Familial sick sinus syndrome with atrioventricular conduction disturbance.

A family with sick sinus syndrome is presented: a mother and her 2 daughters affected with sinus node dysfunction. Electrophysiological studies revealed abnormal atrioventricular conduction in the 2 daughters. All 3 individuals were implanted with a permanent pacemaker to relieve their symptoms. Endomyocardial biopsy from the right ventricle of one daughter showed disarrangement, degeneration, myocyte necrosis and interstitial fibrosis suggestive of myocardial disease.