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[Hypertrophic cardiomyopathy with left ventricular dilatation]
G Iwami1, Y Miyazaki, K Matsuyama
1Third Department of Internal Medicine, Kurume University School of Medicine.
Insights
Some patients with hypertrophic cardiomyopathy (HCM) develop dilated cardiomyopathy (DCM) features, showing reduced function and increased left ventricular size. This dilated HCM variant is observed in 12% of HCM patients and has a significant mortality rate.
Area of Science:
- Cardiology
- Genetics
- Pathology
Background:
- Hypertrophic cardiomyopathy (HCM) can present with diverse clinical and morphological phenotypes.
- Increasing evidence suggests some HCM patients may progress to a dilated cardiomyopathy (DCM)-like state.
Observation:
- A subset of 20 out of 165 HCM patients exhibited left ventricular dilatation (end-diastolic diameter ≥ 50 mm), termed dilated HCM.
- Compared to hypertrophic obstructive cardiomyopathy (HOCM) and typical apical septal hypertrophy (ASH) groups, dilated HCM patients had more frequent family histories of HCM and less frequent hypertension.
Findings:
- Dilated HCM patients demonstrated significantly reduced fractional shortening (FS), decreased interventricular septal thickness, and elevated left ventricular end-diastolic pressure (LVEDP).
- During a 3.5-year follow-up, 35% of dilated HCM patients died, primarily from congestive heart failure (CHF).
- Apical ASH patients shared similarities with dilated HCM, including higher familial frequency, less septal hypertrophy, and higher LVEDP, with a tendency towards left ventricular dilatation and reduced FS.
Implications:
- Dilated HCM is a recognized, albeit less common, manifestation within the HCM spectrum, occurring in 12% of cases.
- The findings highlight the importance of recognizing dilated HCM as a distinct phenotype with a potentially poor prognosis.
- Further research into the genetic and molecular mechanisms underlying the transition from HCM to dilated HCM is warranted.
Abstract:
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)