Atrial fibrillation in the horse: Retrospective study on 30 subjects

The clinical, electrocardiographic, echocardiographic and echo-Doppler findings in thirty horses with atrial fibrillation (AF), paroxysmal in 3 cases and chronic in the remaining, are described. The arrhythmia was associated with a non-restrictive ventricular septal defect and right atrial enlargement in 1 case, mitral and/or aortic regurgitation with left atrial enlargement in 11 cases, tricuspid regurgitation with right atrial enlargement in 2 cases, and insufficiency of at least three cardiac valves with generalised cardiomegaly in 4 cases. No detectable cardiac diseases were found in the remaining 12 subjects. Quinidine sulphate per os, associated with digoxin in 2 cases, was employed in 12 horses, 7 of them converted to stable sinus rhythm. Recurrence of AF was observed in an additional case. Four horses failed to convert to sinus rhythm, even after use of amiodarone per os for 30 days in two of them.