Computed tomography measured epicardial adipose tissue and psoas muscle attenuation: new biomarkers to predict major adverse cardiac events (MACE) and mortality in patients with heart disease and critically ill patients. Part I: Epicardial adipose tissue

Abstract

Over the last two decades, the potential role of epicardial adipocyte tissue (EAT) as a marker for major adverse cardiovascular events has been extensively studied. Unlike other visceral adipocyte tissues (VAT), EAT is not separated from the adjacent myocardium by a fascial layer and shares the same microcirculation with the myocardium. Adipocytokines, secreted by EAT, interact directly with the myocardium through paracrine and vasocrine pathways. The role of the Randle cycle, linking VAT accumulation to insulin resistance, and the relevance of blood flow and mitochondrial function of VAT, are briefly discussed. The three available imaging modalities for the assessment of EAT are discussed. The advantages of echocardiography, cardiac CT, and cardiac magnetic resonance (CMR) are compared. The last section summarises the current stage of knowledge on EAT as a clinical marker for major adverse cardiovascular events (MACE). The association between EAT volume and coronary artery disease (CAD) has robustly been validated. There is growing evidence that EAT volume is associated with computed tomography coronary angiography (CTCA) assessed high-risk plaque features. The EAT CT attenuation coefficient predicts coronary events. Many studies have established EAT volume as a predictor of atrial fibrillation after cardiac surgery. Moreover, EAT thickness has been independently associated with severe aortic stenosis and mitral annular calcification. Studies have demonstrated that EAT volume is associated with heart failure. Finally, we discuss the potential role of EAT in critically ill patients admitted to the intensive care unit. In conclusion, EAT seems to be a promising new biomarker to predict MACE.

Keywords: biomarker; clinical outcomes; computed tomography; coronary artery disease; critically ill patients; epicardial adipose tissue; heart failure; major adverse cardiovascular events; atrial fibrillation.

FIGURE 1

The role of epicardial adipose tissue (EAT) in the development of cardiovascular diseases and cardiovascular complications during COVID-19. Increased EAT volume has been associated with increased body mass index (BMI), subcutaneous adipocyte tissue (SAT), sagittal abdominal diameter (SAD) and waist-to-hip ratio (W : H ratio), suggesting a pathophysiological link between EAT and increased intra-abdominal pressure (IAP) [Figure adapted and reproduced with permission from Konwerski et al. [70] under the open access CC BY 4.0 Licence] AF – atrial fibrillation, Ang 1-7 – angiotensin 1-7, BMI – body mass index, CAD – coronary artery disease, CCL-2, -5, -13 – chemokine ligand-2, -5, -13, CXCL-1 – chemokine ligand 1, FABP4 – fatty acid binding protein 4, GLUT-4 – glucose transporter type 4, HfpEF – heart failure with preserved ejection fraction, IAP – intra-abdominal pressure, IL-1β, -6, -8 – interleukin-1β, -6, -8, RBP4 – retinol binding protein 4, SAD – sagittal abdominal diameter, sPLA2-IIA – secretory phospholipase A2, TNF-α – tumour necrosis factor α, W : H – waist-to-hip ratio

FIGURE 2

Example of a non-contrast enhanced (panel a) and a contrast enhanced cardiac CT image (panel B). Note the good visibility of the pericardium (arrows) allowing a clear delineation of the epicardial fat (EAT) and adipocyte tissue outside the visceral epicardium

FIGURE 3

Example of cardiac CT acquired EAT volume from non-contrast enhanced images used to determine the Agatston calcium score. Panel a shows an upper axial slice of the heart. Panel B shows an axial slice at the level of the mitral valve. Note the mitral annular calcification. After manual contouring of the pericardium in the axial slice, the software calculates the voxels within the region of interest (ROI) with a CT attenuation coefficient attributed to adipose tissue. In this case, the filter setting defines adipose tissue as the voxels with CT attenuation number ranging from –190 HU to –30 HU (marked in the red ellipse). By summing all axial slices portraying the pericardium, the total EAT volume is calculated and mean EAT radiodensity expressed in HU is calculated (marked in the green ellipse)

FIGURE 4

Panel a shows a parasternal long axis view. Epicardial adipose tissue presents as hyperechogenic area between the pericardium (white arrow) and the myocardium. Panel B shows a parasternal short axis view. EAT is best detected at the right atrial free wall. The green line represents EAT thickness measurements. Red line indicates pericardial fat

FIGURE 5

A 4-chamber view (Panel a) and 2-chamber view of the left ventricle from the cine views (SSFP sequence). Adipose tissue is bright in this imaging sequence. Note that it is more difficult to depict the pericardium on CMR compared to cardiac CT (see Figure 1). Note the EAT in the atrioventricular groove (green *) and pericardial outside the pericardium (red *)