Propagation velocity kinetics and repolarization alternans in a free-behaving sheep model of pacing-induced atrial fibrillation.
OBJECTIVE
Experimental models have reported conflicting results regarding the role of dispersion of repolarization in promoting atrial fibrillation (AF). Repolarization alternans, a beat-to-beat alternation in action potential duration, enhances dispersion of repolarization when propagation velocity is involved.


RESULTS
In this work, original electrophysiological parameters were analysed to study AF susceptibility in a chronic sheep model of pacing-induced AF. Two pacemakers were implanted, each with a single right atrial lead. Right atrial depolarization and repolarization waves were documented at 2-week intervals. A significant and gradual decrease in the propagation velocity at all pacing rates and in the right atrial effective refractory period (ERP) was observed during the weeks of burst pacing before sustained AF developed when compared with baseline conditions. Right atrial repolarization alternans was observed, but because of the development of 2/1 atrioventricular block with far-field ventricular interference, its threshold could not be precisely measured. Non-sustained AF was not observed at baseline, but appeared during the electrical remodelling in association with a decrease in both ERP and propagation velocity.


CONCLUSIONS
We report here on the feasibility of measuring ERP, atrial repolarization alternans, and propagation velocity kinetics and their potential in predicting susceptibility to AF in a free-behaving model of pacing-induced AF using the standard pacemaker technology.
Pruvot
Etienne
E
Service of Cardiology, BH10-982, CHUV, Rue du Bugnon 46M, 1011 Lausanne, Switzerland. etienne.pruvot@chuv.ch
Jousset
Florian
F
Ruchat
Patrick
P
Vesin
Jean-Marc
JM
Prudat
Yann
Y
Zerm
Thomas
T
Fromer
Martin
M
D000200:Action Potentials / Q000502:physiology; D000818:Animals; D001281:Atrial Fibrillation / Q000209:etiology* / Q000503:physiopathology*; D002304:Cardiac Pacing, Artificial; D004195:Disease Models, Animal; D006329:Heart Conduction System / Q000503:physiopathology; D007700:Kinetics; D009431:Neural Conduction / Q000502:physiology; D010138:Pacemaker, Artificial; D012756:Sheep