Signal-averaged P-wave abnormalities and atrial size in patients with and without idiopathic paroxysmal atrial fibrillation

Background The relation between abnormalities in the signal-averaged P wave and atrial size has not been determined in patients with paroxysmal atrial fibrillation (PAF) without structural heart disease. Methods Signal-averaged electrocardiograms of P waves were recorded in 38 patients with idiopathic PAF and 34 control subjects. Filtered P-wave duration (FPD) and root-mean-square voltages for the last 20 ms of the vector magnitude were measured. Atrial volume was calculated by cine magnetic resonance imaging. Results FPD was longer (131.7 ± 10.9 ms vs 120.8 ± 8.6 ms, P < .0001) and root-mean-square voltage was lower (2.89 ± 1.29 μV vs 3.62 ± 1.48 μV, P < .05) in the PAF group than in control subjects. However, the various atrial volumes were similar in the 2 groups. In controls, FPD was significantly correlated with left (r = 0.593, P < .0001) and total (r = 0.492, P < .005) atrial volume but not with right atrial volume. In patients with PAF, no significant correlations were found between FPD and any of the atrial volumes. Elderly patients with PAF (age ≥ 60 years) showed longer FPD than younger patients with PAF (139.2 ± 9.4 ms vs 125.6 ± 8.0 ms, P < .0001). Conclusions FPD is influenced by the left and total atrial volumes in the normal heart without PAF. Prolonged FPD seems to be a useful predictor of idiopathic PAF among patients without atrial enlargement, especially in the elderly.