The Clinical Value of FAPI Imaging in Assessing Chronic Total Occlusion Lesions in Patients with Coronary Heart Disease (FACT Trial)

This registry will include consecutive patients presenting with at least one chronic total coronary occlusion (CTO) identified via coronary angiography or cardiac computed tomography angiography (CCTA) at our center. Due to the complexity of CTO lesions, both procedural success rates and prognosis improvements are limited. The progression and development of atherosclerotic plaques involve fibroblast activity, contributing to the formation of fibrous caps and calcified nodules through various mechanisms. Myocardial fibrosis within chronically occluded segments is strongly linked to ventricular remodeling and patient prognosis. The activation of cardiac fibroblasts (CFs) is a critical early phase in myocardial fibrosis, playing a key role in fibrotic progression. However, the role of activated CFs in CTO patients has remained unclear, mainly due to the lack of reliable in vivo assessment techniques for detecting CF activation.

Recent studies have demonstrated that radionuclide-labeled fibroblast activation protein inhibitor (FAPI) imaging is an effective and reliable technique for detecting both myocardial fibrosis and activated CFs in arterial plaques. Preliminary data suggest that FAPI imaging can characterize plaque composition and assess the extent of myocardial fibrosis in various cardiovascular conditions. However, its potential to predict the ease of CTO recanalization and subsequent clinical outcomes remains to be fully explored.

The aim of this prospective cohort study is to evaluate the predictive value of FAPI imaging in patients with at least one untreated CTO. All enrolled patients will undergo baseline assessments prior to intervention, including blood tests, clinical evaluations, and imaging studies. These imaging studies will include myocardial FDG/perfusion imaging, FAPI imaging, and resting perfusion imaging. In selected patients, additional evaluations such as stress myocardial perfusion imaging, magnetic resonance imaging (MRI), and echocardiography will also be performed.

For patients undergoing percutaneous coronary intervention (PCI), follow-up assessments will occur at 6 and 12 months. At the 6-month mark, improvements in left ventricular (LV) wall motion will be assessed using resting perfusion imaging. At 12 months, coronary angiography (CAG) will be performed on all patients to evaluate recanalization outcomes. Additionally, myocardial perfusion imaging, magnetic resonance imaging (MRI), and echocardiography may be selectively used to evaluate patients during the 12-month follow-up.

1. To evaluate the ability of FAPI imaging in predicting the difficulty of CTO recanalization.
2. To investigate the role of myocardial FAPI imaging in predicting the improvement of LV wall motion at 6 months, assessed using follow-up single-photon emission computed tomography (SPECT).

By comparing FAPI imaging with conventional prognostic assessment methods, this study aims to clarify the utility of FAPI imaging in both predicting the recanalization complexity and in assessing long-term clinical outcomes in CTO patients.