Left ventricular myotomy. Physiologic approach to surgical therapy for IHSS.

Twenty patients were operated on for idiopathic hypertrophic subaortic stenosis (IHSS) between 1966 and 1980. All were in New York Heart Association functional class 3 or 4, and 17 had overt congestive failure. The mean resting gradient across the left ventricular (LV) outflow tract preoperatively was 78 mm Hg. Seventeen patients underwent transaortic LV myotomy, one had mitral valve replacement (MVR), and two patients with rheumatic mitral insufficiency (MI) and IHSS underwent myotomy and MVR. There was one operative death (5 percent). Mean follow-up was 5.8 years. Eighteen of 19 survivors were improved to class 1 or 2. One patient whose gradient and symptoms were not relieved by myotomy was improved by myectomy and MVR. The MI was abolished or reduced by myotomy in ten of 13 patients. There were six late deaths, five of which are known or assumed to be cardiac related. We concluded that LV myotomy is a safe and effective technique for surgical management of IHSS. Left ventricular myectomy, MVR, or both are indicated in selected cases.