Mechanisms for recurrent left ventricular outflow tract obstruction after septal myectomy for obstructive hypertrophic cardiomyopathy

Background. Left ventricular septal myectomy provides excellent outcomes for symptomatic patients with severe obstructive hypertrophic cardiomyopathy. However, in a few patients, left ventricular outflow tract obstruction may recur and require repeat myectomy. We reviewed this subset of patients to assess the mechanisms of recurrence. Methods. From 1975 to July 2003, 610 septal myectomies were performed; 13 of these were repeat myectomies after classic myectomies performed at our institution (n = 6) or elsewhere (n = 7). Ages ranged from 4 to 70 years (mean, 32 +/- 22). The interval between initial myectomy and repeat myectomy ranged from 13 months to 11 years (mean, 5.0 +/- 3.7 years). Results. Mechanisms for obstruction included limited myectomy at the initial myectomy (n = 11), septal hypertrophy at the midventricular level (n = 8), and anomalous papillary muscles (n = 3). Mean intraoperative pressure gradients decreased from 82 +/- 24 to 6.2 +/- 4.4 mm Hg. No mitral valve replacement was performed, and there were no early deaths. Mean follow-up was 5.8 +/- 5.8 years. There was one late death. All surviving patients were free from recurrence of outflow tract obstruction and were in the New York Heart Association functional class I or II. Conclusions. Mechanisms for recurrent obstruction included limited myectomy at the initial operation, midventricular obstruction, anomalies of papillary muscles, and ventricular remodeling, especially in pediatric patients. Repeat myectomy can be performed with excellent outcomes. Need for reoperation may be reduced with current surgical approaches that include a more extended resection of the midventricular septum, relief of papillary muscle anomalies, and routine use of intraoperative transesophageal echocardiography.