Pre- and post exercise echocardiography in horses performing treadmill exercise in cool and hot/humid conditions.

The research examined the effect of different climates on horses’ heart function during and after exercise. The findings suggest that a hot and humid environment can significantly impact the heart’s functioning, resulting in prolonged recovery time and major changes in the heart’s dimensions and function as compared to exercise in cooler environments.

Methodology

• The study was conducted with five clinically normal horses who took part in treadmill exercise tests both in a controlled cool environment (20 degrees C/40% relative humidity) and a hotter, more humid environment (30 degrees C/80% relative humidity).
• M-mode echocardiograms were taken of the horses before the exercise test, and then at intervals of 0, 10, 30, and 60 minutes after the exercise to compare the impact of the two climate conditions on the horses’ cardiac structures and general function.

Findings

• Exercise in the hot and humid conditions had a more severe impact on the horses’ heart function as compared to the results from the cooler environment.
• Only one horse was able to complete the exercise test in the hot and humid environment, whereas all the horses completed the exercise in the cooler conditions. This aligned with the initial hypothesis of the study.
• The Relaxation Time Index (RTI) correlated significantly and inversely with the heart rate, which increased immediately after exercise in cool conditions, while the post-exercise RTI significantly decreased in the hot and humid environment.
• The left ventricular internal dimensions (measured in diastole and systole) were lower following exercise in the hot/humid environment and continued to reduce up to 60 minutes after exercise.
• This resulted in the Left Ventricular Fractional Shortening (LVFS %) being lower than resting levels immediately post-exercise under the hot and humid conditions.

Conclusion

• Echocardiography provided useful insights into the cardiac responses of the horses to exercise under different climatic conditions, thereby helping to understand the physiological impacts in more depth.
• This research could be a crucial reference for understanding human cardiac responses to climate changes, serving as a foundation for future research into protective strategies and preventive measures for people residing or performing activities in different weather conditions.