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Background: Enhanced characterization of the atrial electrical substrate may lead to better comprehension of atrial fibrillation (AF) pathophysiology., Objective: With the use of high-density substrate mapping, we sought to investigate the occurrence of functional electrophysiologic phenomena in the left atrium and to assess potential association with arrhythmia recurrences after catheter ablation., Methods: Sixty-three consecutive patients with AF referred for ablation were enrolled. Analysis of conduction abnormalities relied on 2 acquired left atrial electroanatomic maps (sinus and atrial paced rhythm). We classified conduction abnormalities as fixed (if these were present in both rhythms) or functional rhythm dependent (if unmasked in 1 of the 2 rhythms). Esophagus and aorta locations were recorded to check the correspondence with abnormal conduction sites., Results: There were 234 conduction abnormalities detected, of which 125 (53.4%) were functional rhythm dependent. The most frequent anatomic site of functional phenomena was the anterior wall, followed by the posterior wall, in sinus rhythm and the pulmonary venous antra in paced rhythm. Sites of functional phenomena in 82.6% of cases corresponded with extracardiac structures, such as sinus of Valsalva of ascending aorta anteriorly and the esophagus posteriorly. Most (88%) areas with functional phenomena had normal bipolar voltage. After pulmonary vein ablation, the number of residual functional phenomena is an independent predictor of AF recurrence (hazard ratio, 2.539 [1.458-4.420]; P = .001) with a risk of recurrences at multivariable Cox analysis., Conclusion: Dual high-density mapping (during sinus and paced rhythms) is able to unmask functional, rhythm-dependent phenomena that are predictive of AF recurrences during follow-up., Competing Interests: Disclosures Dr Frontera has received speaker fees from Biosense Webster. Francesca Comi is an employee at Biosense Webster. All other authors have reported that they have no relationships relevant to the contents of this manuscript to disclose., (Copyright © 2024 Heart Rhythm Society. All rights reserved.)

Background: Pulmonary vein isolation (PVI) is one of the common endpoints of all atrial fibrillation (AF) ablation procedures and is most often validated using a preshaped circular catheter. However, three-dimensional (3D) electroanatomical systems used for anatomy reconstruction and to guide coalescent delivery of ablation lesions avoid the use of multiple transeptal punctures and multiple catheters in the left atrium., Objective: To assess correspondence in PVI validation between a 3D electroanatomical system and a Lasso catheter., Methods: Twenty-five patients affected by nonpermanent AF were enrolled after giving informed consent. After ablation of all four pulmonary vein (PV) ostia, encircled areas were extensively mapped (15 +/- 5 points acquired for each PV ostium) to assess the absence of any electrical activity conducted from the left atrium to the PV. At the end of the procedure, the physician performing the ablation procedure judged the complete versus incomplete PVI according to Carto/ablation catheter mapping during coronary sinus pacing. Thereafter, a second operator blinded to the result of the ablation procedure positioned a preshaped Lasso catheter in each PV ostium and annotated complete/incomplete PVI during pacing from the coronary sinus., Results: PVI as assessed with CARTO was 100% concordant with Lasso evaluation of PVI. Fluoroscopic times were 2.5 +/- 0.9 minutes to complete circumferential PV ablation and 5.5 +/- 1.9 minutes to properly position the Lasso catheter. No acute complications were reported in this series of patients., Conclusions: PVI assessment using a 3D electroanatomical system is as accurate as Lasso evaluation, with excellent concordance.

Background: Circumferential 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., Objectives: The 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., Methods: Pilot 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., Results: Group 1: Z(LA) was 99.4 +/- 9.0 omega. Z(PVO) was higher (109.2 +/- 8.5 omega), rising further as the catheter advanced into deep PV (137 omega +/- 18). Z(PVO) differed from Z(LA) by 9 +/- 4 omega. Group 2 had a lower Z(LA) and Z(PVO) 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., Conclusion: Impedance mapping reliably identifies the LA-PV transitional zone, facilitating AF ablation, and its use is associated with a low incidence of PV stenosis.