Visceral fat accumulation is a risk factor for atherosclerosis of the aorta

Transcription

1 Visceral fat accumulation is a risk factor for atherosclerosis of the aorta Poster No.: B-0115 Congress: ECR 2014 Type: Scientific Paper Authors: M. Hrabak Paar, R. Stern Padovan; Zagreb/HR Keywords: Cardiovascular system, CT-Angiography, Computer ApplicationsDetection, diagnosis, Arteriosclerosis DOI: /ecr2014/B-0115 Any information contained in this pdf file is automatically generated from digital material submitted to EPOS by third parties in the form of scientific presentations. References to any names, marks, products, or services of third parties or hypertext links to thirdparty sites or information are provided solely as a convenience to you and do not in any way constitute or imply ECR's endorsement, sponsorship or recommendation of the third party, information, product or service. ECR is not responsible for the content of these pages and does not make any representations regarding the content or accuracy of material in this file. As per copyright regulations, any unauthorised use of the material or parts thereof as well as commercial reproduction or multiple distribution by any traditional or electronically based reproduction/publication method ist strictly prohibited. You agree to defend, indemnify, and hold ECR harmless from and against any and all claims, damages, costs, and expenses, including attorneys' fees, arising from or related to your use of these pages. Please note: Links to movies, ppt slideshows and any other multimedia files are not available in the pdf version of presentations. Page 1 of 16

2 Purpose Visceral adiposity is associated with development of metabolic syndrome and cardiovascular diseases. In previous investigations it was shown that visceral adiposity is an independent determinant of carotid intima-media thickness, coronary artery calcium score, and abdominal aortic calcification severity [1-4]. On the contrary, subcutaneous fat tissue could have protective role against atherosclerosis [5,6]. In this study we evaluated the relationship between the amount and distribution of abdominal adipose tissue with development of atherosclerotic changes of different aortic segments, including aortic wall thickness, aortic diameter and grade of calcified and noncalcified atherosclerotic plaques of the aorta. Methods and materials CT angiography of the entire aorta was performed in 94 patients (68 men and 26 women; age range years) using a 40-slice CT scanner. Before scanning nonionic iodine contrast agent ( ml iopromide 300 mg I/mL) was administered intravenously using an automatic injector at rate 4 ml/s. Scanning delay was determined using bolus tracking method 5 seconds after attenuation in ascending aorta reached value of >100 Houndsfield units (HU). Using scout image, the scanning area was limited to the region between clavicles and femoral heads. In all patients significant aortic disease was excluded using CT examination. Informed consent was obtained from each patient after the nature of the procedure has been fully explained to the patient. Total, visceral and subcutaneous abdominal fat areas were measured on a single axial CT scan at the level of umbilicus using standardized technique Fig. 1 on page 3 Fig. 2 on page 3 Fig. 3 on page 4 Fig. 4 on page 5 Fig. 5 on page 6 Fig. 6 on page 7 [7]. Aortic diameter was measured on five anatomic levels: ascending aorta (2 cm above aortic valve), aortic arch (between the origin of the brachiocephalic trunk and the origin of the left common carotid artery), descending thoracic aorta (at the level of T8-T9 intervertebral space), and abdominal aorta on two levels (level of the origin of the superior mesenteric artery (SMA) and the level of the origin of the inferior mesenteric artery (IMA)). Aortic wall thickness was measured on the same levels except the ascending aorta because of the motion artifacts on non-ecg-assisted scan. Atherosclerotic plaques of all aortic segments were semiquantitatively graded using previously described scale Fig. 7 on page 8 Fig. 8 on page 9 Fig. 9 on page 10 Fig. 10 on page 11 Fig. 11 on page 12 [8]. Correlation analysis between abdominal fat areas and aortic diameters, wall thickness and plaque grades was performed. Page 2 of 16

3 Images for this section: Fig. 1: Measurement of total, visceral and subcutaneous abdominal fat areas - step 1. At first, the subcutaneous fat layer was outlined. Page 3 of 16

4 Fig. 2: Measurement of total, visceral and subcutaneous abdominal fat areas - step 2. Attenuation values within the outlined subcutaneous fat layer were displayed as histogram with calculation of fat tissue attenuation (mean ± 2 standard deviations). Page 4 of 16

5 Fig. 3: Measurement of total, visceral and subcutaneous abdominal fat areas - step 3. Visceral fat was outlined following contours of the rectus abdominis, transversus abdominis and quadratus lumborum muscles and ventral border of the vertebral body. Page 5 of 16

6 Fig. 4: Measurement of total, visceral and subcutaneous abdominal fat areas - step 4. The image was segmented according to predefined fat tissue attenuation, and visceral fat area was measured. Page 6 of 16

7 Fig. 5: Measurement of total, visceral and subcutaneous abdominal fat areas - step 5. The circumference of the abdominal wall was outlined. Page 7 of 16

8 Fig. 6: Measurement of total, visceral and subcutaneous abdominal fat areas - step 6. The image was segmented according to predefined fat tissue attenuation, and total abdominal fat area was calculated. Subcutaneous abdominal fat area was calculated by subtraction of visceral fat area from the total abdominal fat area. Page 8 of 16

