September 25, 2025 (Lexington, KY) &#8211; The Horseracing Integrity and Safety Authority (HISA) today announced the key findings from one of two pilot programs it commissioned in August 2024 in connection with an Exercise-Associated Sudden Death (EASD) Working Group launched in October 2023. These findings may allow trainers and veterinarians to spot hidden heart risks before tragedy occurs. HISA has also issued an accompanying Equine Health Advisory on EASD, associated risk factors and what trainers and veterinarians can do to help prevent EASD, which can be found <a href="https://hisaus.org/resources/hisa-equine-health-advisory-exercise-associated-sudden-death">here</a>.
During the first six months of 2025, EASD accounted for approximately 8% of racing fatalities and 18% of training fatalities at racetracks subject to HISA rules (and training centers owned by them). Retrospective analysis of cases since HISA’s inception shows that more than 50% of cases were likely related to cardiac issues, often classified as “Sudden Cardiac Death.” The majority of these EASD events occurred early in horses’ careers, with the highest incidence occurring in horses with zero to five starts in their careers.
HISA launched its EASD Working Group in recognition of the critical importance of addressing and better understanding these risks and preventing EASD. The pilot program, led by Dr. Cristobal Navas de Solis, Associate Professor of Cardiology, Ultrasound and Internal Medicine at the University of Pennsylvania School of Veterinary Medicine, and Dr. Sian Durward-Akhurst, Assistant Professor of Genetics, Genomics and Large Animal Internal Medicine at the University of Minnesota College of Veterinary Medicine, is ongoing. The findings were presented at the American College of Veterinary Internal Medicine Forum in Kentucky in summer 2025, among other meetings of specialists in the field.
Dr. Navas de Solis and Dr. Durward-Akhurst partnered with leading experts to investigate underlying causes and develop prevention strategies. Program collaborators include Dr. Mary Durando (Equine Sports Medicine Consultants, U.S.), Dr. Grace Forbes (Racing Victoria, Australia), Dr. Laura Nath (University of Adelaide, Australia) and wearable technology specialists at Arioneo Equimetre (France).
Through advanced cardiac monitoring via wearable devices, researchers identified that atrial fibrillation (AF)—traditionally considered a benign, performance-limiting condition—can worsen during exercise, causing a more severe arrhythmia that leads to sudden death. Electrocardiogram data from affected horses showed AF both at rest and under exertion, underscoring the need for early detection and highlighting the potential of integrating routine cardiac screening into pre-training and pre-race evaluations.
“Integrating cardiac screening into routine evaluations—whether through wearable devices or veterinary exams—could allow trainers and veterinarians to identify at-risk horses before exercise,” said Dr. Karen Hassan, HISA’s Compliance and Research Veterinarian and chair of HISA’s EASD Working Group. “This opens the door to scalable monitoring protocols and standardized response strategies that could save equine lives.”
The next phase of the program will focus on scalability and the development of real-time cardiac monitoring protocols and risk-based screening criteria. Specifically, AF could be detected either via wearable devices, handheld ECG devices or auscultation by a veterinarian before exercise, allowing trainers to withhold exercise and work with their veterinary team to evaluate affected horses further. Establishing optimal workflows and tools to be used for rhythm analysis with an emphasis on AF, defining the risk of arrhythmia other than AF and proposing and evaluating a standardized response protocol for cardiac adverse events during exercise will be key components of the next phase of work.
To further educate stakeholders on EASD, a series of educational webinars will be held for horsemen and veterinarians in the coming weeks.
“This work would not be possible without the tireless dedication of our working group and the invaluable contributions of our international collaborators,” said Dr. Hassan. “Together, we are advancing equine welfare and building the foundation for lasting change.”