Ventricular arrhythmias induced by snake bite in a horse: A case report.

Overview

• This case report describes a horse that developed serious heart rhythm disturbances (ventricular arrhythmias) after being bitten by a snake, highlighting the importance of monitoring cardiac function in such cases.
• It provides novel clinical observations of specific arrhythmias in horses linked to snake venom from the genus Bothrops.

Introduction and Background

• The study concerns a Mangalarga Marchador mare, a breed of horse, that was referred to a veterinary facility after suffering snake venom poisoning.
• Snake bites, particularly from the Bothrops genus, are known to cause systemic effects including cardiovascular issues, but detailed electrocardiographic findings in horses are rarely documented.
• This report aims to fill that gap by describing the specific types of ventricular arrhythmias induced by the snake bite in this horse.

Clinical Presentation

• The mare presented with tachyarrhythmia—an abnormally fast and irregular heartbeat—detected during cardiac auscultation (listening to heart sounds).
• Because of these abnormal heart sounds, an electrocardiogram (ECG) was performed to better characterize the arrhythmias and provide a detailed cardiac evaluation.

Electrocardiographic Findings

• The ECG identified three key ventricular arrhythmias:
  • Paroxysmal monomorphic ventricular bigeminy (pMVB): repeating pattern of a normal beat followed by a premature ventricular contraction.
  • pMVB with pairs of premature ventricular contractions (pMVBPC): similar to pMVB but includes pairs of premature beats instead of single occurrences.
  • Paroxysmal monomorphic ventricular tachycardia (pMVT): a sudden onset of a rapid, repetitive abnormal ventricular rhythm.
• In all these cases, incomplete atrioventricular dissociation was observed, indicating the atria and ventricles were not fully synchronized during these arrhythmias.
• There were variations in the coupling intervals (time between normal heartbeats and premature beats), but these did not show a progressive shortening pattern typically seen in other arrhythmias such as the Wenckebach phenomenon.
• These ECG characteristics supported the diagnosis of a reentry mechanism causing the arrhythmia, rather than parasystole (a type of arrhythmia due to an ectopic pacemaker). Reentry means abnormal electrical impulses continuously circulate in the heart, causing rapid rhythms.

Significance and Novelty

• This is reportedly the first documented case describing:
  • pMVB and pMVBPC occurrences in horses post snake envenomation.
  • The first detailed account of pMVT caused by Bothrops snake bites in equines.
• The findings underline the importance of thorough cardiac assessments in horses with snake envenomation because arrhythmias may complicate clinical management and prognosis.
• Early detection of such arrhythmias can help guide treatment strategies and improve outcomes in affected horses.

Conclusion

• Snake bites from certain venomous species like Bothrops can induce serious ventricular arrhythmias in horses.
• Arrhythmias like pMVB, pMVBPC, and pMVT involve reentry mechanisms and incomplete atrioventricular dissociation as observed by ECG.
• Veterinarians should consider cardiac monitoring in horses presenting with a history of snake bite to detect and manage these potentially life-threatening arrhythmias.