Geometry guided data averaging enables the interpretation of shear stress related plaque development in human coronary arteries

The average low shear stress (SS) is known to determine predilection sites of atherosclerotic plaques. However, as plaques encroach into the lumen and thereby increase SS, interpretation of patient-specific data obtained at one moment in time regarding the influence of SS in the generation of atherosclerosis is not straightforward. This study aims to compare two methods of data analysis for the aid of data interpretation: (a) point-wise analysis of the raw data, (b) global analysis: to assess the history related natural SS distribution in coronary arteries by averaging the data in the axial vessel direction. Normal to mildly diseased human coronary arteries were investigated applying a combination of 3-D reconstruction technique and computational fluid dynamics (CFD). Point-wise analysis relating local wall thickness to local SS showed in only 4% of the cases an inverse relationship. In contrast, averaging the data in the axial vessel direction, showed in 38% a significant inverse relation between wall thickness and SS, resulting in an average negative slope of -0.70+/-0.46 mm/Pa. These data suggest that using a geometry guided way of data averaging may reveal history related effects of SS, which in part explains localization of atherosclerotic plaques.