The heart of the matter: What causes sudden death in racehorses?

Hugh Bowman and Cheval Grand winning the 2017 Japan Cup.
Hugh Bowman and Cheval Grand winning the 2017 Japan Cup. © Yuki Shimono

A seminar by equine cardiovascular expert Dr Peter Physick-Sheard focusing on sudden death in the racehorse has been made available online.

British-born Physick-Sheard is a leading Clinician and Research Scientist with a focus on cardiovascular diseases, performance medicine, and sudden death in racehorses.

In the seminar at Canada’s University of Guelph, Physick-Sheard described studies at Mohawk Raceway in which the team instrumented 325 standardbred horses during regularly scheduled races and collected data on heart rhythms.

They found that 18 per cent of horses had complex ventricular arrhythmias in early recovery, some very serious, just around the time that sudden deaths tend to occur.

“Some of these rhythms were life-threatening and if you saw it in the patient in the clinic you’d stand back in case the horse fell on you.

“So these are serious – it’s bad, bad news,” said Physick-Sheard, from Population Medicine at Guelph’s Ontario Veterinary College.

Multivariate analyses revealed associations between these rhythm disturbances and factors such as gait, trot, pace, vagal tone, race circumstances, or horses that broke gait at the top of the stretch.

Generally, the animals recovered on their own, suggesting that rhythm disturbances are common to racehorses, but may also be triggers for sudden death.

In another study they investigated what happens in 439 thoroughbreds during regularly scheduled races at Woodbine. Although they found variation between horses, the thoroughbreds tended to do the same thing as standardbred horses on ECGs, but less frequently, even though have a higher rate of sudden death. Physick-Sheard suggested that there may be unique features in ECGs that help to define the characteristics of which horses end up dying suddenly.

He discussed another study looking at the cardiac biomarker cTnI, which showed that highest elevations of the biomarker may be associated with subclinical myocardial damage, and arrhythmias. In a separate study, they looked at QT interval changes – this is a common problem related to sudden cardiac death (SCD) in humans. To date they have created an automated program to interrogate ECG data for QT intervals and have promising preliminary data looking at the relationship between QT interval and heart rate. Finally, he discussed the Ontario Racehorse Death Registry database and recent findings.

The Seminar was organized by the Centre for Cardiovascular Investigations (CCVI) Executive faculty and students.

Reporting: Tami Martino

2 thoughts on “The heart of the matter: What causes sudden death in racehorses?

  • May 3, 2018 at 1:17 pm

    The fact they’re far too young to be worked as hard as they are is probably a big one? 😛

  • May 11, 2018 at 11:16 pm

    Were these horses on lasix at the time of test?….were the arrhythmias also found at rest before the exercise?….does lasix and exercise have great effect on the heart muscle and how it operates?


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