Oral amiodarone therapy in dogs with atrial fibrillation

The medical records of client-owned dogs in which amiodarone was used to manage atrial fibrillation (AF) were reviewed. Data analyzed included signalment, history of heart failure, presenting complaint, clinical diagnosis, prescription drug history, number of re-examinations, outcome, and laboratory analysis including serum biochemical analysis, CBC, and thyroid function testing. Specific data for amiodarone included loading and maintenance dose, duration of loading dose, adverse effects, and reason for decreasing dose or discontinuation of amiodarone therapy. Follow-up data for 17 dogs were included in the analysis. Various cardiac diseases including cardiomyopathy, valvular endocardiosis, and congenital heart disease were diagnosed in the dogs. Median loading and maintenance dosages of amiodarone were 16.5 and 9.0 mg/kg of body weight/d, respectively. A >20% decrease in heart rate was achieved in 13 dogs (76%). Conversion to sinus rhythm was achieved and maintained in 6 dogs (35%). Amiodarone was discontinued in 5 dogs, and the dose was decreased because of symptomatic bradycardia (n = 1), asymptomatic (n = 1) and symptomatic (n = 3) increases in hepatic enzyme activities, and for unknown reason (n = 1). On the basis of >20% decrease in heart rate in 76% of the dogs and conversion to sinus rhythm in 35%, it was concluded that amiodarone may be useful in managing AF in dogs. The use of amiodarone in the medical management of AF in dogs warrants further investigation.