Predictors of Transmural Lesion in High Power Short Duration Ablation of Atrial Fibrillation Guided by Local Impedance

Background: The impact of local impedance (LI) drop in high power short duration (HPSD) for atrial fibrillation (AF) remains unclear. Objective : This study aimed to assess the parameters predicting transmural lesions. Method: Thirty patients (76.7% male, mean 59.6±10.0 years old) with AF who underwent radiofrequency ablation were enrolled. Ablation lesions of pulmonary vein isolation (PVI) were created by HPSD (50W, ≤15s and LI drop ≤30%). Successful and non-successful lesions were defined by electrogram criteria. Absolute and percentage LI drop of ablation lesions were recorded. Results: Of 210 ablation lesions included, 67.6% (n=142) were successful lesions. The mean percentage and absolute LI drop were higher in successful than in non-successful lesions (19.7±4.6% vs. 15.1±3.1%, p<0.001; 33.8±9.8Ω vs. 24.0±5.7Ω, p<0.001). To create successful lesions, higher absolute LI drop was required in the right than in the left PV antrum (35.5±10.0Ω vs. 31.8±9.2Ω, p=0.032), while higher percentage and absolute LI drop were required in the anterior than in the posterior PV antrum (20.8±4.9% vs. 18.3±3.8%, p=0.002; 35.6±10.2Ω vs. 31.4±8.6Ω, p=0.008). Among 142 successful lesions, the higher initial LI group (>190 Ω) had a higher mean percentage and absolute LI drop, and shorter mean duration of ablation compared with lower initial LI groups (<150Ω, 150Ω-170Ω, 170Ω-190Ω). The cut-off values of percentage and absolute LI drop were 16.2% and 26.5Ω, respectively, to predict the successful lesions. Conclusion: In successful lesion of PVI, initial LI was associated with LI drop and duration of ablation. The LI could predict transmural lesions and guide HPSD ablation.