Abstract 14533: Molecular Imaging of Fibroblast Activity in Pressure Overload Heart Failure

Abstract

Introduction: Cardiac fibrosis, mediated by the activation of cardiac fibroblasts, is critical in pressure overload-induced heart failure. Fibroblast activation protein (FAP), specifically expressed by activated fibroblasts, can be visualized by radiolabeled FAP inhibitors (FAPI) PET/CT. Hypothesis: To evaluate whether 68Ga-FAPI-04 could characterize the early stages of cardiac fibrosis in pressure overload heart failure. Methods: Sprague-Dawley rats underwent abdominal aortic constriction (AAC) (n = 12) and sham surgery (n = 10). All rats were scanned with 68 Ga-FAPI-04 PET/CT at 2, 4, and 8 weeks after surgery. Cardiac function was measured by echocardiography. The expression of FAP in the myocardium was detected by immunohistochemistry. Results: Compared with the sham group, the AAC group presented with decreased ejection fraction (EF) and fractional shortening (FS) and increased left ventricular internal dimensions in diastole (LVIDd) and systole (LVIDs) at 4 and 8 weeks (all p < 0.01). The AAC group showed higher 68 Ga-FAPI-04 accumulation in the heart than the sham group at 2, 4, and 8 weeks, respectively (all p < 0.001), and FAPI increased significantly from 2 to 8 weeks. Immunohistochemistry confirmed the higher density of the FAP + area in the AAC group. The intensity of the 68 Ga-FAPI-04 PET signal correlated with the density of the FAP + area on histology (p < 0.001). The expression of the 68 Ga-FAPI-04 at 4 weeks correlated with the deterioration of cardiac function at 8 weeks (EF: R = -0.87; FS: R = -0.72; LVIDd: R = 0.77; LVIDs: R= 0.79; all p < 0.001). The AAC group also showed an increased 68 Ga-FAPI-04 signal in the liver, peaking at 4 weeks and then declining. Cardiac and liver PET signals directly correlated at 4 weeks in the AAC group (R = 0.69, p = 0.0010). A combination of the FAPI intensity in the heart and liver at 4 weeks better predicted the deterioration of cardiac function at 8 weeks. Conclusion: The activated fibroblasts in the heart and liver after pressure overload can be monitored by 68 Ga-FAPI-04 PET/CT. This imaging technique reveals an early fibrotic link in cardio-liver interactions and could better predict nonischemic heart failure prognosis.