Mitral Stenosis

Chapter: Mitral Stenosis
McMaster Section Editor(s): P.J. Devereaux
Section Editor(s) in Interna Szczeklika: Andrzej Budaj, Wiktoria Leśniak
McMaster Author(s): Hisham Dokainish
Author(s) in Interna Szczeklika: Marek Konka, Piotr Hoffman
Additional Information

Definition, Etiology, Pathogenesis Top

Mitral stenosis (MS) is a reduction of the mitral valve orifice area causing obstruction of blood flow from the left atrium to the left ventricle (LV). Classification based on etiology:

1) Structural MS: Limited mobility of the leaflets and chordae tendineae due to organic lesions. Etiology: rheumatic (most frequently, especially if more than mild), degenerative (due to severe mitral annular calcification, increasingly common in aging populations), infective endocarditis; rarely, systemic lupus erythematosus, rheumatoid arthritis, carcinoid syndrome, or storage diseases.

2) Functional MS: Inhibited opening of structurally normal valve leaflets. Etiology: aortic regurgitation, left atrial thrombus, tumor (usually left atrial myxoma).

Clinical Features and Natural History Top

1. Symptoms: Impaired exercise tolerance, fatigue, exertional dyspnea, sometimes cough with expectoration of frothy sputum, hemoptysis, recurrent respiratory tract infections, palpitations, right upper abdominal quadrant discomfort, rarely hoarseness (due to compression of the left recurrent laryngeal nerve by an enlarged left atrium—Ortner syndrome), chest pain (in 15% of patients, due to high right ventricular pressures or coexisting coronary artery disease).

2. Signs: An accentuated first heart sound, opening snap of the mitral valve, a low-pitched decrescendo diastolic rumble with presystolic accentuation (the rumble can occur in patients with preserved sinus rhythm). A Graham Steell murmur caused by pulmonary regurgitation in patients with severe pulmonary hypertension and dilation of the main pulmonary artery. In advanced MS, pinkish-purple patches on the cheeks, peripheral cyanosis, systolic pulsation in the epigastrium, displacement of the apical impulse to the left, symptoms of right ventricular failure (see Chronic Heart Failure).

3. Natural history: The severity of MS gradually increases. The first symptoms usually develop approximately 15 to 20 years after an episode of rheumatic fever. The usual presenting symptoms are exertional dyspnea; supraventricular arrhythmias (particularly atrial fibrillation [AF]; the risk increases with age and with progressive left atrial enlargement); and thromboembolic events (up to 6/100 patients/y; risk factors: age, AF, small mitral valve orifice area, spontaneous left atrial contrast on echocardiography).

Diagnosis Top

Diagnosis is based on typical clinical features and echocardiography results.

Diagnostic Tests

1. Electrocardiography (ECG): Features of left atrial enlargement, often P mitrale (see Standard Electrocardiogram), frequently atrial arrhythmias, particularly AF. In patients with pulmonary hypertension, right axis deviation, incomplete right bundle branch block (less frequently other features of right ventricular hypertrophy and overload), P mitrale that may evolve into P cardiale or P pulmonale.

2. Chest radiographs: Left atrial enlargement, dilation of the upper lobe pulmonary veins, dilation of the main pulmonary artery, pulmonary alveolar edema, pulmonary interstitial edema, right ventricular enlargement, calcifications of the mitral valve (rare).

3. Echocardiography is used to evaluate the anatomic features of the valve (heavily calcified valves are generally not amenable to percutaneous procedures; this is important for the percutaneous vs surgical approach), detect left atrial thrombi (transesophageal echocardiography is useful as most thrombi occur in the left atrial appendage, which is not well-visualized on transthoracic echocardiography), measure the mean transvalvular gradient, calculate the mitral valve area (MVA), estimate the pulmonary artery pressure, and classify the severity of MS (Table. Classification of mitral stenosis).

4. An exercise stress test is used to assess exercise tolerance and the increase in pulmonary artery pressures (especially important for management of patients with moderate MS at rest and exertional symptoms).

5. Cardiac catheterization and coronary angiography are used in cases that are equivocal by clinical and echocardiographic criteria to confirm the severity of MS and to measure pulmonary artery pressures. Coronary angiography is recommended in patients >40 years of age who are undergoing intervention for MS (see below), or in younger patients with LV dysfunction or suspected coronary artery disease.

Treatment Top

General Considerations

1. Mild asymptomatic MS: Pharmacologic treatment.

2. Moderate or severe MS: Management depends primarily on the presence of symptoms and the anatomy of the valve. Specialist referral is usually required; however, in general, the following factors increase the potential benefits of invasive therapy: severe MS; presence of symptoms; and favorable valve morphology (to consider percutaneous options). More details: below.

