This document discusses aortic stenosis, which is the abnormal narrowing of the aortic valve opening. It can be caused by congenital heart defects, calcification of the valve, or rheumatic fever. Symptoms include fatigue, fainting, and heart failure. Diagnosis involves echocardiogram, ECG, and cardiac catheterization. Treatment depends on severity and includes medications, balloon valvuloplasty, transcatheter aortic valve replacement, and surgical aortic valve replacement.