Hypertrophic Cardiomyopathy

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Hypertrophic cardiomyopathy is a fascinating disease entity in which hypertrophy of the myocardium occurs, primarily as a result of mutations of genes encoding the cardiac sarcomere.1–3 Our knowledge of patients with this unique disease of the heart muscle has advanced significantly. Once thought to be a rare malignant disease with a high risk of sudden death, population studies have revealed hypertrophic cardiomyopathy to be a more common disease with a benign outlook in the majority of affected patients.4 Hypertrophic cardiomyopathy is now recognized to comprise a wide spectrum of disease processes, with varying genetics, anatomy, clinical presentation, and prognosis. The dynamic left ventricular outflow tract obstruction that was initially the hallmark of hypertrophic cardiomyopathy continues to be a source of controversy. Article p 2232 The pathophysiology of hypertrophic cardiomyopathy is complex and still not completely understood. The first description of hypertrophic cardiomyopathy came in 1957 when Sir Russell Brock5 found a functional subvalvular obstruction in patients undergoing aortic valvotomy for clinically suspected valvular aortic stenosis. In 1958, Teare6 described the cardiac anatomy of 8 young patients who died suddenly with severe asymmetric left ventricular hypertrophy with bizarre muscle bundle orientation. In the 1960s, Braunwald et al7 defined a specific disease process in which asymmetric septal hypertrophy, myofibril disarray, and dynamic outflow tract obstruction were found. Thus, the early focus of hypertrophic cardiomyopathy was on this dynamic obstruction; the response of the obstruction to changes in preload, afterload, and contractility formed the basis for diagnosis. With the advent of echocardiography, which allowed direct visualization of the hypertrophied myocardium, it became apparent that obstruction was not necessary for the diagnosis of hypertrophic cardiomyopathy. The entire relationship of obstruction to hypertrophic cardiomyopathy was subsequently questioned. Some thought that hypertrophic cardiomyopathy was primarily a disease of diastole, with obstruction …