Patient Specific Modelling of Blood Flow in Coronary ‎Artery

The performance of the heart is considerably affected by the blocks formed because of the deposition of ‎plaque inside the coronary artery. The blocks (stenosis) either in coronary artery or elsewhere force the ‎heart to work harder for pumping the oxygenated blood to the heart muscles and blood vessels. This ‎study analyses the flow through the stenosed coronary arteries via numerical modelling by using ANSYS ‎FLUENT software. Three real cases with different asymmetric stenosis levels (i.e., block level ۳۳%, ۶۶% ‎& ۸۵%) are analysed by considering blood as a non-Newtonian fluid, and blood flow as pulsatile in ‎nature. As the flow regime falls in transition to turbulent region, the transition Shear Stress Transport ‎‎(SST) k-ω turbulence model is used to take care of the changeover stage from laminar to turbulent flow ‎and vice versa. The results show large variation both in Wall Shear Stress (WSS) and pressure drop near ‎the stenosis. Pressure drop becomes more significant at severe degrees of stenosis (۶۶% and ۸۵%) ‎compared to the mild case (۳۳%). The study throws light on the critical distribution of shear stress and ‎pressure drop along the artery wall, which are considered as indicators of the commencement of heart ‎disease and further growth of stenosis. An indicator, viz., Fractional Flow Reserve (FFR), which relates ‎the percentage of stenosis to the pressure variations, can be used as an index to diagnose the severity of ‎stenosis. All the three cases with different stenotic levels were analysed under hyperaemic conditions and ‎found that even ۴۵% stenosis case can go near to critical at hyperaemic flow conditions. The effect of ‎severity due to vessel constriction can be estimated by comparing the simulated pressure drop and WSS ‎before and after the stenosis, with the ones for a healthy artery. The present study developed a ‎methodology to calculate FFR value for unknown percentage of stenosis based on the simulated results ‎obtained from ۳۳%, ۶۶% and ۸۵% stenosis. Thus, criticality of a patient with certain percentage stenosis ‎can also be evaluated. This simulation technique can be recommended as a non-invasive diagnostic tool ‎for the early detection of atherosclerosis‎‎.

Keywords:

Coronary artery , Flow rate , Pressure relation , Stenosis , Fractional flow reserve.‎ , wall shear stress