Age-related distensibility and histology of the ascending aorta in elderly patients with acute aortic dissection.

Degradation and fragmentation of elastic fibers in the media dilate the aortic wall excessively in patients with acute Stanford type A aortic dissection (AD). Such dilatation occurs not via aortic stiffening, which is diagnosed using imaging under physiological loading, but due to the abovementioned intrinsic changes in elastic fibers, which can be detected at the low-stress region of the stress-strain relationship. Our objective is to determine an age-related correlation between distensibility and histology. We conducted uniaxial stretching tests and a histological evaluation of the ascending aorta (AA) using AD samples obtained at surgery from 9 elderly patients (aged 52-85 yr), with no heritable connective tissue disorders, and control (CN) samples from 10 subjects at autopsy (aged 56-86 yr). We compared the distensibility, or an increase in strain for the uniaxial tensile stress of 0-50 kPa, between the AD and CN groups, and correlated it with age and histology. Distensibility was significantly greater in the AD than that in the CN group (p=0.030), but elastin content was significantly lower (p=0.0025). The positive correlation between distensibility and elastin content in CN samples suggests that the distensibility increases with elastic fiber histological abnormalities. The age-matched collagen content decreased with the age of the patients, and did not differ between the AD and CN groups. The age-matched distensibility in the AD and CN groups decreased and became closer with aging. Such intrinsic properties should be considered during imaging to assess distensibility in patients with AD.