Management of two dogs with post-operative new-onset persistent atrial fibrillation following mitral valve repair.

Post-operative new-onset atrial fibrillation (POAF) is a possible complication following cardiac surgery. Digoxin is a drug with positive inotropic and negative chronotropic effects and is listed among antiarrhythmic drugs that can be prescribed in dogs with atrial fibrillation. This report aims at describing the use of digoxin in two dogs with persistent POAF after mitral valve repair. Case 1 was a Toy Poodle, neutered male, 12 years old, weighing 5.0 kg. The patient was diagnosed with the American College of Veterinary Internal Medicine (ACVIM) Stage D myxomatous mitral valve disease without arrhythmia. The day of the surgery was defined as Day 1. Persistent POAF was diagnosed on Day 30 (1-min mean heart rate of 206 bpm by in-clinic electrocardiogram), and treatment with digoxin was started at a dose of 0.0040 mg/kg, p12h. The resolution of atrial fibrillation (AF) was confirmed at the follow-up visit on Day 58 (1-min mean heart rate of 162 bpm by in-clinic electrocardiogram). Case 2 was a mixed-breed dog, neutered male, 12 years old, weighing 7.6 kg. The patient was diagnosed with ACVIM Stage B2 myxomatous mitral valve disease without arrhythmia. After surgery, the patient had a normal sinus rhythm, but a paroxysmal ectopic atrial rhythm was observed on Day 32. Persistent POAF was diagnosed on Day 130 (1-min mean heart rate of 216 bpm by in-clinic electrocardiogram), and treatment with digoxin was started at a dose of 0.0037 mg/kg, p12h. The resolution of AF was confirmed on Day 151 (1-min mean heart rate of 107 bpm by in-clinic electrocardiogram). In this report, the authors suspected that digoxin therapy could have contributed, among other factors, to cardioversion. However, specifically designed studies are needed to confirm this preliminary hypothesis.