Effects of intravenous
atropine on postpacing impulse recovery time of the subsidiary pacemakers were studied by incremental atrial pacing in 9 patients with sinus nodal (SN) dysfunction. Patients having either or both of the following anomalies are used: 1) persistent sinus
bradycardia (sinus cycle length greater than 1000 msec), or documented episodes of
sinoatrial block or arrest and/or 2) maximum corrected SN recovery time of longer than 525 msec before and after
atropine. Seven patients had a history of cerebral ischemic symptoms. The mean +/- SEM of the maximum A-V junctional recovery times (MJRTs) before and after
atropine, measured in 5 patients, were 2,485 +/- 825 msec and 1,164 +/- 281 msec, respectively (p less than 0.01). The average percent reduction of the junctional escape times in these 5 patients was 53.2%. In all 9 patients MJRT shortened to less than 1,610 msec after
atropine. Moreover, a low atrial pacemaker also was the escape mechanism following pacing in 2 patients after
atropine; the maximum atrial recovery times were 2,500 msec and 1,220 msec, respectively. We conclude that
atropine can markedly enhance escape mechanism of the subsidiary pacemakers in patients with SN dysfunction.