Syncope and cerebral dysfunction caused by bradycardia without atrioventricular block

In this paper six patients, aged 50 to 74 years, with chronic symptomatic sinoatrial bradycardia are described; none had more than first degree A-V block. The cause of the bradycardia was not evident except in one, who had coronary artery disease with myocardial infarction. Five patients suffered from syncopal attacks, which in 3 were documented to be related to cardiac slowing or arrest. One patient had evidence of effort fatigue, and another had symptoms of impaired cerebral and peripheral circulation. Electronic cardiac pacing was effective in improving cardiac output and relieving symptoms. Chronic sinoatrial bradycardia is much less common than A-V block as a cause of cardiogenic syncope but must be considered in the differential diagnosis of fainting.