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

Abstract

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.

Incidence, recurrence, and outcome of postrace atrial fibrillation in Thoroughbred horses

“…In our study, a delay occurred between auscultation and ECG recording, which might account for the different diagnoses based on these 2 methods. A previous study in horses identified an association between atrial premature beats postconversion and AF recurrence,17 and ectopy is important in triggering AF 38. Episodes of sinus rhythm with ectopy were retained in our study because they could reflect an intermediate step in resolution of paroxysmal AF.The overall frequency of postrace AF in Hong Kong (2.7 per 1000 starts) was higher than observed in previous studies conducted in the United Kingdom and Japan (0.2-0.3 per 1000 starts),12,13 but similar to a study of Standardbreds in the United States (1.4 per 1000…”

“…4,15,16 However, underlying microstructural myocardial lesions and electrical remodeling that cannot be readily detected by clinical examination are suspected to contribute to the development of AF in horses with recurrent episodes. 17 Recently, electro-anatomical mapping has identified pulmonary vein firing initiating AF in a horse. 18 Atrial fibrillation is not entirely benign and such individuals might also be susceptible to arrhythmias originating in the ventricular myocardium.…”

“…Persistent AF can be converted to sinus rhythm using either transvenous electrocardioversion or pharmacologic intervention, most commonly using quinidine sulfate, and generally carries an excellent prognosis for future athleticism 4,16 . After conversion to sinus rhythm, AF recurrence in horses with AF of recent onset is approximately 15% to 40% 16,17,26‐28 . A longer duration of AF, 26 which induces structural, mechanical, and electrical cardiac remodeling, 27,29‐32 is associated with increased risk of AF recurrence.…”

Increased fibroblast accumulation in the equine heart following persistent atrial fibrillation

“…Over the last couple of years, the horse has gained increasing interest as a large animal model of arrhythmias [18] , [19] , [20] , [21] , [22] . In contrast to other animal models usually used in AF research, such as rodents, pigs, dogs and goats, horses are frequently reported to develop AF spontaneously, just like humans [23] , [24] , [25] , [26] .…”

Irregular hearts and performance horses

“…What is it that causes a genetically predisposed horse to develop a clinical episode of the arrhythmia, because genetic liability alone appears not to be sufficient? Time, perhaps, for some hypothesis‐based studies! 23 …”