Evaluation of Cardiac Arrhythmias before, during, and after Treadmill Exercise Testing in Poorly Performing Standardbred Racehorses.
Authors: Alberti Elena, Stucchi Luca, Lo Feudo Chiara Maria, Stancari Giovanni, Conturba Bianca, Ferrucci Francesco, Zucca Enrica
Journal: Animals : an open access journal from MDPI
Summary
# Editorial Summary Cardiac arrhythmias are common in underperforming Standardbred racehorses, yet their precise contribution to poor athletic function remains poorly understood. Researchers conducted retrospective electrocardiographic analysis of 158 poorly performing Standardbreds using Holter monitoring before, during and after maximal treadmill exercise testing, examining the relationship between arrhythmia type, demographic variables, and performance metrics. Premature complexes (PCs) emerged as the most prevalent finding, occurring in 48.1% of horses, followed by second-degree atrioventricular block (33.5%), with sinus arrhythmia, sinoatrial block and supraventricular PCs each affecting fewer animals; notably, 31.6% of the cohort showed no arrhythmias whatsoever. Multiple regression analysis revealed that PCs tend to increase with advancing age and rising lactate concentrations, whilst higher minimum heart rates showed weak protective association against their occurrence. For equine practitioners, these findings highlight that the presence of arrhythmias—particularly PCs—may not directly explain poor performance in racehorses, suggesting that further investigation into mechanistic links between specific arrhythmia types and functional impairment is essential before attributing underperformance to cardiac electrical disturbances alone.
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Practical Takeaways
- •Cardiac arrhythmias are highly prevalent in poorly performing Standardbreds; baseline electrocardiographic screening during exercise testing should be considered part of performance evaluation protocols
- •The relationship between arrhythmia occurrence and poor athletic performance remains unclear—further investigation is needed before attributing performance issues solely to detected arrhythmias
- •Age and fitness level (indicated by lactate levels) may influence arrhythmia presentation, suggesting individualized assessment strategies based on horse demographics and conditioning status
Key Findings
- •108 of 158 (68.4%) poorly performing Standardbreds exhibited at least one type of cardiac arrhythmia during maximal treadmill exercise testing
- •Ventricular premature complexes were the most common arrhythmia type, occurring in 48.1% of the study population
- •Second-degree atrioventricular block was present in 33.5% of horses, while supraventricular premature complexes occurred in 7.6%
- •Premature complexes showed weak evidence of decreasing with higher minimum heart rate, but tended to increase with age and maximum lactate concentration