ABSTRACT
INTRODUCTION Hypertrophic cardiomyopathy (HCM) is a unique cardiovascular condition that may become symptomatic at any phase of life, from infancy to beyond 90 years of age (1-6). The hallmark of the disease is myocardial hypertrophy that can be manifest in a variety of recognized morphologies. Dynamic left ventricular outflow tract (LVOT) obstruction may or may not be present due to asymmetric hypertrophy of the interventricular septum. With recent estimates suggesting that 1 in 500 of the general adult population is affected by this autosomal dominant condition, HCM is one of the most common cardiac genetic disorders known, and over 12 involved genes have been identified (3,5,6). The genotypic foundation of HCM is directly related to abnormalities of the genes encoding sarcomeric proteins that regulate the contractile, regulatory, and structural functions of the myocardium. The consequent myocardial disarray and hypertrophy result in a complex pathophysiologic interplay among LVOT obstruction, diastolic dysfunction, myocardial ischemia, and mitral regurgitation. Depending on their particular phenotype, patients with HCMmay have a wide spectrum of clinical and pathologic presentations ranging from exertional dyspnea, angina, palpitations, or syncope. The most fearsome and dramatic complication of HCM, sudden cardiac death, is one of the frequent causes of cardiovascular death among young people and the most common cause of mortality in competitive athletes (7). Fortunately, HCM patients at high risk for sudden cardiac death constitute only a small proportion of the affected population (Table 44.1). Despite the widespread availability of genetic screening tests, the diagnosis of HCM remains primarily clinical, involving the use of echocardiography to evaluate for characteristic features such as asymmetric septal hypertrophy, systolic anterior motion of the mitral valve, and LVOT obstruction.
