An equine model of chronic atrial fibrillation: methodology.

We describe the development and the different features of an experimental model of chronic atrial fibrillation (AF) in equines. In four healthy ponies a dual-chamber pacemaker, with an adapted pacemaker program, was implanted transvenously in the standing animal. This adapted pacemaker induced episodes of AF by delivering a 2s burst of electrical stimuli (42 Hz) as soon as sinus rhythm was detected. Simultaneous with a surface electrocardiogram, the intra-atrial electrogram could be recorded to determine the atrial electrogram morphology. Programmed electrical stimulation (PES) was used to determine the atrial effective refractory period (AERP) and the rate adaptation of the AERP, the sinus node recovery time (SNRT) and the corrected SNRT, AF vulnerability, AF cycle length and AF duration. This experimental AF model can be used to study the pathophysiology of chronic AF in equines.