Mitral Stenosis: An Evidence-Based Approach

Background

Mitral stenosis (MS) is a narrowing of the mitral valve orifice that impedes blood flow from the left atrium to the left ventricle during diastole. This obstruction results in increased left atrial pressure, pulmonary venous congestion, and ultimately right heart strain. Over time, it can lead to atrial fibrillation, thromboembolic events, pulmonary hypertension, and right-sided heart failure.

Classification / Types

By Etiology:

• Rheumatic Mitral Stenosis: most common; characterized by leaflet thickening, commissural fusion, and chordal shortening.
• Congenital Mitral Stenosis: rare; includes parachute mitral valve or supravalvular mitral ring.
• Degenerative / Calcific MS: seen in the elderly; primarily involves annular calcification.
• Radiation-induced MS: occurs years after chest radiation.

By Severity (based on mitral valve area on echo):

• Mild: >1.5 cm²
• Moderate: 1.0–1.5 cm²
• Severe: <1.0 cm²

Epidemiology

• Sex: more common in females (2:1 ratio).
• Age: rheumatic MS typically manifests decades after initial infection (30–50 years old).
• Region: high prevalence in developing countries due to untreated streptococcal infections.
• Socioeconomic status: higher in lower-income populations with limited healthcare access and rheumatic fever prevention.

Pathophysiology

Restricted mitral leaflet opening raises left atrial pressure to maintain diastolic filling. The elevated LA pressure propagates backward into the pulmonary venous circulation, producing dyspnea, orthopnea, and — in advanced disease — pulmonary hypertension, right ventricular strain, and right-sided heart failure. LA dilation predisposes to atrial fibrillation and thromboembolism.

Etiology

Causes

• Rheumatic heart disease (most common globally)
• Congenital valve malformations
• Mitral annular calcification (elderly)
• Infective endocarditis with fibrosis
• Chest radiation therapy (late complication)
• Rarely: systemic diseases (e.g., lupus, carcinoid syndrome)

Risk Factors

• History of rheumatic fever
• Recurrent streptococcal pharyngitis
• Untreated bacterial infections in childhood
• Female sex
• Living in endemic regions
• History of chest irradiation

Clinical Presentation

History (Symptoms)

• Progressive exertional dyspnea
• Orthopnea and paroxysmal nocturnal dyspnea (PND)
• Hemoptysis (pulmonary venous hypertension or rupture)
• Fatigue and decreased exercise tolerance
• Palpitations (often from atrial fibrillation)
• Thromboembolic events (e.g., stroke)
• In pregnancy: marked worsening due to increased blood volume

Physical Exam (Signs)

Vital Signs:

• Irregularly irregular pulse (atrial fibrillation)
• Possible signs of low cardiac output in advanced stages

Cardiac Exam:

• Opening snap after S2, best heard at the apex
• Low-pitched diastolic rumbling murmur best at apex with bell, left lateral decubitus position
• Loud S1 (if valve is still pliable)
• Signs of pulmonary hypertension (loud P2, right ventricular heave)

Pulmonary:

• Crackles (pulmonary edema)
• Wheezing ("cardiac asthma")

Peripheral:

• Peripheral edema (late finding)
• Elevated jugular venous pressure (with right heart failure)
• Ascites (advanced cases)

Differential Diagnosis

• Pulmonary hypertension (primary or secondary)
• Mitral regurgitation
• Atrial myxoma
• Constrictive pericarditis
• Heart failure with preserved ejection fraction (HFpEF)
• Tricuspid stenosis
• COPD / asthma
• Pulmonary embolism

Diagnostic Testing

Initial Tests

• Echocardiography (TTE): valve area estimation; mean gradient >5 mmHg suggests significant MS; LA enlargement and pulmonary pressures; presence of thrombus (TEE).
• Electrocardiogram (ECG): atrial fibrillation, left atrial enlargement (P mitrale).
• Chest X-ray: left atrial enlargement (straightened left heart border), pulmonary venous congestion, Kerley B lines.
• BNP / NT-proBNP: may be elevated with heart failure symptoms.
• Cardiac MRI / CT: when echo is inconclusive or for surgical planning.
• Cardiac catheterization: measures pulmonary artery pressure, confirms severity; required pre-op to assess coronary anatomy if surgery is planned.

Treatment

Medical Management

Symptom relief:

• Diuretics for pulmonary congestion
• Beta-blockers or nondihydropyridine calcium channel blockers for heart rate control
• Digoxin in atrial fibrillation

Anticoagulation:

• All patients with MS and atrial fibrillation (warfarin preferred)
• Consider in large left atrium (>55 mm) or left atrial thrombus

Infective endocarditis prophylaxis: not routinely recommended unless prior endocarditis or prosthetic valves.

Interventional / Surgical

• Percutaneous Mitral Balloon Valvotomy (PMBV): first-line for symptomatic severe rheumatic MS with favorable valve morphology (Wilkins score ≤8); contraindicated with left atrial thrombus or moderate/severe MR.
• Mitral Valve Replacement (MVR): non-pliable valves, coexisting MR, or when PMBV is contraindicated.
• Surgical Repair (rare): feasible in select congenital cases.

Consults

• Cardiology: all moderate to severe cases
• Interventional Cardiology: for PMBV consideration
• Cardiothoracic Surgery: for MVR
• Infectious Disease: if endocarditis is suspected
• Obstetrics (high-risk): pregnant patients with MS
• Neurology: if stroke or TIA from embolism

Patient Education, Screening, Vaccines

• Emphasize medication adherence
• Teach signs of worsening heart failure or atrial fibrillation
• Daily weight monitoring for fluid retention
• Avoid exertion in severe cases until evaluated
• Dental hygiene to prevent endocarditis
• Vaccines: annual influenza, pneumococcal, and COVID-19

Follow-Up

• Regular echocardiograms (every 1–2 years if moderate/severe)
• Monitor for development of atrial fibrillation and thromboembolic complications
• Optimize rate control and anticoagulation
• Reassess candidacy for intervention if symptoms progress
• Monitor functional status and quality of life

Published in HMD MedDigest — Substance Over Noise. Written for working physicians, by working physicians.