[Hypertrophic cardiomyopathy with left ventricular dilatation].

There is increasing interest in the notion that some patients with hypertrophic cardiomyopathy (HCM) progress to morphological and functional manifestations similar to those of dilated cardiomyopathy (DCM). From 165 consecutive patients with HCM, 20 patients with left ventricular dilatation (left ventricular end-diastolic diameter greater than or equal to 50 mm) were selected and designated as dilated HCM. The diagnosis of HCM was established in these patients either by detection of the classical form of HCM in family members, with 2-dimensional echocardiographic evidence of asymmetric septal hypertrophy (ASH; septal thickness greater than or equal to 15 mm and a ratio of septal to posterior wall thickness greater than or equal to 1.3); or by demonstrating myocardial fiber disarray in autopsy or biopsy samples. The clinical manifestations of these patients with dilated HCM were then compared with those of other forms of HCM without left ventricular dilatation; 1) 40 patients with hypertrophic obstructive cardiomyopathy (HOCM) who had resting intraventricular pressure gradients of 20 mmHg or more, 2) 80 patients with non-obstructive HCM, each of whom had ASH of the entire ventricular septum (typical ASH), and 3) 25 non-obstructive patients whose hypertrophy was localized to the apical region of the ventricular septum (apical ASH). Patients having apical hypertrophy with a spade-like configuration on the left ventriculogram were excluded from the study. Compared with HOCM and typical ASH groups, the patients with dilated HCM had family histories of significantly more frequent HCM and less frequent hypertension. The patients with dilated HCM also had significantly less fractional shortening (FS), decreased interventricular septal thickness, greater left ventricular end-diastolic pressure (LVEDP), and left ventricular dilatation. During the follow-up period (average: 3.5 years), seven patients (35%) with dilated HCM died; five from congestive heart failure (CHF), one suddenly, and one three days following mitral valve replacement. The other five patients had CHF at the time of their follow-up examination. The patients with apical ASH had clinical features similar to those of dilated HCM; a higher familial frequency, less marked septal hypertrophy, and higher LVEDP. They tended to develop left ventricular dilatation, associated with reduced fractional shortening, although left ventricular diameter at end-diastole did not exceed 50 mm. These findings suggested that dilated HCM is not a rare condition. It is observed in 12% of consecutive patients with HCM.(ABSTRACT TRUNCATED AT 400 WORDS)