Myofiber branching in idiopathic cardiomyopathy under the scanning electron microscope

Myofiber changes in idiopathic cardiomyopathy were examined by the scanning electron microscope in order to elucidate the three-dimensional architecture. Muscle specimens were sampled from the ventricular walls of 13 autopsy cases (7 with the congestive type, 3 with the hypertrophic type and 3 controls), and observed according to the Evan's method. In addition, the same samples were investigated histopathologically using the tribasic staining originated by Kurotaki, and the muscle cell diameters were analyzed with a pendigitizer computer system. In congestive cardiomyopathy, the hypertrophic myofibers branched more frequently and varied more in thickness than in the controls. The complex myofiber architecture seemed to be the result of the compensation for muscle weakness. On the other hand, hypertrophic cardiomyopathy revealed three-dimensional myofiber disarray, which was fundamentally constituted from a ring formation of the myofiber branches, but only at the ventricular septal wall. The structure appeared only to promote muscle stiffness.