Hemodynamic stress in terminal saccular aneurysms: a laser-Doppler study

Area of Science:

• Biomedical Engineering
• Fluid Dynamics
• Medical Physics

Background:

• Aneurysms pose significant health risks, and understanding intra-aneurysmal hemodynamics is critical for predicting rupture.
• Previous studies have explored aneurysm mechanics, but detailed quantitative analysis of flow conditions and stresses at bifurcations is ongoing.

Purpose of the Study:

• To quantitatively determine flow conditions and related stresses in glass and silastic model aneurysms at bifurcations.
• To investigate the influence of aneurysm geometry and vessel branching asymmetry on intra-aneurysmal flow patterns.
• To estimate wall shear stresses in aneurysms and compare them to physiological values.

Main Methods:

• Utilized laser-Doppler anemometry to measure flow velocities in glass and silastic model aneurysms.
• Simulated different bifurcation outflow conditions (balanced and asymmetrical).
• Estimated wall shear stresses based on measured velocity gradients near the walls.

Main Results:

• Unstable flow velocities were observed in straight models with balanced bifurcation outflow.
• Asymmetrical outflow induced rotatory intra-aneurysmal circulation.
• Angled aneurysms exhibited vortex flow, with velocities ranging from 50%-80% of afferent vessel velocity.
• Elastic models showed damped intra-aneurysmal pulse waves.
• Estimated maximum wall shear stresses were approximately 50 dyne/cm², comparable to cerebral artery bifurcations.

Conclusions:

• Aneurysm geometry is the primary determinant of intra-aneurysmal flow patterns.
• Intra-aneurysmal flow dynamics and wall shear stress are influenced by parent vessel geometry and bifurcation asymmetry.
• Findings provide insights into the biomechanics of aneurysm formation and rupture risk.