Interatrial conduction during cardiac pacing.

DDD pacemakers sense and pace right-sided cardiac chambers. The relationship of atrial to ventricular systole on the left side of the heart is of importance for systemic hemodynamics. Effective atrioventricular synchrony is partially determined by interatrial conduction time (IACT). At the time of DDD pacemaker implantation, interatrial conduction was measured using an intraesophageal pill electrode in 25 patients who were on no cardiac medications. Mean interatrial conduction time for all patients prolonged from 95 +/- 18 ms during sinus rhythm to 122 +/- 30 ms during right atrial pacing (p less than 0.001). In 16 patients with P wave duration less than 110 ms interatrial conduction prolonged from 85 +/- 10 ms during sinus rhythm to 111 +/- 9 ms during right atrial pacing (p less than 0.01) compared to 114 +/- 20 ms prolonging to 111 +/- 19 ms (p less than 0.01) in 9 patients with P wave duration greater than 110 ms. In each patient, while atrioventricular conduction prolonged with incremental right atrial pacing, interatrial conduction times did not vary. Interatrial conduction prolongs from baseline during atrial pacing and remains constant at all paced rates from 60-160 beats per minute. In addition to longer interatrial conduction times during sinus rhythm, patients with electrocardiographic P wave prolongation have longer interatrial conduction times during right atrial pacing than do normals (p less than 0.001). Based on interatrial conduction times alone, the AV interval during DDD cardiac pacing should be approximately 25 ms longer during AV pacing as compared to atrial tracking.