Systemic embolism in chronic sinoatrial disorder.

We attempted to estimate the prevalence of systemic embolism in patients with chronic sino-atrial disorder. In a group of 100 patients, evidence of embolism was found in 16, of whom 15 had the bradycardia-tachycardia syndrome. In 712 controls with chronic complete heart block, who were matched for age and sex, embolism had occurred in only 1.3 per cent (P less than 0.001). A second group of 41 patients with chronic ventricular bradycardia and atrial flutter or fibrillation had an embolic prevalence of 7.3 per cent, which was also greater than that in the controls (P less than 0.05). All patients with sinoatrial disorder in whom systemic embolism developed were over 54 years of age; multiple episodes occurred in six. The risk of embolization remains even if the bradycardia-tachycardia syndrome is replaced by stable atrial fibrillation. Impaired atrial function appears to be a key factor in predisposing to intracardiac thrombosis, and paroxysmal supraventricular tachycardia increases the risk of subsequent embolization.