Contribution of cardiac muscle cell disorganization to the clinical features of hypertrophic cardiomyopathy

Heart failure rarely develops in the setting of hypertrophic cardiomyopathy (HCM). Because of this, cardiac muscle cell disorganization (CD), which is a histologic characteristic of HCM, is not believed to be responsible for the development of systolic dysfunction. The aim of the present study was t o clarify whether CD can cause systolic dysfunction and ventricular dilatio n in patients with HCM. Sixteen hearts from patients with HCM obtained at a utopsy were divided into two groups: group A (n = 11), without biventricula r dilation, and group B (n = 5), with dilation. Specimens consisting of tra nsverse and longitudinal tissue sections of the ventricles were prepared, a nd the extent of CD and interstitial fibrosis was quantified, using light m icroscopy. None of the patients in group A had had chronic congestive heart failure, while all of the patients in group B had died of congestive heart failure. In group B, CD was not limited to the interventricular septum. Ra ther, diffuse CD was observed in both ventricular free walls. The extent of CD was significantly greater in group B than in group A, while the degree of interstitial fibrosis was similar in the two groups (13.6% in group A vs 14.6% in group B). These results suggest that CD may be responsible for sy stolic dysfunction and ventricular dilation.