Rheumatic Aortic Stenosis

Obstruction of left ventricular outflow at valve level from rheumatic fusion of the commissures, leaflet thickening and later calcification. It almost always coexists with mitral valve disease and often with regurgitation, and presents in the third to sixth decades, earlier than degenerative stenosis.

• Severity: severe is a mean gradient of 40 mmHg or more, peak velocity 4.0 m/s or more, valve area 1.0 cm2 or less (indexed 0.6 cm2/m2 or less); very severe is a peak velocity 5.0 m/s or more or mean gradient 60 mmHg or more.
• Mechanism: pressure overload causes concentric hypertrophy, diastolic dysfunction, subendocardial ischaemia and, later, systolic failure.
• Natural history: a long asymptomatic phase with a sudden death risk of less than 1% per year in asymptomatic patients. After symptoms, average survival is about 5 years with angina, 3 years with syncope and 2 years with heart failure.

• Exertional angina, exertional syncope or presyncope, exertional dyspnoea and heart failure. Occult gastrointestinal bleeding from angiodysplasia with acquired von Willebrand deficiency (Heyde syndrome).
• Signs: slow rising, low volume pulse, narrow pulse pressure, sustained apex beat, a harsh crescendo decrescendo ejection systolic murmur at the right upper sternal edge radiating to the carotids (peaking later with more severe stenosis), thrill, soft or single second heart sound, S4, paradoxical splitting of the second sound. Signs of mitral disease are common.
• Differential diagnosis: hypertrophic obstructive cardiomyopathy, subvalvular and supravalvular stenosis, bicuspid or degenerative stenosis, mitral regurgitation murmur radiating to the axilla, ventricular septal defect, pulmonary stenosis, and aortic sclerosis.
• Complications: heart failure, sudden death, syncope, atrial fibrillation, endocarditis, embolism, gastrointestinal bleeding, and recurrent rheumatic fever.

• ECG: left ventricular hypertrophy with strain, left atrial enlargement, conduction block. Chest X-ray: normal heart size, post-stenotic aortic dilatation, calcification.
• Echocardiography: thickened, fused, calcified leaflets with reduced opening; peak velocity, mean gradient, valve area by the continuity equation, indexed area, left ventricular wall thickness and ejection fraction, and associated mitral and tricuspid disease.
• Low flow, low gradient stenosis (area 1.0 cm2 or less with mean gradient less than 40 mmHg and ejection fraction less than 50%): dobutamine stress echocardiography at 5 to 20 micrograms/kg/min. A rise in stroke volume of 20% or more shows contractile reserve; if the area stays 1.0 cm2 or less with the gradient rising to 40 mmHg or more, stenosis is truly severe.
• Preserved ejection fraction with a small stroke volume index (less than 35 mL/m2): use CT calcium scoring (severe stenosis is likely at about 2000 arbitrary units or more in men and 1200 or more in women).
• Exercise testing in asymptomatic severe stenosis only (positive if symptoms, a fall in systolic pressure or ST depression of 2 mm or more); never in symptomatic patients.
• Natriuretic peptide (a level greater than 3 times normal predicts early symptoms). Coronary angiography before surgery in men over 40, women over 50 and those with risk factors.

• No drug slows valve disease; relief of obstruction is the treatment for symptoms.
• Medical care:
  • Avoid dehydration, strenuous exertion and potent vasodilators.
  • Hypertension: start low and go slowly with ramipril 1.25 to 2.5 mg daily or amlodipine 2.5 to 5 mg daily, titrated with blood pressure monitoring.
  • Heart failure while waiting for surgery: furosemide 20 to 40 mg daily, used cautiously because the ventricle is preload dependent.
  • Atrial fibrillation: bisoprolol 1.25 to 5 mg daily or digoxin 0.125 to 0.25 mg daily; warfarin to INR 2.0 to 3.0 (direct oral anticoagulants are not advised when there is rheumatic mitral stenosis).
  • Atorvastatin 20 to 40 mg daily when cardiovascular risk warrants it.
• Secondary prophylaxis against further rheumatic attacks:
  • 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. For penicillin allergy: sulfadiazine 1 g daily or erythromycin 250 mg twice daily.
  • Duration: 10 years after the last attack or to age 40, whichever is longer; lifelong in severe disease.
• Aortic valve replacement:
  • Symptomatic severe stenosis: replace promptly (within days to weeks; admit if heart failure, syncope or angina at rest).
  • Asymptomatic severe stenosis: replace if ejection fraction is less than 50%, an exercise test is abnormal, peak velocity is 5.0 m/s or more, velocity rises by 0.3 m/s or more per year, or natriuretic peptide is greater than 3 times normal.
  • Replace the valve when other cardiac surgery is planned and stenosis is moderate to severe.
  • Surgical replacement is preferred in rheumatic disease because fused commissures and coexisting mitral disease limit transcatheter options. Mechanical valve under age 50 if warfarin is acceptable (INR 2.5, range 2.0 to 3.0; INR 3.0, range 2.5 to 3.5 with atrial fibrillation, previous embolism, ejection fraction less than 35% or hypercoagulable state); bioprosthesis over age 65 or if anticoagulation is unsuitable (aspirin 75 to 100 mg daily, or warfarin to INR 2.5 for 3 months). Direct oral anticoagulants must not be used with mechanical valves.
  • Operative mortality about 2 to 5% for isolated replacement and higher when combined with mitral surgery.
  • Balloon valvuloplasty only as a bridge in unstable adults or to treat children and adolescents with pliable valves (peak gradient 50 mmHg or more, or symptoms).
• Endocarditis prophylaxis 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: severe symptomatic stenosis carries high risk of heart failure and arrhythmia, so replace or dilate the valve before conception. In pregnancy use rest, metoprolol 25 to 50 mg twice daily, diuretics for congestion, and balloon valvuloplasty for refractory symptoms. Avoid ACE inhibitors and ARBs.
  • Children and adolescents: balloon valvuloplasty first; the Ross operation is not suitable because of rheumatic disease.
  • Elderly: frailty and combined disease influence the timing and route of replacement.
  • Renal impairment: avoid contrast load where possible; adjust diuretics.
• Red flags: angina, syncope, pulmonary oedema, new atrial fibrillation, gastrointestinal bleeding, fever with a murmur.
• Follow up: severe asymptomatic stenosis every 6 months; moderate every year; mild every 1 to 2 years, each with echocardiography; after replacement at 6 weeks, then yearly, with INR monthly on warfarin.