Occurrence of cardiac arrhythmias in Standardbred racehorses.
Authors: Slack J, Boston R C, Soma L R, Reef V B
Journal: Equine veterinary journal
Summary
# Editorial Summary: Cardiac Arrhythmias in Standardbred Racehorses Cardiac arrhythmias represent a documented but poorly understood concern in racing Standardbreds, yet little data exist to inform screening protocols or establish baseline prevalence. Slack and colleagues obtained 8,657 electrocardiographic recordings from 1,816 horses at a single racetrack over 12 weeks, capturing both pre-race and immediate post-race periods (6–29 minutes) using portable handheld devices. Whilst serious arrhythmias proved rare in the overall population—atrial fibrillation occurred in 0.11% of horses post-race, supraventricular tachycardia in 0.06% pre-race, and ventricular tachyarrhythmias in 0.06% post-race—their frequency among poor-performing race starts climbed substantially to 1.3–2.0% for atrial fibrillation, and advancing age emerged as a consistent risk factor for multiple arrhythmia types. For track veterinarians and racing regulators, these prevalence figures provide a foundation for monitoring trends and identifying at-risk cohorts, whilst the notable association between poor performance and arrhythmia warrants further investigation into cumulative training load as a precipitating factor in future studies.
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Practical Takeaways
- •Track veterinarians should consider implementing pre-race and post-race cardiac screening protocols, particularly for older horses, as a component of fitness and safety assessment for racehorses
- •Poor racing performance warrants cardiac evaluation, especially given the 1.3-2.0% frequency of atrial fibrillation in underperforming horses, which may indicate underlying cardiac pathology affecting performance
- •Baseline prevalence and frequency data provided can serve as a reference standard for monitoring trends in cardiac arrhythmias and evaluating the effectiveness of track safety and conditioning programs
Key Findings
- •Atrial fibrillation occurred in 0.11% of horses after racing with a frequency of 0.14% per race start; prevalence increased to 1.3-2.0% among poor performers
- •Supraventricular tachycardia detected in 0.06% of horses before racing and ventricular tachyarrhythmias in 0.06% after racing
- •Increasing age was a significant risk factor for atrial premature contractions before racing and for atrial fibrillation and ventricular ectopy after racing
- •Noncontinuous handheld electrocardiographic recording can effectively detect both physiological and pathological cardiac arrhythmias in apparently healthy Standardbred racehorses