Visualization of thermal damage using 68 Ga-FAPI-PET/CT after pulmonary vein isolation

Abstract

Purpose 68 Ga-fibroblast-activation protein inhibitor (FAPI) positron emission tomography (PET) is a novel technique targeting FAP-alpha. This protein is expressed by activated fibroblasts which are the main contributors to tissue remodeling. The aim of this proof-of-concept study was to assess 68 Ga-FAPI uptake in the pulmonary vein (PV) region of the left atrium after pulmonary vein isolation (PVI) with cryoballoon ablation (CBA) and radiofrequency (RFA) as a surrogate for thermal damage. Methods Twelve PVI patients (5 RFA, 7 CBA) underwent 68 Ga-FAPI-PET 20.5 ± 12.8 days after PVI. Five patients without atrial fibrillation or previous ablation served as controls. Standardized uptake values of localized tracer uptake were calculated. Results Focal FAPI uptake around the PVs was observed in 10/12 (83.3%) PVI patients, no uptake was observed in 2 PVI patients and all controls. Patients after PVI had higher FAPI uptake in PVs compared to controls (SUVmax: 4.3 ± 2.2 vs. 1.6 ± 0.2, p < 0.01; SUVpeak: 2.9 ± 1.4 vs. 1.3 ± 0.2, p < 0.01). All CBA patients had an intense uptake, while in the RFA, group 2 (40%), 1 (20%), and 2 (40%) patients had an intense, moderate, and no uptake, respectively. We observed higher uptake values (SUVpeak) in CBA compared to RFA patients (4.4 ± 1.5 vs. 2.5 ± 0.8, p = 0.02). Conclusion We demonstrate in-vivo visualization of 68 Ga-FAPI uptake as a surrogate for fibroblast activation after PVI. CBA seems to cause more pronounced fibroblast activation following tissue injury than RFA. Future studies are warranted to assess if this modality can contribute to a better understanding of the mechanisms of AF recurrence after PVI by lesion creation and gap assessment.

Meta‐analysis of pulsed‐field ablation versus cryoablation for atrial fibrillation

“…The PRISMA flow chart provides a systematic description of the literature selection process (Figure 1). Ultimately, this study encompassed 15 trials involving a total of 1880 patients (1036 patients in the PFA group vs. 844 patients in the CBA group) published between 2021 and 2023, 7,[12][13][14][15][16][17][18][19][20][21][22][23][24][25] comprising of 14 observational studies (7 prospective cohort, 7,12,16,17,19,23,25 6 retrospective cohort, 13,14,18,20,22,24 and 1 cross-sectional study 15 ), along with one RCT. 21 Five studies included patients with paroxysmal AF, 7,[17][18][19]21 while the remaining studies enrolled a broader population of AF patients.…”

“…In the CBA arm, the Arctic Front cryoballoon was used in 12 studies, while the POLARx cryoballoon was used in three other studies. 12,14,22 The maximum follow-up period for patients was 12 months. Data regarding cardiac indicators and underlying diseases among AF patients were comparable between both treatment groups.…”

Pulsed field ablation for atrial fibrillation – Lessons from magnetic resonance imaging

“…Late enhancement computed tomography may be an alternative imaging modality, but iodide‐based contrast agents and gadolinium agents share similar kinetics potentially leading to a comparable issue 66 . Positron emission tomography was recently investigated as an imaging modality for lesion formation after thermal cardiac ablation in patients undergoing PVI 67 . In this study, it was possible to visualize ablation‐related lesions after a mean of 20.5 days after ablation procedures 67 .…”

“…Positron emission tomography was recently investigated as an imaging modality for lesion formation after thermal cardiac ablation in patients undergoing PVI 67 . In this study, it was possible to visualize ablation‐related lesions after a mean of 20.5 days after ablation procedures 67 . In another study by the same group, PET CT imaging, which was performed about 20 min after ablation procedures, found less pronounced fibroblast activation as indicated by low tracer uptake in patients who previously underwent PFA as compared to patients who underwent cryoballoon ablation 68 .…”

“…67 In this study, it was possible to visualize ablation-related lesions after a mean of 20.5 days after ablation procedures. 67 In another study by the same group, PET CT imaging, which was performed about 20 min after ablation procedures, found less pronounced fibroblast activation as indicated by low tracer uptake in patients who previously underwent PFA as compared to patients who underwent cryoballoon ablation. 68 The finding of this study is in line with assumed different tissue responses after PFA and thermal ablation.…”