Surgical treatment of idiopathic hypertrophic subaortic stenosis (IHSS). Postoperative results in 30 patients following ventricular septal myotomy and myectomy (Morrow procedure).

Since 1971 we have employed the Morrow procedure in 30 patients with idiopathic hypertrophic subaortic stenosis (IHSS). All manifested obstruction to left ventricular outflow either at rest or with provocation (Valsalva) and 17 had moderate or severe mitral regurgitation. There were no operative deaths. Obstruction was abolished in all patients except one in whom a trivial 15-mm pressure gradient persisted, and all patients with moderate or severe mitral regurgitation evidenced marked amelioration of the mitral regurgitation. Distinct symptomatic improvement has been experienced by all patients, and 20 are entirely asymptomatic postoperatively. No patient has experienced syncope postoperatively although 15 experienced syncope before operation. In 12 patients the electrocardiogram recorded postoperatively was essentially unchanged from the preoperative record. In 16 patients a left anterior hemiblock was apparent postoperatively. In one patient a complete left bundle branch block appeared postoperatively and one patient demonstrated Wolff-Parkinson-White syndrome. One patient died suddenly and unexpectedly 2 years following operation. This patient continued to have palpitations after operation although all other symptoms as well as the left ventricular outflow obstruction were abolished by operation. It is suggested that propranalol administration be continued postoperatively in those patients experiencing palpitations or manifesting arrhythmias. Asymmetrical septal hypertrophy dislocates the cardiac apex and papillary muscles anteriosuperiorly producing abnormal systolic anterior mitral leaflet mition. The Morrow procedure restores more normal ventricular geometry and thereby eliminates the pathophysiological mechanism of obstruction and mitral regurgitation. The myotomies and myectomy should be extended far inferior through the entire width of the septum onto the free lateral ventricular wall. The procedure can be accomplished easily and safely through a transaortic approach. Since the operative risk at present appears to be negligible, prosthetic material is not required, and the risk of significant injury to the conduction tissue is small, we feel the current status of surgery for IHSS is such that the Morrow procedure should be performed earlier in the course of patients with IHSS manifesting obstruction or mitral regurgitation.