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).