Equis ISSN 2398-2977

Heart: sinus block

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

Introduction

  • Cause: high vagal tone.
  • Signs: usually none.
  • Diagnosis: electrocardiography.
  • Treatment: treatment of primary cause and if necessary short term use of atropine or glycopyrrolate; use of an artifical pacemaker has been reported although this is rarely indicated.
  • Prognosis: good.

Pathogenesis

Etiology

Irritation or stimulation of the vagus nerve
  • Commonly alpha 2 adrenoreceptor agonist agents (romifidine   Romifidine  , xylazine   Xylazine  , detomidine   Detomidine hydrochloride  ).
  • Normal homeostatic mechanism to reduce arterial blood pressure.
  • More rarely surgical manipulation.
  • Thoracic neoplasia   Respiratory: neoplasia  .
  • Cervical neoplasia.
  • Electrolyte imbalance.
  • Pathologic conditions of the atria, including fibrosis and cardiomyopathy   Heart: cardiomyopathy   (rare).

Pathophysiology

  • Sinus block is caused by the failure of impulses to either be formed or leave the sinoatrial node due to a depression in automaticity and conductivity in the node. This is most commonly attributable to high vagal tone.
  • Sinus arrest is said to have occured when more than two consecutive sinus impulses are blocked.

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.
  • Gasthuys F et al (1990) A preliminary study on the effects of atropine sulfate on bradycardia and heart blocks during romifidine sedation in the horse. Vet Res Commun 14 (6), 489-502 PubMed.
  • McGuirk S M et al (1985) Diagnosis and treatment of cardiac arrhythmias. Vet Clin North Am Eq Pract (2), 353-370 PubMed.


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