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.

中文翻译：

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肺静脉隔离后使用 68 Ga-FAPI-PET/CT 可视化热损伤。

目的 68 Ga-成纤维细胞活化蛋白抑制剂 (FAPI) 正电子发射断层扫描 (PET) 是一种针对 FAP-α 的新技术。这种蛋白质由活化的成纤维细胞表达，它是组织重塑的主要贡献者。这项概念验证研究的目的是评估用冷冻球囊消融术 (CBA) 和射频 (RFA) 进行肺静脉隔离 (PVI) 后左心房肺静脉 (PV) 区域的 68 Ga-FAPI 摄取情况。替代热损伤。方法 12 名 PVI 患者（5 名 RFA，7 名 CBA）在 PVI 后 20.5 ± 12.8 天接受了 68 Ga-FAPI-PET。5 名无心房颤动或既往消融史的患者作为对照。计算了局部示踪剂摄取的标准化摄取值。结果 在 10/12 (83.3%) PVI 患者中观察到 PV 周围的局灶性 FAPI 摄取，2 名 PVI 患者和所有对照组均未观察到摄取。与对照组相比，PVI 后患者在 PV 中的 FAPI 摄取量更高（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）。所有 CBA 患者都有强烈摄取，而在 RFA 中，第 2 组 (40%)、1 (20%) 和 2 (40%) 组患者分别有强烈、中度和无摄取。与 RFA 患者相比，我们观察到 CBA 的摄取值（SUVpeak）更高（4.4 ± 1.5 对 2.5 ± 0.8，p = 0.02）。结论 我们展示了 68 Ga-FAPI 摄取的体内可视化作为 PVI 后成纤维细胞活化的替代物。与 RFA 相比，CBA 似乎在组织损伤后引起更明显的成纤维细胞活化。