Mechanical properties of the aneurysmal aorta

Abstract

The mechanical properties of the abdominal aorta were investigated non‐invasively in 30 patients with aortic anaeurysm and II with peripheral arterial disease. The distensibility of the aorta was measured using M‐mode ultrasonography, permitting non‐invasive assessment of the pressure‐strain elastic modulus or aortic stiffness, E_p. The median E_p value increased, from 4.0 N/cm² in control subjects in their third decade of life ( n = 10) to 10.4 N/cm² in middle age ( n = 11) to 14.0 N/cm² in the elderly (n = 13). In the presence of a normal diameter.peripheral arterial disease with aortic atherosclerosis had little effect on aortic stiffness, median E_p being 16.0 N/cm². Aneurysmal dilatation was associated with a significant increase in aortic stiffness, median E_p being 31.3 N/cm² ( P < 0.001). For aortas of normal diameter, E_p was at all ages dependent on mean arterial pressure. In patients with aortic aneurysms there was no clear relationship between E_p and mean arterial pressure or aortic diameter. Of the patients studied, 15 underwent aortic rcconstruction; increasing aortic stiffness (log E_p) was associated with a decreased medial elastin content of the aortic biopsy ( r = −0.63, P < 0.02 ). This study demonstrates the marked stiffness or inelasticity of dilated or aneurysmal vessels, part of which is attributable to the loss of elastin.