Factors Influencing Blood Flow Patterns in the Human Right Coronary Artery

Abstract

Evidence suggests that atherogenesis is linked to local hemodynamic factors such as wall shear stress. We investigated the velocity and wall shear stress patterns within a human right coronary artery (RCA), an important site of atherosclerotic lesion development. Emphasis was placed on evaluating the effect of flow waveform and inlet flow velocity profile on the hemodynamics in the proximal, medial, and distal arterial regions. Using the finite-element method, velocity and wall shear stress patterns in a rigid, anatomically realistic model of a human RCA were computed. Steady flow simulations (ReD=500) were performed with three different inlet velocity profiles; pulsatile flow simulations utilized two different flow waveforms (both with Womersley parameter=1.82, mean ReD=233), as well as two of the three inlet profiles. Velocity profiles showed Dean-like secondary flow features that were remarkably sensitive to the local curvature of the RCA model. Particularly noteworthy was the "rotation" of these Dean-like profiles, which produced large local variations in wall shear stress along the sidewalls of the RCA model. Changes in the inlet velocity profiles did not produce significant changes in the arterial velocity and wall shear stress patterns. Pulsatile flow simulations exhibited remarkably similar cycle-average wall shear stress distributions regardless of waveform and inlet velocity profile. The oscillatory shear index was very small and was attributed to flow reversal in the waveform, rather than separation. Cumulatively, these results illustrate that geometric effects (particularly local three-dimensional curvature) dominate RCA hemodynamics, implying that studies attempting to link hemodynamics with atherogenesis should replicate the patient-specific RCA geometry.

Non-Newtonian blood flow in human right coronary arteries: steady state simulations

“…In most cases, regions of low wall shear stress predominate at the proximal end of the artery with further areas of low wall shear stress decreasing in size and frequency as the artery is traversed. This is in agreement with results presented by Kirpalani et al (Kirpalani et al, 1999) and Myers et al (Myers et al, 2001). The reason for this is probably related to the fact that most of the arteries taper towards the distal end.…”

“…The wall shear stress patterns differ most significantly when the flow is either slow or reversing, which is perhaps not surprising. This is in agreement with experimental observations (Asakura and Karino, 1990) as well as previous simulations which suggest that cycle averaged wall shear stress patterns are in good agreement with steady flow patters (Myers et al, 2001;van de Vosse et al, 2001;Feldman et al, 2002). Simulations presented here suggest that this is a reasonable approximation for about 70% of the cardiac cycle, ie from t = 0.30 to t = 1.00, ignoring the slight bumps around t = 0.43 and t = 0.63.…”

“…Experimental and numerical investigation of these relationships has been the subject of recent reviews (Caro, 2001;Liepsch, 2002). Much of the early numerical modelling was focused on the carotid artery bifurcation (Perktold and Resch, 1990;Perktold et al, 1991b;Perktold et al, 1991a), but, recently, this focus has shifted to the right coronary artery, both in terms of simulation (Krams et al, 1997;Kirpalani et al, 1999;van Langenhove et al, 2000;Myers et al, 2001;Wentzel et al, 2003;Zeng et al, 2003) and experimentally (Krams et al, 1997;Ojha et al, 2001;Feldman et al, 2002;Zhu et al, 2003).…”

Magnetic resonance imaging-based computational modelling of blood flow and nanomedicine deposition in patients with peripheral arterial disease

“…4 in the baseline case for example). It was further contended that both these haemodynamic metrics are affected more by variation in three-dimensional vessel geometry (geometric factors such as curvature of the vessel) among patients [66][67][68], which is the main objective of this work and a planned future study. In addition, using the subject's own flow waveform over a non-specific (generalized) waveform leads to more accurate results [58].…”

Reconstruction of shape and its effect on flow in arterial conduits

“…Ascribing greater precedence to errors in geometry than errors in specifying the inflow conditions appears to be justified for initial work such as this. For example, the study of flow in a human right coronary artery of Meyers et al [16] found the inflow conditions to be of secondary importance to the geometry. As the flow must respond both to continuous changes in geometry, and to viscous diffusion from the wall, inflow effects are bound to diminish with distance so that finding is not unexpected.…”