Intravenous administration of quinidine and metoprolol for treatment of atrial fibrillation in 2 neonatal foals.
Authors: Leduc Laurence, Abraham Michelle, Slack JoAnn
Journal: Journal of veterinary internal medicine
Summary
Atrial fibrillation in healthy newborn foals is exceptionally rare, with only isolated case reports in the literature, yet it can severely compromise nursing behaviour and clinical stability. Two neonatal Thoroughbred colts presented with irregularly irregular tachyarrhythmias and failure to nurse; ECG and echocardiographic examination ruled out underlying structural cardiac disease and confirmed lone atrial fibrillation. The first foal required combination therapy with intravenous metoprolol and quinidine to achieve cardioversion to normal sinus rhythm, whilst the second converted following metoprolol administration alone, which had been intended for rate control rather than rhythm restoration. Both foals demonstrated marked clinical improvement after conversion, with sustained normal sinus rhythm documented for 6 weeks and 2 years respectively. These cases suggest that pharmacological cardioversion combining rate-controlling agents (beta-blockers) with antiarrhythmic drugs (Class Ia agents such as quinidine) represents a viable treatment strategy for persistent lone atrial fibrillation in neonatal foals, offering an alternative to the procainamide-based approach previously described in the literature.
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Practical Takeaways
- •Consider rate control and cardioversion with IV antiarrhythmic drugs (metoprolol and/or quinidine) as treatment options for persistent lone atrial fibrillation in neonatal foals, even without structural heart disease
- •Monitor neonatal foals presenting with irregular tachycardia and nursing difficulties, as AF may be the underlying cause and is treatable
- •Successful cardioversion can result in sustained normal sinus rhythm and marked clinical improvement in demeanor and nursing ability
Key Findings
- •Atrial fibrillation occurred in 2 neonatal Thoroughbred colts without underlying structural heart disease
- •First foal converted to normal sinus rhythm with combined IV metoprolol and quinidine treatment
- •Second foal converted to normal sinus rhythm with single IV dose of metoprolol alone
- •Both foals maintained normal sinus rhythm for extended periods (6 weeks to 2 years) with improved nursing behavior post-conversion