Rheumatic Mitral Stenosis

Obstruction of left ventricular inflow from rheumatic fusion of the mitral commissures, thickening of the leaflets, and fusion and shortening of the chordae, often with calcification later.

• It is the commonest form of mitral stenosis worldwide and nearly all of it in low income regions. Women are affected about 2 to 3 times as often as men. The latent period after acute rheumatic fever is 10 to 20 years or more; in endemic areas juvenile mitral stenosis presents in children and adolescents.
• Normal valve area is 4 to 6 cm2. Severe (clinically significant) stenosis is an area of 1.5 cm2 or less; very severe is 1.0 cm2 or less.
• Mechanism: the valve gradient rises with tachycardia and exercise (shorter diastole), raising left atrial and pulmonary venous pressure, causing pulmonary oedema, then pulmonary arterial hypertension and right ventricular failure. A dilated left atrium causes atrial fibrillation and left atrial appendage thrombus.
• Untreated, 10-year survival is about 80% in asymptomatic patients and about 0 to 15% with severe pulmonary hypertension. Causes of death: heart failure (60 to 70%), embolism (20 to 30%) and infection (about 10%).

• Exertional dyspnoea, orthopnoea, paroxysmal nocturnal dyspnoea, fatigue, palpitations, haemoptysis (pulmonary vein rupture, bronchitis, pulmonary oedema), hoarseness (left recurrent laryngeal nerve compression by the left atrium), dysphagia, embolic stroke, and chest pain. Symptoms are triggered by atrial fibrillation, pregnancy, fever, anaemia and thyrotoxicosis.
• Signs: malar flush, irregularly irregular pulse in atrial fibrillation, tapping apex (palpable first sound), loud first sound, opening snap (a shorter interval between the second sound and the opening snap means more severe stenosis), low pitched mid-diastolic rumble at the apex in the left lateral position (with presystolic accentuation in sinus rhythm), loud pulmonary second sound, right ventricular heave, raised jugular venous pressure, Graham Steell murmur, tricuspid regurgitation, hepatomegaly.
• Differential diagnosis: left atrial myxoma, cor triatriatum, mitral annular calcification with stenosis, congenital mitral stenosis (parachute valve), obstructing thrombus, vegetation, Austin Flint murmur of aortic regurgitation, tricuspid stenosis, and hypertrophic cardiomyopathy.
• Complications: atrial fibrillation (30 to 40%), thromboembolism (stroke in about 10 to 20% of those in atrial fibrillation), pulmonary oedema, pulmonary hypertension, right heart failure, infective endocarditis, haemoptysis, and obstetric complications.

• ECG: P mitrale, atrial fibrillation, right ventricular hypertrophy, right axis deviation. Chest X-ray: straightened left heart border, double right heart border, enlarged left atrium, pulmonary congestion with Kerley B lines, prominent pulmonary arteries.
• Transthoracic echocardiography: diastolic doming (hockey stick) of the anterior leaflet, thick leaflets, fused commissures, restricted posterior leaflet, valve area by planimetry (the reference measure) and by pressure half time (area equals 220 divided by the half time in ms), mean gradient (severity judged at heart rate 60 to 80; a mean gradient of 10 mmHg or more is usually severe), pulmonary systolic pressure (greater than 50 mmHg at rest or greater than 60 mmHg on exercise is significant), left atrial size, and associated mitral, aortic and tricuspid disease.
• Valve score for balloon suitability: leaflet mobility, thickening, calcification and subvalvular thickening, each graded 1 to 4 (total 16); a total of 8 or less predicts a good result from balloon commissurotomy.
• Transoesophageal echocardiography before balloon commissurotomy or cardioversion to exclude left atrial appendage thrombus. Exercise echocardiography when symptoms and resting findings disagree (exercise gradient greater than 15 mmHg or pulmonary systolic pressure greater than 60 mmHg is significant).
• Coronary angiography before surgery in men over 40, women over 50, or those with risk factors. Blood tests: full blood count, thyroid function, INR when anticoagulated.

