ACUTE EFFECTS OF DUAL-SITE RIGHT ATRIAL-PACING IN PATIENTS WITH SPONTANEOUS AND INDUCIBLE ATRIAL-FLUTTER AND FIBRILLATION

Objectives. We tested the ability of dual-site right atrial pacing to prevent atrial fibrillation (AF) or atrial putter induced by single-si te atrial pacing and correlated its efficacy with clinical patient cha racteristics, atrial activation times and refractory periods. Backgrou nd. Prevention of recurrent AF with long-term dual-site right atrial p acing has been demonstrated in our previous studies. However, the mech anism of antiarrhythmic benefit is unclear. Methods. Using standard el ectrophysiologic methods, baseline electrocardiographic and electrophy siologic measurements (mean +/- SD) were obtained. Programmed atrial s timulation was performed for AF or atrial butter induction. Atrial pac ing was performed at two drive cycle lengths (600 and 400 ms) and foll owed by one to three atrial extrastimuli at one to four pacing sites i n the right atrium. In patients with inducible AF or atrial flutter, r einduction was then attempted during a dual-site atrial pacing drive t rain. This was achieved by simultaneously pacing at the high right atr ium and coronary sinus ostium at an identical rate to the baseline sti mulation, with the atrial extrastimuli being delivered at the pacing s ite responsible for the initial AF episode initiation.Results. Twenty patients (10 men, 10 women, mean [+/-SD] age 64 +/- 16 years) with sym ptomatic AF (n = 10) or atrial butter (n = 10) were studied. There,vas a significant abbreviation of the P wave duration to 103 +/- 17 ms wi th dual-site pacing compared with sinus rhythm (120 +/- 12 ms, p = 0.0 05) and high right atrial pacing (121 +/- 17 ms, p = 0.005). This was also associated with a characteristic change in P wave configuration w ith an inferior and leftward axis shift. The effective refractory peri od at the high right atrium remained unchanged with dual-site atrial p acing compared with single-site high right atrial pacing. Sixteen pati ents had inducible AF or atrial flutter and could be tested after dual -site atrial pacing. The induced atrial tachyarrhythmia was suppressed in nine patients (56%), who had either induced AF (n = 5) or atrial p utter (n = 4). The difference in the effective refractory period betwe en the high right atrium and the coronary sinus ostium pacing sites wa s significantly greater (33 +/- 12 ms) in patients with suppression of atrial tachyarrhythmia with dual-site atrial pacing compared with pat ients without suppression (15 +/- 13 ms, p = 0.001). P wave abbreviati on did not correlate with arrhythmia suppression. There was no correla tion between suppression of inducible AF or atrial putter and demograp hic or clinical patient characteristics. Conclusions. Dual-site right atrial pacing from the high right atrium and coronary sinus ostium can suppress inducible AF or atrial putter elicited after single-site hig h right atrial pacing in selected patients. Acute suppression is more likely in patients with greater dispersion of right atrial refractorin ess between these two sites.