Septal Myectomy With Vs Without Subvalvular Apparatus Intervention in Patients With Hypertrophic Obstructive Cardiomyopathy: A Prospective Randomized Study.

Surgical septal myectomy is a standard treatment option for patients with hypertrophic obstructive cardiomyopathy. Subvalvular abnormalities of the mitral valve might play an important role in residual left ventricular outflow tract obstruction. This randomized study aimed to compare the surgical outcomes of septal myectomy with vs without subvalvular interventions. Between July 2015 and December 2016, 80 eligible patients were randomly assigned to undergo septal myectomy with vs without subvalvular intervention. The peak gradient was 92.3 ± 16.9 and 88.1 ± 15.4 mm Hg, respectively (P = 0.281). The mean septum thickness was 26.8 ± 4.5 and 26.1 ± 4.2 mm, respectively (P = 0.504). Moderate or severe systolic anterior motion syndrome-mediated mitral regurgitation was observed in all patients. There was no residual mitral regurgitation in the group with subvalvular intervention, while 15% of patients in the control group had regurgitation (P = 0.013). Residual systolic anterior motion syndrome was observed in 5% and 27.5% of patients, respectively (P = 0.007). The median postoperative gradient was 13 (interquartile range 9-16) mm Hg and 8 (interquartile range 4-12) mm Hg, respectively (P = 0. 0.019). At the 12-month follow-up, all patients were alive. There were 87.5% vs 77.5%, and 12.5% vs 22.5% of patients categorized as having New York Heart Association functional classes I and II, respectively (P = 0.378). The prevalence rate of residual mitral regurgitation was 10% and 32.5%, respectively (P = 0.010). Concomitant subvalvular intervention during septal myectomy more effectively eliminates left ventricular outflow tract obstruction, providing better freedom from residual mitral regurgitation without clinical benefit 1 year after surgery.