Abstract

The localized nature of atherosclerosis has led to extensive study of blood flow patterns and their possible involvement in atherogenesis. Vessel geometry has always been considered a primary factor in determining blood flow patterns. In the coronary arteries, the geometry varies dynamically due to myocardial contraction. The effects of physiologic axial (Moore et al., 1994) and lateral (Delfino et al., 1994) vessel movement on coronary blood flow patterns have been shown to be important in producing oscillations in wall shear stress. Those studies were limited to straight vessels that translated in one direction only. Previous studies of flow in curved tubes with time-varying curvature showed that large quasi-static wall shear rate amplitudes relative to the static case when the curvature change was 50% of the mean curvature (Santamarina et al., 1997). The largest variation in wall shear rate from the minimum curvature to the maximum curvature was 52%, and was found at the mid-wall location (halfway between the inner and outer wall of curvature along the circumference) for the highest mean curvature ratio studied (δ = 0.12). A comparison of the shear rate amplitudes found in a tube whose radius of curvature varies dynamically at 1 Hz to the variations noted in the quasi-static analysis revealed differences of less than 1%. Changes in the mean wall shear rate predicted with the dynamic analysis were less than 7%, relative to the wall shear rate at the static mean radius of curvature. It was concluded that, although the change in curvature creates a relatively large shear rate amplitude, the fact that the curvature varies dynamically at 1 Hz is not important in predicting wall shear rates.

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