Acute myocardial infarction (AMI) initiates a complex myocardial repair process involving inflammation, fibroblast activation, and extracellular matrix remodeling, which may ultimately lead to adverse left ventricular remodeling and impaired cardiac function. Fibroblast activation protein (FAP)-targeted positron emission tomography (PET) enables noninvasive visualization of activated fibroblasts and may provide an early imaging biomarker of myocardial remodeling. This prospective single-center observational study aims to evaluate myocardial fibroblast activation using Ga-68 FAPI PET/MR performed approximately 10 ± 2 days after AMI and to investigate its association with subsequent left ventricular remodeling. Serial cardiac magnetic resonance (CMR) examinations will be performed at 3 and 6 months to assess changes in ventricular function and remodeling. The study will investigate whether early myocardial FAPI uptake is associated with subsequent structural and functional changes detected by CMR and evaluate the potential role of Ga-68 FAPI PET/MR as an imaging biomarker for post-infarction remodeling.

Acute myocardial infarction (AMI) initiates a dynamic myocardial repair process characterized by inflammation, fibroblast activation, extracellular matrix remodeling, and scar formation. Although these processes are essential for infarct healing, excessive or dysregulated remodeling may result in adverse left ventricular (LV) remodeling, progressive deterioration of cardiac function, and subsequent heart failure. Early identification of patients at risk for adverse remodeling remains an important unmet clinical need.

Fibroblast activation protein (FAP) is transiently expressed by activated fibroblasts during tissue repair and fibrosis. Ga-68 FAPI PET enables noninvasive visualization of fibroblast activation in vivo and has recently emerged as a promising molecular imaging technique for assessing myocardial remodeling following AMI. However, the relationship between early myocardial FAPI uptake and subsequent structural and functional cardiac remodeling has not been fully established.

This prospective, single-center observational study aims to evaluate myocardial fibroblast activation using integrated Ga-68 FAPI PET/MR performed approximately 10 ± 2 days after acute myocardial infarction. Participants will subsequently undergo serial cardiac magnetic resonance (CMR) examinations at 3 and 6 months to assess left ventricular remodeling, ventricular function, infarct characteristics, and myocardial fibrosis.

The primary objective is to investigate the association between early myocardial FAPI uptake and subsequent left ventricular remodeling assessed by serial CMR. Secondary objectives include evaluating the relationship between quantitative FAPI PET parameters and changes in left ventricular function, infarct characteristics, myocardial fibrosis, and relevant clinical and laboratory parameters. This study seeks to evaluate the potential value of Ga-68 FAPI PET/MR as an early imaging biomarker of post-infarction myocardial remodeling.

Inclusion Criteria:

• Age ≥18 years.
• Diagnosis of acute myocardial infarction according to current guideline criteria.
• Successful coronary revascularization when clinically indicated.
• Ability to undergo FAPI PET/MR.
• Written informed consent.

Exclusion Criteria:

• Contraindications to MRI (e.g., non-MR-compatible implanted devices, severe claustrophobia).
• Pregnancy or breastfeeding.
• Severe renal impairment precluding gadolinium administration (if contrast-enhanced MR is performed).
• Inability to provide informed consent.
• Any condition considered by the investigator to interfere with study participation.

Adult patients with acute myocardial infarction prospectively enrolled to undergo hybrid 68Ga-FAPI PET/MR imaging for assessment of myocardial fibroblast activation following infarction.

Individual participant data will not be shared because of institutional policies and the need to protect participant confidentiality.