². Although they may not have any symptoms at rest, moderate exercise or any factors that increase the heart rate will result in exertional dyspnea. This is due to increased transmitral gradient causing higher pulmonary wedge pressure.

Severe mitral stenosis occurs with a valve area less than 1 cm². As the valve progressively narrows, the resting diastolic mitral valve gradient, and hence left atrial pressure, increases. This leads to transudation of fluid into the lung interstitium and decreased pulmonary compliance with dyspnea at rest or with minimal exertion. Hemoptysis may occur because of the rupture of bronchial veins. The elevated pressure in the left atrium provokes its dilatation and increases the risk of atrial fibrillation, with subsequent left atrial appendage thrombus formation and thromboembolism.

Pulmonary hypertension develops because of (1) retrograde transmission of left atrial pressure, (2) pulmonary arteriolar constriction, (3) interstitial edema, and (4) obliterative changes in the pulmonary vascular bed. These changes in the pulmonary vascular bed protect the pulmonary capillaries from the surge of blood passing into the capillaries during activity and thus from pulmonary congestion. As pulmonary hypertension increases, right ventricular dilation occurs, which leads to tricuspid regurgitation. Right ventricular failure leads to elevated jugular venous pressure, liver congestion, ascites, and pedal edema.

Left ventricular end-diastolic pressure and cardiac output are usually normal in persons with isolated mitral stenosis. However, associated significant mitral regurgitation, systemic hypertension, aortic stenosis, and myocardial infarction can affect left ventricular function and lead to decreased cardiac output. Approximately one third of patients with mitral stenosis have depressed left ventricular systolic function (ejection fraction 0.35-0.50) based on rheumatic heart disease (ie, no evidence of coronary artery disease).

Frequency

United States

The prevalence of rheumatic disease among persons in developed nations, such as the United States, is steadily declining. An estimated 1 in 100,000 people are affected.

International

The prevalence is higher in developing nations. In India, for example, the prevalence is approximately 100-150 cases per 100,000 people.

Mortality/Morbidity

• The 10-year survival rate for asymptomatic persons is approximately 80%.
• The 10-year survival rate for patients with mild symptoms is approximately 60%.
• The 10-year survival rate among patients who develop congestive heart failure is 15%. See Medscape's Heart Failure Resource Center.

Sex

• For reasons not clearly known, mitral stenosis is more common in females than in males. Nearly two thirds of patients with mitral stenosis are female.

Age

• The onset of symptoms usually occurs between the third and fourth decade of life.

CLINICAL

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History

• Symptoms of mitral stenosis usually develop in the third or fourth decade of life. Nearly half of the patients do not recall a history of acute rheumatic fever.
• The rate of disease progression is faster in patients in developing countries and slower in patients in Western countries.
• The patient is generally asymptomatic in the early phase of the disease. However, factors that increase the heart rate precipitate dyspnea by increasing the gradient between the left atrium and the left ventricle. These factors include fever, severe anemia, thyrotoxicosis, sexual intercourse, exercise, excitement, pregnancy, paroxysmal tachycardia, and atrial fibrillation.
• As the disease progresses, the patient develops dyspnea on exertion, orthopnea, paroxysmal nocturnal dyspnea, and atrial arrhythmia.
• Nearly 15% of patients develop embolic episodes that are usually associated with atrial fibrillation. Rarely, embolic episodes have developed in patients with sinus rhythm.
• Systemic embolization leads to stroke, renal failure, and myocardial infarction.
• Hoarseness can develop from compression of the left recurrent laryngeal nerve against the pulmonary artery by an enlarged left atrium. Also, compression of bronchi by the enlarged left atrium can cause a persistent cough. 
• Hemoptysis may occur and is usually not fatal. It occurs because of the rupture of thin, dilated bronchial veins due to left atrial hypertension.
• Pregnant women with mild mitral stenosis may become symptomatic during their second trimester because of the increase in blood volume and cardiac output.
• Some patients present with chest pain, the reason for which is not clearly known. Most of the time, chest pain can be related to pulmonary hypertension, coronary embolization, or coronary atherosclerosis.

