Cardiac arrhythmias during and after treadmill exercise in poorly performing thoroughbred racehorses.

The research study explores the prevalence and severity of heart arrhythmias in Thoroughbred racehorses that underperform, specifically during and after rigorous treadmill exercises. It studies cardiac activity patterns during these periods to better understand the potential relationship between poor performance and heart irregularities.

Research Methods

• The research involved 88 Thoroughbred racehorses that didn’t exhibit any significant symptoms of heart disease or arrhythmias at rest.
• EKGs (Electrocardiograms) were recorded from these horses throughout an incremental exercise test (IET) to fatigue on a treadmill, using a modified version of base-apex EKG recording.
• The recorded data was independently analysed by two observers to prevent any skewed findings due to bias.
• Out of 88, various prevalent conditions were diagnosed in horses including dorsal displacement of the soft palate, soft palate instability, aryepiglottic fold collapse and other respiratory issues. In 27 cases, no definitive diagnosis was provided.

Research Findings

• Results showed that 55 horses had at least one either type of depolarisation – Ventricular (VPD) or Supraventricular (SVPD). Out of these, 23 horses had VPDs, 17 had SVPDs, and 15 had both at least once during the exercise.
• These premature depolarisations were majorly observed during the first minute of recovery post the intense treadmill exercise.
• The recorded ranges of these premature beats post-exercise were 1-30 VPDs and 1-9 SVPDs.
• The research did not find any significant associations between age, sex, race type, any specific diagnosis, peak heart rate or run time to fatigue during the exercise test, and the occurrence of either ≥1 premature beat or more severe forms of arrhythmias.
• However, the study does mention that a larger sample size may be required to determine these associations with greater confidence.

Conclusions

• The study finds that isolated VPDs and SVPDs are frequently found in underperforming racehorses during high intensity treadmill exercises. The clinical significance of these observations, however, is yet to be established.
• The conclusions propose further evaluation and detailed interpretation of premature depolarisations found during and immediately after treadmill tests in Thoroughbred racehorses showing underperformance, for better understanding of their effects and relevance.