Aortic stenosis is caused by narrowing of the orifice of the aortic valve and leads to obstruction of left ventricular outflow. This stenosis is rare in persons less than 50 years old. Calcification of the aortic valve is the most common cause of aortic stenosis in adults in industrialized countries and affects more than 4% of North American and Europeans more than 75 years old. In a study of 338 North American patients with severe asymptomatic aortic stenosis, the mean age was 71 (SD, 15) years. Aortic stenosis was also associated with higher morbidity and mortality rates than were diseases involving other cardiac valves. For example, in a study of 161 patients, patients with moderate and severe aortic stenosis had 2-year mortality rates of 40.2% and 58.2%, respectively. In another study of 274 medically managed patients...

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