Arrhythmias in Thoroughbreds During and after Treadmill and Racetrack Exercise. (June 2014)

• Record Type: Journal Article
• Authors: Navas de Solis, C; Green, C; Sides, R; Seino, K; Bayly, W
• Is Part Of: Equine veterinary journal. Volume 46(2014)Supplement 46
• Page Start: 24
• Page End: 25
• Publication Date: 2014-06
• Subjects: Horses -- Diseases -- Periodicals; 636.108905
• DOI: 10.1111/evj.12267_74
• Languages: English
• ISSNs: 0425-1644

Abstract

Abstract : Introduction: Healthy and poorly performing horses can display arrhythmias during exercise and immediately afterwards. The relationship of arrhythmias to exercise intensity or type, and their frequency of recurrence, are poorly understood. Clarification of these issues was the objective of this investigation. Methods: Electrocardiograms were recorded on 9 Thoroughbreds during maximal and submaximal exercise on a racetrack (RA) and treadmill (TM). The frequency of atrial and ventricular arrhythmias for RA and TM were compared using Fisher's Exact Test. Results: 65 workouts (TM = 46, RA = 19; median[range]: 4/horse[2–14]) were performed. Exercising arrhythmias were detected in 4/9 horses (12/65 workouts) and there were post‐exercise arrhythmias in 7/9 horses (20/65 workouts). A single exercising electrocardiogram per horse often did not display all arrhythmias detected over several workouts. 3/9 horses exhibited arrhythmias during the first and second runs while the other 6 had none. 4/9 had 1 post‐exercise arrhythmia. Of 6 horses with >3 runs, 1 displayed arrhythmias each time, 3 never had arrhythmias and 2 sometimes showed arrhythmias during exercise (1/9 and 4/8 workouts, respectively). All 6 intermittently had post‐exercise arrhythmias (median[range]: 50% [9–75%] of workouts). Presence of arrhythmias was positively related to intensity and all occurred at ≥94%HRmax. The frequency of arrhythmias following RA (29%) and TM (12.5%) was not statistically different. Conclusions: Gallops on TM or RA were equally effective for detecting arrhythmias. The presence/absence of exercising arrhythmias was more repeatable than post‐exercise arrhythmias. Arrhythmias are more likely to be detected at maximal or near‐maximal intensities. A larger population needs to be studied before firm conclusions are drawn. Ethical Animal Research: The study was approved by an Institutional Animal Care and Use Committee protocol.Sources of funding: Department of VCS, Washington State University.Competing interests: none.