Conduction Abnormalities and Long-Term Mortality Following Septal Myectomy in Patients With Obstructive Hypertrophic Cardiomyopathy

BACKGROUND Conduction abnormalities including bundle branch block are recognized sequelae following septal myectomy in patients with hypertrophic cardiomyopathy, but their incidence and effect on long-term mortality have not been well studied. OBJECTIVES This study was conducted to determine the impact of conduction abnormalities on mortality in patients with obstructive hypertrophic cardiomyopathy following myectomy. METHODS The outcomes of 2,482 patients with obstructive hypertrophic cardiomyopathy who underwent transaortic septal myectomy from 1961 to 2016 were analyzed. Pre-operative and early post-operative electrocardiograms were reviewed to determine conduction status. The study endpoint was all-cause mortality. RESULTS Mean age at operation was 54.2 +/- 14.6 years, and 1,370 patients (55.2%) were men. Pre-operatively, 2,159 patients (87.0%) had normal conduction, of whom 38.8% developed left bundle branch block, 1.1% developed right bundle branch block (RBBB), and 0.6% had complete heart block (CHB) after myectomy. Among 112 patients with baseline RBBB, 34.8% developed CHB post-operatively. Overall, only 2.3% of patients developed CHB. Over a median follow-up period of 8.6 years, overall mortality differed among post-operative conduction groups after adjustment for age, sex, and concomitant procedures (p = 0.015). Specifically, mortality in those with paced rhythm after myectomy was significantly increased relative to those with normal conduction (hazard ratio: 1.57; 95% confidence interval: 1.15 to 2.14; p = 0.005), although no significant difference was observed in left bundle branch block and RBBB (vs. normal) groups. CONCLUSIONS Left bundle branch block is a common sequela after septal myectomy but does not influence post-operative mortality. Myectomy-related CHB is rare in patients with baseline normal conduction, while pre-existing RBBB greatly increases the risk for CHB. Persistent paced rhythm after operation is an independent predictor of mortality. (C) 2019 by the American College of Cardiology Foundation.