1 Introduction
Left atrial (LA) posterior wall isolation (LAPWI) added to pulmonary vein isolation (PVI) can improve ablation outcomes for persistent atrial fibrillation (PerAF) by modifying ganglionated plexi, debulking LA tissue including the substrate and rotors, and reinforcing the results of PVI.1 Sometimes LAPWI is challenging, however, requiring numerous high-power radiofrequency (RF) energy applications. Residual posterior wall conduction can exist after first-pass LAPWI and may be the result of failure to create transmural lesions or of gaps in the LA roof or floor line, explaining, at least in part, the questionable efficacy of this strategy.2–4 Ablation index (AI)-guided high-power short-duration ablation in which the catheter-tip contact force (CF), output power, and duration of RF application are monitored is a well-developed strategy for the creation of durable lesions and has substantially improved ablation outcomes in patients with AF.5–7 Therefore, in clinical practice, first-pass AI-guided LAPWI can be expected.
We have reported high-voltage zones (HVZs) within the PV-encircling lines to be a major determinant of acute PV reconnections after PVI; the HVZs might reflect thickened wall or non-diseased cardiomyocytes, which can impede the creation of transmural lesions.8,9Based on these findings, we proposed a novel index, the “modified AI”, calculated as AI/bipolar voltage at the target ablation site, and showed this index to be useful in predicting acute durable PVI.8 We have since hypothesized that HVZs and a thickened LA wall are obstacles to complete LAPWI, and, in this study, we evaluated association between gap locations after first-pass LAPWI and local preprocedural bipolar voltage and computed tomography (CT)-based measured LA wall thickness under the ablation line, and we determined the modified AI predictive of acute durable LAPWI.