Long‐term monitoring with an implantable loop recorder detects multiple episodes of paroxysmal atrial fibrillation after electrical cardioversion in a Warmblood horse

Abstract

Summary Atrial fibrillation (AF) is a pathological arrhythmia affecting performance horses and is termed paroxysmal (pAF) when self‐terminating to sinus rhythm. Little is known about pAF as its sporadic nature makes it difficult to diagnose. Therefore, continuous electrocardiographic monitoring devices, such as implantable loop recorders (ILR), are necessary to detect the time of onset and episode duration. This case report presents the detection of pAF in a 9‐year‐old Warmblood horse after successful transvenous electrical cardioversion (TVEC). An ILR continuously monitored the heart rhythm over 28 months and detected 12 episodes of pAF of which two episodes were associated with reduced performance, while others occurred asymptomatically at rest. The estimated episode duration ranged from 6 min to 46.5 h. The antiarrhythmic drug sotalol (2 mg/kg bwt BID PO) was given prior to TVEC and then for 4 weeks. As episodes continued to occur, sotalol was prescribed for another 4 weeks, 6 months after TVEC. Continuous monitoring after TVEC allows for detection of AF recurrence and identification of AF burden, approximate time of onset and possible identification of trigger events. Early diagnosis and antiarrhythmic treatment may prevent a progression to persistent AF.

Implantable loop recorders for detecting arrhythmia in horses: Research tool or diagnostic technique?

“…Antiarrhythmic treatment may be useful to reduce the presence and duration of paroxysmal AF episodes and counteract harmful atrial remodelling. In the case report of Kjeldsen, Jensen, et al (2023), the longest duration between episodes of paroxysmal AF (8 months) was after a 4-week treatment with 2 mg/kg bwt sotalol administered orally. Although it is unsure whether there was a causal relationship between sotalol treatment and the absence of AF episodes in the following months, the use of sotalol has been suggested as a strategy to reduce the risk of AF recurrence after cardioversion (Decloedt et al, 2021).…”

“…However, no recordings during collapse were obtained due to lack of battery power. Kjeldsen, Jensen, et al (2023) suggest that ILRs may be useful for early diagnosis of recurrent AF after cardioversion. Close followup of these patients is indeed important as the recurrence rate of AF after electrical or pharmacological cardioversion is up to 40% (Decloedt et al, 2015;Premont et al, 2022;Vernemmen et al, 2022).…”

“…However, the question arises whether early detection of paroxysmal AF is clinically relevant in equine athletes, as treatment options are limited. Kjeldsen, Jensen, et al (2023) suggest that early detection of paroxysmal AF is important to initiate antiarrhythmic treatment and prevent the development of persistent AF. Episodes of paroxysmal AF may result in electrical, contractile and structural remodelling of the atrial myocardial tissue, which could in turn give rise to progression to persistent AF (Hesselkilde et al, 2019).…”

“…Paroxysmal atrial fibrillation (AF) has been associated with poor performance in equine athletes but diagnosing this arrhythmia can be daunting (Kjeldsen, Nissen, et al, 2022; Nath et al, 2021). The case report of Kjeldsen, Jensen, et al (2023) describes the use of an implantable loop recorder (ILR) to detect multiple episodes of paroxysmal AF in a Warmblood dressage horse after successful transvenous electrical cardioversion. Paroxysmal AF is defined as AF which spontaneously converts to sinus rhythm within 24–48 h (Reef et al, 2014) up to 5 days (van Loon, 2019).…”

“…As a class III antiarrhythmic drug, sotalol prolongs the atrial and ventricular effective refractory period and lowers heart rate, thereby decreasing the risk of re‐entry and recurrence of AF (Broux, De Clercq, Decloedt, Vera, et al, 2017; Decloedt et al, 2018). However, the drug also prolongs the QT interval and therefore Kjeldsen, Jensen, et al (2023) only recommended mild exercise during sotalol treatment. In addition, sotalol is listed on the FEI prohibited substances list as controlled medication and a withdrawal time must be observed before competing (Fédération Equestre Internationale, 2022).…”