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

Summary Background The number of atrial premature depolarisations (APDs) is a known risk factor for atrial fibrillation (AF) recurrence in humans. Objectives To evaluate if the number of APDs over a 24‐h period 5 days post cardioversion predicts AF recurrence within 1 year in horses, taking the multifactorial nature of AF into account. Study design Retrospective case series. Methods Eighty horses met these inclusion criteria: first AF episode, no AF recurrence within 5 days post cardioversion, cardioversion by transvenous electrical cardioversion (TVEC), 24‐h ECG recording and echocardiographic examination 5 days post cardioversion, no antiarrhythmic treatment during the ECG recording and follow‐up of minimum 1 year. 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. Results The patient population mainly consisted of Warmbloods (93%). Twenty‐six horses (33%) experienced AF recurrence within 1 year. 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 ≥25/24 h (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. Main limitations This study did not evaluate early AF recurrence within 5 days. The results cannot necessarily be extrapolated to other treatment methods, as only horses converted by TVEC were included. Conclusions The APD burden 5 days post cardioversion could be a useful predictive value for AF recurrence within 1 year in horses. However, other factors such as mitral regurgitation and atrial contractile function must also be taken into account.