Felis ISSN 2398-2950

Atrial fibrillation

Contributor(s): Mark Oyama, Mark Rishniw

Introduction

  • Cause: secondary to atrial enlargement that accompanies advanced cardiomyopathy in cats.
  • Signs: may be non-specific or signs of underlying pathology.
  • Diagnosis: auscultation, electrocardiography.
  • Treatment: antidysrhythmic drugs, treatment of accompanying heart failure.
  • Prognosis: AF secondary to advance cardiomyopathy has poor prognosis.
    Print off the owner factsheet onHeart rhythm disturbance (atrial fibrillation)  Heart rhythm disturbance (atrial fibrillation)  to give to your client.

Pathogenesis

Etiology

  • Secondary - atrial enlargement (usually left) secondary to cardiac pathology.
  • Primary AF (as occasionally detected in giant breed dogs and horses) is not identified in cats.

Specific

Atrial stretching

Pathophysiology

  • Disorganized atrial depolarizations and variable conduction of atrial depolarizations to the ventricles results in irregularly timed ventricular depolarizations. The ventricular rate depends on the number of impulses that are conducted through the AV node.
  • Atrial depolarization rapid and disorganized (~600 depolarizations/min).
  • Rapid generation of electrical impulses in the atria cannot be conducted through the AV node - 'AV block'. This limits the number of impulses reaching the ventricles.
  • Degree of vagal tone determines AV conduction - high vagal tone results in a normal ventricular rate; low vagal tone, which is commonly experienced in secondary AF results in a high ventricular rate.
  • With high ventricular rates, alterations in cardiac output from beat to beat   →  variable pulse intensity and occasional absent pulses   →   pulse deficit.
  • Loss of atrial contraction.
  • With high ventricular rates   →    poor filling and contraction   →    reduced CO.

Timecourse

  • May be acute, ie develops during anesthesia or associated with toxemic episode.
  • More usually presented some time after development.

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.
  • Côté E, Harpster N K, Laste N J et al (2004) Atrial fibrillation in cats: 50 cases (1979-2002). JAVMA 225 (2), 256-60 PubMed.
  • Gelzer A M & Kraus M S (2004) Management of atrial fibrillation. Vet Clin North Am Small Anim Pract 34 (5), 1127-1144 PubMed.
  • Uchino M, Koyama H, Washizu M et al (1987) Atrial fibrillation in the pig, cow, dog, and cat. Heart Vessels Suppl 2, 7-13 PubMed.


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