Endomyocardial biopsy findings in patients with atrioventricular block in the absence of apparent heart disease

The purpose of this study was to examine the histopathological findings of right ventricular endomyocardial biopsies from ten patients less than 60 ye ars of age (47 +/- 9.8 (mean +/- SD) years) with documented atrioventricula r block but without apparent heart disease. They underwent electrophysiolog ical testing, echocardiography, coronary angiography, and right ventricular endomyocardial biopsy. Biopsy specimens were assessed for morphologic chan ges in myocyte diameter, fibrosis, disarray, and degeneration. Electrophysi ological testing demonstrated atrioventricular nodal block in 2, intra-His bundle block in 2, and infra-His bundle block in 6 patients. Histology reve aled evidence of myocardial fibrosis with either myocyte hypertrophy or dis array in 7 of the 10 patients. The results of electrophysiological testing did not correlate with the histopathological findings or severity. In one p atient, heart failure appeared during the follow-up period. We conclude tha t patients with atrioventricular block of unknown etiology have histologica l abnormalities of the ventricular endomyocardium in addition to the conduc tion system disturbances. We consider such cases as constituting one of the disease groups of cardiomyopathy, and suggest that it is necessary to foll ow up the clinical course in these patients.