Midventricular obstruction and clinical decision-making in obstructive hypertrophic cardiomyopathy

The presence of intraventricular obstruction is a powerful predictor of outcome in patients with hypertrophic cardiomyopathy (HCM) and, when associated with severe, drug-refractory symptoms, should be managed aggressively. Resting left ventricular outflow obstruction is found in approximately 20% of the patients, classically occurs at the subaortic level, and is associated with mitral valve systolic anterior motion (SAM). In a minority of patients, however, the impedance to flow occurs at midventricular level, unrelated to SAM. Symptomatic midventricular obstruction represents a clinical challenge, and its treatment is not standardized. In these patients, both surgical myectomy and alcohol septal ablation (ASA) are technically feasible. A rational approach to the management of these patients depends on accurate characterization of the pathophysiology, coupled with comparison of the results of different management strategies. To illustrate these points, the details of a patient who first underwent percutaneous ASA and subsequently required redo surgical treatment are described here, with special emphasis on the implications to the management of midventricular obstruction, as well as to the more global issue of obstructive HCM.