Discrete subaortic stenosis: a study of 20 cases.

Twenty patients with discrete subaortic stenosis were studied during last 11 years. Cross sectional echocardiography and angiography demonstrated a membrane in 17 (85%), fibromuscullar collar in 2 (10%), and diffuse tunnel type of obstruction in 1 (5%) patient. Eighty five percent of patients had severe obstruction with average peak systolic gradients being 96.5 +/- 36.3 mm of Hg. Eight patients with membranous obstruction seen during the last 5 years underwent successful balloon dilatation with decrease in peak systolic gradient from 107.1 +/- 24.2 to 32.3 +/- 14.2. The haemodynamic benefits were sustained during 4 to 24 (mean 9.6) months followup. The results indicate that balloon dilatation can be a safe and effective treatment for thin subaortic membrane. Surgical resection is needed in patients with collar or tunnel type of obstruction.