Numerical simulation of coronary blood flow: from idealised to patient-specific studies

© 2021 Bo JiangHaemodynamic indices such as endothelial shear stress (ESS) resulting from disturbances in arterial blood flow are associated with pathological processes underlying atherosclerosis and other complications after stent implantation. Computational fluid dynamics (CFD) allows in vivo estimation of ESS and other flow indices, offering insights into the progression of coronary artery diseases and optimising treatment. Stenting is an effective treatment method to unblock the artery. Unfortunately, stents are not always placed perfectly. Incomplete stent apposition (ISA), defined as a lack of contact between the stent and arterial wall, can lead to complications after stenting, such as late stent thrombosis and restenosis. Simplified 2-dimensional simulations show that ISA leads to recirculation bubbles behind the stent struts, which is one of the leading causes of abnormal ESS. The faster the heart pumps, the quicker blood flow accelerates and decelerates and hence larger flow recirculation bubbles. This undesirable effect, however, can be improved by changing the strut profiles (e.g. from square to circular). As atherosclerotic plaque accumulates, artery cross-sections may change from circular to elliptical. The simulations of the full-scale stent model in elliptical cross-sectional arteries demonstrate high shear rates at ISA regions, which increases the risk of platelet activation. When activated platelets accumulate at low ESS regions, it may indicate a site for thrombosis. The knowledge gained from the analysis in idealised models can be applied to study the haemodynamics inside a patient’s artery. Using high-resolution intravascular imaging such as Optical Coherence Tomography (OCT), a total of 59 cases of coronary arteries with active lesions including plaque rupture and erosion has been analysed. The CFD results showed active lesions with higher ESS compared to those of non-lesions and ESS change between baseline and follow-up cases. Temporal ESS change (baseline vs. follow-ups) showed correlations to plaque erosion, but other factors, such as medications etc., were effective during the time and could affect the lesion condition and should also be taken into consideration