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Electrical cardioversion in a dog with atrial fibrillation and hypothyroidism
  1. Joonbum Seo1,2 and
  2. Manreet K Singh2,3
  1. 1 Royal Veterinary College, North Mymms, UK
  2. 2 Small Animal Specialist Hospital, North Ryde, New South Wales, Australia
  3. 3 Veterinary Cardiac Referrals, Terrey Hills, New South Wales, Australia
  1. Correspondence to Dr Joonbum Seo; jseo7{at}


A three-year-old male neutered Bullmastiff cross was assessed for lethargy. The dog had recently been diagnosed with atrial fibrillation and hypothyroidism and had been started on thyroid supplementation and cardiac medications. ECG on presentation confirmed atrial fibrillation. Echocardiography showed normal chamber dimensions, making heart failure unlikely. With the lack of structural heart disease, a diagnosis of lone atrial fibrillation was made. After initial medical management of the atrial fibrillation with rate control, the client elected electrical cardioversion. The dog was pretreated with amiodarone and transthoracic electrical cardioversion was performed. Atrial fibrillation was successfully converted to normal sinus rhythm, and the dog was discharged on a maintenance dose of amiodarone. The dog remained in a normal sinus rhythm at the 1-, 2-, 4-, 8- and 14-month revisits. This case report describes management options for atrial fibrillation and the potential association with hypothyroidism.

  • amiodarone
  • arrhythmias
  • cardiology
  • atrial fibrillation
  • hypothyroidism
  • dogs
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  • Contributors Both authors were directly involved in this case and contributed to writing this manuscript. Both authors have read and approved this manuscript for publication.

  • Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.

  • Competing interests None declared.

  • Provenance and peer review Not commissioned; externally peer reviewed.

  • Data sharing statement No additional data are available.

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