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

Abstract

Background:\nIndependent investigations demonstrate greater radiofrequency (RF) ablation effects at left-sided left atrial posterior wall (LAPW) sites.\nObjective:\nTo investigate mechanisms underlying RF ablation heterogeneity during contact-force (CF) and VISITAG™ Module (Biosense Webster)-guided pulmonary vein isolation (PVI). \nMethods:\nConsecutive 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, 48oC) RF data was retrospectively assessed at first-annotated (target 15s) LAPW sites: 30W during IPPV; 20W at left-sided sites during HFJV.\nResults:\nTwenty-five and 15 patients underwent PVI during IPPV and HFJV, respectively. During IPPV, left versus right-sided median impedance drop (ImpD) was 13.6Ω versus 9.9Ω (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 (9.7Ω versus 7.4Ω, 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 ΔBI. Left-sided sites demonstrated significantly greater ΔBI, 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, ΔBI and Ln(ImpD) were without correlation during IPPV, but correlation was modest during HFJV (r=0.54, -0.007 - 0.84). \nConclusions:\nΔBI 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 ΔBI may improve PVI safety and efficacy.