Evolving Treatment for Patients With Hypertrophic Obstructive Cardiomyopathy.

D ynamic left ventricular outflow obstruction is a major cause of exertional symptoms in patients with hypertrophic cardiomyopathy. The obstruction is secondary to systolic anterior motion of the mitral valve abutting against a hypertrophied septum, resulting in diastolic dysfunction, myocardial oxygen supply-demand mismatch, reduced forward output, and secondary mitral regurgitation. Medical treatment directed at decreasing contractility, improving diastolic filling, and slowing heart rate can be successful in reducing symptoms in many patients. However, there is a subset of patients who remain severely symptomatic, despite optimal medical therapy. Although surgical resection of the septal hypertrophy has been an accepted treatment for these severely symptomatic patients for >5 decades, techniques have evolved and become highly refined. Most experienced surgeons favor wider (“extended”) resection of septal muscle (1,2) rather than resection of a narrower portion of muscle in the early reports of Morrow (3). Other interventions have been utilized to treat left ventricular outflow obstruction, including dual chamber pacing (4), alcohol septal ablation (5,6), radiofrequency septal ablation, and, most recently, implantation of a MitraClip (7). Less invasive and less demanding procedures appeal to patients and to many clinicians, especially those who treat obstructive HCM infrequently, but transaortic septal myectomy has remained the optimal therapy for carefully selected patients with severely symptomatic hypertrophic cardiomyopathy. When performed by