Canis ISSN: 2398-2942

Ventricular tachycardia

Contributor(s): Mark Rishniw

Introduction

  • Can be serious life-threatening dysrhythmia, often incidental non-life-threatening arrhythmia.
  • Cause: usually myocardial irritation due to primary cardiac or systemic disease.
  • Signs: weakness, collapse and death.
  • Diagnosis: electrocardiography.
  • Treatment: treat underlying disease, antidysrhythmic agents.
  • Prognosis: guarded for some, good for others.

Pathogenesis

Etiology


Primary cardiac disease Extra-cardiac pathology

Predisposing factors

General
  • Underlying heart failure with poor cardiac output resulting in myocardial hypoxia (especially Dobermanns).

Specific

Pathophysiology

  • Spontaneous depolarization of ventricular myocardial cells.
  • More than 3 ventricular premature complexes (VPCs) in a row Ventricular premature contraction.
  • May progress to ventricular fibrillation in some cases.
  • Severe shock or autonomic stimulation → myocardial ischemia and myocyte damage.
  • Myocardial disease or damage → changes in resting potential, sodium and calcium currents across cell membranes → arrhythmogenesis.
  • This effect may be enhanced by other factors, eg hypoxemia.
  • Ectopic depolarization occurs in ventricular myocardial cells outside the normal impulse generating nodes and below the atrioventricular junction.
  • Ventricles are incompletely filled by the time of the ectopic discharge and contraction of myocardium follows abnormal sequence → reduced cardiac output on ectopic beat.
  • Hypotension and myocardial ischemia may → syncope, seizures or progression of arrhythmia to ventricular fibrillation → death.

Timecourse

  • Often incidental finding in VT 2° to extracardiac pathology, eg trauma
  • Severity of signs ensures early diagnosis.

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.
  • Willis R (2005) Treatment of tachydysrhythmias. UK Vet 10 (3), 45-51.
  • Moïse N S (1998) From cell to cageside: Autonomic influences on cardiac rhythms in dogs. JSAP 39 (10), 460-468 VetMedResource.
  • Moïse N S, Gilmour R F, Riccio M L et al (1997) Diagnosis of inherited ventricular tachycardia in German shepherd dogs. JAVMA 210 (3), 403-410 PubMed.
  • Marino D J, Matthieson D T & Fox P R et al (1994) Ventricular arrhythmias in dogs undergoing splenectomy - a prospective study. Vet Surg 23 (2), 101-106 PubMed.
  • Knapp D W, Aronsohn M G & Harpster N K (1993) Cardiac arrhythmias associated with mass lesions of the canine spleen. JAAHA 29 (2), 122-128 VetMedResource.


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