Atrial premature depolarisations five days post electrical cardioversion are related to atrial fibrillation recurrence risk in horses.

Abstract

The number of atrial premature depolarisations (APDs) is a known risk factor for atrial fibrillation (AF) recurrence in humans. To evaluate if the number of APDs over a 24-h period 5days post cardioversion predicts AF recurrence within 1year in horses, taking the multifactorial nature of AF into account. Retrospective case series. Eighty horses met these inclusion criteria: first AF episode, no AF recurrence within 5days post cardioversion, cardioversion by transvenous electrical cardioversion (TVEC), 24-h ECG recording and echocardiographic examination 5days post cardioversion, no antiarrhythmic treatment during the ECG recording and follow-up of minimum 1year. To compare the APD burden between the recurrence and non-recurrence group a Mann-Whitney U test was used. A multivariable survival model was built to identify additional risk factors for AF recurrence. The patient population mainly consisted of Warmbloods (93%). Twenty-six horses (33%) experienced AF recurrence within 1year. The number of APDs (median [range]) was significantly higher (P=0.01) in the recurrence group (15 [1-152]) compared with the non-recurrence group (7 [0-304]). In the multivariable survival model, APDs≥25/24h (hazard ratio [HR] 2.9, 95% confidence interval [CI] 1.2-6.8, P=0.02), mitral regurgitation (HR 8.6, 95% CI 2.6-28.9, P<0.001), left atrial active fractional area change ≤9.6% (HR 2.6, 95% CI 1.0-6.5, P=0.04) and lower body weight (HR 0.99, 95% CI 0.98-0.99, P=0.001) were significantly associated with AF recurrence. This study did not evaluate early AF recurrence within 5days. The results cannot necessarily be extrapolated to other treatment methods, as only horses converted by TVEC were included. The APD burden 5days post cardioversion could be a useful predictive value for AF recurrence within 1year in horses. However, other factors such as mitral regurgitation and atrial contractile function must also be taken into account.