Propagation velocity kinetics and repolarization alternans in a sheep model of pacing-induced atrial fibrillation

Repolarization alternans, a beat-to-beat alternation in action potential duration, enhances dispersion of repolarization when propagation velocity is involved. In this work, repolarization dynamics and propagation velocity kinetics are studied in a chronic sheep model of pacing-induced atrial fibrillation. Two pacemakers were implanted in four sheep, the first one to deliver pacing protocols and the second one to record a unipolar electrogram. Measuring in vivo in a free-behaving sheep model right atrial CV kinetics and repolarization alternans during electrical remodelling was shown to be feasible. A significant and gradual decrease of propagation velocity and right atrial effective refractory period during the weeks preceding sustained atrial fibrillation was observed. Repolarization alternans and propagation velocity kinetics are promising parameters for in vivo assessment of atrial fibrillation susceptibility.