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Mitral stenosis

Mitral stenosis is a valvular heart disease characterized by the narrowing of the orifice of the mitral valve of the heart. It is almost always caused by rheumatic valvular heart disease. Mitral stenosis is almost always rheumatic in origin, although in older people it can be caused by heavy calcification of the mitral valve. There is also a rare form of congenital mitral stenosis.  Early diagnosis of mitral stenosis in pregnancy is very important as the heart cannot tolerate increased cardiac output demand as in the case of exercise and pregnancy. Atrial fibrillation is a common complication resulting from left atrial enlargement, which can lead to systemic thromboembolic complications like stroke.

In rheumatic mitral stenosis, the mitral valve orifice is slowly diminished by progressive fibrosis, calcification of the valve leaflets, and fusion of the cusps and subvalvular apparatus. The mitral valve orifice is normally about 5 cm2 in diastole but can be reduced to < 1 cm2 in severe mitral stenosis. The patient is usually asymptomatic until the orifice is < 2 cm2. As stenosis progresses, left ventricular filling becomes more dependent on left atrial contraction. There is dilatation and hypertrophy of the left atrium and left atrial pressure rises, leading to pulmonary venous congestion and breathlessness. Any increase in heart rate shortens diastole when the mitral valve is open and produces a further rise in left atrial pressure. Situations that demand an increase in cardiac output, such as pregnancy and exercise, also increase left atrial pressure and are poorly tolerated. Atrial fibrillation is very common due to progressive dilatation of the left atrium. Its onset often precipitates pulmonary edema because the accompanying tachycardia and loss of atrial contraction lead to marked hemodynamic deterioration and a rapid rise in left atrial pressure. In the absence of atrial fibrillation, a more gradual rise in left atrial pressure may occur. In the presence or absence of atrial fibrillation, pulmonary hypertension may occur, which can protect the patient from pulmonary edema. Pulmonary hypertension leads to right ventricular hypertrophy and dilatation, tricuspid regurgitation, and right heart failure. Symptoms most commonly begin in the fourth decade, but mitral stenosis often causes severe disability at earlier ages in developing nations. Principal symptoms are dyspnea and cough precipitated by exertion, excitement, fever, anemia, tachy­cardia, orthopnea, hemoptysis, Pink frothy sputum, and Fatigue.

Clinical features

Effort-related dyspnea is usually the dominant symptom and produces a gradual reduction in exercise tolerance over many years, culminating in dyspnea at rest. Acute pulmonary edema or pulmonary hypertension may cause hemoptysis. On examination, the patient is usually in atrial fibrillation and a malar flush may be apparent. All patients with mitral stenosis, and particularly those with atrial fibrillation, are at risk from left atrial thrombosis and systemic thromboembolism. The apex beat is characteristically tapping in nature. On auscultation there may be a loud first heart sound, an opening snap and a low-pitched mid-diastolic murmur. An elevated Jugular venous pulsation (JVP), loud pulmonary component of the second heart sound and features of tricuspid regurgitation all signify the presence of pulmonary hypertension.

Investigations                                                 

Electrocardiogram (ECG): may show bifid P waves due to left atrial hypertrophy, or atrial fibrillation.

Chest X-ray: may show an enlarged left atrium and features of pulmonary congestion.

Doppler echocardiography: provides the definitive evaluation of mitral stenosis, allowing estimation of valve area, the pressure gradient across the valve, and pulmonary artery pressure.

Management

Medical management consists of diuretics for pulmonary congestion, with anticoagulants and rate-limiting agents in the presence of atrial fibrillation. For persistent symptoms or pulmonary hypertension, balloon valvuloplasty is the treatment of choice, although valvotomy is an alternative. Valve replacement is indicated for severe reflux or rigid, calcified valves. The at-risk patient should receive prophylaxis for recurrent rheumatic fever (penicillin V 250–500 mg PO bid or benzathine penicillin G 1–2 M units intramuscular monthly). For dys­pnea, prescribe sodium restriction and oral diuretic therapy; beta-blockers, rate-limiting calcium channel antagonists (i.e., verapamil or diltiazem), or digoxin are used to slow ventricular rate in atrial fibrillation. Warfarin for patient with atrial fibrillation or history of thromboembolism (direct-acting oral anticoagulants [e.g., apixaban, rivaroxaban, dabigatran] are not approved for a patient with rheumatic mitral stenosis). For atrial fibrillation of recent onset, consider conversion (chemical or electri­cal) to sinus rhythm, ideally after ≥3 weeks of anticoagulation.     

Published : Apr 4 2022
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