Sudden death and left ventricular outflow disease.

Aortic stenosis is a well-recognized cause of sudden death, but in our experience, it is uncommon as the sole cause of sudden death. The most common overall cause of AS is the calcified congenitally bicuspid valve. There is an increased incidence of subaortic stenosis in relatives of patients with subaortic stenosis, although Mendelian inheritance has not been reported. Supravalvular AS may be an autosomal dominant with variable penetrance, it may be sporadic, or it may be one of the manifestations of Williams' syndrome. The principal mechanisms of sudden death in AS appear to be due to (1) activation of left ventricular baroreceptors which causes reflex bradycardia and cardiac arrhythmias, or (2) arrhythmias as complications of LVH. Myocardial ischemia has been anatomically proven and may be due to diastolic compression of intramural coronary arteries. Aortic dissection occurs with increased frequency in patients with a bicuspid aortic valve. Heart block can result from calcification of the bundle of His in AS of any cause. Supravalvular AS may be complicated by adherence of an aortic valve cusp to the aorta resulting in coronary ostial stenosis, and coronary narrowing by intimal hyperplasia. AS at any level may lead to IE, which has been responsible for occasional sudden deaths.