Purpose of Review <p>The diagnosis of light-chain cardiac amyloidosis (AL-CA) is often delayed owing to nonspecific clinical symptoms and comorbidities, making early detection and risk stratification essential for early intervention. Activated cardiac fibroblasts play a vital role in cardiac remodeling and cardiac damage progression, leading to heart failure. Emerging imaging modalities visualize fibroblast activation protein (FAP) as a marker of activated fibroblasts, enabling non-invasive and accurate measurement of cardiac remodeling for risk stratification. This review summarizes the status of diagnosis and treatment, pathogenic basis of AL-CA, and positron emission tomography (PET) imaging to assess the potential of gallium 68 (⁶⁸Ga)-labeled FAP inhibitor 04 (⁶⁸Ga-FAPI-04) for AL-CA diagnosis and treatment.</p> Recent Findings <p>⁶⁸Ga-FAPI-04 PET/computed tomography (CT) can detect myocardial fibroblast activation in patients with AL-CA, with significant uptake observed in most patients. The degree of activation correlates with cardiac function, morphology, and serum markers, suggesting its utility in prognostic assessments. ⁶⁸Ga-FAPI-04 PET/CT may enable more robust risk stratification and prognostic assessment than that via ¹⁸F-florbetapir PET/CT, underscoring the significance of cardiac fibroblast activation in predicting the outcomes of patients with AL-CA.</p> Summary <p>⁶⁸Ga-FAPI-04 PET/CT has emerged as a promising tool for diagnosing AL-CA, offering insights into the molecular characteristics of the disease and aiding in clinical decision-making. Existing findings suggest the potential of ⁶⁸Ga-FAPI-04 PET/CT for enhancing myocardial fibrosis management in AL-CA. Future multicenter trials are warranted to validate these findings and explore the integration of ⁶⁸Ga-FAPI-04 PET/CT with other imaging modalities to improve the diagnosis and prognostic prediction of patients with AL-CA.</p>