A hemodynamic model with a seepage condition and fluid-structure interactions for blood flow in arteries with symmetric stenosis

Numerical investigation of arterial stenosis location affecting hemodynamics considering microcirculation function

BACKGROUND

In recent years, arterial stenosis has become one of the serious diseases threatening people's life and health.

OBJECTIVE

The main purpose of the present study is to examine the changes of hemodynamic parameters in different stenosis locations of arteries.

METHODS

An arterial stenosis model with fluid-structure interaction and microcirculation as the outlet boundary of seepage is adopted in this paper. Considering the interaction between blood and arterial wall, a numerical simulation is carried out using the finite element method.

RESULTS

The results show that hemodynamic parameters are sensitive to the change of stenosis location. The closer to the microcirculation zone the stenosis location, the lower the blood flow velocity, pressure and the wall shear stress. In addition, the velocity trend is transformed from the gradual increase to decrease with the increasing distance away from the inlet when the stenosis location moves to the microcirculation zone.

CONCLUSION

This work proves that the stenosis location has a great influence on hemodynamics based on microcirculation function. Microcirculation is an important factor that cannot be ignored in the numerical simulation of arterial hemodynamics. The numerical results could provide the potential of clinical preconditions for disease diagnosis and treatment.

Effect of stenosis and dilatation on the hemodynamic parameters associated with left coronary artery

BACKGROUND AND OBJECTIVE

The main objective of the work is to examine the curvature effects of stenosis/dilatation region pertaining to left coronary artery. The hemodymamic features during the cardiac cycle is thoroughly examined.

METHODS

A numerical fluid structure interaction model incorporating multi- layered elastic artery wall, non-Newtonian blood viscosity and pulsating boundary conditions is developed. The composite arterial wall consists of a thin layer tunica intima, atheroma and a thick wall. Higher stiffness of atheroma is captured by using higher Young's modulus. The CFD and FSI models are validated with available experimental and analytical data. Computations are done with five different non-Newtonian models and arterial wall with various elasticity levels. The local and time averaged WSS, velocity contours downstream of stenosis, wall pressure and pressure drop during various phases of cardiac cycle are provided in detail.

RESULTS

The influence of non-Newtonian effects of blood viscosity is found to be significant especially at stenosis regions. The flexible wall caused wall deformation and the associated flow and pressure wave propagation affecting WSS and pressure drop compared to the rigid wall. Flow recirculation is noticed at stenosis downstream locations and its strength increases with increased severity of the stenosis. A stenosis is characterised by a sudden drop in wall pressure and a slower two stage recovery during peak velocity periods of the cardiac cycle.

CONCLUSIONS

The pressure drop, local WSS at stenosis centre, and radial velocity increase are significantly higher for stenosis cases and the effect is severe during peak diastole. The variation in hemodynamic parameters is found to be less significant for dilatation. Significantly lower WSS is noticed for the recirculation regions downstream of stenosis which can enhance the tendency for monocytes to attach to the endothelium. The radius of curvature of the stenosis is found to be the most sensitive parameter affecting the hemodynamic characteristics rather than the detailed geometry of the stenosis. The main effect of variation of artery wall stiffness is noted at recirculation regions present downstream of stenosis. The results from the study may be useful for predicting wall shear stress signatures associated with stenosis/dilatation changes and the management of specific cases.

Influence of microcirculation load on FFR in coronary artery stenosis model

BACKGROUND

The coronary artery hemodynamics are impacted by both the macrocirculation and microcirculation. Whether microcirculation load impact the functional assessment of a coronary artery stenosis is unknown. The purpose of this study is to investigate the effect of porous media of the microcirculation on fractional flow reserve (FFR) in stenotic coronary artery model.

METHODS

A three dimensional computational simulation of blood flow in coronary artery symmetric stenotic model was constructed. The computational fluid dynamics (CFD) model was developed with Fluent 16.0. Blood was modeled as a shear thinning, non-Newtonian fluid with the Carreau model. A seepage outlet boundary condition and transient inlet conditions were imposed on the model. Coronary physiologica diagnostic parameter such as pressure, velocity and fractional flow reserve (FFR) were investigated in the model and compared with the microcirculation load (ML) and constant pressure load (PL) condition.

RESULTS

The present study showed the different hemodynamics in the ML and PL condition. The pre-stenotic pressure is almost the same in the two model. However the pressure in the post-stenotic artery domain is much lower in the PL model. The fluctuation range of the pressures is much higher in ML model than those in PL model. The velocity flow was more steady and lower in the ML model. For the PL model with 75% artery stenosis the FFR was 0.776, while for the ML model with the same stenosis, the FFR was 0.813.

CONCLUSIONS

This study provides evidence that FFR increased in the presentation of ML condition. There is a strong hemodynamic effect of microcirculation on coronary artery stenosis.