Summary: Background: Cardiac arrhythmias in exercising horses are the focus of much interest, both in terms of what is considered normal and potential associations with poor performance and sudden cardiac death. One barrier to performing large‐scale studies is the lack of an easily applicable device, to allow recording of large numbers of high‐quality exercising electrocardiograms (ECGs). The Equimetre^TM is a new wearable device, which records a single lead ECG, among other parameters. Validation of such wearable devices is essential before further studies are undertaken.Objectives: To evaluate the quality of ECG using the Equimetre^TM and compare arrhythmia detection during exercise with the reference Televet^TM system.Study design: Prospective blinded clinical study.Methods: Simultaneous ECGs were recorded with both systems in 49 healthy horses during exercise. High‐intensity exercise (>40 km/h) was performed by 29 racehorses, and lower‐intensity exercise for the remainder of the racehorses and show jumpers. Tracings were excluded if >10% artefact was present (duration of artefact relative to duration of exercise). For included ECGs, the duration of artefact was recorded and compared. ECGs were evaluated using Kubios premium software. Arrhythmia detection (yes/no) and arrhythmia classification (sinus arrhythmia, narrow complex of similar morphology to the sinus complexes or wide complex with a different morphology) were compared using Cohen's Kappa coefficient.Results: Nine Televet^TM ECGs and 3 Equimetre^TM ECGs were excluded due to artefact >10%. Televet^TM ECGs included significantly more artefact during exercise than Equimetre^TM ECGs (5% vs. 0.25% P < .001). Arrhythmia analysis was performed on 38 horses’ paired ECGs. The kappa coefficient was excellent for arrhythmia detection (K = 0.97) and arrhythmia classification (K = 0.93).Main limitations: Relatively low numbers of horses with arrhythmias (n = 21) were included. The ECG recordings only provided one lead, making arrhythmia classification challenging in some cases.Conclusions: The Equimetre device provides a reliable ECG for arrhythmia detection during exercise. This system may be useful clinically and for future large‐scale investigations into the occurrence and significance of exercising arrhythmias.

Summary: Tongue‐ties are frequently used in an attempt to prevent dorsal displacement of the soft palate (DDSP). The aim of this study was to determine the efficacy of a tongue‐tie in horses clinically affected with the disorder. Videoendoscopic recordings and measurements of respiratory airflow were made simultaneously during high intensity treadmill exercise in 6 Thoroughbred racehorses with confirmed DDSP, with and without a tonguetie. DDSP was confirmed in all 6 horses without the tongue‐tie but occurred in only 4 horses with the tongue‐tie in place. In one horse the palate displaced only on slowing down after intense exercise and in the other horse DDSP did not occur although palatal instability remained. The presence of the tongue‐tie did not result in any significant alteration in run‐time to fatigue or in any of the respiratory variables measured. The results suggest that the use of a tongue‐tie may prevent DDSP in individual horses although it is not effective in the majority, consistent with the widely accepted anecdotal reports of success rates for its use. Where DDSP was not prevented, application of a tongue‐tie did not improve ventilation.

Cardiac arrhythmias resulting in sudden cardiac death (SCD) are an important cause of racehorse fatalities. The objective of this study was to determine risk factors for SCD in Thoroughbreds by evaluating a sample with a policy of mandatory post-mortem following racing or training fatalities. Risk factors were compared between case horses with SCD (n = 57) and control horses with other fatal injury (OFI, n = 188) by univariable and multivariable logistic regression. Survival in years for horses with SCD was compared to OFI using the Kaplan–Meier method with log rank test. The following variables were most important in the multiple logistic model: Horses with SCD were more likely to die during training than during racing, SCD (42/57, 74%) vs. OFI (82/188, 44%; odds ratio [OR], 95% confidence interval [CI], 2.5, 1.2–5.4; p = 0.01), had fewer lifetime starts, median (interquartile range [IQR]), SCD (3.0 [0.0–9.0]) vs. OFI (9.0 [0.0–22.8]; OR, 95% CI, 0.96, 0.9–1.0; p = 0.02 and were less likely to be entire (uncastrated) males, SCD 9/57 (16%) vs. OFI (46/188, 25%; OR, 95% CI, 0.47, 0.1–0.9; p = 0.03). Survival in years (median (IQR)) for horses with SCD was 3.6 (3.1–4.4), which was shorter than OFI (4.5 [3.1–6.0], hazard ratio, 95%CI, 1.6,1.2–2.3; p < 0.001). SCD occurs more commonly in training than racing, which suggests exercise intensity is less important in precipitating this fatality. In this study, SCD occurred early in the careers of affected horses.