Altered systolic left ventricular function in horses completing a long distance endurance race.

The research article investigates the effects of long-distance endurance races on the left ventricular systolic function in horses. The study utilizes echocardiography both before and after the race to measure various parameters to determine the possibility of exercise-induced cardiac fatigue.

Objective and Methods

The study aims to understand if exercise-induced cardiac fatigue (EICF), previously observed in human athletes, also occurs in endurance horses. EICF typically happens after long-duration exercises where the performance of the heart muscles, particularly the left ventricle, decreases.

• The study made use of echocardiography, a technique using ultrasound waves to image the heart, on 11 horses before and after their participation in a 2 or 3 star international endurance race with distances between 106 to 132 km.
• Various parameters of the heart were measured and compared, including systolic and diastolic interventricular and left ventricular free wall thickness, left ventricular, left atrial and aortic internal diameter, fractional shortening, ejection fraction, heart rate, peak flow velocity, flow velocity integral, ejection time, pre-ejection period, velocity of circumferential fibre shortening, stroke volume, and cardiac output.

Results

• Post-race measurements indicated several significant adjustments in the above-mentioned parameters. Notably, the ejection fraction, fractional shortening, flow velocity integral, stroke volume, ejection time, and other parameters dropped post-race, suggesting a decrease in the left ventricular systolic function.
• In contrast, the diastolic interventricular and left ventricular free wall thickness, heart rate, pre-ejection period, and velocity of circumferential fibre shortening increased after the race.
• Changes pre- to post-exercise in the measured parameters did not significantly correlate with alterations in heart rate or the left ventricular internal diameter (diastolic).

Conclusions

Based on the changes observed in the results, the study suggests that EICF might occur post-exercise in horses running long-duration endurance races, marked by a sizable decrease in left ventricular systolic function. However, the study also cautions that these observed changes could be due to a combined effect of varied preload and heart rate, and thus should not be entirely attributed to EICF.