Atherosclerosis is an arterial disease that forms plaque, occludes the lumen and is stratified with stenosis severity. The proximal shape of the plaque disrupts hemodynamics and causes disease progression. The present study aims to numerically address the hemodynamics in distinct plaque shapes with varying severity and proximal slope.
Fluid flow simulations in stenosis are performed using the open-source software OpenFOAM. The inlet pulsatile nature is addressed with physiological rest and exercise conditions of Womersley profiles. The axisymmetric plaque surfaces are generated with varying proximal slopes and are termed as high, medium and low-slope stenoses. Distinct severities, including mild (56%), moderate (75%) and severe (89%) are integrated into respective stenosis shapes. Further, three-dimensional studies are performed on severe stenosis at rest condition.
The results show that during rest condition, high slope stenosis exhibits a substantial rise in time-averaged wall shear stress (TAWSS) and records a peak value, irrespective of severity. The exercise condition imposed higher wall shear stress gradients in high-slope stenoses. It mitigates plaque progression on the distal region of low-slope stenosis, quantified with low oscillatory shear index (OSI) values. Further, the shear thinning behavior of blood is analyzed with a power-law model on severe stenosis. This effect shows a notable variation in TAWSS on high slope stenosis and reduced in low slope when compared with the Newtonian model.
In spite of the same severity (89%), stenotic walls of high and medium slope shapes are prone to high disease progression. The phenomenon is quantified with high OSI (> 0.4) on stenosis walls, which is over 20% of the total surface area in high and medium slope shape and limited to 4% in low slope shape. Overall, this study proposes the importance of the proximal slope supplement for stenosis severity that influences hemodynamics.
