Healthier hearts, healthier horses


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Thoroughbred horses running in a field

The recent discovery of heart muscle scarring in some thoroughbred horses has the potential to change how the thoroughbred industry keeps horses healthy and performing their best.

Key points

  • Armed with new knowledge about how horses’ hearts can respond to high intensity training, the thoroughbred industry has the potential to create new training regimes and trial medications to reduce heart muscle scarring.
  • This is in response to new research that has shown that a small number of horses may develop heart muscle scarring following athletic training.
  • This heart muscle scarring has the potential to cause an abnormal heart rhythm.
  • More research is required to investigate viral heart inflammation and gender or genetic factors that contribute to thoroughbred horses experiencing abnormal heart rhythm.

Caring for incredible athletes

Leading the research project was equine internal medicine specialist veterinarian Laura Nath who is a PhD candidate at the University of Adelaide. Dr Nath explained, “We know from other research that horses’ hearts get bigger as they do more athletic training. The same goes for human athletes too, the fitter the person gets with sustained exercise, the bigger their heart gets.

“Thoroughbred horses are incredible athletes, but their hearts are not indestructible. The more we know about keeping their hearts healthy the better we can manage their training and performance to ensure their long-term wellbeing.”

Dr Nath said, “Sometimes there is pressure put on the heart from doing intense exercise that can cause heart muscle inflammation. This in turn has the potential to cause some scarring in the horse’s heart muscle which in rare instances can lead to abnormal heart rhythms.”

“We need to do more research to understand how and why this scarring occurs and if it can be prevented with a different approach to training or treated and repaired with medication. We also need to investigate whether viral illness could be causing some inflammation in the hearts of horses which could contribute to the heart muscle scarring.

Dr Nath said, “Other questions we want to examine now include whether rest periods between races or high-intensity training could allow for heart muscle repair, if gender or genetic factors put some horses at greater risk than others, and whether there are any novel drug therapies that could block the inflammation that causes scarring.”

Improving safety and wellbeing

AgriFutures Australia Manager, Research Annelies McGaw said, “We want racing industry regulators and thoroughbred horse trainers to be aware that high-intensity training in thoroughbred racehorses causes changes to the heart muscle that could in some cases lead to abnormal heart rhythm development.”

“While incidents of sudden abnormal heart rhythm are rare and infrequent, it has a big impact on the thoroughbred racing industry. If we can reduce the incidences of abnormal heart rhythm in thoroughbred horses, we’ll not only improve the welfare of the horses involved but also improve safety for jockeys and trainers and enhance the sustainability of the industry.”

Ms McGaw said, “Now that we’ve improved our knowledge about how racehorses’ hearts function, we have the potential to reduce the incidence and impact of abnormal heart rhythm through creating new training programs or finding medications to reduce scar tissue.”

More research to come

Read more about the Australian thoroughbred horse industry, the latest research projects and register to receive updates from the AgriFutures Thoroughbred Horses Program at

Funding for this research project was provided by AgriFutures Australia with support from Racing Victoria, the South Australian Health and Medical Research Institute and the University of Melbourne.

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