Global P wave duration on the 65-lead ECG: single-site and dual-site pacing in the structurally normal human atrium.

Introduction: Pacing is believed to prevent atrial fibrillation by reducing atrial activation time. Exact correlation between P wave duration (PWD) on surface ECG and endocardial atrial activation time is still unexplored.

Methods And Results: In 15 patients without structural heart disease (9 women, age 45 +/- 14 years), single site [high right atrium (HRA), coronary sinus ostium (CSos), distal CS (CSd), high RA septum (Bachmann's bundle, BB)] and dual-site pacing (various combinations) was performed after ablation of supraventricular tachycardia. A 65-lead surface ECG was recorded simultaneously. Endocardial atrial activation time was measured off-line (stimulus - last bipolar recording), and the respective PWD was assessed using the root mean square and 65-channel summary plots. PWD during pacing from BB was significantly shorter (96 +/- 12 msec) than during HRA (121 +/- 15 msec), CSos (108 +/- 9 msec), and CSd pacing (126 +/- 14 msec; P < 0,01, respectively). PWD during dual-site pacing (HRA+BB, 91 +/- 14 msec; HRA+CSos, 96 +/- 7 msec; HRA+CSd, 90 +/- 7 msec; BB+CSd, 96 +/- 12 msec) was not significantly shorter than during pacing from BB. Correlation between endocardial atrial activation time and PWD was 0.83.

Conclusion: PWD during single-site and dual-site atrial pacing represents endocardial atrial activation time and can be measured precisely using the 65-lead surface ECG. The fact that high septal pacing results in the shortest PWD may have implications for preventive pacing in patients with atrial fibrillation.