Predictors of exercise capacity following septal myectomy in patients with hypertrophic cardiomyopathy

Patients with hypertrophic obstructive cardiomyopathy (HOCM) have impaired exercise capacity. The gold standard therapy for patients with HOCM is septal myectomy surgery; however, changes in maximum oxygen uptake (VO₂peak) following myectomy are variable, with VO₂peak decreasing in some patients. Therefore, we evaluated changes in VO₂peak following surgical myectomy to determine clinical predictors of those exhibiting decreased VO₂peak post-myectomy.

HOCM patients (N = 295) who performed symptom limited cardiopulmonary exercise testing prior to and following surgical myectomy were included for analysis. The VO₂peak non-responder group (n = 128) was defined as <0% change in VO₂peak from pre- to post-myectomy. Step-wise regression models using demographics, clinical, and physiologic characteristics were created to determine predictors of hypertrophic cardiomyopathy patients in the VO₂peak non-responder group.

Independent predictors of the VO₂peak non-responder group included higher pre-myectomy VO₂peak (% predicted), older age, women, history of dyslipidemia, lack of cardiac rehabilitation enrollment, and lower body mass index (all p < 0.03). Forty-three (14.6%) patients reached the primary end-point of all-cause mortality during a median follow up of 11.25 years (interquartile range 6.94 to 16.40). After adjustment for age, sex, beta-blocker use, coronary artery disease history, and body mass index, the VO₂peak non-responder group had greater risk of death compared with the VO₂peak responder group (adjusted hazard ratio: 1.77, 95% confidence interval: 1.06–3.34, p = 0.01).

This large hypertrophic cardiomyopathy cohort demonstrated that demographic (i.e. female sex), lack of cardiac rehabilitation enrollment, and cardiovascular risk factors (i.e. history of dyslipidemia) are predictive of those patients that did not exhibit increases in VO₂peak following septal myectomy surgery.