Mitral Stenosis

Mitral stenosis is obstruction to left ventricular inflow at the mitral valve, most often rheumatic in origin.

Rheumatic fever causes commissural fusion, leaflet thickening and chordal shortening; latency 20 to 40 years after the acute episode. Women account for 70%.

Other causes: calcific mitral annular disease in the elderly, radiation, congenital, lupus, carcinoid, rheumatoid disease.

Severity: valve area 1.5 cm2 or less is significant; severe 1.0 cm2 or less; mean gradient over 10 mmHg at heart rate 60 to 80 beats per minute; pulmonary pressure over 50 mmHg.

Complications: atrial fibrillation (30 to 40%), left atrial thrombus and stroke, pulmonary hypertension, haemoptysis, right heart failure, endocarditis.

• Exertional dyspnoea, fatigue, orthopnoea, palpitations, haemoptysis, hoarseness (Ortner syndrome), embolic events.
• Symptoms are triggered by tachycardia, pregnancy, fever and atrial fibrillation.
• Loud S1, opening snap, low pitched mid diastolic rumbling murmur at the apex with presystolic accentuation (absent in atrial fibrillation), malar flush, tapping apex, right ventricular heave, loud P2.

• Echocardiography: doming of anterior leaflet, restricted posterior leaflet, valve area by planimetry or pressure half time (220/PHT), mean gradient, Wilkins score (suitability for balloon valvotomy: 8 or less favourable), left atrial thrombus (TOE), pulmonary pressure.
• ECG: P mitrale, atrial fibrillation, right ventricular hypertrophy.
• Chest radiograph: straightening of left heart border, double right heart border, Kerley B lines.
• Exercise or dobutamine echo in discordant symptoms and severity.
• Cardiac catheterisation seldom needed.

Medical

• Heart rate control to lengthen diastole: bisoprolol 2.5 to 10 mg, metoprolol, verapamil 40 to 120 mg three times daily, ivabradine in sinus rhythm; digoxin if atrial fibrillation.
• Diuretics (furosemide 20 to 80 mg) for congestion.
• Anticoagulation with warfarin (INR 2 to 3) for atrial fibrillation, left atrial thrombus, prior embolism; DOACs are not recommended in moderate to severe rheumatic mitral stenosis (INVICTUS trial showed warfarin superior).
• Rhythm control (cardioversion after 3 weeks of anticoagulation or TOE).
• Secondary rheumatic fever prophylaxis: benzathine penicillin G 1.2 million units IM every 3 to 4 weeks.

Intervention (symptomatic with area 1.5 cm2 or less, or asymptomatic with high embolic risk or pulmonary hypertension)

• Percutaneous mitral balloon commissurotomy (first choice for suitable anatomy: Wilkins 8 or less, no more than mild regurgitation, no left atrial thrombus): valve area typically doubles; restenosis 20 to 40% at 10 years.
• Surgical commissurotomy or mitral valve replacement for unsuitable anatomy, calcification, significant regurgitation. Mechanical prosthesis needs warfarin (INR 3.0 target).
• Pregnancy: beta blocker, diuretics; balloon valvotomy for refractory symptoms in the second trimester; delivery by vaginal route with epidural.
• Endocarditis prophylaxis for prosthetic valves. Echo surveillance every 1 to 3 years.