Mechanistic insights into heterogeneous radiofrequency ablation effects at the left atrial posterior wall during pulmonary vein isolation

BackgroundIndependent investigations demonstrate greater radiofrequency (RF) ablation effects at left- sided left atrial posterior wall (LAPW) sites. ObjectiveTo investigate mechanisms underlying RF ablation heterogeneity during contact-force (CF) and VISITAG Module (Biosense Webster)-guided pulmonary vein isolation (PVI). MethodsConsecutive patients undergoing PVI during atrial overdrive pacing comprised 2 cohorts: intermittent positive pressure ventilation (IPPV, 14-16/min, 6-8ml/kg); high frequency jet ventilation (HFJV, 150/min, Monsoon III, Acutronic). Temperature-controlled (17ml/min, 48{degrees}C) RF data was retrospectively assessed at first-annotated (target 15s) LAPW sites: 30W during IPPV; 20W at left-sided sites during HFJV. ResultsTwenty-five and 15 patients underwent PVI during IPPV and HFJV, respectively. During IPPV, left versus right-sided median impedance drop (ImpD) was 13.6{Omega} versus 9.9{Omega} (p<0.0001) respectively and mean time to pure R unipolar electrogram (UE) morphology change 4.9s versus 6.7s (p=0.007) respectively. During HFJV, ImpD was greater at left-sided sites (9.7{Omega} versus 7.4{Omega}, p=0.21) and time to pure R UE significantly shorter: 4.3s versus 6.1s (p=0.02). Minimum case impedance subtracted from pre-RF baseline impedance (BI) generated site-specific {Delta}BI. Left-sided sites demonstrated significantly greater {Delta}BI, correlating strongly with Ln(ImpD) - IPPV r=0.84 (0.65 - 0.93), HFJV r=0.77 (0.35 - 0.93). At right-sided sites, {Delta}BI and Ln(ImpD) were without correlation during IPPV, but correlation was modest during HFJV (r=0.54, -0.007 - 0.84). Conclusions{Delta}BI may usefully indicate catheter-tissue contact surface area (SA). Consequently, greater left-sided LAPW RF effect may result from greater contact SA and in-phase catheter-tissue motion; HFJV may reduce right-sided out-of-phase catheter-tissue motion. Modifying RF delivery based on {Delta}BI may improve PVI safety and efficacy.