Heart block in Kearns Sayre syndrome: electrophysiologic pathologic correlation

A 13 yr old boy with Kearns Sayre syndrome, consisting of retinitis pigmentosa, external ophthalmoplegia, and myocardial fibrosis, is presented. A review of the clinical findings and electrocardiographic changes over a period of three years showed progressive atrioventricular and intraventricular conduction system disturbances. Electrophysiologic documentation by His bundle recordings localized the atrioventricular (AV) block distal to the AV node. Postmortem examination revealed microscopic degeneration and fibrosis in the distal portion of the bundle of His and the right and left bundle branches. An approach to cardiac evaluation and therapy is discussed.