Transient complete atrioventricular block following transvenous electrical cardioversion of atrial fibrillation in a horse.
Authors: van Loon G, De Clercq D, Tavernier R, Amory H, Deprez P
Journal: Veterinary journal (London, England : 1997)
Summary
# Editorial Summary Atrial fibrillation resistant to pharmacological treatment presents a significant clinical challenge in equine practice, prompting investigation into interventional techniques such as transvenous electrical cardioversion. A case study documented the attempted cardioversion of drug-refractory atrial fibrillation using progressively increasing monophasic shocks (100–360 J) delivered via transvenously placed defibrillation catheters positioned in the right atrium and pulmonary artery, with a temporary pacing catheter positioned at the right ventricular apex for backup support. Whilst the procedure failed to restore sinus rhythm, a critical complication emerged: transient third-degree atrioventricular block occurred following the higher-energy shocks, lasting 15 seconds after the 200 J shock, 40 seconds after 300 J, and 55 seconds after 360 J, with profound bradycardia requiring temporary ventricular pacing to maintain haemodynamic stability until spontaneous conduction returned. These findings underscore that conduction disturbances are a predictable risk of electrical cardioversion in horses, proportional to shock magnitude. For practitioners considering or supporting horses undergoing electrical cardioversion, the availability of temporary pacing capability is essential; without it, the iatrogenic bradycardia following attempted defibrillation could rapidly become haemodynamically catastrophic.
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Practical Takeaways
- •When performing electrical cardioversion for atrial fibrillation in horses, have temporary pacing capability available as atrioventricular conduction disturbances may occur post-shock
- •Be prepared for transient but significant bradycardia following defibrillation attempts; temporary pacing support may be necessary while waiting for spontaneous recovery
- •This complication highlights the risks of transvenous electrical cardioversion in horses and suggests careful case selection and preparation are essential
Key Findings
- •Transvenous electrical cardioversion with 100-360 J monophasic shocks failed to restore sinus rhythm in an equine patient with drug-refractory atrial fibrillation
- •Third-degree atrioventricular block occurred transiently after 200 J (15 s), 300 J (40 s), and 360 J (55 s) shocks
- •Temporary right ventricular pacing successfully corrected profound bradycardia during periods of atrioventricular block until spontaneous conduction resumed