Ischemic heart failure (IHF) is the final stage of coronary heart disease. Coronary revascularization is an important treatment method for IHF, but it has high perioperative risks and not all patients can benefit from it. Evaluation of viable myocardium is one of the important decision-making methods for IHF, but recent research results have raised doubts about its value. The clinical community urgently needs more precise and comprehensive non-invasive decision-making methods. Fibroblast activation protein inhibitor (FAPI) imaging can specifically identify activated fibroblasts and achieve non-invasive diagnosis of the early and reversible stage of myocardial injury. Previous studies have shown that FAPI imaging can identify more damaged myocardium in various heart diseases compared to existing imaging techniques, demonstrating good clinical application potential. This study aims to conduct a prospective cohort trial for IHF patients who have undergone revascularization, using 18F-FAPI and viable myocardium (18F-FDG) imaging to analyze the degree of improvement in left ventricular ejection fraction after revascularization and major adverse cardiovascular events, and to explore the independent or additive predictive value of 18F-FAPI imaging, in order to provide a more reliable non-invasive imaging decision-making method for the revascularization strategy of IHF patients.

Ischemic heart failure (IHF) represents the end-stage of coronary artery disease and carries a poor prognosis, with an annual mortality rate of approximately 25%. Revascularization therapies, including percutaneous coronary intervention (PCI) and coronary artery bypass grafting (CABG), are important treatment modalities for IHF that improve patient outcomes by enhancing myocardial perfusion and reversing ventricular remodeling. However, the perioperative risks associated with revascularization are significantly higher in IHF patients compared to the general coronary artery disease population, and not all IHF patients derive benefit from revascularization. Consequently, accurately identifying IHF patients who are most likely to benefit from revascularization remains a major clinical challenge in cardiovascular medicine.

Noninvasive imaging techniques are important tools for selecting IHF patients who may benefit from revascularization. Multiple imaging parameters have been shown to correlate with post-revascularization prognosis in IHF, including cardiac function, myocardial ischemia, and myocardial viability. However, several recent international multicenter studies, including STICH, have failed to demonstrate that myocardial viability imaging can effectively identify potential beneficiaries of revascularization, raising doubts about its clinical utility. These findings suggest that relying solely on myocardial viability status for treatment decision-making in IHF has inherent limitations and that a more comprehensive evaluation of affected myocardial tissue is needed.

The myocardial pathological process in IHF is complex. Beyond the viability status of cardiomyocytes, the pathological state of the myocardial interstitium is also a critical determinant of ventricular remodeling and functional recovery. Theoretically, a comprehensive evaluation encompassing both cardiomyocytes and the myocardial interstitium may enable more precise identification of patients likely to benefit from revascularization. Fibroblast activation protein (FAP)-targeted imaging (FAPI PET) enables dynamic visualization of myocardial fibroblast activation by specifically targeting FAP expressed on the surface of activated fibroblasts. This technique has demonstrated unique value across various cardiovascular diseases, allowing earlier detection of active fibrotic regions and significantly improving the prediction of adverse ventricular remodeling. These findings suggest that FAPI imaging may offer greater precision and the potential to assess the reversibility of fibrotic activity, thereby providing a more comprehensive imaging basis for risk stratification and therapeutic decision-making in IHF. However, the value of FAPI imaging in IHF remains unclear.

Therefore, this study aims to conduct a prospective cohort study enrolling IHF patients scheduled for revascularization. All patients will undergo both ¹⁸F-FAPI and ¹⁸F-FDG imaging prior to the procedure. By analyzing postoperative improvements in left ventricular ejection fraction (LVEF) and the incidence of major adverse cardiovascular events (MACE), this study seeks to determine the independent predictive value of ¹⁸F-FAPI imaging for post-revascularization prognosis and its incremental value over conventional myocardial viability imaging.

Study Objectives The primary objective of this prospective cohort study is to evaluate the value of ¹⁸F-FAPI imaging in predicting outcomes following revascularization in IHF patients.

Specific objectives include:

1. To determine the independent predictive value of ¹⁸F-FAPI imaging for post-revascularization outcomes, including LVEF improvement and MACE incidence.
2. To investigate the incremental predictive value of ¹⁸F-FAPI imaging over ¹⁸F-FDG imaging.

Study Design This is a prospective cohort study. All enrolled patients will receive standard revascularization therapy (PCI or CABG) according to current clinical guidelines, and the study is strictly observational without intervention in clinical decision-making.