Physical

• Patients may develop pinkish-purple patches (malar flush) on their cheeks, which usually correlates with severe mitral stenosis due to reduced cardiac output and vasoconstriction.
• The jugular vein is distended. In patients with sinus rhythm, a prominent a wave is noted, which reflects increased right atrial pressure from pulmonary hypertension and right ventricular failure. A prominent v wave is noted in patients with significant tricuspid regurgitation.
• The apical impulse may be laterally displaced or may not be felt, especially in cases of severe mitral stenosis. This can be explained by the decreased left ventricular filling. However, a right ventricular heave can be palpated because the enlarged left atrium displaces the right ventricle anteriorly. Rarely, a diastolic thrill can be felt at the apex with the patient in the left lateral recumbent position.
• The auscultatory findings characteristic of mitral stenosis are a loud first heart sound, an opening snap, and a diastolic rumble.
• • The first heart sound is accentuated because of a wide closing excursion of the mitral leaflets. The degree of loudness of the first heart sound depends on the pliability of the mitral valve. The intensity of the first heart sound diminishes as the valve becomes more fibrotic, calcified, and thickened.
  • The second heart sound is normally split, and the pulmonic component is accentuated if pulmonary hypertension is present. The opening snap follows the second heart sound. The sudden tensing of the valve leaflets after they have completed their opening excursion causes an opening snap. In patients with elevated left atrial pressure and hence with severe mitral stenosis, the opening snap occurs closer to the second heart sound. 
  • The diastolic murmur of mitral stenosis is of low pitch, rumbling in character, and best heard at the apex with the patient in the left lateral position. It commences after the opening snap and the duration of the murmur correlates with the severity of the stenosis. It is absent in persons with severe disease. The murmur is accentuated by exercise, cough, and amyl nitrate, whereas it decreases with rest and with Valsalva maneuver. In patients with sinus rhythm, the murmur increases intensity in late diastole (so called, presystolic accentuation) due to increased flow across the stenotic mitral valve as a result of left atrial contraction.
• Diastolic murmurs secondary to pulmonary regurgitation and aortic regurgitation might be present.

Causes

See Background.

DIFFERENTIALS

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Other Problems to be Considered

Left atrial myxoma
Endocarditis
Massive annular calcification

WORKUP

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Lab Studies

• Perform routine baseline tests such as CBC count, electrolyte status, and renal and liver function tests.

Imaging Studies

• Chest radiographic findings suggestive of mitral stenosis include left atrial enlargement (eg, double shadow in right cardiac silhouette, straightening of left cardiac border due to the large left atrial appendage), prominent pulmonary vessels, redistribution of pulmonary vasculature to the upper lobes, mitral valve calcification, and interstitial edema (Kerley A and B lines).
• Echocardiography (ECG) is the most specific and sensitive method of diagnosing and quantifying the severity of mitral stenosis. Using a transthoracic 2-dimensional echocardiogram, Doppler study, and color-flow Doppler imaging, the anatomic abnormalities of the stenotic valve (ie, thickening, mobility, diastolic doming especially of the anterior leaflet, restricted motion usually of the posterior leaflet, calcification, involvement of the subvalvular apparatus and the characteristic fusion of the commissures are usually well defined.
• • With echocardiography, the size of the mitral valve orifice can be precisely quantified. Important information about the ventricular and atrial chamber sizes, the presence of a left atrial thrombus, measurement of transvalvular gradient, and pulmonary arterial pressure can also be obtained.
  • With the use of Doppler echocardiography, sufficient information can be obtained to develop a therapeutic plan, and, consequently, most patients do not require invasive procedures such as cardiac catheterization.
  • Transesophageal echocardiography (TEE) provides better quality images and is more accurate in assessing the anatomic features of the valve and the presence of left atrial appendage thrombus.

