The Intrusive nature of epicardial adipose tissue as revealed by cardiac magnetic resonance

Figure 1. (a)Cardiac magnetic resonance cine-sequence still frame obtained with steady-state free precession (CMR SSFP) sequence. The area in the red box is magnified in panel B. (b) These images clearly show the parietal and the visceral pericardium. The epicardial adipose tissue is confined between the visceral and parietal pericardium, i.e., fully enclosed in the pericardial sac (*), while the paracardial adipose tissue (**) is external to pericardium

Figure 2. (a) Cardiac magnetic resonance steady-state free precession still frames. The images clearly show that the interatrial groove (the embryonic septum secundum) is made up by the folding of right and left atrial walls. (b) Anatomic specimen displayed in similar view. (c) In a more posterior cut, the fossa ovalis disappears and this enfolding assumes a “three layered” aspect (see text). (d) Magnified image of the red box of panel c

Figure 3. (a) CMR SSFP still frames showing the AVS (dotted line) sited in between the hinge of TV and the hinge of MV. The image clearly shows the EAT (asterisk) in between the RA wall and the crest of IVS. This particular anatomical arrangement has been named “atrio-ventricular muscular sandwich.” (b) Anatomic specimen showing the offset arrangement between the hinges of the tricuspid and mitral valves (arrows), the AVS (dotted line), and the EAT (asterisk) (see text). IA = Interatrial. AVS = Atrioventricular septum, CMR SSFP = Cardiac magnetic resonance steady-state free precession, TV = Tricuspid valve, MV = Mitral valve, RA = Right atrial, IVS = Interventricular septum, EAT = Epicardial adipose tissue

Figure 4. (a-d) CMR SSFP still frame. In the panel a is shown a two-chamber longitudinal plane, showing on the inferior-posterior aspect of the heart, the IPS filled with EAT (yellow dotted line). The two dotted lines in panel b refer to the two short axis planes shown in panel c and d respectively. Panel c shows a short axis plane with the IPS bordered by the right and left atrial walls, while the panel d shows a lower short axis plane where the IPS is bordered by the right atrial wall and by the crest of interventricular septum (see text). Panel (e) is an anatomic specimen displayed in similar fashion as the image on panel a. The IPS is located between the two dotted lines. Within it there are the CS, the MCV and a coronary artery (short arrow). RA = Right atrium, LA = Left atrium, LV = Left ventricle, Ao = Aorta, AVJ = Atrioventricular junction, MCV = Middle cardiac vein, CS = Coronary sinus, EAT = Epicardial adipose tissue, CMR SSFP = Cardiac magnetic resonance steady-state free precession, IPS = Inferior pyramidal space

Figure 5. CMR SSFP still frame. The area in the red box in the panel (a) is magnified in panel (b). The images show a single ridge (LLR) formed by the two walls so close each other that cannot be distinguished. (c) The area in the red box is magnified in panel (d). In this patient with abundant EAT, the images clearly show the folding of the left atrial wall between the LAA and the LUPV protruding into the left atrium. Panels (e) and f (f) are cuts through anatomical specimens showing the fold of the atrial wall that makes up the LLR. Ao = Aorta, LA = Left atrium, LAA = Left atrial appendage, LUPV = Left upper pulmonary vein, CMR SSFP = Cardiac magnetic resonance steady-state free precession, LLR = Left lateral ridge, EAT = Epicardial adipose tissue

Figure 6. CMR SSFP still frame in long axis (a and b) and in 2 chamber (c and d) views. The areas in the red box in the panels a and c are magnified in panels b and d. The images clearly show the EAT occupying the atrioventricular groove up to the base of the posterior leaflet insertion. e and f are anatomic specimens showing the hinge (arrow) of the mitral leaflet interposing between atrial and ventricular walls and the yellow colored EAT. Ao = Aorta, LA = Left atrium, LV = Left ventricle, CS = Coronary sinus, CMR SSFP = Cardiac magnetic resonance steady-state free precession, EAT = Epicardial adipose tissue

Figure 7. CMR SSFP still frame in four chamber view (a and b) and in right ventricular inflow (c and d) view. The areas in the red box in the panels a and c are magnified in panels b and d. (b) The image clearly shows the juxtaposition of the four components that form the tricuspid annulus. (d) The image shows how deeply the EAT penetrates into the atrioventricular groove. e and f are corresponding cuts through anatomic specimens to show the hinge of the tricuspid valve leaflet (white arrow) and the deep excursion of EAT into the right atrioventricular groove. RA = Right atrium, RV = Right ventricle, LA = Left atrium, LV = Left ventricle, RAA = Right atrial appendage, CMR SSFP = Cardiac magnetic resonance steady-state free precession, EAT = Epicardial adipose tissue

Figure 8. (a) CMR SSFP still frame in long axis view showing in patient with abundant EAT as the adipose tissue separates the aortic wall from the atrial wall in the transverse pericardial sinus. Panel (b) shows anatomic specimen displayed in similar view showing EAT (asterisk) between the outside of the aortic sinus and the anterior wall of the LA. Aortic-mitral fibrous continuity is circled. Panel (c) is a histologic section in similar orientation to show fibrous tissue (stained red between the two arrows). The LA wall (stained brownish) is on the outside but there is no ventricular muscle in between aortic and mitral leaflets (see text). LA = Left atrium, CMR SSFP = Cardiac magnetic resonance steady-state free precession, EAT = Epicardial adipose tissue