Frequency of cardiac arrhythmias in horses during straight and untethered swimming.
Authors: Santosuosso Emma, David Florent, Massie Shannon, Filho Silvio A, McCrae Persephone, Johnson Sarah, Leguillette Renaud
Journal: Equine veterinary journal
Summary
# Cardiac Arrhythmias During Repetitive Swimming in Horses Whilst swimming is increasingly prescribed as a rehabilitation and conditioning modality, the cardiac responses to this exercise remain poorly characterised. Santosuosso and colleagues addressed this knowledge gap by acquiring continuous underwater electrocardiograms from 16 horses completing five pool lengths (75 m) separated by active-recovery walking periods, analysing 80 individual ECG recordings across pre-swim, swimming and recovery phases and categorising any detected arrhythmias as either physiological (sinus arrhythmia, sinus block, second-degree atrioventricular block) or non-physiological (supraventricular and ventricular premature depolarisations). Although 94% of horses experienced at least one arrhythmia, their frequency remained consistently low and clinically inconsequential. Swimming heart rate reached 162 bpm (interquartile range 141–173), with premature depolarisations occurring rarely and almost exclusively as isolated events rather than dangerous clusters; notably, all second-degree atrioventricular blocks appeared only during pre-swim periods and resolved during exercise. During active recovery at 105 bpm, sinus arrhythmia predominated (81% of horses), whilst ventricular premature depolarisations were entirely absent. These findings substantially reassure practitioners that swimming with adequate recovery intervals presents negligible arrhythmic risk and represents a physiologically sound conditioning approach, though the small sample size limits confidence in establishing population-wide prevalence figures. For farriers and coaches incorporating aquatic work into rehabilitation or training programmes, this evidence validates swimming as a low-risk modality unlikely to provoke pathological cardiac responses in healthy horses.
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Practical Takeaways
- •Swimming is a safe cardiovascular exercise for horses when interspersed with active recovery periods; the low frequency of arrhythmias and absence of pathological patterns during these cycles suggests minimal cardiac risk
- •Sinus arrhythmias during recovery are normal physiological responses and do not indicate cardiac problems; practitioners can confidently recommend swimming as part of conditioning programs
- •High-quality underwater ECG monitoring is now feasible in swimming horses, enabling better assessment of cardiac responses to aquatic exercise for individual horses with pre-existing concerns
Key Findings
- •15 of 16 horses (94%) experienced at least one arrhythmia during swimming, though frequency remained low
- •Swimming heart rate averaged 162 bpm [141-173], with second degree atrioventricular block observed only during pre-swim period
- •Sinus arrhythmia was most common during active recovery (81% of horses), while ventricular premature depolarisations were absent during active recovery
- •Swimming with active recovery periods is not high-risk for cardiac arrhythmias, with mostly physiological rather than pathological arrhythmias observed