PhD fellow Ghent University Merelbeke, Oost-Vlaanderen, Belgium
Abstract:
Background: Myocardial sleeves (MS) in the caudal vena cava and pulmonary veins are a potential trigger for initiation and perpetuation of atrial fibrillation (AF) in horses. Hypothesis/
Objectives: Isolation of these MS might reduce the arrhythmogenic substrate, thereby lowering the AF recurrence risk. Animals: Six horses with recurrent AF. Horses had one (n=4) or two (n=2) recurrences, after a median of 91 [0.02-304] days post-cardioversion.
Methods: After transvenous electrical cardioversion of AF, voltage mapping of the caudal vena cava was performed in all horses. In two horses, also pulmonary vein ostium I (n=2), II (n=1) and IV (n=2) were mapped. Point-by-point, ablation index-guided radiofrequency ablation was performed to isolate MS.
Results: Voltage mapping identified MS in the caudal vena cava (n=5), ostium II (n=1) and IV (n=2), which were subsequently isolated, as confirmed by demonstrating entrance and exit block. To date, three horses remain in sinus rhythm with a follow-up of 9-32 months post-ablation. Three horses showed recurrence after 2 days, 6 months and 11 months. The horse that relapsed after 6 months underwent a second procedure to isolate ostium III and remains in sinus rhythm 2 months post ablation. Conclusions and clinical importance: Isolation of MS reduced arrhythmogenic tissue. Isolating pulmonary vein ostia, especially ostium III, remains challenging. To date, 4 of 6 horses with recurrent AF remain in sinus rhythm but it remains difficult to demonstrate the additional benefit of ablation. This is the first study suggesting that ablation might benefit horses with AF but more data are needed.