Other Tests

• In persons with moderate-to-severe mitral stenosis, ECG shows signs of left atrial enlargement (P wave duration in lead II >0.12 seconds, P wave axis of +45° to -30°, marked terminal negative component to the P wave in V₁ [1 mm wide and 1 mm deep]) and, commonly, atrial fibrillation. The mean QRS axis in the frontal plane is greater than 80°, and an R-to-S ratio of greater than 1 in lead V₁ indicates the presence of right ventricular hypertrophy. As the severity of the pulmonary hypertension increases, the mean QRS axis in the frontal plane moves toward the right.

Procedures

• Cardiac catheterization was formerly a routine procedure used to assess the severity of mitral stenosis. However, the accuracy of echocardiographic findings has resulted in only selective use of catheterization. Cardiac catheterization is now indicated in the following situations:
• • When a discrepancy exists between clinical and echocardiographic findings
  • In patients with associated severe lung disease and pulmonary hypertension in whom the contribution that mitral stenosis has to their symptoms needs to be distinguished
  • In patients in whom left atrial myxoma must be excluded
  • In men older than 40 years and women older than 50 years who have risk factors for coronary artery disease or a positive stress test result, performing a coronary angiogram is useful.
  • In patients with angina pectoris or coronary risk factors, a preoperative coronary angiogram helps determine if the patient needs a coronary bypass at the time of surgery.
  • In patients who underwent mitral valvotomy and developed serious symptoms

TREATMENT

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Medical Care

The goals of medical treatment for mitral stenosis are to reduce the recurrence of rheumatic fever, provide prophylaxis for infective endocarditis, reduce the symptoms of pulmonary congestion (eg, orthopnea, paroxysmal nocturnal dyspnea), control the ventricular rate in patients with atrial fibrillation, and prevent thromboembolic complications.

• Asymptomatic patients with mitral valve disease must receive secondary prophylaxis against beta-hemolytic streptococci (benzathine penicillin G 1.2 million U IM q3-4 wk) for their lifetime to prevent the recurrence of rheumatic fever. They also need to receive prophylaxis for infective endocarditis prior to surgical or dental procedures.
• Initial symptoms of pulmonary congestion are secondary to increased left atrial pressure, which can be safely reduced by diuretics. Dietary sodium restriction and nitrates decrease preload and can be of additional use. Careful use of beta-blockers in patients with a normal sinus rhythm can prolong the diastolic filling time and thus decrease left atrial pressure. In general, afterload reduction is avoided because it can cause hypotension in these patients who are unable to increase cardiac output adequately because of their stenotic valve.
• Atrial fibrillation is common in mitral stenosis and often leads to a rapid ventricular rate. An increased ventricular rate in atrial fibrillation markedly reduces diastolic filling time and increases left atrial pressure. It can be controlled by intravenous beta-blocker or calcium channel blocker therapy (diltiazem or verapamil). The rate can be controlled long-term with beta-blockers, calcium channel blockers, amiodarone, or digoxin.
• Recent-onset atrial fibrillation (<6 mo) in a patient with mild mitral stenosis and normal atrial size can be easily converted to a sinus rhythm either pharmacologically or with electrical counter shock. For this purpose, anticoagulation therapy should be given for at least 3 weeks prior to cardioversion. Alternatively, a TEE can be performed to exclude the presence of left atrial thrombus. If no thrombus is present, immediate cardioversion can be performed once the patient is anticoagulated.
• Patients who are successfully converted to sinus rhythm need to receive long-term anticoagulation and antiarrhythmic drugs.
• Patients with mitral stenosis and an enlarged left atrium and patients with atrial fibrillation receive anticoagulation for life. 
• Surgical correction of the mitral valve is indicated if embolization is recurrent, despite adequate anticoagulation therapy.

