Subaortic Stenosis

Subaortic stenosisSubaortic stenosis (SAS) is a rare congenital heart defect affecting 8 in 10,000 live births. SAS refers to a group of diverse defects with obstruction to systemic blood flow originating below the aortic valve, including subaortic membrane, fibromuscular ridgeFibromuscular ridge, accessory mitral valveMitral valve tissue, septal hypertrophySeptal hypertrophy, acute aortoventricular angle, and funnel-shaped left ventricular outflow tract (LVOT). Patients with SAS present similarly to aortic stenosisAortic stenosis, with symptoms of exertional angina, syncope/presyncope, or even heart failureHeart failure if diagnosed late. SAS can also be an incidental finding in asymptomatic patients. SAS is associated with other left-sided stenotic lesions, including congenital mitral stenosisMitral stenosis, bicuspid aortic valveBicuspid aortic valve, aortic arch hypoplasiaAortic arch hypoplasia, or coarctation. Diagnosis is generally made by doppler echocardiography and can also be identified by computed tomography angiography or cardiac magnetic resonanceCardiac magnetic resonance (CMR) imaging. Definitive surgical intervention to relieve the obstructing lesion is indicated if symptomatic, mean pressure gradient is ≥ 50 mmHg, or presence of left ventricular hypertrophy. Iatrogenic ventricular septal defectVentricular septal defect (VSD), mitral or aortic valve injury, complete heart block, residual stenosis due to incomplete resection, and left ventricular diastolic dysfunctionDiastolic dysfunction are postoperativePostoperative complications that must be monitored closely.