Signal-averaged P wave duration predicts early recurrence of atrial fibrillation after cardioversion

Thirty-two patients had signal-averaged P wave duration measured after elec trical cardioversion of AF, and were followed for 1 year or until there was a recurrence. The use of antiarrhythmic medications was left to the discre tion of the attending physician. Among 20 patients not taking antiarrhythmi c medication, the 11 patients who had a recurrence of AF within 3 months of cardioversion had a significantly longer signal-averaged P wave duration c ompared to the 9 patients who did not (148 +/- 17 vs 135 +/- 20 ms, P = 0.0 05). There was no difference in clinical parameters or left atrial diameter . A signal-averaged P wave duration cutoff anywhere between 130 and 135 ms correctly classified 85% of patients with a sensitivity of 81% and a specif icity of 89%. In patients faking antiarrhythmic medications, signal-average d P wave duration did not correlate with the risk of recurrence. In patient s not taking antiarrhythmic medications, signal-averaged P wave duration ca n be used to predict the risk of an early recurrence of AF after cardiovers ion. The poor predictive value in patients taking antiarrhythmics may be du e to changes in the atrial refractory period, which are not reflected in P wave duration.