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  Discussion on Research Summary: Lasting Effects of Atrial Fibrillation
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DrO

Posted on Sunday, Jul 14, 2013 - 8:13 am:

AF-induced atrial contractile dysfunction gradually improves in the weeks following cardioversion, but at 7 weeks post-cardioversion, significant differences remain compared to healthy controls. Hopefully they will continue to follow these horses out to see what happens at greater than 7 weeks.
DrO

Vet J. 2013 Jun 30.
Long-term follow-up of atrial function after cardioversion of atrial fibrillation in horses.

Decloedt A, Verheyen T, Van Der Vekens N, Sys S, De Clercq D, van Loon G.
Department of Large Animal Internal Medicine, Faculty of Veterinary Medicine, Ghent University, Salisburylaan 133, 9820 Merelbeke, Belgium. Electronic address: annelies.decloedt@ugent.be.
Abstract

Atrial fibrillation (AF) causes atrial electrical and contractile remodelling in horses. The aim of this study was to quantify left atrial (LA) contractile function and its time course of recovery after cardioversion of naturally-occurring AF in horses. The study population included 42 AF horses which were successfully treated using transvenous electrical cardioversion TVEC (n=39) or quinidine sulfate (n=3), with trivial or mild mitral regurgitation present in 25 horses. Thirty-seven healthy horses were used as controls. AF duration was estimated based on the history and previous examinations. Echocardiography was performed during general anaesthesia after TVEC (day 0) and on days 1, 2, 6 and then 7weeks after cardioversion. The two-dimensional (2D) echocardiographic measurements included LA diameter, area and ejection phase indices such as fractional shortening. Atrial TDI measurements included peak myocardial velocity during atrial contraction (A), time to onset A, time to peak A and duration of A. During follow-up after cardioversion, atrial contractile function measured by 2D echocardiography and TDI gradually improved. At 7weeks following cardioversion, TDI-based myocardial velocities returned to reference values. However, AF horses still showed significantly larger atrial dimensions, lower 2D ejection phase indices and prolonged TDI-based conduction time compared to the control group. In conclusion, AF-induced atrial contractile dysfunction gradually improves in the weeks following cardioversion, but at 7weeks post-cardioversion, significant differences remain compared to healthy controls.
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