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KEY FEATURES

ESSENTIALS OF DIAGNOSIS

  • Chest pain, exertional dyspnea, exercise intolerance, orthopnea, peripheral edema

  • Systolic ejection murmur with characteristic changes during bedside maneuvers

  • Markedly asymmetric left ventricular hypertrophy on echocardiogram with greatest involvement most commonly of the basal interventricular septum

  • Absence of other etiologies causing left ventricular hypertrophy, including abnormal loading conditions, systemic hypertension, aortic stenosis, or physiologic hypertrophy of athletes

  • First-degree relatives of patients of hypertrophic cardiomyopathy (HCM) should be screened (clinical, with or without genetic testing)

GENERAL CONSIDERATIONS

  • HCM is a primary disorder of the heart caused by mutations in genes that encode the protein components of the cardiac sarcomere

  • Single-gene disorder that has an autosomal dominant with incomplete penetrance pattern of inheritance

  • Together, mutations in the cardiac myosin-binding protein-C (MYBPC3) and beta-myosin heavy chain (MYH7) genes account for up to 50% of all clinically recognized cases

  • The clinical manifestations of the disease vary from asymptomatic carriers to severely disabled patients

  • Two-thirds of affected individuals have asymmetric hypertrophy often involving the intraventricular system but occasionally limited to the apex of the left ventricle

  • One-third of those affected have diffuse concentric hypertrophy

  • Histologic changes include myocyte and cardiac hypertrophy, disarray, and interstitial fibrosis

  • The left ventricle cavity is nondilated and usually shows hyperdynamic function

  • Patients with symmetric hypertrophy may demonstrate intracavitary gradients that worsen with increased contractile stimuli and improve with increased afterload

  • Asymmetric septal hypertrophy often results in systolic anterior motion of the anterior mitral valve leaflet, which narrows the left ventricular outflow tract, producing a gradient and a characteristic systolic murmur that varies in intensity with loading conditions

  • Systolic anterior movement of the mitral valve often leads to mitral regurgitation

CLINICAL PRESENTATION

SYMPTOMS AND SIGNS

  • May be asymptomatic

  • Exertional dyspnea, fatigue

  • Chest pain

  • Syncope

  • Palpitations

PHYSICAL EXAM FINDINGS

  • May be unremarkable

  • Left ventricle lift; may be bifid

  • S4

  • Systolic ejection murmur that increases in intensity with maneuvers that decrease left ventricular filling, such as standing, and softens with increased filling, such as squatting

DIFFERENTIAL DIAGNOSIS

  • Left ventricular hypertrophy secondary to other conditions (eg, hypertension, athlete’s heart)

  • Aortic stenosis with marked left ventricular hypertrophy

  • Restrictive cardiomyopathy with hypertrophy, such as amyloidosis

  • Athlete’s heart

DIAGNOSTIC EVALUATION

LABORATORY TESTS

  • Elevated brain natriuretic peptide

  • Genetic testing

ELECTROCARDIOGRAPHY

  • Almost all patients have an abnormal ECG, but the patterns are nonspecific

  • Voltage criteria for left ventricular hypertrophy with repolarization abnormalities are common

  • Some patients have giant negative T waves in the precordium, especially the apical variant

IMAGING STUDIES

  • Echocardiography is recommended in the initial evaluation of all patients with suspected HCM. Morphologic diagnosis is based on presence of hypertrophy (usually ...

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