Residual and recurrent gradients after septal myectomy for hypertrophic cardiomyopathy-mechanisms of obstruction and outcomes of reoperation

Objective: The aims of the present study were to identify the mechanisms of residual or recurrent left ventricular outflow tract obstruction in patients undergoing repeat septal myectomy for hypertrophic cardiomyopathy and to assess the early and late results of reoperation. Methods: From January 1980 to June 2012, we performed 52 repeat myectomies in 51 patients. We reviewed the medical records and preoperative transthoracic echocardiograms to evaluate the adequacy of the previous resection and mechanism of left ventricular outflow tract obstruction. The complications of previous and repeat myectomy, New York Heart Association class, and survival were analyzed. Results: The mean interval from previous myectomy to reoperation was 43 +/- 51 months. In 6 patients (12%) residual or recurrent gradients were caused by isolated midventricular obstruction. In the remaining 46 operations, the mechanism of residual or recurrent gradients was identified as systolic anterior motion of mitral valve-related subaortic obstruction caused by inadequate length of previous subaortic septal excision in 31 patients (59% of the total), both an inadequate length and an inadequate depth of septectomy in 13 patients (25%), and both residual subaortic obstruction due to systolic anterior motion of the mitral valve and midventricular obstruction in 2 patients (4%). Preoperatively, 96% of patients were in New York Heart Association class III or IV; postoperatively, 93.8% were in class I or II (P < .001). The 10-year survival after reoperation was 98% and similar to that of an age-and gender-matched Minnesota population (P = .46). Conclusions: The most common cause of recurrent left ventricular outflow tract obstruction and symptoms in patients undergoing septal myectomy has been an inadequate length of septal excision. Reoperation is safe, with excellent long-term survival and functional improvement.