Sino-atrial syncope

Abstract Thirteen patients are described in whom cardiovascular syncope occurred due to disorder of sino-atrial conduction and depression of the atrioventricular (A-V) junctional escape pacemaker system. Significant atrioventricular block was not present in these patients. Two mechanisms of cardiac slowing were observed. Type I sino-atrial syncope was characterized in six patients by severe sino-atrial block and bradycardia. Type II sino-atrial syncope was characterized in seven patients who experienced periods of bradycardia and tachycardia, with asystole and syncope occurring at the termination of the tachycardia. In one of these patients it occurred transiently after an acute myocardial infarction. In twelve patients, sinoatrial syncope was a chronic and recurrent problem, and in eleven of these it was treated successfully with ventricular demand pacing.