Transient atrial fibrillation in dogs with mitral valve disease

Abstract

OBJECTIVE: To report the occurrence of transient atrial fibrillation in dogs with degenerative mitral valve disease (DMVD) American College of Veterinary Medicine (ACVIM) stage C/D, presenting with acute clinical signs. MATERIALS AND METHODS: Retrospective multicentric case series of dogs with DMVD ACVIM stage C/D and transient atrial fibrillation (AF) hospitalised in referral centres (2020 to 2024). Signalment, clinical findings, treatments, electrocardiographic and echocardiographic data and outcomes were recorded. RESULTS: Eight dogs were included. All dogs presented for acute deterioration of clinical signs:tachypnoea with worsening cough (5/8) and syncopal episodes (3/8). Electrocardiographic findings were compatible with AF with a fast ventricular rate in all dogs. Active congestive heart failure (CHF) was identified in 5/8 patients. Antiarrhythmic treatment with digoxin (4/8), diltiazem (1/8) or digoxin/diltiazem (2/8) was instituted in seven dogs. Treatment for active CHF was also performed. Sinus rhythm was subsequently observed either during hospitalisation (4/8, average 30 hours) or at the first recheck after stabilisation (4/8, average 22 days). In 6/7 dogs, antiarrhythmic treatment was discontinued. Three dogs showed a recurrence of AF a few months after the first episode. Five dogs died of cardiac disease, two of which died suddenly. CLINICAL SIGNIFICANCE: Paroxysmal AF has been previously described in dogs; the pathophysiological mechanism is presumed to be neurally mediated. Transient AF has not been extensively reported in dogs with clinically significant DMVD and is a possible event in dogs presenting with acute clinical signs and AF. The pathophysiological mechanism in this population may be slightly different from previously reported cases. After cardioversion, variation in clinical outcomes was observed.