Wall thickness-based adjustment of ablation index improves efficacy of pulmonary vein isolation in atrial fibrillation: Real-time assessment by intracardiac echocardiography

Background: Ablation index (AI) linearly correlates with lesion depth and may yield better therapeutic performance in pulmonary vein isolation (PVI) when tailored to a patient's wall thickness (WT) in the left atrium (LA). Methods and results: First study: In paroxysmal atrial fibrillation patients (PAF; n = 20), the average LA WT (mm) in each anatomical segment for PVI was measured by intracardiac echocardiography (ICE) placed in the LA; the optimal AI for creating 1-mm transmural lesion (AI/mm) was calculated. Second study: PAF (n = 80) patients were randomly assigned either to a force-time integral protocol (FTI; 400 g·s, n = 40) or a tailored-AI protocol (TAI; n = 40). In TAI, the LA WT in each segment was individually measured by ICE before starting ablation; a target AI was adjusted according to the individual WT in each segment (AI/mm × WT). The acute procedure outcomes and the 1-year AF-recurrence rate were compared between FTI and TAI. TAI had higher success rate of first-pass isolation (88% vs. 65%) and had lower incidence of residual PV-potentials/conduction-gaps after a circular ablation than FTI (15% vs. 45%). The procedure time to complete PVI decreased in TAI compared to FTI (52 vs. 83 min), being attributed to the increased radiofrequency power and the decreased radiofrequency application time in each point in TAI. TAI had a lower 1-year AF-recurrence rate than FTI. Conclusion: TAI increased acute procedure success, decreased time for PVI, and reduced the 1-year AF-recurrence rate, compared to FTI. Understanding the precise ablation target and tailoring AI would improve the efficacy of PVI.