• Medical therapy relieves symptoms but does not relieve the obstruction.
• Heart rate control to lengthen diastole (target resting rate 60 to 80 beats/min):
  • Bisoprolol 1.25 to 10 mg daily or metoprolol 25 to 100 mg twice daily.
  • Diltiazem 60 to 120 mg three times daily or verapamil 40 to 120 mg three times daily if beta blockers are not tolerated.
  • Digoxin 0.125 to 0.25 mg daily in atrial fibrillation, as an adjunct.
• Congestion:
  • Furosemide 20 to 80 mg daily, with spironolactone 25 mg daily; salt restriction; avoid strenuous exertion.
• Anticoagulation:
  • Warfarin to INR 2.0 to 3.0 for atrial fibrillation (paroxysmal, persistent or permanent), previous embolism, or left atrial thrombus. Direct oral anticoagulants are not advised in rheumatic mitral stenosis with atrial fibrillation.
  • Consider warfarin for a left atrial diameter greater than 50 mm or dense spontaneous echo contrast in sinus rhythm.
• Rhythm control: electrical cardioversion (100 to 200 J biphasic synchronised) after transoesophageal exclusion of thrombus or 3 weeks of therapeutic anticoagulation, for recent onset atrial fibrillation (less than 1 year) with left atrium less than 50 mm, preferably after relief of the obstruction; amiodarone 200 mg daily after a loading period to maintain sinus rhythm.
• Secondary prophylaxis (to prevent further rheumatic damage): benzathine benzylpenicillin 1.2 million units IM every 3 to 4 weeks (600,000 units if under 30 kg), or penicillin V 250 mg orally twice daily; sulfadiazine 1 g daily or erythromycin 250 mg twice daily for penicillin allergy. Continue for 10 years after the last attack or to age 40, whichever is longer, and often for life in persistent valve disease.
• Interventions for symptomatic patients with valve area 1.5 cm2 or less:
  • Percutaneous balloon mitral commissurotomy is the first choice when the valve is pliable (valve score 8 or less), without left atrial thrombus, with no more than mild regurgitation and no severe commissural calcification. Success (area greater than 1.5 cm2 without worse than moderate regurgitation) is 80 to 95%. Complications: severe regurgitation needing surgery (2 to 10%), tamponade (1 to 2%), embolism (1 to 2%), mortality less than 1 to 2%. Re-stenosis occurs in about 20 to 40% by 10 years; about 60 to 70% of favourable patients remain event free at 10 years.
  • Asymptomatic patients with area 1.5 cm2 or less and suitable anatomy should also be offered balloon commissurotomy when pulmonary systolic pressure is greater than 50 mmHg, atrial fibrillation is new, there was a prior embolism, or major non-cardiac surgery or pregnancy is planned.
  • Surgery: open commissurotomy where balloon therapy is unavailable, or valve replacement when the valve is unsuitable (calcified, rigid, valve score greater than 8, significant regurgitation, left atrial thrombus that persists after 3 months of warfarin, or other valve disease needing surgery). Operative mortality about 3 to 8%. Mechanical valve: warfarin to INR 3.0 (range 2.5 to 3.5); bioprosthesis for patients over 65 or those unable to take warfarin. Repair tricuspid regurgitation with an annulus greater than 40 mm, and ablate or exclude the left atrial appendage when atrial fibrillation is present.
• Acute decompensation:
  • Pulmonary oedema: sit upright, oxygen, furosemide 40 mg IV, and slow the heart rate.
  • Rapid atrial fibrillation: metoprolol 2.5 to 5 mg IV, or digoxin 0.5 mg IV loading dose (then 0.25 mg every 6 hours to a total of 1 to 1.5 mg), and synchronised cardioversion if unstable.
• Infective endocarditis prophylaxis only after valve replacement or previous endocarditis: amoxicillin 2 g orally (50 mg/kg in children) 30 to 60 minutes before dental procedures; azithromycin or clarithromycin 500 mg (15 mg/kg in children) if allergic to penicillin (clindamycin is no longer recommended).
• Special groups:
  • Pregnancy: high risk when the area is less than 1.5 cm2, with pulmonary oedema in the second and third trimesters (maternal mortality 1 to 3% in severe disease). Metoprolol 25 to 100 mg twice daily, furosemide for congestion, avoid atenolol. Balloon commissurotomy before conception when the area is 1.5 cm2 or less, or during pregnancy (with abdominal shielding) for symptoms refractory to drugs. Anticoagulate atrial fibrillation or left atrial thrombus with enoxaparin 1 mg/kg SC twice daily (anti-Xa peak 0.8 to 1.2 IU/mL).
  • Children and adolescents: juvenile mitral stenosis; early balloon commissurotomy and strict secondary prophylaxis.
  • Elderly: calcified valves reduce balloon success; consider surgery or repeat intervention carefully.
• Red flags: acute pulmonary oedema, rapid atrial fibrillation, stroke, haemoptysis, fever, syncope, missed penicillin injections.
• Follow up: mild stenosis every 3 to 5 years with echocardiography, moderate every 1 to 2 years, severe or symptomatic yearly; after balloon commissurotomy at 1 month, 6 months, then yearly; INR every 4 weeks on warfarin.