Surgical Care

Surgical therapy for mitral stenosis consists of mitral valvotomy (which can be either surgical or percutaneous) or mitral valve replacement. The surgical mitral valvotomy approach can be through an open or closed technique; however, currently, the latter is rarely used and has been replaced by the percutaneous balloon technique.

Asymptomatic patients with moderate or severe mitral stenosis (mitral valve area <1.5 cm²) with a suitable valve should be considered for percutaneous balloon valvuloplasty if the pulmonary pressure is 50 mm Hg or above at rest or 60 mm Hg or above with exercise, or pulmonary capillary wedge pressure is 25 mm Hg or above with exercise.

Symptomatic patients with moderate or severe mitral stenosis (mitral valve area <1.5 cm²) who have suitable valves are also candidates for percutaneous balloon valvuloplasty.

If percutaneous balloon valvuloplasty is not an option, patients should be referred for surgical repair or mitral valve replacement when they develop class III or IV symptoms.

• Percutaneous balloon valvuloplasty 
• • Percutaneous balloon valvuloplasty is the procedure of choice for patients with uncomplicated mitral stenosis. Patients with pliable, mobile, relatively thin, minimally calcified mitral leaflets with minimal or no subvalvular stenosis are good candidates for this procedure. A TEE should be performed prior to valvotomy to clearly define the valve anatomy and exclude the presence of a left atrial thrombus, which is a contraindication to this procedure.
  • The echocardiographic scoring system has been used as a valuable tool for patient selection. Leaflet mobility, valvular thickening, valvular calcification, and subvalvular disease are each scored from 0-4. A score of less than 8 is found to have a significantly better short- and long-term outcome. A score of greater than 8 is associated with less impressive results.   
  • In the percutaneous balloon valvuloplasty, a catheter is directed into the left atrium after transseptal puncture, and a balloon is directed across the valve and inflated in the orifice. This results in separation of the mitral leaflets. The valve size is increased to approximately 2 cm².
  • Improvement in symptoms is dramatic immediately following the procedure. When only a little symptomatic improvement occurs after valvuloplasty, the valvuloplasty was likely ineffective or mitral regurgitation present.
  • The short- and long-term prognoses are good compared with surgical valvotomy. Nearly half of all patients who undergo valvotomy require reoperation within 10 years.
  • Balloon valvuloplasty offers certain distinct advantages to surgical valvotomy, which include avoidance of thoracotomy and general anesthesia.
  • The major contraindications to balloon valvuloplasty are the presence of thrombus in the left atrium or its appendage and mitral regurgitation that is more severe than grade 2.
  • Complications of a balloon mitral valvuloplasty include embolization, mitral regurgitation, ventricular rupture, residual atrial septal defect, stroke, and death. 
• Surgical valvotomy 
• • Open surgical commissurotomy allows direct visualization of the mitral valve that must be repaired or replaced. 
  • Using current techniques, even severe regurgitant or stenotic valves can often be repaired, with good long-term results. Valves that are not suitable for repair can be replaced using either bioprosthetic or metallic prosthetic valves. 
  • With bioprosthetic valves, the patient does not require anticoagulation, as long as he or she remains in sinus rhythm; however, 20-40% of these valves fail within 10 years, secondary to structural deterioration. 
  • Mechanical valves are placed in young patients who do not have any contraindications for anticoagulation, and these valves are associated with good long-term durability. 
  • Patients who have chronic atrial fibrillation and who undergo mitral valve surgery can have simultaneous Cox Maze procedure or pulmonary vein ablation, which helps to maintain sinus rhythm in up to 80% of the cases during the postoperative period.

MEDICATION

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The goals of pharmacotherapy are to reduce morbidity and to prevent complications.

Drug Category: Antiarrhythmics

These agents alter the electrophysiologic mechanisms responsible for arrhythmia.

Drug Category: Calcium channel blockers

In specialized conducting and automatic cells in the heart, calcium is involved in the generation of the action potential. Calcium channel blockers inhibit movement of calcium ions across the cell membrane, depressing both impulse formation (automaticity) and conduction velocity.

