Abstract
Two apparently healthy racehorses (horses 1 and 2) showed abrupt decelerations during a race and finished a long way behind the winners. ECG examinations of both the horses, shortly after the race, exhibited atrial fibrillation (AF). In particular, the AF of horse 1 coexisted with ventricular premature contractions (VPCs) on the ECG recording at 10 min after the race. The VPCs were frequent and multifocal. Horse 2 had no association with VPC. The repeated post-race examination revealed spontaneous disappearance of the AF with both of the horses resuming a normal sinus rhythm within 24 hrs. Thereafter, horse 1 had no start and retired from a race. On the other hand, horse 2 had 28 starts, winning 6 races, and 3 with placings. With no association with PVC, the prognosis as regards paroxysmal AF could be favorable in the racehorse.
