Cardiovascular variables in eventing and endurance horses over a season

The objectives of this study were to describe the changes in clinical cardiovascular examination variables over a competition season in groups of competitive eventing and endurance horses and to compare these findings to non-competitive controls of the same breeds. This study included two eventing horses, 11 endurance horses, and 13 eventing and seven endurance control breed-matched horses. Cardiovascular examinations were performed before starting the competition season, in the middle and at the peak/end of the competition season. Examinations included auscultation of the heart; M-mode echocardiographic measurements and calculated values; left atrial, pulmonary artery, and aortic diameters; color flow Doppler; exercise electrocardiograms (ECG) measuring peak heart rates and quantifying premature complexes; and 24-h continuous ECGs quantifying premature complexes per hour. Auscultation, echocardiograms, arrhythmias during exercise, and 24-h continuous ECGs did not change significantly throughout the season (p > 0.05 for all variables). Cardiovascular examination variables of eventing and endurance horses throughout a competition season are reported here for the first time. Although the present study did not reveal significant changes, data should be interpreted carefully as only a small number of horses were examined.