Normal thoracic aorta diameter on cardiac computed tomography in healthy asymptomatic adults: impact of age and gender.

RATIONALE AND
OBJECTIVES: To establish the normal criterion of ascending aortic diameter (AAOD) measured by 64 multidetector computed tomography (MDCT) and electron beam computed tomography (EBT) based on gender and age.
MATERIALS AND METHODS: A total of 1442 consecutive subjects who were referred for evaluation of possible coronary artery disease underwent coronary computed tomographic (CT) angiography (CTA) and coronary artery calcium scanning (CACS) (55 + 11 years, 65% male) without known coronary heart disease, hypertension, chronic pulmonary and renal disease, diabetes, and severe aortic calcification. The AAOD aortic diameter, descending aortic diameter (DAOD), pulmonary artery (PAD), and chest anteroposterior diameter (CAPD), posterior border of the sternal bone to the anterior border of the spine, were measured at the slice level of mid-right pulmonary artery using end systolic trigger imaging. The volume of four chambers, ejection fraction of left ventricle, and cardiac output were measured in 56% of the patients. Patients' demographic information, age, gender, weight, height, and body surface area were recorded. The mean value and age-specific and gender-adjusted upper normal limits (mean +/- 2 standard deviation) were calculated. The linear correlation analysis was done between AAOD and all parameters. The reproducibility, wall thickness, and difference between end-systole and end-diastole were calculated.
RESULTS: AAOD has significant linear association with age, gender, DAOD, and pulmonary artery diameter (P < .05). There is no significant correlation between AAOD and body surface area, four-chamber volume, left ventricular ejection fraction, cardiac output, and CAPD. The mean intraluminal AAOD was 31.1 +/- 3.9 and 33.6 +/- 4.1 mm in females and males, respectively. The upper normal limits (mean +/- 2 standard deviations) of intraluminal AAOD, were 35.6, 38.3, and 40 mm for females and 37.8, 40.5, and 42.6 mm for males in age groups 20-40, 41-60, and older than 60 years, respectively. Intraluminal aortic diameters should parallel echocardiography and invasive angiography. Traditional cross-sectional imaging (with CT and magnetic resonance imaging) includes the vessel wall. The mean total AAOD was 33.5 and 36.0 mm in females and males, respectively. The upper normal limits (mean +/- 2 standard deviations) of intraluminal AAOD were 38.0, 40.7 and 42.4 mm for females and 40.2, 42.9, and 45.0 mm for males in age group 20 to 40, 41 to 60, and older than 60 years, respectively. The inter- and intraobserver, scanner, and repeated measurement variabilities were low (r value >0.91, P < .001, coefficient variation <3.2%). AAOD was 1.7 mm smaller in end-diastole than end-systole (P < .001).
CONCLUSIONS: The AAOD increases with age and male gender. Gender-specific and age-adjusted normal values for aortic diameters are necessary to differentiate pathologic atherosclerotic changes in the ascending aorta. Use of intraluminal or total aortic diameter values depends on the comparison study employed.