9 Fig. 7: Semiquantitative gradation of aortic atherosclerotic plaques: grade 1 - no lumen irregularity and no wall thickening. Page 9 of 16

10 Fig. 8: Semiquantitative gradation of aortic atherosclerotic plaques: grade 2 - wall thickening of more than 2 mm without lumen irregularity. Page 10 of 16

11 Fig. 9: Semiquantitative gradation of aortic atherosclerotic plaques: grade 3 - wall thickening with lumen irregularity including plaques containing calcifications of less than 0.10 ccm in volume. Page 11 of 16

12 Fig. 10: Semiquantitative gradation of aortic atherosclerotic plaques: grade 4 - wall thickening with a high plaque burden and abundant calcification equal to or greater than 0.10 ccm in volume. Page 12 of 16

13 Fig. 11: Semiquantitative gradation of aortic atherosclerotic plaques: grade 4 - wall thickening with a high plaque burden and abundant calcification equal to or greater than 0.10 ccm in volume. Page 13 of 16

14 Results We found statistically significant correlation between diameter of all aortic segments and visceral fat area, that was mostly pronounced in the aortic arch (r=0.42, p<0.05). Aortic wall thickness was associated with visceral fat area, this relationship was strongest at the level of descending thoracic aorta (r=0.32, p<0.05). We also found positive correlation between the visceral fat area and the grade of the largest atherosclerotic plaque of all aortic segments, with the strongest correlation at the level of descending thoracic and abdominal aorta (rs=0.32, p<0.05). We did not find any correlation between subcutaneous fat area and aortic wall thickness and atherosclerotic plaque grade. Table 1: Correlation between abdominal fat areas with diameter, wall thickness and the grade of the largest atherotic plaque of different aortic segments. References: Department of Diagnostic and Interventional Radiology, University of Zagreb School of Medicine - Zagreb/HR Conclusion Visceral fat tissue accumulation is associated with larger aortic diameter, larger aortic wall thickness and more advanced grade of aortic atherosclerotic plaques. Enlargement Page 14 of 16

15 of aortic diameter could be explained as an adaptation process to the increased blood volume, as a consequence of higher systolic blood pressure, or as a result of underlying structural or functional aortic abnormality specific to obesity [9]. Visceral fat accumulation accelerates vascular aging, with consequent increase of the risk for future cardiovascular events. The effect of subcutaneous fat tissue on development of aortic atherosclerosis in our study was negligible. Personal information Department of Diagnostic and Interventional Radiology University Hospital Center Zagreb University of Zagreb School of Medicine Kišpati#eva 12 HR Zagreb Croatia Tel: Fax: maja.hrabak.paar@mef.hr References Kim SK, Kim HJ, Hur KY, Choi SH, Ahn CW, Lim SK, Kim KR, Lee HC, Huh KB, Cha BS. Visceral fat thickness measured by ultrasonography can estimate not only visceral obesity but also risks of cardiovascular and metabolic diseases. Am J Clin Nutr 2004;79; Liu KH, Chan YL, Chan JCN, Chan WB. Association of carotid intima-media thickness with mesenteric, preperitoneal and subcutaneous fat thickness. Atherosclerosis 2005;179: Arad Y, Newstein D, Cadet F, Roth M, Guerci AD. Association of multiple risk factors and insulin resistance with increased prevalence of asymptomatic coronary artery disease by an electron-beam computed tomographic study. Arterioscler Thromb Vasc Biol 2001;21: Page 15 of 16

16 Golledge J, Jayalath R, Oliver L, Parr A, Schurgers L, Clancy P. Relationship between CT anthropometric measurements, adipokines and abdominal aortic calcification. Atherosclerosis 2008;197: Tankó LB, Bagger YZ, Alexandersen P, Larsen PJ, Christiansen C. Peripheral adiposity exhibits an independent dominant antiatherogenic effect in elderly women.circulation 2003;107: Narumi H, Yoshida K, Hashimoto N, Umehara I, Funabashi N, Yoshida S, Komuro I. Increased subcutaneous fat accumulation has a protective role against subclinical atherosclerosis in asymptomatic subjects undergoing general health screening. Int J Cardiol 2009;135: Yoshizumi T, Nakamura T, Yamane M, Waliul Islam AHM, Menju M, Yamasaki K, Arai T, Kotani K, Funahashi T, Yamashita S, Matsuzawa Y. Abdominal fat: standardized technique for measurement at CT. Radiology 1999;211: Takasu J, Mao S, Budoff MJ. Aortic atherosclerosis detected with electronbeam CT as a predictor of obstructive coronary artery disease. Acad Radiol 2003;10: Danias PG, Tritos NA, Stuber M, Botnar RM, Kissinger KV, Manning WJ. Comparison of aortic elasticity determined by cardiovascular magnetic resonance imaging in obese versus lean adults. Am J Cardiol 2003;91: Page 16 of 16