Surgical management of subaortic stenosis.

The two most common causes for left ventricular outflow tract obstruction are discrete fibromuscular membrane (DMS) and idiopathic hypertrophic subaortic stenosis (IHSS). From 1955 to 1980, 195 patients were seen with subaortic obstruction, 50 of whom required operation. Thirty patients had excision of a subaortic membrane; 20 had resection of the hypertrophic muscular obstruction. The average preoperative gradient across the left ventricular outflow tract was 79 mm Hg. Postoperatively 40 patients were catheterized; two had gradients over 40 mm Hg, and both were in the DMS group. There were four operative and six late deaths (mean follow-up, 8.5 years), five occurring in the IHSS group (25%) and one in the DMS group (3.5%). Recurrent symptoms required reoperation in three patients with IHSS and one with DMS. Both groups benefitted from operation, but those with DMS had a better overall survival rate and fewer postoperative symptoms than those with IHSS.