Quantitative determination of age-related geometric changes in the normal abdominal aorta
Journal of Vascular Surgery
Vessel geometry not only determines flow-dynamics, but also plays a crucial role in the pathogenesis of vascular diseases such as atherosclerosis, aneurysm formation, or dissection. 1 In vivo assessment of the threedimensional configuration of arterial flow channels, however, poses substantial methodological difficulties, and traditional imaging techniques, such as ultrasound scan, contrast arteriography, or conventional computed tomography are unsuitable means of obtaining accurate
... in more than two dimensions. Thus, in spite of its well-recognized role in hemodynamics, our knowledge of the normal three-dimensional anatomy and shape of the flow channel of the abdominal aorta is limited. This is also true for the relation of vascular geometry to physiologic variables such as age, sex, and body size. We recently developed and validated three-dimensional image analysis tools that take advantage of the true volumetric nature of the image-data acquired with contrast-97 enhanced helical computed tomographic (CT) angiography. 2,3 We will refer to this technique as quantitative vascular CT. This technique allows us to obtain contiguous cross-sectional area (CSA) measurements of a vessel lumen automatically and independently of the operator, measure the true lengths of vascular segments, and quantify vessel curvature from helical CT datasets. The objective of this study was to assess the normal three-dimensional geometry of the flow channel of the abdominal aorta in healthy adults with quantitative vascular CT and to establish the relationship between aortic geometry and sex, age, and body size. Purpose: We conducted a novel quantitative three-dimensional analysis of computed tomography (CT) angiograms to establish the relationship between aortic geometry and age, sex, and body surface area in healthy subjects. Methods: Abdominal helical CT angiograms from 77 healthy potential renal donors (33 men/44 women; mean age, 44 years; age range, 19-67 years) were selected. In each dataset, orthonormal cross-sectional area and diameter measurements were obtained at 1-mm intervals along the automatically calculated central axis of the abdominal aorta. The aorta was subdivided into six consecutive anatomic segments (supraceliac, supramesenteric, suprarenal, inter-renal, proximal infrarenal, and distal infrarenal). The interrelated effects of anatomic segment, age, sex, and body surface area on crosssectional dimensions were analyzed with linear mixed-effects and varying-coefficient statistical models. Results: We found that significant effects of sex and of body surface area on aortic diameters were similar at all anatomic levels. The effect of age, however, was interrelated with anatomic position, and gradually decreasing slopes of significant diameter-versus-age relationships along the aorta, which ranged from 0.14 mm/y (P < .0001) proximally to 0.03 mm/y (P = .013) distally in the abdominal aorta, were shown. Conclusion: The abdominal aorta undergoes considerable geometric changes when a patient is between 19 and 67 years of age, leading to an increase of aortic taper with time. The hemodynamic consequences of this geometric evolution for the development of aortic disease still need to be established. (J Vasc Surg 2001;33:97-105.) JOURNAL OF VASCULAR SURGERY Volume 33, Number 1 Fleischmann et al 103 Fig 3. Diameter of aortic segments versus body surface area. Plots show segmental diameters versus body surface area in women (left panels) and men (right panels) for all vascular segments (uppermost panels, segment A; lowest panel, segment IL). Linear regression lines (full lines) and CIs (dotted lines) are indicated.