Cardiology · Valvular Heart Disease
The facts most likely to be tested
The most common etiology of mitral stenosis is rheumatic heart disease, typically presenting years after an episode of Group A Streptococcus pharyngitis.
The classic auscultatory finding is a mid-diastolic rumble heard best at the cardiac apex with the patient in the left lateral decubitus position.
An opening snap following the second heart sound (S2) is a hallmark finding that occurs due to the abrupt tensing of the stenotic mitral valve leaflets.
The interval between S2 and the opening snap is inversely proportional to the severity of the stenosis, with a shorter interval indicating more severe disease.
Chronic mitral stenosis leads to left atrial enlargement, which increases the risk of atrial fibrillation and thromboembolic stroke.
Patients with mitral stenosis often present with dyspnea on exertion, orthopnea, and paroxysmal nocturnal dyspnea due to elevated left atrial pressure causing pulmonary venous hypertension.
Percutaneous mitral balloon commissurotomy is the treatment of choice for symptomatic patients with favorable valve morphology and no significant mitral regurgitation.
Vignette unlocked
A 34-year-old woman presents to the clinic with a 3-month history of progressive dyspnea on exertion and occasional palpitations. She emigrated from a developing country as a child and reports a history of recurrent sore throats during her youth. On physical examination, a low-pitched mid-diastolic rumble is heard at the cardiac apex. An opening snap is audible shortly after S2. An ECG reveals atrial fibrillation with a controlled ventricular rate.
What is the most likely underlying pathophysiology of this patient's condition?
Rheumatic mitral valve stenosis
The patient's history of recurrent childhood infections and classic physical exam findings (mid-diastolic rumble and opening snap) are pathognomonic for rheumatic mitral stenosis, which is the most common cause of this valvular lesion.
Full handout
High yield triage
Etiology / Epidemiology
Predominantly caused by rheumatic heart disease in developing nations. Affects females more than males.
Clinical Manifestations
Classic opening snap followed by a diastolic rumble at the apex. Symptoms include dyspnea and hemoptysis.
Diagnosis
The transthoracic echocardiogram is the gold standard. Mitral valve area < 1.5 cm² indicates severe disease.
Treatment
Manage symptoms with diuretics and beta-blockers. Avoid vasodilators in severe stenosis.
Prognosis
High risk of atrial fibrillation and thromboembolism. Requires lifelong monitoring.
Full handout
Epidemiology & Etiology
The most common cause remains rheumatic heart disease, often presenting decades after the initial infection. Non-rheumatic causes include calcification of the mitral annulus in the elderly or congenital defects. It is significantly more common in women.
Pertinent Anatomy
The mitral valve apparatus includes the leaflets, chordae tendineae, and papillary muscles. Stenosis restricts blood flow from the left atrium to the left ventricle during diastole.
Pathophysiology
Obstruction leads to increased left atrial pressure, causing left atrial dilation and pulmonary venous hypertension. Chronic elevation of pulmonary pressures results in pulmonary hypertension and eventual right-sided heart failure. The fixed cardiac output leads to exertional symptoms.
Clinical Manifestations
Patients present with exertional dyspnea, orthopnea, and hemoptysis due to bronchial vein rupture. Physical exam reveals an opening snap and a low-pitched diastolic rumble. Atrial fibrillation is a common complication due to atrial stretch, which can lead to systemic embolization.
Diagnosis
The transthoracic echocardiogram is the diagnostic test of choice to assess valve morphology and gradients. A mitral valve area < 1.5 cm² is considered severe. Transesophageal echocardiogram is superior for detecting left atrial thrombi.
Treatment
Symptomatic patients receive diuretics for congestion and beta-blockers or calcium channel blockers to slow heart rate and increase diastolic filling time. Avoid vasodilators like nitrates or hydralazine as they reduce preload. Percutaneous mitral balloon valvuloplasty is the treatment of choice for symptomatic patients with favorable anatomy.
Prognosis
Major complications include atrial fibrillation and systemic embolization, necessitating long-term anticoagulation if AFib is present. Patients with severe disease require serial echocardiography to monitor progression and timing for surgical intervention.
Differential Diagnosis
Left atrial myxoma: positional symptoms and tumor plop
Mitral regurgitation: holosystolic murmur at the apex
Tricuspid stenosis: diastolic rumble heard at the left sternal border
Atrial septal defect: fixed split S2
Pulmonary hypertension: loud P2 and right ventricular heave