Surgical Myectomy for Hypertrophic Obstructive Cardiomyopathy

Hypertrophic cardiomyopathy (HCM) has been one of the most interesting and controversial disorders in cardiovascular medicine. Although initial descriptions of the pathology of HCM were published over a century ago, it was not until the surgical and pathological observations of Brock and Teare, respectively, that this cardiac entity came to attention in the modern era. HCM is a primary disorder of the myocardium characterized by myocyte hypertrophy and fiber disarray, myocardial fibrosis, and abnormal coronary intramural microvasculature. Although HCM is characterized by tremendous diversity in terms of phenotypic expression, genetic substrate, and clinical presentation, left ventricular outflow tract (LVOT) obstruction is an integral component of the disease, occurring in up to 70% of patients either at rest or with provocation.1 Article see p 209 Dynamic LVOT obstruction has long been recognized as a clinical feature of HCM, but the pathophysiology and clinical significance of intraventricular pressure gradients sparked much controversy and debate. While initially thought to result from early excessive and rapid ejection from a hypercontractile left ventricle (LV) as opposed to true mechanical impedance to blood flow, this hypothesis was later refuted by Wigle and colleagues,2 who demonstrated a prolonged LV ejection time in the presence of such intraventricular pressure gradients. The pathophysiology of LVOT obstruction is now widely accepted to be attributable to an eject-obstruct-leak concept, driven by Venturi and drag forces of the anterior mitral valve leaflet. Echocardiographic and cardiac magnetic resonance studies have documented that reduction in the LVOT cross-sectional area is attributable to morphological features such as narrowing of the LVOT by septal hypertrophy, intrinsic abnormalities of the mitral valve leaflets, anterior displacement of the mitral apparatus, and anterior malposition of the papillary muscles, either alone or in combination. Rapid LV ejection through a narrowed outflow tract results in the anterior mitral leaflet …