Equis ISSN 2398-2977

Heart: ventricular fibrillation

Contributor(s): Karen Blissitt, Christopher Brown, Wendy Furness, Lesley Young

Introduction

  • Usually a terminal event in which there are no organized ventricular depolarizations or contractions.
  • Cause: variable.
  • Signs: cardiovascular collapse.
  • Diagnosis: ECG.
  • Treatment: IV lidocaine, transthoracic electrical defibrillation in foals and small ponies under GA.
  • Prognosis: almost invariably fatal.

Pathogenesis

Etiology

  • Associated with increased myocardial irritability.
  • Usually preceded by ventricular tachycardia   Heart: ventricular tachycardia  .
  • Can be spontaneous, but usually associated with severe systemic or cardiac disease   Heart: disease - overview  , eg:
    • Ruptured bladder   Bladder: rupture  (and associated electrolyte imbalance).
    • Endotoxic shock
    • Drug induced, eg quinidine therapy   Quinidine  .
  • Likely to account for 2/3 of sudden death cases during exercise; myocardial irritability is believed to be increased by autonomic inbalance, metabolic changes, increased temperature, hypoxia and acidosis dudring this period causing ventricular ectopic activity   Heart: ventricular premature complex 02 - ECG    Heart: ventricular premature complex 03 - ECG      Heart: ventricular premature complex 06 - ECG  .

Predisposing factors

General
  • Any cause of severe electrolyte imbalance.
  • Severe cardiac pathology.
  • Hypoxia.
  • High speed exercise in previously asymptomatic animals.

Timecourse

  • Once ventricular fibrillation becomes established, time to death is very rapid.

Diagnosis

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Treatment

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Outcomes

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Further Reading

Publications

Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Reimer J M, Reef V B & Sweeney R W (1992) Ventricular arrhythmias in horses, 21 cases (1984-1989). JAVMA 201 (8), 1237-1243 PubMed.
  • Geddes L A & Tacker W A (1983) Ventricular fibrillation and defibrillation. JAVMA (1), 9-19 PubMed.


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