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Aortic Size Assessment by Noncontrast Cardiac Computed Tomography: Normal Limits by Age, Gender, and Body Surface Area

Arik Wolak, MD^_*, Heidi Gransar, MS^_*, Louise E.J. Thomson, MB ChB^_*, John D. Friedman, MD, FACC^_*, Rory Hachamovitch, MD, FACC^_*, Ariel Gutstein, MD^_*, Leslee J. Shaw, PhD, FACC^_*, Donna Polk, MD, MPH^_*, Nathan D. Wong, PhD, Rola Saouaf, MD^_*, Sean W. Hayes, MD^_*, Alan Rozanski, MD, FACC^_*, Piotr J. Slomka, PhD^_*, Guido Germano, PhD, FACC^_*, Daniel S. Berman, MD, FACC^_*,_*

^_* Departments of Imaging (Division of Nuclear Medicine), Department of Medicine (Division of Cardiology), and CSMC Burns & Allen Research Institute, Cedars-Sinai Medical Center, and the Department of Medicine, University of California at Los Angeles, School of Medicine, Los Angeles, California
Heart Disease Prevention Program, Division of Cardiology, University of California, Irvine, California.

^_* Reprint requests and correspondence: Dr. Daniel S. Berman, Director, Cardiac Imaging, Cedars-Sinai Medical Center, 8700 Beverly Boulevard, Los Angeles, California 90048. (Email: bermand{at}cshs.org).

Objectives: To determine normal limits for ascending and descending thoracic aorta diameters in a large population of asymptomatic, low-risk adult subjects.

Background: Assessment of aortic size is possible from gated noncontrast computed tomography (CT) scans obtained for coronary calcium measurements. However, normal limits for aortic size by these studies have yet to be defined.

Methods: In 4,039 adult patients undergoing coronary artery calcium (CAC) scanning, systematic measurements of the ascending and descending thoracic aorta diameters were made at the level of the pulmonary artery bifurcation. Multiple linear regression analysis was used to detect risk factors independently associated with ascending and descending thoracic aorta diameter and exclude subjects with these parameters from the final analysis. The final analysis groups for ascending and descending thoracic aorta included 2,952 and 1,931 subjects, respectively. Subjects were then regrouped by gender, age, and body surface area (BSA) for ascending and descending aorta, separately, and for each group, the mean, standard deviation, and upper normal limit were calculated for aortic diameter as well as for the calculated cross-sectional aortic area. Also, linear regression models were used to create BSA versus aortic diameter nomograms by age groups, and a formula for calculating predicted aortic size by age, gender, and BSA was created.

Results: Age, BSA, gender, and hypertension were directly associated with thoracic aorta dimensions. Additionally, diabetes was associated with ascending aorta diameter, and smoking was associated with descending aorta diameter. The mean diameters for the final analysis group were 33 ± 4 mm for the ascending and 24 ± 3 mm for the descending thoracic aorta, respectively. The corresponding upper limits of normal diameters were 41 and 30 mm, respectively.

Conclusions: Normal limits of ascending and descending aortic dimensions by noncontrast gated cardiac CT have been defined by age, gender, and BSA in a large, low-risk population of subjects undergoing CAC scanning.

Abbreviations and Acronyms   BMI = body mass index   BSA = body surface area   CAC = coronary artery calcium   CAD = coronary artery disease   CHD = coronary heart disease   CT = computed tomography   DSCT = dual source computed tomography   EBCT = electron beam computed tomography   LDL = low-density lipoprotein   MDCT = multidetector computed tomography   MRI = magnetic resonance imaging   TEE = transesophageal echocardiography