Progression from hypertrophic obstructive cardiomyopathy to typical dilated cardiomyopathy-like features in the end stage.

An autopsied patient who had shown typical dilated cardiomyopathy (DCM)-like feature in the end stage of familial obstructive hypertrophic cardiomyopathy (HCM) is presented. The patient, a 38-year-old male, had 2 sisters with HCM. Six years before death, the echocardiogram revealed marked asymmetric septal hypertrophy (ASH) with systolic anterior motion (SAM). The ventricular septum (VS) to left ventricular posterior wall (LVPW) ratio was 19 mm/10 mm and LVEDd was 47 mm. Subsequently, the signs and symptoms of congestive heart failure became progressively worse and DCM-like findings appeared insidiously. Two months before death, the echocardiogram revealed LV dilatation (LVEDd = 55 mm) with diffuse poor contraction, no ASH (VS/LVPW = 7 mm/9 mm) and no SAM. At autopsy, the heart weighed 480g and showed dilated LV hypertrophy with normal wall thickness (VS/LVPW = 9 mm/13 mm). Massive fibrosis (30% in the VS), diffuse disarray (18% in the VS) and severe narrowing of the intramural small arteries and arterioles were found in the middle and outer thirds of the VS and the anterior LV wall. The extramural coronary arteries were not stenosed. The insidious progression from HCM to typical DCM-like feature related to the chronic progression of necrosis and massive fibrosis, due to severe stenosis of the intramural coronary artery. The data indicate that patients diagnosed clinically as DCM may be HCM, especially in those with family history of HCM.