Electrocardiographic features of P waves from patients with transient atrial fibrillation.

The electrocardiographic characteristics of P waves from patients having more than two episodes of transient atrial fibrillation (T-af) were examined during an episode-free period. The P waves of these patients recorded from the X Y Z leads of Frank's lead system on high-speed and high-gain recordings revealed longer durations than those of the normal control subjects (p less than 0.001), while the standard 12 lead ECG did not show any difference in width between the 2 groups. The configuration of the P loops on VCGs showed abnormal irregularities, such as bites or notches, in 16 of 28 cases of the T-af group. The maximum magnitudes of the P loops in VCGs and those in SVECGs were greater in the T-af group than those in the normal group (p less than 0.05). Body surface maps during atrial excitation showed that the duration of the anterior maximum was longer than that of the left maximum, and that the values of both maxima of the T-af group were longer than those of the normal group (p less than 0.01). These findings suggest the presence of intra-atrial conduction disturbances in patients with this disease, which might contribute to the genesis of this arrhythmia. Furthermore, these electrocardiographic characteristics of the P waves in the T-af group can be used as predictive and diagnostic signs of this arrhythmia even during an episode-free period.