Electrophysiologic testing in patients with sinus pauses and/or sinoatrial exit block

28 symptomatic patients with documented episodes of sinus pauses and/or sinoatrial exit block underwent electrophysiologic study. Abnormal responses to electrophysiologic testing were observed in 23/28 patients (82%). Abnormal prolongation of the maximum sinus node recovery time (SNRT max) occurred in 17/28 (61%) patients, of postpacing cycles 2.10 (secondary pauses) occurred in 21/28 (75%), and of estimated sinoatrial conduction time occured in 15/28 (54%). The incidence of abnormal responses to rapid atrial pacing (prolonged SNRT max or secondary pauses) (22/28, 79%) was higher than the incidence of abnormal responses to premature atrial stimulation (15/28, 54%) (P less than 0.005). Life-threatening cardiac arrhythmias were observed, prior to electrophysiologic study, in 5 out of 28 (18%) patients. Symptomatic patients with sinus pauses and/or sinoatrial exit block frequently (23/28, 82%) showed abnormal responses to electrophysiologic testing and have a relatively high incidence of life-threatening arrhythmias.