Histopathologic findings of endomyocardial biopsies in pediatric patients with arrhythmias or conduction disturbances.

Histopathologic findings of endomyocardial biopsy in 23 pediatric patients with arrhythmias or conduction disturbance were analyzed. ECG abnormalities consisted of atrioventricular block (AVB) in 11, ventricular arrhythmia including premature ventricular contractions (PVC) and ventricular tachycardia in 7, sick sinus syndrome (SSS) in 3, and bundle branch block in 2 cases. Biopsy specimens were obtained from the right ventricle in all cases and, additionally, from the right atrium in SSS cases. Biopsy revealed significant pathology in 19 cases (83%). Advanced histologic changes, including myocyte hypertrophy, disarrangement of muscle bundles, and interstitial fibrosis with or without myocyte degeneration, were observed in 7/11 AVB cases and 1/6 PVC cases. SSS cases showed interstitial fibrosis with disarrangement of muscle bundles in the right atrium, but no significant pathologic changes were seen in the right ventricle. There was no clinical evidence of hypertrophic or dilated cardiomyopathy, cardiac defects, or other heart disease in these patients. It is suggested that these cases may fall under the arrhythmia-conduction disturbance type of cardiomyopathy.