Heart failure (HF) is a clinical syndrome with increasing incidence and prevalence, associated with high morbidity, mortality, and economic impact, despite therapeutic advances.

Myocardial fibrosis is a common feature across different pathophysiological processes and plays a key role in HF development, with growing research interest specifically in non-ischemic dilated cardiomyopathy (HFrEF phenotype) and hypertrophic cardiomyopathy (HFpEF phenotype). Given its potential reversibility with certain drugs, fibrosis is an attractive therapeutic target, requiring non-invasive methods to monitor fibrogenesis and treatment efficacy.

Cardiac magnetic resonance imaging (CMR) is the gold standard for detecting fibrosis but cannot distinguish between active and inactive fibrosis or detect early stages, limitations that may be addressed by gallium-68-labeled fibroblast activation protein inhibitor positron emission tomography/computed tomography (68Ga-FAPI PET/CT).

This single-center, prospective, observational pilot study aims primarily to assess myocardial fibrosis in patients with HFrEF (non-ischemic dilated cardiomyopathy) and a subtype of HFpEF (hypertrophic cardiomyopathy) using 68Ga-FAPI PET/CT compared to CMR.

Secondary objectives include developing 68Ga-FAPI uptake assessment methodologies for future anti-fibrotic therapy studies and correlating fibrosis with serum cardiac biomarkers and cardiovascular events.

Inclusion Criteria:

• ≥ 18 years old;
• Signs and symptoms of heart failure (HF);
• [Preserved left ventricular ejection fraction (LVEF) (≥50%) and Evidence of structural/functional abnormality consistent with diastolic dysfunction/increased ventricular filling pressures, including elevated natriuretic peptides and Imaging diagnosis of hypertrophic cardiomyopathy and Genetic diagnosis of hypertrophic cardiomyopathy due to sarcomeric gene mutation] OR [Reduced LVEF (≤40%) and Imaging diagnosis of dilated cardiomyopathy: left ventricular end-diastolic diameter >58 mm in men and >52 mm in women, and left ventricular volume ≥75 mL/m² in men and ≥62 mL/m² in women, not explained solely by loading conditions]
• Recent transthoracic echocardiogram (< 3 months);
• Recent cardiac magnetic resonance imaging (< 3 months).
• Normal coronary angiogram or computed tomography coronary angiography within 6 months of enrolment

Exclusion Criteria:

• Inability to provide informed consent;
• Inability to tolerate the supine position;
• Hemodynamic instability;
• Claustrophobia;
• Chronic kidney disease with glomerular filtration rate <30 mL/min/1.73m²;
• Pregnant or breastfeeding women;
• Malignant neoplasms within the past 5 years;
• Significant primary valvular disease;
• Significant atherosclerotic coronary artery disease;
• Grade 2 or 3 arterial hypertension;
• Presence of an implanted cardiac electrical device;
• Recent hospitalization for heart failure (<30 days).

Fifteen patients with HFrEF (non-ischemic dilated cardiomyopathy) and Fifteen patients with HFpEF (hypertrophic cardiomyopathy)