Relevance of electrical remodeling in human atrial fibrillation: results of the Asymptomatic Atrial Fibrillation and Stroke Evaluation in Pacemaker Patients and the Atrial Fibrillation Reduction Atrial Pacing Trial mechanisms of atrial fibrillation study.

BACKGROUND: In animal models of atrial fibrillation (AF), changes in atrial electrophysiological properties are associated with the development of AF. Their relevance to human AF is unclear.

METHODS AND RESULTS: The Asymptomatic Atrial Fibrillation and Stroke Evaluation in Pacemaker Patients and the Atrial Fibrillation Reduction Atrial Pacing Trial enrolled 2580 patients receiving a dual-chamber pacemaker, who were older than the age of 65 and had a history of hypertension, but no history of AF. Serial noninvasive electrophysiological testing was performed over 2 years in a subgroup of 485 patients. There were no differences in the clinical characteristics between patients with and those without device-detected atrial tachyarrhythmias during the first year. Patients with atrial tachyarrhythmias had longer paced (153±29 versus 145±28 ms; P=0.046) and sensed (128±46 versus 118±25 ms; P=0.06) P-wave durations and were more likely to have AF induced during electrophysiological testing (23.5% versus 13.6%; P=0.03). They had similar corrected sinus node recovery times at 90 bpm (388±554 versus 376 ± 466 ms; P=0.86), atrial effective refractory periods at 90 bpm (250±32 versus 248±36 ms; P=0.70), and rate-adaptive shortening of the atrial effective refractory periods (14±13 versus 12±14 ms; P=0.11). There were no significant differences in the change in electrophysiological properties over 2 years between patients with and those without atrial tachyarrhythmias.

CONCLUSIONS: Prolonged P-wave duration, but not differences in atrial effective refractory periods, was associated with the development of atrial tachyarrhythmias in pacemaker patients.