Fehmi Keçe

Chapter 8 164 8.2 Methods 8.2.1 Inclusion Consecutive patients with symptomatic drug-refractory persistent AF who underwent PVI and isolation of the posterior LA between the PV’s (box lesion) between 2013 and 2017 at the Leiden University Medical Center (LUMC) were retrospectively analyzed. During this period all patients in the LUMC with persistent atrial fibrillation referred for ablation were treated with PVI plus box lesion. All consecutive patients with an (attempted) box lesion were included in the study. In all patients, a box lesion was performed in addition to a circumferential PVI referred to/defined as index procedure. Patients were treated according to the institutional clinical protocol and provided informed consent. Approval for the current retrospective analysis was obtained from the Institutional Review Board. 8.2.2. Ablation procedure Prior to the procedure, patients underwent a 320-slice Computer Tomography (Aquilion ONE, Toshiba Medical Systems, Otawara, Japan) and image segmentation to visualize the anatomy of the LA and PV’s and to guide the ablation (15). The CT-scan was performed in a phase window between 65-85% of R-R interval in patients with an HR ≥ 60 beats per minute and 75% of R-R interval in patients with a heart rate below 60 (16). Antiarrhythmic drugs (AAD) were discontinued for 5 half-lives before ablation, with the exception of amiodarone which was continued until 1 month after ablation. Catheter mapping and ablation was performed under uninterrupted anticoagulation with a double transseptal approach using a 3D electroanatomical mapping system (CARTO3, Biosense Webster, Diamond Bar, CA, USA or Ensite Velocity System, Model EE3000, St. Jude Medical, MN, USA), an irrigated 3.5-mm ablation catheter (Biosense Thermocool, Biosense Thermocool Smarttouch or St. Jude Medical Coolpath Duo) and a 10-polar circular mapping catheter (Lasso 2515, Biosense Webster). During the index procedure, a box lesion was applied in all patients in addition to a circumferential first or redo PVI. A roof line between the superior ostia of the superior PV’s and a posterior line between the inferior ostia of the inferior PV’s were created to complete the LA box lesion. The posterior line was drawn directly across the posterior wall between the inferior ostia of the inferior pulmonary veins. The operators did not extend the box lesion inferiorly below this level. Radiofrequency energy was delivered with a power of 25 W at the roof and the posterior LA wall and with 30 W at the anterior LA (maximum temperature, 43°C; flow rate, 17-20 ml/min, 30 seconds). If patients were