Associations between postrace atrial fibrillation and measures of performance, racing history and airway disease in horses.
Authors: Nath Laura C, Elliott Adrian, La Gerche Andre, Weir Joe, Forbes Grace, Thomas Gijo, Franklin Samantha
Journal: Journal of veterinary internal medicine
Summary
# Editorial Summary Atrial fibrillation remains the primary performance-limiting cardiac arrhythmia in racehorses, yet its epidemiological drivers remain poorly characterised; this Australian and Hong Kong study of 479 horses with poor race performance (164 diagnosed with postrace AF, 315 without) and 314 performing to expectation sought to identify which factors distinguish AF cases from non-AF underperformers. Univariable and multivariable logistic regression analyses revealed that greater distance behind the winner, higher cumulative prize money per start, and younger age were independently associated with AF diagnosis, whilst exercise volume itself did not emerge as a risk factor. Strikingly, horses with AF exhibited substantially elevated rates of moderate-to-severe exercise-induced pulmonary haemorrhage (EIPH ≥ grade 3) at 21.1% compared to 3.3% in poor performers without AF (odds ratio 7.9), suggesting a mechanistic link between pulmonary pathology and arrhythmia development. For practitioners, these findings indicate that postrace endoscopy revealing significant EIPH warrants cardiac investigation, and that AF presentation in younger earners should prompt assessment of underlying airway disease rather than attributing arrhythmia solely to cumulative racing stress.
Read the full abstract on PubMed
Practical Takeaways
- •Postrace endoscopic evaluation showing high-grade EIPH should raise suspicion for underlying AF, as the association is 7.9 times stronger in AF horses
- •AF presents suddenly in previously earning racehorses; declining race performance with poor finishing position may warrant cardiac evaluation regardless of prior earnings history
- •Airway disease management may be relevant to AF prevention or management, given the demonstrated association between EIPH grades and AF occurrence
Key Findings
- •Horses with postrace AF finished substantially further behind winners (OR 1.41 per length) compared to horses performing to expectation
- •AF horses had significantly higher grades of exercise-induced pulmonary hemorrhage (21.1% with grade ≥3) versus poor performers without AF (3.3%), suggesting a mechanistic relationship
- •Career earnings before the AF event were not inferior in AF horses despite acute performance impairment, indicating AF develops in established performers
- •Exercise volume did not promote AF development, contradicting the high-dose exercise hypothesis observed in human populations