242 Loss of Local Capture of the Pulmonary Vein Myocardium After Antral Isolation: Prevalence and Clinical Significance FABIEN SQUARA, M.D., ∗ IOAN LIUBA, M.D.,† WILLIAM CHIK, M.D.,† PASQUALE SANTANGELI, M.D.,† ERICA S. ZADO, PA.-C.,† DAVID J. CALLANS, M.D.,† and FRANCIS E. MARCHLINSKI, M.D.† From the ∗ Department of Cardiology, Pasteur University Hospital, Nice, France; and †Electrophysiology Section, Cardiovascular Division, Hospital of the University of Pennsylvania, Philadelphia, Pennsylvania, USA Loss of Pulmonary Vein Capture After Isolation. Introduction: Capture of the myocardial sleeves of the pulmonary veins (PV) during PV pacing is mandatory for assessing exit block after PV isolation (PVI). However, previous studies reported that a significant proportion of PVs failed to demonstrate local capture after PVI. We designed this study to evaluate the prevalence and the clinical significance of loss of PV capture after PVI. Methods and Results: Thirty patients (14 redo) undergoing antral PVI were included. Before and after PVI, local PV capture was assessed during circumferential pacing (10 mA/2 milliseconds) with a circular multipolar catheter (CMC), using EGM analysis from each dipole of the CMC and from the ablation catheter placed in ipsilateral PV. Pacing output was varied to optimize identification of sleeve capture. All PVs demonstrated sleeve capture before PVI, but only 81% and 40% after first time and redo PVI, respectively (P < 0.001 vs. before PVI). In multivariate analysis, absence of spontaneous PV depolarizations after PVI and previous PVI procedures were associated with less PV sleeve capture after PVI (40% sleeve capture, P < 0.001 for both). Loss of PV local capture by design was coincident with the development of PV entrance block and importantly predicted absence of acute reconnection during adenosine challenge with 96% positive predictive value (23% negative predictive value). Conclusion: Loss of PV local capture is common after antral PVI resulting in entrance block, and may be used as a specific alternate endpoint for PV electrical isolation. Additionally, loss of PV local capture may identify PVs at very low risk of acute reconnection during adenosine challenge. (J Cardiovasc Electrophysiol, Vol. 26, pp. 242-250, March 2015) ablation, atrial fibrillation, pulmonary veins, pulmonary vein isolation Introduction Pulmonary vein isolation (PVI) has become the cornerstone of therapy for atrial fibrillation (AF). 1,2 The critical primary endpoint for PVI is attainment of electrical entrance block from the left atrium (LA) to the pulmonary vein (PV). 3 Demonstrating the presence of concurrent PV exit block (PV–LA block) has also been proposed to confirm bidirec- tional electrical dissociation. 4 Nevertheless, local capture of the PV myocardium—a prerequisite for demonstrating PV exit block—can be difficult to elicit following PVI presum- ably due to the relatively small volume of myocardial tissue Funded in part by the Mark S. Marchlinski and F. Harlan Batrus Research Funds. FS has received a research grant from the Societ´ e Francaise de Cardiologie, Sorin Group, and Endosense. Other authors: No disclosures. Address for correspondence: Francis E. Marchlinski, M.D., Electrophys- iology Section, Cardiovascular Division, Hospital of the University of Pennsylvania, 3400 Spruce St., 9 Founders Cardiology, Philadelphia PA, USA. 19104. Fax: 215-662-2879; E-mail: francis.marchlinski @uphs.upenn.edu Manuscript received 14 July 2014; Revised manuscript received 29 October 2014; Accepted for publication 30 October 2014. doi: 10.1111/jce.12585 extending from the LA into the PV. Furthermore, a significant proportion of electrically isolated PVs can no longer demon- strate local sleeve capture after successful antral PV isolation procedures, 5 despite the fact that all connected PVs could be captured before electrical isolation. 4,5 Therefore, the purpose of our study is to (1) systematically define the prevalence and electrophysiologic factors associated with loss of PV sleeve capture after antral PVI; and (2) evaluate the clinical implica- tions of loss of PV sleeve capture after antral PVI as assessed by acute intravenous administration of adenosine. Methods Patient Selection We included consecutive patients undergoing first time or repeat AF ablation at the Hospital of the University of Pennsylvania. Patient characteristics were recorded, includ- ing age, gender, comorbidities, medications, and type of AF. For the patients presenting for a repeat ablation, all the pre- vious procedures were reviewed to determine the ablation strategy: PVI alone and/or additional ablation including lines, and specifically the presence of previous ablation lesion ap- plied to the carina of ipsilateral PV. Ablation Procedure All procedures followed the institutional guidelines of the University of Pennsylvania Health System and all