Impact of Body Mass Index on Outcome of Septal Myectomy for Obstructive Hypertrophic Cardiomyopathy

Background: Obesity is highly prevalent in patients with obstructive hypertrophic cardiomyopathy (HCM). In this study, we investigated the impact of body mass index (BMI) in patients undergoing septal myectomy (SM) for obstructive HCM. Methods: We reviewed 2746 patients who underwent transaortic SM for obstructive HCM from February 1993 through September 2018. Patients were stratified into 3 groups based on BMI (normal weight, <25 kg/m²; overweight, 25 to <30 kg/m²; and obese, ≥30 kg/m²). Results: Preoperatively, the median left ventricular outflow tract gradient was 58 mm Hg, and there was no difference in gradients across BMI strata (P = .35). The percentage of obese patients with moderate or greater mitral valve regurgitation was lower (45.8%) compared with normal weight (52.9%) and overweight (55.4%) patients (P < .001). However, patients with a higher BMI were more likely to have New York Heart Association Functional Classification III/IV limitation at presentation (P < .001). After myectomy, anteroseptal thickness (P = .115) and left ventricular outflow tract gradient (P = .210) did not differ between groups. There were 14 (0.5%) deaths within 30 days postoperatively, and the risk was similar across BMI strata (P = .448). Model-estimated changes in average BMI at 10 years postprocedure showed stratum-specific increases ranging from 0.60 to 1.56 kg/m². During a median follow-up of 7.2 years (interquartile range, 3.2-13.3 years), a higher BMI was associated with reduced survival after adjusting for baseline covariates (P = .001). Conclusions: SM is safe and effective in HCM patients with obesity, but the risk of late death increased with increasing BMI. Attention to risk factor management through weight loss may improve late results after SM.