Atrial repolarization in patients with left ventricular dysfunction.

BACKGROUND

Atrial depolarization is represented by the P wave on the electrocardiogram (ECG), while atrial repolarization (Ta wave) is usually obscured by the QRS complex. In patients with third-degree atrioventricular block, the Ta wave can be observed and studied. Although atrial repolarization has been described in healthy subjects and in those with paroxysmal atrial fibrillation, it has not been studied in left ventricular dysfunction.

METHODS

Patients with pacemaker implanted for third-degree AV block were studied. Group 1 included patients with normal ejection fraction (LVEF ≥55 %), and group 2 included patients with reduced ejection fraction (LVEF ≤40 %). Pacemakers were programmed to VVI pacing at 40 bpm, and six standard 12‑lead ECGs were recorded. P waves not followed by QRS complex for 500 ms were identified. PTa segments were extracted, averaged, and analyzed for duration, amplitude, axis and dispersion.

RESULTS

Of 31 enrolled patients, 25 were included in the final analysis (13 in group 1, 12 in group 2). The mean PTa duration was 482 ± 36 ms and was not different between the groups. P wave duration, Ta amplitude, and Ta axis also were not different. Ta axis was northwest in all patients, opposite to the direction of atrial depolarisation. PTa dispersion was significantly higher in group 2 (74 ± 21 ms) compared to group 1 (54 ± 14 ms, p = 0.008).

CONCLUSION

PTa wave amplitude, duration, and axis are not altered in left ventricular dysfunction. PTa dispersion is increased in these patients and may be a marker of elevated risk for atrial arrhythmias.