Background

Atrial fibrillation (AF) is uncommonly described in cats. One treatment strategy is re-establishment of normal sinus rhythm (NSR) to decrease ventricular response rate and rehabilitate atrial contribution to ventricular filling. This can be attempted by biphasic, direct-current, transthoracic electrical cardioversion (TtEC). To the best of our knowledge, there are no reports of using TtEC for feline AF.

Case Presentation

Three cats presented over the course of two months with AF. These included a five-year-old female spayed British-blue with hypertrophic cardiomyopathy (HCM) and arterial thromboembolism (ATE); a four-year-old male neutered Maine-coon with HCM, left-sided congestive heart failure, and occasional ventricular ectopy; and a 13-year-old male neutered Maine-coon with HCM. All three cats received antiarrhythmic drugs upon presentation (diltiazem and procainamide, diltiazem, amiodarone and procainamide, and amiodarone, respectively) while remaining in AF. All three cats were anesthetized and went through echocardiography in preparation for TtEC. In cat 1 - TtEC was applied three times using 10, 20, and 30 joules. NSR was achieved following the third cardioversion attempt. For the other two cats, 30 Joules were applied once, resulting in immediate cardioversion to NSR. No adverse effects were seen during and following the procedure in two of the cats, while the third experienced two short convulsion episodes and developed anisocoria, which resolved by the time the cat fully recovered from anesthesia. Although no intra-cardiac clots have been echocardiographically detected prior to TtEC, this outcome might have reflected a transient embolic event following the resolution of NSR. All three cats maintained NSR>3 weeks from the procedure.

New/Unique Information

To the best of our knowledge this is the first description of using TtEC to restore NSR in a series of cats with AF. While TtEC appears safe and effective, embolic event might occur and should be anticipated. Although AF is relatively rare in cats, because severe left atrial enlargement is a predisposition to both ATE and AF, and because AF is yet another risk factor for developing ATE, cardioversion should be considered as soon as AF is recognized, while every effort should be made prior to cardioversion to minimize the risk of TtEC-related thromboembolism.

Disclosures

No disclosures to report.