Training vs. racing: A comparison of arrhythmias and the repeatability of findings in Thoroughbred Chuckwagon racehorses.

This research evaluates the consistency of arrhythmias findings in racehorses during both training and competition times, besides analyzing the repeatability of these findings. It concludes that the number of arrhythmias is fairly stable, but identification of specific types may vary.

Objective and Methodology

• The study aimed to compare the arrhythmias (abnormal heart rhythms) detected in Thoroughbred Chuckwagon racehorses during training and competition and to evaluate the consistency of these findings.
• Researchers examined 152 electrocardiograms (ECGs), which provide records of the electrical activity of the heart, from a sample set of 52 healthy Thoroughbred horses aged 8.7 ± 2.5 years who compete in the World Professional Chuckwagon Association.
• Speed, heart rate, and specific types of arrhythmias (SVPCs – Supraventricular Premature Complex and VPCs – Ventricular Premature Complex) were taken into account.
• Additionally, blood samples were analysed for lactate and high-sensitivity troponin-T, both before and approximately six minutes after exercise. The latter is a protein that signifies heart muscle injury.

Findings and Conclusion

• Out of the entire sample set, data from 40 horses who had clean ECG results from both training and competition were considered. The study found no significant difference between the number and type of arrhythmias in both settings.
• During training, seven out of these 40 horses had VPCs, and during competition, the same number of horses had VPCs. The number of VPCs detected in the active recovery phase was slightly higher.
• Most arrhythmias were single premature complexes, and the intensity of exercise, whether training or competition, did not influence the speed, heart rate, lactate or troponin-T values of the horses.
• However, the timing of the blood sample collection might have been too early to capture peak serum Troponin-T levels, as this rises a few hours after a heart injury.
• The consistency of total detected arrhythmias between different ECGs was found to be high, indicating that the overall number of arrhythmias was repeatable.
• However, the reliability for detecting specific types of arrhythmias (SVPCs and VPCs) varied, ranging from poor to moderate, suggesting that the type of arrhythmia detected could be influenced by variable factors.