Intravenous amiodarone treatment in horses with chronic atrial fibrillation.
Authors: De Clercq D, van Loon G, Baert K, Tavernier R, Croubels S, De Backer P, Deprez P
Journal: Veterinary journal (London, England : 1997)
Summary
# Intravenous Amiodarone for Equine Chronic Atrial Fibrillation Chronic atrial fibrillation in horses often proves refractory to conventional treatments, yet few pharmacological options exist for cases where the arrhythmia persists beyond several months; this Belgian study investigated whether intravenous amiodarone—a potent antiarrhythmic agent commonly used in human cardiology—could restore sinus rhythm in six horses with established AF (5–12 months' duration) and no underlying structural heart disease. Using a loading protocol of 5 mg/kg/hour for 1 hour followed by stepwise dose reduction to 0.83 mg/kg/hour over 23 hours and then 1.9 mg/kg/hour for a further 30 hours, the researchers monitored clinical signs, surface electrocardiography, and intra-atrial electrograms to detect conversion or adverse effects. Four of the six horses successfully cardioverted, though two of the responders and both non-responders developed transient hind limb weakness and weight shifting; importantly, neuromuscular side effects resolved within 6 hours of stopping treatment, whilst no pro-arrhythmic events occurred and only mild bilirubin elevations (normalising within 4 days) were observed. Although these results suggest amiodarone's potential for chronic AF in horses without cardiac disease, the modest success rate and inconsistent safety profile warrant optimisation of dosing schedules before this approach can be confidently recommended as a first-line alternative to conventional management strategies such as digoxin or quinidine therapy.
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Practical Takeaways
- •Intravenous amiodarone shows promise for treating chronic atrial fibrillation in horses without underlying cardiac disease, with a 67% cardioversion success rate
- •Expect temporary neuromuscular side effects (hind limb weakness, weight shifting) in most treated horses, but these resolve quickly after stopping infusion and should not prevent treatment attempts
- •Current infusion protocol requires refinement; monitor liver function (bilirubin) during treatment as mild elevation may occur
Key Findings
- •Four of six horses (67%) successfully converted to sinus rhythm with intravenous amiodarone treatment
- •Side effects including hind limb weakness and weight shifting occurred in 4 of 6 horses (67%) but resolved within 6 hours of treatment cessation
- •No pro-arrhythmic cardiac side effects were observed during amiodarone infusion
- •Total bilirubin slightly increased in three horses but normalized within four days