Study Population The study will consecutively enroll IHF patients scheduled for revascularization at Beijing Chaoyang Hospital, Capital Medical University, from January 2026 to December 2027. All patients must have a confirmed diagnosis of IHF (LVEF ≤ 40%) with clear evidence of ischemic heart disease (e.g., prior myocardial infarction, previous revascularization, or angiographically confirmed coronary artery disease), be ≥ 18 years of age, have NYHA functional class II-IV, and be suitable for revascularization as determined by coronary angiography. Written informed consent will be obtained from all participants.

Key exclusion criteria include: heart failure of non-ischemic etiology (e.g., dilated cardiomyopathy, valvular heart disease, myocarditis); acute myocardial infarction within the past 3 months; life expectancy < 1 year; concomitant severe systemic disease; history of malignancy; and any contraindications to revascularization.

Imaging Protocol

All enrolled patients will undergo three imaging assessments prior to revascularization:

• F-FAPI PET/CT for assessment of myocardial fibroblast activation
• F-FDG PET/CT for assessment of myocardial viability ⁹⁹ᵐTc-MIBI SPECT for assessment of myocardial perfusion All imaging data will be analyzed quantitatively (including myocardial viability area, fibroblast activation extent, and perfusion defect size) and semi-quantitatively (target-to-background ratio) by a core laboratory blinded to clinical outcomes.

Clinical Data Collection Baseline data will be collected upon enrollment, including demographic information, medical history, cardiovascular risk factors, laboratory biomarkers (cardiac injury markers, inflammatory markers, and fibrotic markers), and echocardiographic parameters.

Follow-up and Outcomes All patients will be followed up at 12 months post-revascularization. The primary outcome is the absolute change in LVEF from baseline to 12-month follow-up (ΔLVEF). The secondary outcome is the incidence of MACE within 12 months, defined as a composite of cardiovascular death, non-fatal recurrent myocardial infarction, and heart failure rehospitalization.

Sample Size Estimation Based on previous literature reporting LVEF improvement rates of approximately 3.8% in IHF patients undergoing revascularization as predicted by ¹⁸F-FDG imaging, and preliminary data from our team's recent prospective study in chronic total occlusion patients with heart failure, we anticipate a predicted LVEF improvement rate of approximately 5.8% with ¹⁸F-FAPI imaging. Using PASS software with a two-sided α of 0.05 and a power of 0.8, and accounting for a 10% loss to follow-up, the estimated total sample size is 116 patients.

Statistical Analysis For the primary objective (independent predictive value): Multivariable linear regression will be used to examine the association between ¹⁸F-FAPI parameters and ΔLVEF, and multivariable Cox proportional hazards regression will be used to evaluate the association between ¹⁸F-FAPI parameters and MACE risk, after adjusting for baseline clinical factors and ¹⁸F-FDG-derived myocardial viability status.

For the secondary objective (incremental predictive value):

For ΔLVEF (continuous outcome): Linear regression models will be constructed, and the improvement in model fit will be evaluated by comparing the adjusted R² before and after adding ¹⁸F-FAPI parameters, assessed by likelihood ratio tests or analysis of variance (ANOVA).

For MACE (binary outcome): Logistic regression or Cox proportional hazards models will be used. Model performance will be compared using the area under the receiver operating characteristic curve (AUC) or C-statistic, and incremental improvement will be quantified by calculating the net reclassification improvement (NRI) and integrated discrimination improvement (IDI).

Inclusion Criteria:

① Age ≥ 18 years; ② Meet the above-mentioned IHF diagnostic criteria; ③ Coronary angiography shows suitability for revascularization (PCI or CABG); ④ NYHA cardiac function classification is II-IV; ⑤ Sign the informed consent form.

Exclusion Criteria:

① Heart failure caused by non-ischemic etiologies (such as dilated cardiomyopathy, valvular heart disease, myocarditis, etc.); ② Acute myocardial infarction occurred within the last 3 months; ③ Expected lifespan < 1 year; ④ Complicated with other severe systemic diseases; ⑤ Has a history of tumors; ⑥ Has any conditions that are unsuitable for revascularization (such as uncorrectable coagulation dysfunction, active bleeding, etc.)

It meets the relevant standards for IHF as stipulated in the "2024 Chinese Guidelines for the Diagnosis and Treatment of Heart Failure", and has a clear history of ischemic heart disease (such as previous myocardial infarction, history of revascularization, or confirmed coronary artery lesions by coronary angiography), and the echocardiogram shows that LVEF is ≤ 40%.