Cardiopulmonary exercise test in patients with obstructive hypertrophic cardiomyopathy

Abstract

Objective: The study objective was to analyze performance on cardiopulmonary exercise testing and its prognostic value in patients with obstructive hypertrophic cardiomyopathy undergoing septal myectomy.

Methods: We reviewed patients with obstructive hypertrophic cardiomyopathy who had cardiopulmonary exercise testing before septal myectomy from 2005 to 2016. Causes of functional impairment and their impact on survival were analyzed.

Results: A total of 752 patients had cardiopulmonary exercise testing at a median of 16 days (interquartile range, 2-56) before myectomy. The median exercise time was 6.6 (5.3-8.0) minutes. Functional aerobic capacity was 64% (53%-75%) of predicted, and metabolic equivalent of task was 5.2 (4.1-6.4). The peak oxygen consumption was 18.0 (14.2-21.9) mL/kg/min, which was 60% (49%-72%) of the predicted value. The primary causes for low peak oxygen consumption were impaired cardiac output (73.7%), limited heart rate reserve (52.0%), and obesity (48.2%). Resting outflow tract gradient correlated poorly to peak oxygen consumption, but the use of beta-blockers was associated with reduced peak oxygen consumption. During a median (interquartile range) of 9.0 (6.8-11.7) years of follow-up, the estimated 5- and 10-year survivals were 97% and 91%, respectively. Greater adjusted peak oxygen consumption (hazard ratio, 0.98; P = .011) and abnormal pulse oxygen increase (hazard ratio, 0.44; P = .003) were independently associated with better long-term survival after myectomy.

Conclusions: Among patients with hypertrophic cardiomyopathy undergoing septal myectomy, functional capacity is severely impaired despite receiving optimal medical treatment. We identified risk factors of reduced long-term survival from preoperative cardiopulmonary exercise testing that may aid risk stratification in patients undergoing septal myectomy.

Keywords: cardiopulmonary exercise testing; hypertrophic cardiomyopathy; septal myectomy.