Cardiac arrhythmia prevalence and risk factors in 24-h electrocardiograms of sedentary horses.

Background: Cardiac arrhythmias are common in horses, but their clinical relevance remains controversial.

Objectives: To describe prevalence and identify risk factors for arrhythmias that may warrant additional screening in a sedentary mixed-breed population of horses.

Study design: Prospective cross-sectional.

Methods: Ninety-four clinically healthy, university-owned, sedentary horses underwent 24-h ambulatory electrocardiograms and echocardiograms. Potential risk factors were recorded for all horses. Affected individuals were defined as those with >1 supraventricular premature complex/h or with any ventricular premature complexes for risk factor analysis. Forward stepwise logistic regression was used to identify factors associated with the presence of arrhythmia. The p value <0.15 was considered significant in univariable screening and p ≤ 0.05 was considered significant overall.

Results: During recording, 92.6% (87/94) of horses experienced an arrhythmia. Supraventricular premature complexes were present in 86.2% (81/94) of the horses, and ventricular complexes were present in 24.5% (23/94) of the horses. Of the sample, 38.3% (36/94) were considered affected by arrhythmias. Increased heart girth score was associated with detection of arrhythmias (OR 1.06, 95% CI 1-1.12, p = 0.05) and age was retained in the final model as a confounder.

Main limitations: The study sample included a limited range of body condition scores and number of stallions for risk factor analysis.

Conclusion: Arrhythmias occurred with high frequency in this group of horses despite no known history or clinical signs of cardiovascular disease. Increased heart girth is a potential risk factor for arrhythmia in the horse.