B-PO02-030 ELECTROPHYSIOLOGICAL CHANGES IN PERSISTENT ATRIAL FIBRILLATION IN A CHRONICALLY PACED CANINE MODEL

Previous studies have described slowly conducting regions in patients experiencing atrial fibrillation (AF). However, no studies have shown changes in conduction as AF progresses. We investigated the conduction changes that occur during the progression of AF in a canine model and relate them to the underlying substrate remodeling. High-density electrophysiological (EP) studies were performed on a chronically, rapidly paced canine model (n=10) using an Orion catheter and the Rhythmia (Boston Scientific) cardiac mapping system. Substrate information came from LGE MRI performed on a 3T Prisma (Siemens) scanner. Both EP and MRI procedures were performed before AF induction and repeated after 6 months of AF. Left atrial activation times were mapped in sinus rhythm and registered onto the MRI geometry. Conduction velocity was calculated using a triangulation-based approach. Left atrial wall fibrosis was characterized using normalized intensity (NI). Overall conduction speed decreased after sustained AF (1.32 ± 0.43 m/s at baseline to 1.14 ± 0.32 m/s after 6 months of AF, p<0.01). The speed decrease was larger in areas that developed fibrosis compared to the healthy region (0.23m/s vs. 0.14m/s, p<0.01) with a correlation of 0.015 m/s decrease per NI unit increase. The conduction direction changed by a mean of 54 degrees. Conduction changes in both magnitude and direction occur in areas of increased fibrosis, supporting the theory that structural remodeling plays a role in AF development and sustainability. These changes could contribute to making AF sustain beyond pulmonary vein triggers as it progresses from paroxysmal to persistent.