Research/Cardiovascular Biomechanics/02 / 03

Abdominal Aortic Aneurysm Hemodynamics and Mechanics

Abdominal aortic aneurysm involves substantial changes in both blood-flow dynamics and the load-bearing behavior of the aortic wall. Our research develops computational models to examine pulsatile and transitional flow, wall deformation, intraluminal thrombus, and regional mechanical loading. We combine patient-specific computational fluid dynamics, fluid–structure interaction, and stress-to-strength analysis to investigate how vascular geometry, material properties, and physiological conditions influence biomechanical indicators associated with rupture.

One aneurysm, two fields — the flow inside the sac on one half, wall and thrombus loading on the other — A patient-specific abdominal aortic aneurysm seen from two directions, with the computed surface field mapped over the aneurysmal segment and the adjoining aorta and iliac arteries left uncoloured.

Patient-Specific Aneurysmal Hemodynamics

We perform pulsatile CFD simulations in patient-specific aneurysm geometries to characterize disturbed and transitional flow within the aneurysm sac. Phase-averaged analysis over multiple cardiac cycles is used to distinguish persistent flow structures from instantaneous fluctuations, and to establish how many cycles an average has to cover before it can be relied on.

Patient-specific lumen geometry, velocity at peak systole and through deceleration, the instantaneous field beside the phase-averaged one, and convergence against the number of cycles averaged — Normal velocity magnitude with in-plane vectors at three cross-sections of the aneurysm sac, evaluated at five instants of the cardiac cycle marked on the inlet flow waveform.

Fluid–Structure Interaction and Wall Mechanics

We couple hemodynamic and structural analyses to quantify aneurysm-wall deformation and regional mechanical stress under pulsatile loading. The models account for variations in aneurysm geometry, wall properties, intraluminal thrombus, and blood pressure. Pressure obtained from the flow solution is applied to a structural model in which the wall and the thrombus carry separate material descriptions, so that the response of each can be read on its own.

AAA geometry → pulsatile blood-flow simulation → pressure loading → wall and thrombus mechanics → stress and deformation — Pulsatile inflow with Windkessel outlet conditions produces the pressure field applied to the aneurysm wall and intraluminal thrombus, both modelled as hyperelastic materials.

Stress-to-Strength Assessment of Rupture Susceptibility

We evaluate regional rupture susceptibility through dimensionless stress-to-strength metrics that compare mechanical loading with the estimated strength of the aneurysm wall and intraluminal thrombus. The framework examines the combined effects of thrombus morphology, wall thickness, blood pressure, tissue stiffness, and aneurysm geometry. This work is ongoing: the metric is being evaluated as a biomechanical indicator across idealized aneurysm models with variations in morphology, material properties, and physiological loading, and the study listed below is under revision.

The same aneurysm mapped twice — equivalent wall stress on the left, stress-to-strength ratio on the right — with the regions each measure emphasises marked — Systolic von Mises stress, maximum principal strain and stress-to-strength ratio over the same aneurysm wall. Each measure emphasises a different region: the neck, the lateral wall, and the anterior and posterior surfaces.

Selected work

Under review

Efficient estimation of vessel wall stress under pulsatile hemodynamics via a snapshot-based coupling framework

Computer Methods and Programs in Biomedicine

Under revision

Stress-to-strength ratio for assessing rupture risk in abdominal aortic aneurysms: a computational study

Computers in Biology and Medicine

2023

Convergence of phase-averaged, transitional flow in an abdominal aortic aneurysmal model

Journal of Biomechanical Engineering 145(11):111007

Cardiovascular Biomechanics3 topics in this area

Coronary Hemodynamics and Ischemic Heart DiseaseAbdominal Aortic Aneurysm Hemodynamics and MechanicsVenous Hemodynamics and Intermittent Pneumatic Compression