Evaluation of myocardial fibrosis and wall motion abnormality with (68)Ga-FAPI PET/MR in coronary heart disease.

BACKGROUND: To explore the characteristics of cardiac fibroblast activation protein inhibitor (FAPI) PET/MR in coronary heart disease (CHD) and its association with abnormal wall motion. RESULTS: In this prospective study, participants with CHD after PCI (Percutaneous Coronary Intervention) underwent gallium 68 ((68) Ga)-labeled FAPI PET/MR imaging. FAP signal was quantified using standardized uptake values. Cardiac MRI yielded functional parameters and area of injury (MRI non-viable). Abnormal wall motion identified by myocardial strain analysis was evaluated using integrated analysis of late gadolinium enhancement (LGE) and FAP signal. The correlations between FAP signal and clinical parameters were explored. Forty-two participants were included and FAP signal was higher in left ventricle regional myocardium compared with remote normal areas (SUVmax, 5.0 ± 1.8 vs 1.2 ± 0.4; p < .001). In total, 432 segments (432/714, 60.50%) displayed impaired wall motion. In integrated analysis, the highest wall motion abnormality score was observed in the FAPI active/MRI non-viable group (11.0 ± 5.2). FAP signal was positively correlated with K time (SUVpeak: R = 0.48; p = .046; SUVmean: R = 0.57; p = .014) and negatively correlated with Angle (SUVpeak: R =  - 0.52; p = .026; SUVmean: R =  - 0.56; p = .026) in thromboelastography. Immunohistochemical analysis revealed FAP-positive fibroblasts in the infarct and border zone, and robust expression of α-smooth muscle actin and vimentin. CONCLUSIONS: Simultaneous (68) Ga- FAPI PET/MR offers novel insights into the regional pattern of fibroblast activation in CHD, and the fibroblast activation protein signal is associated with abnormal wall motion. Trial registration ClinicalTrials: ClinicalTrials.gov ID: NCT05867589. Registered 01 May 2023, https://clinicaltrials.gov/study/NCT05867589.