Exercising electrocardiograms from Thoroughbred racehorses with exercise associated sudden death

Area of Science:

• Equine cardiology
• Veterinary sports medicine
• Cardiac electrophysiology

Background:

• Exercise-associated sudden death (EASD) is more prevalent in equine athletes than human athletes.
• EASD involves fatal collapse during or shortly after exercise in seemingly healthy horses.
• Understanding the cardiac mechanisms behind EASD is crucial for prevention.

Purpose of the Study:

• To characterize electrocardiogram (ECG) findings in Thoroughbred racehorses that experienced EASD.
• To identify potential pre-existing cardiac conditions or arrhythmias associated with EASD.
• To explore the utility of wearable ECG devices in studying EASD.

Main Methods:

• Retrospective case series design.
• International data collection via racing authorities for consented ECG data from horses experiencing EASD.
• Evaluation of wearable ECG recordings by a single observer.

Main Results:

• Eleven horses with 24 readable ECGs were analyzed.
• Atrial fibrillation (AF) was present in three horses at the time of death, leading to malignant arrhythmias.
• Ventricular fibrillation and late recovery arrhythmias were observed in other cases, with some ECGs recorded days prior to death.

Conclusions:

• The study identified a small cohort of EASD cases, with limitations due to single-lead ECG use.
• ECG screening for AF before training or racing shows potential to decrease EASD incidence.
• Further research is needed to stratify risks for late recovery and other arrhythmias in equine athletes.