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Research article - Peer-reviewed, 2022

Atrial fibrillatory rate as predictor of recurrence of atrial fibrillation in horses treated medically or with electrical cardioversion

Buhl, Rikke; Hesselkilde, Eva M.; Carstensen, Helena; Hopster-Iversen, Charlotte; van Loon, Gunther; Decloedt, Annelies; van Steenkiste, Glenn; Marr, Celia M.; Reef, Virginia B.; Schwarzwald, Colin C.; Mitchell, Katharyn J.; Nostell, Katarina; Nogradi, Nora; Nielsen, Soren S.; Carlson, Jonas; Platonov, Pyotr G.;


Background The recurrence rate of atrial fibrillation (AF) in horses after cardioversion to sinus rhythm (SR) is relatively high. Atrial fibrillatory rate (AFR) derived from surface ECG is considered a biomarker for electrical remodelling and could potentially be used for the prediction of successful AF cardioversion and AF recurrence. Objectives Evaluate if AFR was associated with successful treatment and could predict AF recurrence in horses. Study design Retrospective multicentre study. Methods Electrocardiograms (ECG) from horses with persistent AF admitted for cardioversion with either medical treatment (quinidine) or transvenous electrical cardioversion (TVEC) were included. Bipolar surface ECG recordings were analysed by spatiotemporal cancellation of QRST complexes and calculation of AFR from the remaining atrial signal. Kaplan-Meier survival curve and Cox regression analyses were performed to assess the relationship between AFR and the risk of AF recurrence. Results Of the 195 horses included, 74 received quinidine treatment and 121 were treated with TVEC. Ten horses did not cardiovert to SR after quinidine treatment and AFR was higher in these, compared with the horses that successfully cardioverted to SR (median [interquartile range]), (383 [367-422] vs 351 [332-389] fibrillations per minute (fpm), P < .01). Within the first 180 days following AF cardioversion, 12% of the quinidine and 34% of TVEC horses had AF recurrence. For the horses successfully cardioverted with TVEC, AFR above 380 fpm was significantly associated with AF recurrence (hazard ratio = 2.4, 95% confidence interval 1.2-4.8, P = .01). Main limitations The treatment groups were different and not randomly allocated, therefore the two treatments cannot be compared. Medical records and the follow-up strategy varied between the centres. Conclusions High AFR is associated with failure of quinidine cardioversion and AF recurrence after successful TVEC. As a noninvasive marker that can be retrieved from surface ECG, AFR can be clinically useful in predicting the probability of responding to quinidine treatment as well as maintaining SR after electrical cardioversion.


AFR; arrhythmia; cardiology; ECG; electrophysiology; horse; surface electrocardiogram

Published in

Equine Veterinary Journal

2022, volume: 54, number: 6, pages: 1013-1022
Publisher: WILEY

Authors' information

Buhl, Rikke
University of Copenhagen
Hesselkilde, Eva M.
University of Copenhagen
Carstensen, Helena
University of Copenhagen
Hopster-Iversen, Charlotte
University of Copenhagen
van Loon, Gunther
Ghent University
Decloedt, Annelies
Ghent University
van Steenkiste, Glenn
Ghent University
Marr, Celia M.
Rossdales Equine Hospital
Reef, Virginia B.
University of Pennsylvania
Schwarzwald, Colin C.
University of Zurich
Mitchell, Katharyn J.
University of Zurich
Swedish University of Agricultural Sciences, Department of Clinical Sciences
Nogradi, Nora
Dubai Equine Hospital
Nielsen, Soren S.
University of Copenhagen
Carlson, Jonas
Lund University
Platonov, Pyotr G.
Lund University

UKÄ Subject classification

Clinical Science

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