Risk Factors for Exercise-Associated Sudden Cardiac Death in Thoroughbred Racehorses.
Authors: Nath Laura, Stent Andrew, Elliott Adrian, La Gerche Andre, Franklin Samantha
Journal: Animals : an open access journal from MDPI
Summary
# Exercise-Associated Sudden Cardiac Death in Thoroughbreds: What the Data Tell Us Whilst cardiac arrhythmias account for a significant proportion of Thoroughbred fatalities during racing and training, the specific risk factors predisposing individual horses to sudden cardiac death (SCD) remain poorly characterised. Nath and colleagues analysed 57 cases of SCD against 188 horses that died from other fatal injuries, using mandatory post-mortem records to identify distinguishing features through logistic regression modelling. Three factors emerged as statistically significant: horses experiencing SCD were 2.5 times more likely to die during training rather than racing, had substantially fewer career starts (median 3 versus 9 starts), and were considerably less likely to be entire males (16% versus 25%). Survival analysis revealed affected horses had a markedly shortened lifespan—median 3.6 years compared to 4.5 years for those with other fatal injuries—suggesting cardiac pathology develops early in a horse's life. The counterintuitive finding that SCD occurs predominantly during training rather than high-intensity racing implies that cardiac vulnerability may be constitutive rather than exacerbated by peak exercise demands, warranting investigation into early-career screening protocols and genetic factors in young stock, particularly fillies and geldings entering training programmes.
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Practical Takeaways
- •SCD occurs more frequently during training than racing, suggesting that exercise intensity alone may not be the primary trigger; training protocols should incorporate monitoring for early warning signs in young horses
- •SCD predominantly affects horses early in their racing careers (median 3.6 years), indicating screening and cardiac evaluation should be prioritized before race entry
- •Entire males appear to have some protective effect against SCD; sex-specific risk stratification may be warranted in pre-race cardiac assessments
Key Findings
- •Horses with SCD were 2.5 times more likely to die during training than racing (74% vs 44%)
- •SCD cases had significantly fewer lifetime starts (median 3.0 vs 9.0 starts)
- •Entire males were less likely to experience SCD (16% vs 25%)
- •Median survival age for SCD horses was 3.6 years, significantly shorter than control horses at 4.5 years