Estimates of heritability of atrial fibrillation in the Standardbred racehorse.

Summary

# Atrial Fibrillation in Standardbreds: A Heritable Concern Atrial fibrillation (AF) cases amongst Standardbred racehorses presenting to the Ontario Veterinary College Teaching Hospital have increased markedly since the early 1990s, with a disproportionate number of affected animals tracing back to a small cohort of sires. Using pedigree analysis and genetic modelling on the hospital's clinical records, Kraus and colleagues quantified the heritability of AF in this population to establish whether selective breeding could meaningfully reduce disease incidence. Their findings revealed a substantial heritable component to AF susceptibility in Standardbreds, suggesting genetic factors play a significant role alongside environmental stressors in determining an individual horse's risk. For breeding programmes and stud management, these results underscore the value of incorporating AF prevalence data into selection decisions—identifying carrier sires and limiting their use could reduce disease burden in future generations. Veterinary practitioners should remain alert to familial clustering of AF cases and consider genetic predisposition when counselling owners about prognosis and breeding intentions.

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Key Findings

• •Atrial fibrillation cases in Standardbred racehorses admitted to Ontario Veterinary College Teaching Hospital have increased since the early 1990s
• •A small number of sires have contributed to a large proportion of AF cases, suggesting genetic predisposition
• •Study estimates heritability of atrial fibrillation in the Standardbred breed

Conditions Studied

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