The Horse Racing Integrity and Safety Authority launched a pilot program to monitor the hearts of certain horses, trying to find factors in sudden deaths.
LOUISVILLE, Ky. — The deaths of racehorses during Kentucky Derby Week and the Spring Meet in 2023 shook the horse racing world.
12 horses died at Churchill Downs over two months, a number considered “unusually high” to a national horse racing safety entity.
In the months that followed, the Horse Racing Integrity and Safety Authority (HISA) formed a work group to investigate exercise-associated sudden deaths—deaths of clinically healthy horses during or within an hour of exercise.
Dr. Karen Hassan, HISA’s compliance and research veterinarian, told WHAS 11 that the organization conducted a retrospective analysis of horses that died from exercise-associated sudden death (ESAD).
“During that analysis, we found the largest number to be horses early in their career, between zero and five starts,” Dr. Hassan said. “And also we did an exercise history analysis and found that these horses, when compared to their cohorts, so similar age, gender, that these horses exercise less and exercise less intensely than their match cohorts.”
HISA also launched a pilot study in which horses wore devices during exercise that allowed experts to analyze electrocardiograms (ECGs). Four horses that died while wearing the devices were later found to have been in atrial fibrillation at the time.
“When the device was put on the horse, the horse went out and exercised and died of a fatal arrhythmia,” said Dr. Hassan. “People go into atrial fib and get out of atrial fib, you could self convert. It was thought to be relatively benign, and now we know now that it isn’t. And if a horse is an atrial fibrillation, the horse shouldn’t go out and train,” said Dr. Hassan.
Dr. Hassan says the condition was not detected in real time, but discovered later. She says they are working with a company to create a tracker that will be available for trainers and veterinarians so they can detect atrial fibrillation before it’s too late.
HISA says during the first six months of 2025, EASD accounted for 8% of horse racing deaths and 18% of training deaths at racetracks subject to their rules.
In the same report, HISA says retrospective analysis of cases shows more than 50% were likely related to cardiac issues.
“And we don’t know how many of those were atrial fibrillation or another arrhythmia, and that’s where the research is going,” said Dr. Hassan.
Louisville-based trainer Dale Romans says there’s nothing worse in his profession than experiencing the death of a horse, which he did in 2023.
“We’re very close to these animals, and also the health and welfare of our jockeys is so important. When a horse goes down a lot of times, a jockey gets hurt,” Romans said.
He said that over the past two years, they have increased monitoring of all his horses’ movements to detect problems before they become fatal. He is optimistic about new wearable technology that could track potential heart conditions.
“If we can figure out a way, which we’re on the path to doing, to identifying the horses at risk for heart failure, then we can maybe do something different or even treat it and get them over it,” Romans said.