Dispersion of signal-averaged P wave duration on precordial body surface in patients with paroxysmal atrial fibrillation

Aims This study sought to investigate whether the spatial dispersion of sig nal-averaged P wave duration would be increased in patients with paroxysmal atrial fibrillation, by use of precordial mapping of the P wave signal-ave raged EGG. Methods and Results The P wave signal-averaged ECG was recorded by the P wa ve-triggering method from 16 precordial leads in 55 patients with paroxysma l atrial fibrillation and 57 control subjects. As an index of the dispersio n of signal-averaged P wave duration, we obtained the difference between th e maximum and minimum in 16 recording sites. The dispersion was significant ly greater in the patients with paroxysmal atrial fibrillation than the con trols (26.6 +/- 9.5 vs 14.8 +/- 6.7 ms, P<0.0001). In 25 patients with symp tomatic attacks of paroxysmal atrial fibrillation, the signal-averaged ECG was repeated 1 h after a single dose of orally administered pilsicainide, a new class Ic drug. These patients were prospectively followed-up for 10 +/ - 11 months with pilsicainide. The rate of freedom from recurrence of parox ysmal atrial fibrillation attacks was significantly (P<0.0001) higher in pa tients with whom dispersion was decreased by the single dose (54%[7/13]) th an in those in whom dispersion increased (8%[1/12]). Conclusion Increased dispersion of signal-averaged P wave duration would pl ay an important role in generating paroxysmal atrial fibrillation and would be useful in the prediction of drug efficacy to evaluate the change in dis persion by a single administration of pilsicainide.