Pre- and postoperative echocardiographic features of discrete subaortic stenosis.

In two patients with discrete membranous subaortic stenosis, partial early systolic closure of the aortic valve was noted on the preoperative record. Postoperatively, this abnormality was found to be less pronounced. Narrowing of the left ventricular outflow tract was seen in the preoperative tracing in each patient. Echocardiograms taken after resection of the subaortic membrane showed widening of the left ventricular outflow tract as compared with the preoperative tracing. Thus, echocardiography may be of value in distinguishing between discrete subaortic stenosis and other forms of left ventricular outflow tract obstruction.