Invasive Treatment

1. Percutaneous mitral commissurotomy (PMC), also referred to as percutaneous balloon mitral valvuloplasty (PBMV): Separation or tearing apart of the fused commissures with a balloon inserted via the atrial septum using a catheter. Owing to high efficacy and low risk of complications (death, cardiac tamponade, peripheral embolism), it is the first therapeutic choice for appropriate MS cases.Evidence 1Strong recommendation (benefits clearly outweigh downsides; right action for all or almost all patients). Moderate Quality of Evidence (moderate confidence that we know true effects of intervention). Quality of Evidence lowered due to a limited number of patients enrolled in studies (imprecision). Ben Farhat M, Ayari M, Maatouk F, et al. Percutaneous balloon versus surgical closed and open mitral commissurotomy: seven-year follow-up results of a randomized trial. Circulation. 1998 Jan 27;97(3):245-50. PubMed PMID: 9462525.

Indications: Patients with severe MS (MVA <1.5 cm2), symptoms attributable to MS (or asymptomatic patients with new-onset AF), mild or mild to moderate mitral regurgitation, and valve anatomy amenable to PMC (generally, the less calcified and mobile valves are amenable to PMC, whereas heavily calcified, immobile valves require surgical treatment).

ContraindicationsMVA >1.5 cm2; left atrial thrombus; concomitant moderate or greater mitral regurgitation; nonrheumatic etiology of MS; poorly mobile valves; severe leaflet or bicommissural calcification; absence of commissural fusion; severe concomitant aortic valve disease, or severe combined tricuspid stenosis and regurgitation; concomitant coronary artery disease requiring bypass surgery.

2. Surgical valve repair:

1) Open (direct vision) mitral commissurotomy using cardiopulmonary bypass.

2) Closed mitral commissurotomy using a transatrial approach (this is rarely if ever used).

3. Mitral valve replacement (MVR) is indicated in patients with New York Heart Association class III/IV heart failure and severe abnormalities of the valvular apparatus when balloon and surgical commissurotomy are not possible. MVR is associated with higher hospital and long-term mortality rates as well as more frequent complications than PMC (this may be confounded by patient selection, ie, candidates not amenable to PMC [higher risk, with more severe valvular calcification] are referred for surgery). In patients with mechanical valves, lifetime oral anticoagulant treatment is necessary (target international normalized ratio [INR] values: Table. Antithrombotic treatment in patients with…).

Medical Treatment

1. Patients not eligible for or refusing consent to invasive treatment: Diuretics (in the case of symptoms of pulmonary congestion), beta-blockers +/- digoxin (particularly in the case of AF with a fast ventricular rhythm), and angiotensin-converting enzyme inhibitors (in the case of coexisting LV dysfunction).

2. Anticoagulant treatment (INR 2.0-3.0): In patients with AF, after embolic events, or with a documented left atrial thrombus, anticoagulation is definitely indicated. In patients with an enlarged left atrium (>55 mm), spontaneous left atrial contrast on echocardiography, and/or coexisting systolic LV failure, anticoagulation may be considered but is not supported by evidence. There is no current evidence supporting novel oral anticoagulants for patients with MS and indication for anticoagulation.

3. Electrical cardioversion: In patients with AF and hemodynamic instability. Electrical cardioversion may be considered in the case of the first AF occurrence in patients with mild to moderate MS, and after successful invasive treatment of MS in patients with a short episode of AF and minor left atrial enlargement. If medical therapy fails and AF is producing heart failure, clinical instability, or both, electrical cardioversion can be considered in patients with MS who are therapeutically anticoagulated; transesophageal echocardiography may also be helpful in such patients to exclude left atrial and left atrial appendage thrombi prior to cardioversion, particularly those with severe MS and marked left atrial enlargement. Pharmacologic cardioversion (usually with amiodarone) is generally less effective than electrical.

4. Prevention of infective endocarditis and of recurrent rheumatic fever.

Follow-Up Top

The frequency of follow-up visits in patients receiving noninvasive treatment depends on the severity of MS. Patients with mild asymptomatic MS: follow-up visits every 2 to 3 years. Asymptomatic patients with significant MS and patients after successful PMC: clinical and echocardiographic examination every year; in symptomatic patients, every 6 months.

Prognosis Top

In asymptomatic patients, the 10-year survival rates are >80% and 20-year survival rates are ~40%. The prognosis is affected by the onset of even minor symptoms and significantly improved by PMC or MVR in patients with severe MS, symptoms attributable to MS, or both. The causes of death are heart failure and thromboembolic events.

TablesTop

Table. Classification of mitral stenosis

Stenosis

 

Mild

Moderate

Severe

Mean MVG (mm Hg)

<5

5-10

>10

PASP (mm Hg)

<30

30-50

>50

MVA (cm2)

>2.0

1.5-2.0

<1.5 (<1.0: very severe)

Based on: Nishimura RA, Otto CM, Bonow RO, et al; ACC/AHA Task Force Members. 2014 AHA/ACC Guideline 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. 2014 Jun 10;129(23):e521-643.

MVA, mitral valve area; MVG, mitral valve gradient; PASP, pulmonary artery systolic pressure.

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