Mitral stenosis

Definition

In mitral stenosis (MS) the mitral leaflets are thickened and immobile, and the orifice is narrowed by fusion of the commissures and by shortened, thickened and matted chordae tendineae. The normal mitral valve area (MVA) is 4–5 cm².

Classification

Severity grades and forms

• Moderate: MVA above 1.5 to 2.5 cm² or diastolic pressure half-time below 150 ms.
• Severe: MVA up to 1.5 cm² or pressure half-time of 150 ms or more; symptoms are usually present.
• By cause: rheumatic (commissural fusion) or degenerative due to mitral annular calcification extending into the leaflets.

Occurrence & epidemiology

The most common cause is rheumatic fever, which many patients do not recall. In regions with a high prevalence of rheumatic fever, patients often become symptomatic by the age of 30; in regions with a low prevalence, typically between 50 and 70 years. In older people mitral annular calcification is a prevalent cause. About 80 % of patients with rheumatic MS or annular calcification are women.

Aetiopathogenesis

• Rheumatic: commissural fusion; with late presentation additionally calcified, fibrotic leaflets and involvement of the subvalvular apparatus. The aortic or tricuspid valve may also be affected.
• Degenerative: mitral annular calcification that extends to the leaflets and stiffens them.
• Rare: congenital or radiogenic.
• Pathophysiology: left atrial size and pressure increase; pulmonary venous and capillary pressures rise, and secondary pulmonary hypertension with right heart failure, tricuspid and pulmonary regurgitation may develop. The enlarged atrium predisposes to atrial fibrillation and thromboembolism; a fast heart rate and loss of atrial contraction often cause sudden worsening of symptoms.

Clinical features

• Symptoms correlate poorly with severity; many patients are asymptomatic until pregnancy or atrial fibrillation occurs. Symptoms often appear only 15 or more years after rheumatic fever.
• First symptoms are usually signs of heart failure: exertional dyspnea, orthopnea, paroxysmal nocturnal dyspnea, fatigue.
• Atrial fibrillation with palpitations and pulmonary edema; an embolic event such as stroke may be the first manifestation.
• Less commonly hemoptysis and hoarseness due to pressure of the enlarged atrium or pulmonary artery on the left recurrent laryngeal nerve (Ortner syndrome).
• Mitral facies (plum-colored malar flush with peripheral cyanosis) when cardiac output is low and pulmonary hypertension severe.
• Auscultation: loud first heart sound; early diastolic opening snap that moves closer to the second heart sound as severity increases; low-pitched rumbling diastolic murmur at the apex, best heard with the bell in the left lateral position and in expiration; presystolic accentuation due to atrial contraction.

Diagnosis

• Echocardiography: two-dimensional imaging of the abnormal valve and subvalvular structures, calcification, degree of stenosis and atrial size; Doppler for transvalvular gradient and pulmonary artery pressure; color Doppler for associated MR.
• TOE: detection or exclusion of small thrombi in the left atrium and left atrial appendage.
• Stress echocardiography: behavior of gradient and pulmonary artery pressure on exercise.
• ECG: P mitrale (P wave longer than 0.12 s, broad negative terminal component in V1, broad notched P wave in II); right axis deviation and tall R waves in V1 with right ventricular hypertrophy.
• Chest X-ray: straightened left heart border due to the dilated left atrial appendage, widened carina, double contour at the right heart border, prominent pulmonary artery, Kerley B lines with interstitial edema.

Keep learning in the app

Further reading (open access)

1. MSD Manual Professional: Mitral Stenosis
2. StatPearls: Mitral Stenosis

Cross-references