Abdominal aortic aneurysm classification based on dynamic intraluminal thrombus analysis during cardiac cycle

Area of Science:

• Biomedical Engineering
• Cardiovascular Research
• Medical Imaging Analysis

Background:

• Abdominal aortic aneurysm (AAA) rupture is a life-threatening complication with high mortality.
• Current risk assessment for AAA rupture relies primarily on aneurysm size (maximum diameter).
• The role of intraluminal thrombus (ILT) in AAA rupture dynamics remains incompletely understood.

Purpose of the Study:

• To investigate the motion of intraluminal thrombus (ILT) within abdominal aortic aneurysms (AAAs) throughout the cardiac cycle.
• To hypothesize that thrombus response to cyclic blood pressure offers insights into AAA rupture propensity.
• To develop a novel classification system for AAAs based on ILT behavior.

Main Methods:

• Utilized multiphase computed tomographic (CT) images from 14 patients with AAAs.
• Segmented aortic wall and lumen geometries, and determined thrombus volume across ten cardiac cycle phases.
• Correlated geometric changes with ex vivo mechanical properties, growth data, and clinical outcomes where available.

Main Results:

• Classified AAAs into four types based on relative changes in wall, lumen, and thrombus volumes during the cardiac cycle.
• Type IV AAAs exhibited lumen expansion exceeding wall expansion, with minimal thrombus deformation, suggesting over-pressurization and potential for channel formation.
• Identified associations between specific types and potential risks: Type I (stiff wall, dissection risk), Type IV (permeable channels, rupture risk).

Conclusions:

• Dynamic analysis of ILT motion during the cardiac cycle provides a new method for assessing AAA rupture risk.
• The proposed four-type classification system offers improved clinical risk stratification beyond aneurysm diameter alone.
• Understanding thrombus behavior, particularly in Type IV AAAs, can predict the likelihood of channel development and potential rupture.