Drug Category: Anticoagulants

These agents prevent recurrent or ongoing thromboembolic occlusion of the vertebrobasilar circulation.

Drug Category: Beta-adrenergic blockers

These agents inhibit chronotropic, inotropic, and vasodilatory responses to beta-adrenergic stimulation.

Drug Category: Antibiotics

Must cover all likely pathogens in the context of this clinical setting. Use as prophylaxis against streptococcal infections.

Drug Category: Diuretics

Diuretics are used for treatment of pulmonary congestion. Treatment may improve symptoms of venous congestion through elimination of retained fluid and preload reduction.

MULTIMEDIA

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Media file 1:  M-mode across the mitral valve showing a flat E-F slope resulting from elevated left atrial pressure throughout diastole due to a significant gradient across the mitral valve. Increased thickness and calcification of anterior leaflet of the mitral valve and decreased opening of the anterior and posterior leaflets in diastole are also shown.
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Media file 2:  Parasternal long-axis view demonstrating calcification and doming in diastole of the anterior valve leaflet and mild restriction in the opening of posterior mitral valve leaflet.
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Media file 3:  Apical 4-chamber view demonstrating restricted opening of the anterior and posterior mitral valve leaflet with diastolic doming of anterior leaflet with left atrial enlargement.
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Media file 4:  Transesophageal echocardiogram with continuous wave Doppler interrogation across the mitral valve demonstrating an increased mean gradient of 16 mm Hg consistent with severe mitral stenosis.
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Media file 5:  Apical 4-chamber view with color Doppler demonstrating aliasing in the atrial side of the mitral valve consistent with increased gradient across the valve. This figure also shows mitral regurgitation and left atrial enlargement.
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Media file 6:  Magnified view of the mitral valve in apical 4-chamber view revealing restricted opening of both leaflets.
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Media file 7:  Transesophageal echocardiogram in an apical 3-chamber view showing calcification and doming of the anterior mitral leaflet and restricted opening of both leaflets.
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Media type:  Video

Media file 8:  Transesophageal echocardiogram in an apical 3-chamber view with color Doppler interrogation of the mitral valve revealing aliasing, which is consistent with increased gradient across the mitral valve secondary to stenosis. Also shown in this image, a posteriorly directed jet of severe mitral regurgitation.
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Media type:  Video

REFERENCES

Section 9 of 9

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
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• Medication
• Multimedia
• References

• Bonow RO, Carabello BA, Kanu C, et al. ACC/AHA 2006 guidelines for the management of patients with valvular heart disease: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines. Circulation. Aug 1 2006;114(5):e84-231.
• Bonow RO, Braunwald E. Valvular heart. In: Braunwald's Heart Disease: A Textbook of Cardiovascular Medicine. 7^th ed. Philadelphia, Pa: WB Saunders; 2005:1553-1602.
• Bruce CJ, Nishimura RA. Newer advances in the diagnosis and treatment of mitral stenosis. Curr Probl Cardiol. Mar 1998;23(3):125-92. [Medline].
• Carabello BA. Modern management of mitral stenosis. Circulation. Jul 19 2005;112(3):432-7. [Medline].
• Feldman T. Rheumatic Mitral Stenosis. Curr Treat Options Cardiovasc Med. Apr 2000;2(2):93-104. [Medline].
• Horstkotte D, Niehues R, Strauer BE. Pathomorphological aspects, aetiology and natural history of acquired mitral valve stenosis. Eur Heart J. Jul 1991;12 Suppl B:55-60. [Medline].
• Marcus RH, Sareli P, Pocock WA, et al. The spectrum of severe rheumatic mitral valve disease in a developing country. Correlations among clinical presentation, surgical pathologic findings, and hemodynamic sequelae. Ann Intern Med. Feb 1 1994;120(3):177-83. [Medline].

Article Last Updated: Jun 27, 2007