Wall shear stress gradient topography in the normal left coronary arterial tree: possible implications for atherogenesis

Objective: Wall shear stress gradient (WSSG) in vitro has shown its importance in atherogenesis, probably as a local modulator of endothelial gene expression. The purpose of this study is to numerically analyse the WSSG distribution over the normal human left coronary artery (LCA) tree. Research design and methods: A three-dimensional computer generated model of the LCA tree, based on an averaged human data set extracted from angiographies, was adopted for finite-element analysis. The LCA tree includes the left main coronary artery (LMCA), the left anterior descending (LAD), the left circumflex artery (LCxA) and their major branches. Results: In proximal LCA tree regions where atherosclerosis frequently occurs, low WSSG appears. At distal segments, the WSSG increases substantially due to increased velocity resulting from increased vessel tapering. Low WSSG occurs at bifurcations in regions opposite the flow dividers, which are anatomic sites predisposed for atherosclerotic development. Conclusions: This computational work determines, probably for the first time, the topography of the WSSG in the normal human LCA tree. Spatial WSSG differentiation indicates that low values of this parameter probably correlate to atherosclerosis localization. However, further studies are needed to clarify the role of WSSG in atherogenesis.