Visualization of fibroblast activation using 68 Ga-FAPI PET/CT after pulmonary vein isolation with pulsed field compared with cryoballoon ablation.

BACKGROUND: Pulsed-field ablation (PFA) is a novel ablation modality for atrial fibrillation (AF) ablating myocardium by electroporation without tissue-heating. With its different mechanism of tissue ablation, it is assumed that lesion creation is divergent to thermal energy sources. 68 Ga-fibroblast-activation protein inhibitor (FAPI) PET/CT targets FAP-alpha expressed by activated fibroblasts. We aimed to assess 68 Ga-FAPI uptake in pulmonary veins as surrogate for ablation damage after PFA and cryoballoon ablation (CBA).

METHODS: 26 patients (15 PFA, 11 CBA) underwent 68 Ga-FAPI-PET/CT after ablation. Standardized uptake values (SUV) and fibroblast-activation volumes of localized tracer uptake were assessed.

RESULTS: Patient characteristics were comparable between groups. In PFA, focal FAPI uptake was only observed in 3/15 (20%) patients, whereas in the CBA cohort, 10/11 (90.9%) patients showed atrial visual uptake. We observed lower values of SUVmax (2.85 ± 0.56 vs 4.71 ± 2.06, P = 0.025) and FAV (1.13 ± 0.84 cm3 vs 3.91 ± 2.74 cm3 , P = 0.014) along with a trend towards lower SUVpeak and SUVmean in PFA vs CBA patients, respectively.

CONCLUSION: Tissue response with respect to fibroblast activation seems to be less pronounced in PFA compared to established thermal ablation systems. This functional assessment might contribute to a better understanding of lesion formation in thermal and PFA ablation potentially contributing to better safety outcomes.