Experimental model of atrial fibrillation induced by transesophageal cardiac pacing

Abstract

Introduction. Atrial fibrillation (AF) is the most frequently encountered cardiac arrhythmia in clinical practice. Several studies demonstrated that pacing-induced rapid atrial rates result in sustained non-valvular atrial fibrillation, but this finding has been considered to be restricted to large animal models, while small rodents are generally considered refractory to such arrhythmias due to their small cardiac mass. The aim of our study was to develop an experimental model of spontaneous AF in rats using transesophageal cardiac pacing. Material and Methods. Seven 15-week-old male Wistar rats were implanted with radiotelemetry devices to dynamically record ECG signals over 24-h. After 2 weeks of post-surgical recovery, three of the rats (AF group) were submitted to daily transesophageal cardiac pacing. Burst pacing was performed using 20 consecutive cycles of 30 sec (rate: 4,000 bpm, voltage: 14-16), with 5 min of recovery between the stimulation cycles. After 5 consecutive days of cardiac pacing, a 24-h ECG recording was performed in the rats from the AF group, as well as in the four rats assigned to the control (C) group. All arrhythmic events were analysed with dedicated software. Results. During the cardiac pacing protocol, a total of 9 AF episodes were observed, with the highest incidence in the last day of stimulation. The first arrhythmic event was recorded in the third day of the study. All three stimulated rats presented at least one episode of stimulation-induced AF. On the 24-h ECG recordings, rats from the AF group presented a total of 76 atrial arrhythmic events, including37 atrial extrasystoles (AES), 33 atrial couplets, and 6 short episodes of spontaneous, non-sustained AF, whereas only 10 arrhythmic events (i.e., 6 AES and 4 atrial couplets) and no AF episodes were observed in the C group. Conclusions. The onset and the persistence of reentrant arrhythmias have been shown to depend on a minimum tissue mass. Accordingly, such arrhythmias have generally been considered to be restricted to large animal models. The present data demonstrate that spontaneous, non-sustained AF can be easily induced by rapid transesophageal atrial pacing in small rodents, providing a new experimental model for the study of the electrophysiological mechanisms involved in AF genesis.