Analysis of the P Wave with Signal Averaging to Assess the Risk of Atrial Fibrillation after Coronary Artery Bypass Surgery

Abstract

P wave signal averaging was performed in 91 consecutive patients undergoing coronary artery bypass grafting to detect patients at risk of postoperative atrial fibrillation (AF). Sixteen patients (17.5%) developed AF after surgery. The P wave duration on the signal-averaged electrocardiogram (ECG) and on surface ECG was prolonged in AF patients compared to others (respectively 141 ± 12 vs. 132 ± 12 ms and 124 ± 9 vs. 113 ± 9 ms). The root mean square voltages (RMS) of the total P wave were not different between the two groups; the RMS of the late portion of the P wave (late RMS) was significantly higher (0.25 ± 0.15 vs. 0.17 ± 0.10 µV) and the RMS of the first 110 ms of the P wave (early RMS) significantly lower (0.88 ± 0.28 vs. 1.09 ± 0.33 µV) in AF. The late/early RMS ratio was different (0.29 ± 0.16 vs. 0.17 ± 0.11). In a multivariate analysis only age and the late/early RMS ratio were predictive for AF.