Electrocardiograms from different types of exercise in Eventing horses with and without cardiac signs.

Background: Exercising arrhythmias can be clinically irrelevant or associated with poor performance, collapse and sudden cardiac death.

Objectives: To test if readable exercising ECGs can be recorded by grooms or riders and to describe arrhythmias in ECGs from different types of exercise in Eventing horses and investigate associations with type of workout, the presence of previous cardiac signs and intensity of exercise.

Study Design: Cohort study.

Methods: Single lead exercising ECGs were obtained by riders or grooms during training and competition from a convenience sample of horses in training for Eventing competitions. Arrhythmias were described, and associations between different arrhythmia categories and variables that described the horse and the workouts were sought.

Results: There were 1002 ECGs from 62 horses (median [range] 7 [2-97] ECGs/horse) evaluated and 737 workouts (73.6%) were >95% readable and included in the analysis. There were arrhythmias in 250 (33.9%) of the workouts, complex arrhythmias in 13 (1.8%) and the number of premature complexes was median (range) 0 (0-118). Peak heart rate and duration of exercise were associated with the number of premature complexes, the presence of arrhythmias and complex arrhythmias and were colinear with the type of exercise. Having previous signs of cardiac disease and the type of workout were associated with higher odds of having arrhythmias.

Conclusions: Monitoring the rhythm of equine athletes with ECGs obtained by riders and transmitted to an online cloud was feasible. Arrhythmias were frequent, and complex arrhythmias were rare. The presence of cardiac signs, type of exercise and peak heart rate were associated with the presence of arrhythmias. None of the horses developed poor performance or collapse attributed to cardiac disease. The arrhythmias that should be concerning for equine veterinarians need further definition.