Comparison of expected and observed outcomes for septal myectomy in hypertrophic obstructive cardiomyopathy

Background: Septal myectomy remains the criterion standard for treatment of symptomatic, medically refractory hypertrophic cardiomyopathy (HCM). There is no specific surgical risk calculator for septal myectomy. Methods: This study compares the outcomes of septal myectomy at a tertiary referral center with predicted outcomes of mitral valve (MV) repair and aortic valve replacement (AVR) using the Society of Thoracic Surgeons Adult Cardiac Surgery Risk Calculator (STS Calculator). A total of 298 consecutive patients with HCM underwent isolated septal myectomy from 2011 to 2014. Observed outcomes of septal myectomy were compared with the STS Calculator predicted risk of isolated MV repair and AVR predicted within this population using 1-sample tests of proportions. Results: Thirty-day mortality for myectomy in this cohort was zero. STS Calculator predicted risk of mortality for MV repair was 0.7% (P = .14) and for AVR = 1.1% (P = .06). Follow-up for vital status was 6.0 ± 0.7 years, at which 294 (98.7%) patients were alive. Hospital stay length was 4.9 ± 1.9 days. One (0.3%) patient experienced a postoperative deep sternal wound infection, and 1 (0.3%) patient experienced a prolonged ventilated state. Postoperative atrial fibrillation occurred in 64 (21.5%) patients. During 30 days of follow-up, no patients experienced stroke, renal failure, or needed dialysis. Conclusions: Septal myectomy, performed in a tertiary referral center, had a 30-day mortality rate of 0% and low morbidity rate. There was no difference between observed myectomy mortality and STS Calculator predicted risk for AVR and MV repair. It is possible that a larger sample could reveal lower mortality than STS prediction.