Naoyuki Misaki

Anatomical basis of P wave duration dispersion for the prediction of the development of atrial fibrillation after cardiac surgery

Background: Atrial fibrillation (AF) is a common arrhythmia in climcal practice, and occurs frequently after cardiac surgery. Previous studies have described greater dispersion of P wave duration (P-disp) in patients (pts) with a history of AF. However, the possible predictive value of P-disp for the prediction of the development of AF remained to be clarified. Furthermore, the pathogenesis of P-disp is also unclear. The aim of this study is to evaluate prospectively whether P-disp could predict the AF development after cardiac surgery and to elucidate the pathophysiology of P-disp from the viewpoint of atrial fibrosis. Methods: We studied 30 consecutive pts undergoing cardiac surgery. Before the surgery, P wave signal-averaged ECG was recorded from standard 12 leads and 10 extraprecordial leads (two intercostal spaces upper and lower V1, V2 and V4-6). P-disp was defined as the difference between the maximum and minimum of filtered P wave duration in all of the leads. Abnormal P-disp was defined as more than 20 ms, mean+PSD of Pdisp (13.3t3.1 ms) in 12 age and sex-matched controls. The right atrial auricle resected for pump on was sampled at each surgery. The extent of atrial fibrosis (%F) of all samples was estimated by the point count method. Results: During the follow-up period of 3ltl9 days, 13 of 30 pts developed AF. Eleven (43%) of 16 pts with abnormal P-disp had the development of AF, while AF development was observed in 2 (14%) of 14 pts without abnormal P-disp. Kaplan-Meier analysis revealed that AF development was significantly more often observed in pts with than without abnormal P-disp (p=O.O035). Relative risk for the development of AF in abnormal P-disp was 4.82 (95%CI 1.28 to 18.1). Pts wth AF development had significantly greater P-disp (28.1*6.1 vs 17.8*4.0 ms, p=O.OOOl) and larger %F (23.8i8.0 vs 11.5+5.5 %, p<O.ooOl) than those without AF development. There was a significant correlation between P-disp and %F (r=O.842, p<O.OOOl). Conclusion: P-disp IS a potent predictor of AF development after cardiac surgery. Atrial fibrosis might play a role in the genesis of greater P-disp in patients with AF.