Quantitative analysis of the distribution of cardiac muscle cell disorganization in the left ventricular wall of patients with hypertrophic cardiomyopathy.

The distribution of cardiac muscle cell disorganization in different regions of the left ventricular wall was studied quantitatively in 52 patients with hypertrophic cardiomyopathy. Cellular disorganization in the ventricular septum was both common and extensive (mean area of septal tissue section disorganized, 35 ± 4%). Disorganization was also substantial (24 ± 3%) in the left ventricular free wall of these patients, although less marked than in the ventricular septum (p < 0.05). Anterior left ventricular free wall disorganization was particularly extensive (32 ± 4%) and did not differ significantly from that present in the ventricular septum. Marked cardiac muscle cell disorganization (⩾ 5% of the tissue section) was diffusely distributed in the ventricular septum and left ventricular free wall in 33 of the 52 patients (63%).Particularly marked left ventricular free wall and combined free wall and septal disorganization was present in 14 patients without functional limitation in whom sudden death occurred early in life (⩽ 25 years of age) and was the initial manifestation of cardiac disease. In contrast, although abnormally arranged cardiac muscle cells were identified in the left ventricular free wall in 47% of patients with other congenital or acquired heart diseases or normal hearts, this disorganization was usually limited in extent (mean area of section disorganized, 2 ± 0.5%).Hence, in a large population of patients with hypertrophic cardiomyopathy, cellular disorganization was widely distributed throughout both the ventricular septum and left ventricular free wall. No definitive conclusions can be made regarding the significance of this distribution of cellular disorganization; however, our data suggest that this pattern may represent a diffuse cardiomyopathic process and be a determinant of clinical outcome in certain patients with hypertrophic cardiomyopathy.