Abstract
BACKGROUND: Adjunctive posterior wall isolation (PWI) to pulmonary vein isolation (PVI) has not demonstrated convincing benefit during atrial fibrillation (AF) ablation. To provide mechanistic insight for null PWI trials, we undertook Granger causality (GC) analysis of noncontact left atrial (LA) electroanatomic maps. OBJECTIVE: This study aimed to apply GC to intracardiac electrograms to uncover patient-specific AF dynamics and describe a proof-of-concept approach to targeted PWI after PVI. METHODS: A prospective cohort study was undertaken at Royal Brompton Hospital. Consecutive patients undergoing PVI with noncontact mapping (AcQmap; Acutus Medical) before and after PVI were included. RESULTS: In 21 patients, causality pairing index, a GC measure of organization, was unchanged after PVI (overall, 0.087 ± 0.012 vs 0.086 ± 0.015; P = .64) or by region (posterior wall [PW], 0.084 ± 0.020 vs 0.079 ± 0.017; P = .20; rest of LA, 0.087 ± 0.013 vs 0.086 ± 0.016; P = .80). Directional dispersion, quantifying conduction heterogeneity, was lower in the PW than the rest of the LA (0.093 ± 0.036 vs 0.11 ± 0.043; P = .017) and increased after PVI (0.093 ± 0.036 vs 0.12 ± 0.043; P = .045), whereas there was no change in the rest of the LA (0.11 ± 0.034 vs 0.11 ± 0.030; P = .52). PW net outflow overall decreased after PVI (before, -0.0086 ± 0.047 vs -0.033 ± 0.054; P = .011) with a minority of patients exhibiting a net positive outflow from the PW. CONCLUSION: GC provides mechanistic insight into the null trials for PWI and identifies a minority of patients who may benefit. GC is positioned as a clinical decision tool to guide personalized persistent AF ablation strategies.