Effects of atrial pacing site on atrial and atrioventricular nodal function

The effects of the site used for atrial pacing on atrial and atrioventricular nodal conduction were assessed in 16 patients. In 13 patients, 3 atrial pacing sites were used: high right atrium, low lateral right atrium, and midcoronary sinus. Two recording sites were used: low septal right atrium, including His electrogram, and high right atrium. Stimulus (S) to high right atrium interval was longest with coronary sinus pacing (76 ± 7 msec) (P < 0.001), and shortest with right atrial pacing (41 ± 3 msec) (P < 0.05). There was no significant difference in stimulus to low septal right atrium from all 3 pacing sites. Atrial functional and effective refractory periods were not significantly different. Mean low septal right atrium to His was significantly shorter from the coronary sinus (93 ± 8 msec) (P < 0.001), as compared to high right atrium (139 ± 16 msec), and low lateral right atrium (129 ± 13 msec) pacing. AV nodal functional and effective refractory periods, and the paced rate producing AV nodal Wenckebach were not significantly different when comparing the three sites. Left atrial appendage and high right atrium were similarly compared in 3 additional patients, and no significant differences were found in conduction times and refractory periods.