P-wave dispersion index: a marker of patients with paroxysmal atrial fibrillation.

The P-wave triggered signal-averaged ECG (PSA-ECG) has shown controversial results in the evaluation of patients with paroxysmal atrial fibrillation (PAF). Previously tested PSA-ECG parameters, i.e. P-wave filtered duration (Pd), root mean square voltage of the last 20 ms of the P-wave vector magnitude (RMS20) were compared with an index of P-wave dispersion (PDi = Pd (X, Y, Z lead) S.D./mean value x 100) in the evaluation of 40 subjects (24 M, 54 +/- 7 years) with or without PAF, without anti-arrhythmic therapy. Patients presented vs. controls higher Pd values (138 +/- 14 ms vs. 120 +/- 12 ms, P < 0.0005), PDi (8 +/- 2 ms vs. 1 +/- 1 ms, P < 0.0001) but no difference in RMS20. In the comparison of patients vs. controls, Pd > or = 125 ms presented 62% sensitivity and 78% specificity, PDi > or = 5.5 ms showed 83% sensitivity and 81% specificity: the combination of these two criteria differentiated a subgroup of patients with no recurrence of PAF in a 12 +/- 4 months follow-up PDi and Pd could be powerful criteria in the identification of patients and could be able to identify patients with low recurrences of PAF.