Sudden cardiac death has been reported as a cause of fatality in up to 25% of unexpected racehorse deaths in flat racing. In a study published last month in the journal Animals Laura Nath and colleagues published a retrospective case-control study of all Thoroughbred fatalities at racetracks or training facilities in Melbourne, Victoria. The study included deaths over a 14 year period. The authors determined that there were 57 cases of sudden cardiac death on the basis of post mortem reports. This group was compared to a larger group (n=188) of “other fatal injuries”, including horses with catastrophic musculoskeletal injury and horses with sudden death deemed unrelated to cardiac pathology. This group was referred to as the control group.
The author identified several factors associated with sudden cardiac death (SCD) when compared to the control group. Horses with SCD were more likely to die during training rather than racing. The SCD horses also had fewer race starts and they were less likely to be entire horses. It is thought that entire males were more likely to experience musculoskeletal breakdown than females or geldings because of increased body size. When compared to the Australian Thoroughbred population horses with SCD were younger at the time of their death, suggesting that SCD occurred in the early phase of their race careers.
The authors concluded that because SCD occurred in younger horses during training it supports a role for inherited or congenital disorders in these horses. At this point in time we do not routinely screen all horses for cardiac disease. Furthermore, the spectrum of tools available for examining exercising Thoroughbreds is improving all the time. It would be a worthwhile but difficult project to screen all young racing Thoroughbreds with a resting and exercise ECG and echocardiogram.
The study is titled: Risk Factors for Exercise-Associated Sudden Cardiac Death in Thoroughbred Racehorses by Laura Nath and others, published in Animals 2022, 12, 1297. The article is open access: https://doi.org/10.3390/ani12101297
