Biomechanical changes in abdominal aortic aneurysms involve a prolonged post-failure phase.

Area of Science:

• Biomedical Engineering
• Cardiovascular Research
• Materials Science of Tissues

Background:

• Previous research on abdominal aortic aneurysm (AAA) tensile strength overlooked the post-failure phase of rupture propagation.
• Understanding changes in the infra-renal aortic wall's three layers after failure is crucial for AAA progression insights.

Purpose of the Study:

• To investigate aneurysm-induced alterations in the post-failure mechanical properties of the intact infra-renal aortic wall.
• To examine the distinct contributions of the intima, media, and adventitia to AAA wall mechanics.

Main Methods:

• Ex vivo tensile testing was performed on aortic tissues from 27 abdominal aortic aneurysm (AAA) patients and 27 non-aneurysmal aorta (NAA) controls.
• Analysis focused on comparing failure stress, failure stretch, pre-failure stretches, and post-failure stretches across the aortic wall layers.

Main Results:

• AAA intact wall circumferential failure stress and intimal failure stress (circumferential and longitudinal) were significantly lower than in NAAs.
• While failure stretch remained unchanged, pre-failure stretches of the intact wall and media (circumferential) were higher in AAAs.
• Post-failure stretches of the intact wall, media (both directions), and adventitia (circumferential) were significantly elevated in AAAs.

Conclusions:

• Abdominal aortic aneurysms exhibit earlier damage onset and reduced overall wall strength.
• The medial and adventitial layers play a significant role in determining AAA intact-wall properties.
• Increased post-failure stretch in the medial and adventitial layers may delay outward rupture progression, maintaining aortic integrity.