Acute Conversion of Atrial Fibrillation in Two Dogs by Intravenous Amiodarone Administration

Abstract

A 30-kg, 10-year-old, castrated male Siberian Husky (dog 1) was presented to the Emergency Service of the Veterinary Teaching Hospital of the University of Illinois with a 14-day history of cardiac arrhythmias after splenectomy for a benign splenic mass. On presentation, the dog was bright, alert, and responsive. Heart rate was 200 beats per minute (bpm) and cardiac murmurs were not ausculted. Femoral pulses were weak, and pulse deficits were noted, resulting in a rate of approximately 60 bpm. The abdominal incision from the recent splenectomy appeared to be healing normally. A small subcutaneous mass in the left inguinal area was noted. The dog had been diagnosed previously with a seizure disorder and was receiving phenobarbital (81 mg PO q12h). In response to the cardiac arrhythmia, atenolol (25 mg PO q8h) administration had been started 24 hours before presentation at the hospital.Hematologic (CBC) and serum biochemical analyses, blood pressure measurement, mass aspiration, and electrocardiography were performed. The CBC was unremarkable, except for mild thrombocytopenia of 170 3 10 3 cells/mL (reference interval [RI], 200-900 3 10 3 cells/mL). Serum biochemical analysis revealed mild decrease in c-globulin concentration (2.3 g/dL; RI, 2.7-4.4 g/dL); increased total alkaline phosphatase (ALP: 4,416 U/L; RI, 12-110 U/L), alanine transaminase (ALT: 289 U/L; RI, 17-87 U/L), and c-glutamyltransferase (24 U/L; RI, 1-11 U/L) activities; and increased total bilirubin concentration (0.6 mg/dL; RI, 0.08-0.50 mg/dL). Systolic, diastolic, and mean blood pressures measured by oscillometric technique were 124, 110, and 116 mm Hg, respectively. Results of an examination of a fine needle aspirate of the inguinal mass were consistent with benign lipoma. A 6-lead ECG identified atrial fibrillation, with a ventricular rate of 130 bpm. The dog was admitted to the intensive care unit for overnight evaluation, and was placed on telemetric ECG monitoring.Over the next 8 hours, heart rate varied from 162 to 211 bpm. The next morning, the dog was referred to the Cardiology Service for evaluation of atrial fibrillation. A 10-lead ECG was obtained, and confirmed atrial fibrillation, with a ventricular rate of 145 bpm. The QRS amplitudes and durations were within normal limits. Cardiac ultrasonography was performed and normal cardiac size and systolic function were identified. A small echogenic mass was visualized on the dorsal portion of the left atrium, from which a finger-like appendage projected into the left atrial chamber. On the basis of the presence of atrial fibrillation and the location and echocardiographic appearance of the mass, atrial thrombus was considered the most likely diagnosis. Heparin therapy (1,000 U SC q8h) was initiated. In an attempt to restore sinus rhythm, procainamide (230 mg, slow bolus) was administered IV. An effect on the ECG was not observed. The dog was returned to the intensive care unit (ICU), and 24 hours later, cardioversion with amiodarone was attempted.A solution of 5 mg of amiodarone/mL was mad...

Effects of an adapted intravenous amiodarone treatment protocol in horses with atrial fibrillation

“…AD administration have been described (Agozzino et al 2002;Fransi and Briedis 2004;Bravo et al 2005). Also, in dogs, adverse effects due to chronic AD treatment include hepatopathy, anorexia, lethargy, pruritis, neutropenia and thrombocytopenia Gilbert et al 2000;Kraus et al 2005;Oyama and Prosek 2006). In a previous equine AD study, adverse clinical signs included an increase of total bilirubin and weakness of the hindlimb (De Clercq et al 2006a).…”

Retrospective evaluation of the use of amiodarone in dogs with arrhythmias (from 2003 to 2010)

“…This is similar to results in human medicine, where amiodarone is used in patients with structural heart disease or CHF because of its minor negative inotropic and minimal pro‐arrhythmic effects (Vassallo and Trohman 2007). In humans, amiodarone is important in converting and preventing recurrence of AF and atrial flutter (The AFFIRM First Anti‐arrhythmic Drug Substudy Investigators 2003, Singh and others 2005, Zimetbaum 2007) and this has also been an indication in dogs (Oyama and Prosek 2006). In this study, two dogs with atrial arrhythmias were successfully converted to sinus rhythm with amiodarone.…”

“…It is also effective for atrial arrhythmias, and is nowadays considered one of the most effective drugs for maintaining the sinus rhythm after conversion of atrial arrhythmias such as atrial fibrillation (AF) (Singh and others 2003, The AFFIRM First Anti‐arrhythmic Drug Substudy Investigators 2003, van Erven and Schalij 2010). Similarly, amiodarone has been used in veterinary medicine for successful treatment of ventricular tachycardia and conversion of AF into sinus rhythm (Oyama and Prosek 2006, Saunders and others 2006).…”

“…Intravenous administration of amiodarone in dogs can result in an anaphylactic reaction, most likely due to the solvent used rather than the amiodarone itself (Cushing and others 2009, Souney 2009). However, these effects were reversible with discontinuation of amiodarone and administration of corticosteroids ± antihistamine (Oyama and Prosek 2006, Cober and others 2009).…”

Efficacy of pentamidine analogue 6 in dogs with chronic atrial fibrillation

“…Dogs with lone AF have a better survival than do those with concomitant heart disease, but the arrhythmia is strongly associated with dilated cardiomyopathy . Currently, several drugs and procedures exist to treat AF in dogs . Treatment focusses on controlling ventricular response rate rather than on rhythm control .…”