Case 153

Apical Hypertrophic Cardiomyopathy

Etiology and Clinical Features

HCM is inherited as an autosomal dominant trait with variable penetrance. Patients have a variable clinical presentation; they may be asymptomatic, or they may have atrial fibrillation, heart failure, syncope, or sudden cardiac death, which is the leading cause of mortality in these patients. Asymmetric hypertrophy of the ventricular septum accounts for 90% of cases of HCM. Other patterns exhibit a right ventricular, left ventricular, septal, apical, midventricular, or concentric distribution. The apical pattern can account for 25% of patients in Japan, but it is uncommon elsewhere. Patients with heart failure secondary to significant hypertrophy can be treated with myectomy.

Imaging

MRI (Figs. A–C) can provide anatomic and functional information in HCM and can be most useful when the diagnosis is in question, when invasive therapy is being considered, or when clinical concern requires more thorough assessment than provided by echocardiography. MRI can be used to identify the distribution of thickened myocardium and to calculate left ventricular mass. Therapy may depend on the distribution of hypertrophy. MRI also can be used for functional evaluation of left ventricular outflow tract obstruction and myocardial perfusion and viability.