Endocardial impedance mapping during circumferential pulmonary vein ablation of atrial fibrillation differentiates between atrial and venous tissue

BackgroundCircumferential pulmonary vein ablation (CPVA) is an effective treatment for atrial fibrillation (AF). Accurate left atrial (LA) mapping is essential for creating lesions at the LA–pulmonary vein (PV) junction, avoiding PV stenosis.ObjectivesThe purpose of this study was to establish whether endocardial impedance varies within the LA and PVs and whether it is a useful tool for mapping and ablation.MethodsPilot Phase: Three-dimensional LA maps were created using CARTO. Impedance (Z) was measured using a radiofrequency generator at multiple points in the LA, PV ostia (PVO), and deep PVs in 79 patients undergoing their first AF ablation (group 1) and 29 patients undergoing repeat CPVA (group 2). Prospective Phase: In an additional 20 patients, using pilot phase data, one operator defined catheter tip location as either LA or PVO based on CARTO and fluoroscopy. A second operator blinded to CARTO simultaneously did the same based on impedance at 15 ± 4 points per patient.ResultsGroup 1: ZLA was 99.4 ± 9.0 Ω. ZPVO was higher (109.2 ± 8.5 Ω), rising further as the catheter advanced into deep PV (137 Ω ± 18). ZPVO differed from ZLA by 9 ± 4 Ω. Group 2 had a lower ZLA and ZPVO compared with group 1 (P <.05). Impedance monitoring differentiated between LA and PVO, with 91% specificity and sensitivity, 96% positive predictive value, and 81% negative predictive value. At 3-month follow-up, no patients had evidence of PV stenosis on magnetic resonance imaging.ConclusionImpedance mapping reliably identifies the LA–PV transitional zone, facilitating AF ablation, and its use is associated with a low incidence of PV stenosis.