Significance for exercise capacity of some electrocardiographic findings in racehorses.

The study examines the impact of certain abnormal electrocardiographic (ECG) findings, such as T wave changes and second-degree atrio-ventricular (AV) block, on the exercise capacity of Thoroughbred and Standardbred racehorses. Results showed no significant differences in the horses’ heart rate, plasma lactate concentration, arterial blood gases, oxygen uptake, run time, peak velocity, or blood and red cell volumes whether they had these ECG abnormalities or not.

Research Methodology

• Various cardiorespiratory and metabolic indices were assessed during treadmill exercise in Thoroughbred and Standardbred racehorses. These indices span from the horses’ heart rate to their blood and red cell volumes.
• Two groups of horses were observed – those with T wave changes in 4 or more leads on the electrocardiogram or second-degree atrio-ventricular (AV) block, and those that showed no abnormalities on clinical examination, resting electrocardiography or upper respiratory tract endoscopy. The T wave changes and the second-degree AV block are certain electrocardiographic findings that some consider to imply cardiac dysfunction.

Research Findings

• Surprisingly, the results illustrated no significant differences in the horses’ cardiorespiratory or metabolic indices, whether the horse had these ECG abnormalities or not. Regardless of the state of the horse, no significant variations were found in heart rate, plasma lactate concentration (a measure of how much lactic acid is in your blood), arterial blood gases (measurements that help check how well your lungs are moving oxygen into your bloodstream and removing carbon dioxide), oxygen uptake (the amount of oxygen that the body uses during a minute), run time, peak velocity (the maximal speed achieved), or blood and red cell volumes.

Conclusions

• This study challenges the belief held by some clinicians that certain ECG findings, such as T wave changes and second-degree AV block, indicate cardiac dysfunction. The study’s findings suggest that these particular ECG abnormalities may have little to no effect on a horse’s exercise capacity. In other words, even horses with these ECG changes could still maintain regular levels of physical exertion and performance, contradicting the conventional belief.
• The research provides valuable insights into the interpretation of electrocardiographic findings in racehorses, which could potentially affect the way these animals are medically evaluated and their health and performance managed.