A transvenous, screw-in electrode was implanted in the right atrium of a he
althy pony and connected with an implantable pulse generator programmed to
deliver bursts of electrical stimuli to the atrium. Initially, cessation of
burst pacing resulted in short (less than 1 minute), self-terminating epis
odes of atrial fibrillation. As burst pacing continued, the episodes of ind
uced atrial fibrillation became longer. After 3 weeks of continuous atrial
pacing, atrial fibrillation became sustained (56 hours). This model of paci
ng induced atrial fibrillation can be used to study the mechanisms leading
to atrial fibrillation, its perpetuation and therapy. Our preliminary obser
vations support the concept that once atrial fibrillation starts, it sets u
p changes in the electrical characteristics of the atrium that favor its ow
n perpetuation.