Transapical Septal Myectomy for Hypertrophic Cardiomyopathy With Midventricular Obstruction

Background: Midventricular obstruction (MVO) is an uncommon variant of hypertrophic cardiomyopathy (HCM). In patients receiving septal myectomy for HCM, failure to recognize the concurrent MVO in the context of basal septum thickening can lead to inadequate excision and residual gradient. In this report, we detail the operative outcomes of MVO with and without coexistent basal septal hypertrophy. Methods: From February 1997 through September 2018, 196 patients underwent midventricular myectomy. Medical records and follow-up databases were reviewed to obtain patient characteristics and perioperative features. Results: At baseline, 156 patients (80%) were in New York Heart Association Functional Classification III/IV. Obstruction was isolated to the midventricle in 80 patients, and 63 (79%) were treated by isolated transapical myectomy. The remaining 116 patients had intraventricular obstruction at both subaortic and midcavity levels; in 108 (93%), a combined transaortic and transapical approach was adopted to achieve complete relief of the obstruction. After septal myectomy, the resting peak instantaneous gradient decreased from a median 48 mm Hg (interquartile range [IQR], 23-77 mm Hg) preoperatively to 8 mm Hg (IQR, 0-19 mm Hg) before hospital dismissal. Median follow-up was 2.9 years (IQR, 0.7-5.0 years), and the estimated 1-, 5-, and 10-year survivals were 99%, 98%, and 90%, respectively. There were no late complications attributable to the transapical incision. Conclusions: Transapical exposure is a safe and effective approach for relief of midventricular obstruction, and hemodynamic results are similar to those achieved by standard myectomy for subaortic obstruction. The technique can be combined with transaortic myectomy for patients with left ventricular outflow obstruction at both levels.