Geometrical effects in the hemodynamics of stenotic and non‐stenotic left coronary arteries—numerical and in vitro approaches

Abstract

Atherosclerosis is a common cardiovascular disease found in the left coronary artery (LCA), closely linked to local hemodynamic, which, in turn, is highly influenced by the artery geometry. The hemodynamics in the LCA was studied in a patient‐specific geometry without any sign of disease using both numerical and in vitro approaches. The influence of non‐planarity was evaluated through two models of the patient‐specific LCA that deviate from its original geometry in their planarity. Afterwards, in all models, irregular stenoses were created by a procedure in which the stenosis emerges by diffusion from low wall shear stress (WSS) areas. The WSS distribution and flow patterns were evaluated in all the models. The experimental results validate the numerical code developed to study the blood flow assuming a steady state Newtonian behavior. Comparison between the planar and non‐planar idealized LCA revealed no significant differences in low WSS regions forming stenotic regions with identical shape. In the patient‐specific LCA, the low WSS regions are not consistent with the idealized models leading to a different stenosis shape. The results revealed that the non‐planarity has an unquestionable effect in helicity. It was also demonstrated that eccentricity of the vessels cross section and the position of the apex in relation to the axis of the parent branch contribute to the flow patterns observed. Numerical results of pulsatile blood flow assuming a non‐Newtonian behavior, in the patient‐specific LCA, reinforce the non‐planarity effect in local hemodynamics.

Modeling Blood Pulsatile Turbulent Flow in Stenotic Coronary Arteries

“…• , which are similar to those used in previous studies [4], [14], [43]. For the pulsatile non-Newtonian blood flow simulations, the selected viscosity model was the Carreau model, since it is commonly used by several authors [14], [15], [44] to simulate the shear-thinning blood behavior and it is considered the most suitable to perform these simulations. In the Carreau model, the viscosity (μ) is given by Equation 6:…”

“…In addition, to ensure that the present study reflects the realistic simulation of in vivo conditions, a physiological inlet velocity profile adopted by Doutel et al [14], as seen in Fig. 2, was applied.…”

“…Nevertheless, over the past few decades, the investigation into hemodynamics has grown exponentially and researchers have taking different assumptions, because of the blood flow complexity. Some authors assumed the blood flow in coronary arteries to be laminar [4], [14]- [19] and behave as Newtonian fluid [17], [20]- [23]; others studied turbulence transition [2], [3], [24]- [26] and non-Newtonian effects [2], [5], [15], [21], [27]. In fact, in large vessels, blood can be considered as a homogeneous fluid with constant viscosity.…”

“…Another important factor to the local hemodynamics is the shape of the stenosis. Some researchers apply idealized stenosis shapes [23], [27], [28], while others make use of artery stenotic models based on medical images [14], [19], [29]. In a recent study, Wong et al [30] studied both idealized and patient-specific coronary arteries and showed how the curvilinearity and narrowing complications affect the computed WSS, associated with the risk of atherosclerosis.…”

Coronary artery plaque growth: A two‐way coupled shear stress–driven model

“…In the context of our model, it may be hypothesized that the parameter k in Equation (2) changes as the stenosis grows, therefore allowing for a different sensitivity to WSS at later growth stages. A diffusion‐based stenosis growth model based on WSS was recently proposed . However, this model does not update the WSS values as the stenosis grows.…”