[18F]-FAPI PET/CT delineates FAP expression dynamics and distribution in acute aortic syndrome: clinical prognosis and intervention implications
S Wang, Y Xue, Y Lu, X L Zhang, H J Zhang, H Y LiAbstract
Background
Acute aortic syndrome (AAS) is a life-threatening disease characterized by extracellular matrix (ECM) remodeling responses, with fibroblast activation protein (FAP) playing a crucial role. Nevertheless, FAP activation pattern after AAS and its prognostic value remain undetermined.
Purpose
To characterize the temporal dynamics and segmental distribution of FAP expression in AAS patients, and evaluate its prognostic value.
Methods
The prospective cohort included 62 AAS patients (41 aortic dissection [AD], 21 aortic intramural hematoma [IMH]), and 21 control participants. [¹⁸F]AlF-NOTA-FAP inhibitor ([¹⁸F]-FAPI) positron emission tomography (PET) / computed tomography (CT) was performed at different phases after symptom onset. The [¹⁸F]-FAPI uptake was quantified by the maximum target-to-background ratio (TBRmax) and meanTBRmax to evaluate the temporal dynamics. The relationship between meanTBRmax and major aortic adverse events (MAAEs) was analyzed using Cox regression and Kaplan-Meier analysis, and uptake-time fitting curve was used to select the optimal intervention time.
Results
[¹⁸F]-FAPI uptake was significantly higher in AAS than that in control group (TBRmax: 6.06 ± 2.90 vs. 2.41 ± 0.50, P < 0.0001). Temporally, [¹⁸F]-FAPI uptake peaked subacutely and decreased at the chronic phase in AAS (confirmed by aortic immunofluorescence staining). A similar temporal pattern was observed in AD, whereas it increased continuously in IMH. Segmentally, increased [¹⁸F]-FAPI uptake was observed in entire aorta of type A AAS, in contrast with the distal segments of the ascending aorta in type B AAS. Higher meanTBRmax (≥ 4.211) experienced fewer MAAEs (36.6% vs. 56.6%, log-rank, P = 0.014). The optimal intervention windows were identified as 6–16 days after the onset for AD and 11–32 days for IMH, respectively.
Conclusion
Our study firstly delineates the temporal dynamics and segmental distribution of the pathophysiological process of FAP in AAS and its subtypes, offering both risk stratification and a precise intervention window for decision-making.Figure 1For image description, please refer to the figure legend and surrounding text.Figure 2For image description, please refer to the figure legend and surrounding text.