B-PO03-090 ABLATION SCAR CAUSES A DECREASE IN PULMONARY VEIN DIAMETER IN ATRIAL FIBRILLATION PATIENTS AND IN HEALTHY SHEEP

Abstract

A decrease in pulmonary vein (PV) diameter and in left atrial (LA) volume is observed in atrial fibrillation (AF) patients after PV isolation (PVI) ablation. It is unknown whether the changes are due to a direct effect of the ablation scar or to a reverse remodeling initiated by successful ablation. To evaluate PVI-induced changes in 1) PV dimensions in AF patients with successful ablation and in healthy sheep and, 2) atrial contractility in the patients. An increase in contractile force is compatible with reverse remodeling. We retrospectively studied 21 paroxysmal AF patients with functional cardiac magnetic resonance (CMR) before and 3 months after successful PVI (absence of AF during CMR and re-catheterization 3 months post-ablation). PV-LA conduction was observed in all patients upon re-catheterization indicating an incomplete PVI. We therefore studied healthy sheep (n=12) 3 months after incomplete PVI of the right PV. Local LA contractility was measured with a feature-tracking algorithm. The maximal diameter of all PVs decreased after ablation in the patients (19±5 (overall mean±SD) vs. 17±5mm, pre- vs. post-ablation, p=0.019). The PV diameter of the ablated right PV in sheep was also smaller after ablation (14±3 vs. 12±2mm, pre vs. post, p=0.024), whereas the control left PVs were unchanged. The percentage decrease of the ablated PV diameter was similar (11±17% and 9±11% in patients and sheep, respectively, p=0.725). In patients, the maximal LA volume decreased from 103±38 to 92±31ml after ablation (p=0.006). The ablation induced a decrease in the active LA emptying fraction from 27±11 to 22±11% (p=0.031). Moreover, maximal radial strain (defined as motion fraction towards the LA center) during the atrial contractile phase decreased in the posterior LA wall from 8 (11)% (median (IQR)) to 5 (7)% after ablation (p=0.016). The diameter of ablated PVs decreased similarly in AF patients and healthy sheep without AF and was therefore caused by the ablation scar and not by reverse remodeling. Moreover, the atrial contractility decreased after successful ablation in patients, which is incompatible with reverse remodeling. Therefore, the reduction in LA volume was likely also caused by the ablation scar.