SIGNAL-AVERAGED P-WAVE IN PATIENTS WITH WOLFF-PARKINSON-WHITE SYNDROME AFTER SUCCESSFUL RADIOFREQUENCY CATHETER ABLATION

Objectives. We attempted to establish a relation between the atrial co nduction time assessed by the signal-averaged P wave electrocardiogram and episodes of paroxysmal atrial fibrillation in patients with the W olff-Parkinson-White syndrome. Background. The incidence of paroxysmal atrial fibrillation is higher in patients with the Wolff-Parkinson-Wh ite syndrome than in normal persons. However, the role of intraatrial conduction delay in precipitating the disorganization of atrial rhythm is not completely understood. Methods. The total duration of the sign al-averaged P wave and the P wave in standard lead II was evaluated af ter successful radiofrequency catheter ablation in 28 patients with th e Wolff-Parkinson-White syndrome. The data obtained from 17 patients ( 61%) with a documented history of prior paroxysmal atrial fibrillation (group 1) were compared with those obtained from 11 patients (39%) wi thout a history of atrial fibrillation (group 2). Both groups were fur ther compared with a normal control population. Results. The mean a SD signal-averaged P wave duration in group 1 was 141.94 +/- 9.47 ms (ra nge 130.0 to 171.0). Fourteen patients (82%) in this group showed a P wave duration > 135.0 ms. In group 2, the signal averaged P wave durat ion was 126.64 +/- 8.72 ms (range 111.0 to 136.0). Only one patient in this group (9%) showed a P wave duration > 135.0 ms (p < 0.000, group 1 vs. group 2). The signal-averaged P wave duration in the control gr oup was 124.46 +/- 4.49 ms (range 115.0 to 129.5; p < 0.000, group 1 v s. the control group; p < 0.454, group 2 vs. the control group). The P wave duration in lead II was 92.06 +/- 8.85 ms in group 1 and 92.27 /- 7.86 ms in group 2 (p < 0.949). Using a cutoff value of < 135.0 ms for a normal signal averaged P wave duration, the method had a sensiti vity and specificity and positive and negative predictive values of 82 %, 91%, 93% and 77%, respectively, for identifying patients with clini cal paroxysmal atrial fibrillation. Conclusions. In the current study, the signal-averaged P wave showed a prolonged intraatrial conduction time in patients with the Wolff-Parkinson-White syndrome and paroxysma l atrial fibrillation. These patients can be differentiated from those with the pre excitation syndrome without clinical atrial fibrillation as well as from normal subjects. The prolonged intraatrial conduction time may serve as an atrial substratum for development and maintenanc e of the fibrillatory state.