Determination of Unsteady LDL Transport through Patient-specific Multi-layer Left Coronary Artery

Aims: Aim of this study is the transport and distribution of Low Density Lipoprotein (LDL) within patient-specific multi-layer arterial wall model under unsteady flow using computational fluid dynamic analysis.

Study Objectives: The performed analysis takes into account the specific geometry (properly modified with a constant wall intima layer thickness whereas the media layer has variable wall thickness derived by the IVUS Angio tool),the interfacial coupling (lumen-media) achievement by the Kedem-Katchalsky equation, the volume flux, the pressure drop across the endothelium and the physical values of the multi-layer arterial materials in order to study the LDL transport and distribution within patient-specific multi-layer arterial wall.

Methods: A Left Coronary Artery (LCA) patient-specific model was incorporated. Both flow-mass transport equations in lumen as well as flow-mass transport equations within the patient-specific multi-layer arterial wall are numerically analyzed.

Results: The lumen-side LDL concentration preferably occurs at the concave geometry parts denoting concentration polarization. The Average Wall Shear Stress (AWSS) is not the only factor that can determine the lumen-side LDL concentration. Increased time-averaged luminal concentration develops mainly in the proximal rather than in distal segment flow parts. The LDL concentration at the endothelium/intima interface is substantially lower than its value at lumen/endothelium interface, (almost 90 times).The concentration drop across the intima layer is negligible, whereas the concentration reduction across the Internal Elastic Layer (IEL) is remarkable. LDL concentration values at the IEL/media interface are one order of magnitude smaller to ones occurring at the intima layer.

Conclusions: The transportation of LDL through the multi-layer arterial wall is affected by the flow pattern itself, the arterial wall thickness and the physical values of the layers.