Transvenous electrical cardioversion of equine atrial fibrillation: patient factors and clinical results in 72 treatment episodes.
Authors: McGurrin M K J, Physick-Sheard P W, Kenney D G
Journal: Journal of veterinary internal medicine
Summary
# Transvenous Electrical Cardioversion for Equine Atrial Fibrillation Atrial fibrillation represents a significant performance-limiting arrhythmia in horses, and transvenous electrical cardioversion (TVEC) offers a minimally invasive treatment alternative to pharmacological or watchful management approaches. McGurrin and colleagues evaluated 72 cardioversion episodes across 63 client-owned horses (predominantly 54 Standardbreds) to characterise how patient variables influence treatment success and the energy requirements needed to restore sinus rhythm. Electrodes were positioned in the right atrium and pulmonary artery via jugular catheterisation, with biphasic shocks delivered under general anaesthesia at progressively increasing energy levels up to a maximum of 300 J per shock. Cardioversion succeeded in 71 of 72 episodes (98.6% success rate) at a mean energy of 165 J, though important sex and weight interactions emerged: females required significantly more energy than males, and whilst weight inversely correlated with energy requirements in females, it showed positive correlation in males—a finding warranting careful case selection and counselling regarding anaesthetic risk. Notably, the duration of AF preceding treatment bore no relationship to either cardioversion success or energy thresholds, suggesting that clinicians need not necessarily prioritise urgent referral on grounds of chronicity alone, though early intervention may still confer other physiological advantages.
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Practical Takeaways
- •TVEC is a highly effective treatment option for lone atrial fibrillation in horses, with nearly 99% success rate in this referral population
- •Sex and age of the horse influence the energy levels needed for successful cardioversion, which should inform pre-treatment planning and anesthetic management
- •Chronicity of atrial fibrillation does not predict treatment success, so delayed presentation should not discourage treatment attempts
Key Findings
- •Transvenous electrical cardioversion achieved successful conversion in 71 of 72 episodes (98.6% success rate) at mean energy of 165.43 J
- •Cardioversion energy was significantly higher in females compared to males, with weight showing opposite relationships by sex (negative in females, positive in males)
- •Age was positively correlated with cardioversion energy in females but not males
- •Duration of arrhythmia prior to treatment had no relationship with success rate or energy requirements