High incidence of significant pathology in endomyocardial biopsy and familial occurrence in cases with arrhythmia and/or conduction disturbance.

In our series of studies of cardiomyopathy with endomyocardial biopsy in 1500 cases, we have noticed that there were a certain number of patients with arrhythmias and/or conduction disturbance who showed no evidence of hypertrophic or dilated form of caridiomyopathy but showed significant pathology in the biopsy. Significant pathology was determined when the biopsy findings from the right atrium and the right ventricle showed apparent pathology such as interstitial fibrosis, myocyte degeneration, and fragmentation of muscle bundles. Among 226 biopsied patients in whom arrhythmia and/or conduction disturbance were the main clinical feature, 85 patients (38%) demonstrated significant pathology in their biopsy. Familial occurrence was note-worthy among these patients. We propose that these cases should be grouped as nonhypertrophic, nondilated, and nonrestrictive cardiomyopathy, and suggest the term electric disturbance type of cardiomyopathy (ECM).