Mechanical properties of the aneurysmal aorta

Area of Science:

• Cardiovascular physiology
• Biomedical engineering
• Vascular biology

Background:

• Aortic stiffness, a measure of the aorta's mechanical properties, increases with age.
• Aortic aneurysms and peripheral arterial disease are associated with vascular changes.
• Non-invasive assessment of aortic mechanical properties is crucial for understanding vascular health.

Purpose of the Study:

• To investigate the mechanical properties, specifically aortic stiffness, in patients with aortic aneurysms and peripheral arterial disease.
• To assess the relationship between aortic stiffness, age, arterial pressure, and aortic diameter.
• To correlate aortic stiffness with elastin content in aortic tissue.

Main Methods:

• Utilized M-mode ultrasonography to measure aortic distensibility and calculate the pressure-strain elastic modulus (Ep), a marker of aortic stiffness.
• Recruited control subjects across different age groups, patients with peripheral arterial disease, and patients with aortic aneurysms.
• Analyzed aortic biopsy samples for medial elastin content in a subset of patients.

Main Results:

• Aortic stiffness (Ep) increased significantly with age, from 4.0 N/cm² in young adults to 14.0 N/cm² in the elderly.
• Peripheral arterial disease with atherosclerosis showed minimal impact on aortic stiffness in normal-diameter aortas (median Ep 16.0 N/cm²).
• Aneurysmal dilatation was associated with a substantial increase in aortic stiffness (median Ep 31.3 N/cm², P < 0.001) and a decrease in medial elastin content (r = -0.63, P < 0.02).

Conclusions:

• Dilated or aneurysmal aortas exhibit significantly increased stiffness, a condition partly due to elastin loss.
• Aortic stiffness is age-dependent and influenced by mean arterial pressure in normal aortas.
• Reduced elastin content is a key factor contributing to the increased aortic stiffness observed in aneurysmal disease.