Resolution of sustained ventricular tachycardia in a horse presenting with colic with magnesium sulfate
Authors: Pratt Stefanie L., Bowen Mark, Redpath Adam
Journal: Equine Veterinary Education
Summary
# Editorial Summary Ventricular tachycardia (VT) is an uncommon but potentially life-threatening arrhythmia in horses, particularly those presenting with acute gastrointestinal disease, yet published cases demonstrating successful pharmacological conversion back to sinus rhythm remain scarce in the equine literature. This case report documents a 19-year-old Warmblood gelding with prior colic surgery history who developed sustained VT (75 beats/min on ECG) during a subsequent colic episode; despite already receiving lidocaine, the arrhythmia persisted with an irregularly irregular rhythm audible on auscultation. Multiple intravenous boluses of magnesium sulfate administered over several hours successfully converted the VT to normal sinus rhythm (44 beats/min), with the horse maintaining stable cardiac rhythm throughout its 8-day hospitalisation and discharge. Whilst both lidocaine and magnesium sulfate are recognised first-line antiarrhythmic agents for horses with haemodynamically significant VT, this case highlights the potential utility of magnesium as an adjunctive or alternative therapy when initial lidocaine treatment proves inadequate—a particularly valuable consideration in colic cases where electrolyte disturbances commonly contribute to arrhythmia development. For practitioners managing critically ill horses with concurrent colic and cardiac dysrhythmias, awareness of multi-agent antiarrhythmic protocols may improve outcomes in cases where monotherapy fails.
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Practical Takeaways
- •Magnesium sulfate should be considered as a treatment option for sustained ventricular tachycardia in horses when lidocaine alone is insufficient, particularly in colic cases
- •Multiple boluses of magnesium sulfate administered over several hours may be necessary to achieve conversion to normal sinus rhythm
- •Sustained ventricular tachycardia can occur secondary to gastrointestinal disease and should prompt both cardiac and abdominal investigation
Key Findings
- •A 19-year-old Warmblood gelding with sustained ventricular tachycardia (heart rate 75 bpm on ECG) converted to normal sinus rhythm following multiple intravenous magnesium sulfate boluses administered over several hours
- •The horse maintained normal sinus rhythm with a resting heart rate of 44 bpm through discharge 8 days post-treatment
- •Magnesium sulfate was effective as a second-line antiarrhythmic agent in a horse already receiving lidocaine therapy