Haemodynamic stress in terminal aneurysms.

Area of Science:

• Biomedical Engineering
• Fluid Dynamics
• Medical Device Modeling

Background:

• Aneurysms pose significant risks, and understanding intra-aneurysmal hemodynamics is crucial for predicting rupture.
• Previous studies often relied on simplified models or computational methods.

Purpose of the Study:

• To quantitatively assess blood flow velocities and patterns within aneurysm models at bifurcations.
• To investigate the influence of aneurysm geometry and vessel branching on intra-aneurysmal flow.
• To estimate wall shear stress in aneurysm models.

Main Methods:

• Utilized non-invasive laser-Doppler velocimetry to measure flow velocities in glass and silastic aneurysm models.
• Modeled aneurysms at arterial bifurcations, varying geometry and outflow conditions.
• Calculated wall shear stress based on measured velocity gradients.

Main Results:

• Aneurysm geometry was the primary determinant of intra-aneurysmal flow patterns.
• Stagnant flow was observed in straight terminal models with balanced bifurcation outflow.
• Turbulent fluctuations and rotatory vortex flow were identified in angled terminal aneurysms.
• Maximum intra-aneurysmal velocities ranged from 50-80% of parent vessel velocity.
• Elasticity damped pulse waves but did not alter global flow rates.
• Estimated wall shear stresses were approximately 50 dynes/cm² (5 Pa).

Conclusions:

• Aneurysm geometry significantly influences hemodynamic patterns, impacting flow stagnation, turbulence, and vortex formation.
• Laser-Doppler velocimetry provides valuable quantitative data for aneurysm flow studies.
• Estimated shear stresses in models align with those found in human aneurysms, suggesting model validity.