ABSTRACT
Objective To conduct a comprehensive study on pulsatile blood flow in arteries by proposing a convenient theoretical research system for hemodynamics. Methods Based on Womersley algorithm for fully developed pulsatile flow, numerical algorithm was introduced to establish the solving and analytical system of hemodynamics based on flow rate in arteries during one cardiac cycle. The flow rate of carotid artery in pig was measured under three blood flow states: the ideal state with a sinusoidal inflow waveform, the normal physiological state and the enhanced external counterpulsation (EECP) state for comprehensive hemodynamic research. Results Important hemodynamic parameters such as the axial speed vector, the wall shear stress (WSS), and the oscillatory shear index (OSI) during one cardiac cycle under the mentioned three flow states were solved respectively. The waveform of flow rate had a certain effect on WSS distributions and OSI level; the EECP performance obviously resulted in a significant increase in the level of WSS (WSS peak in particular) and OSI. Conclusions The solving system developed in this paper can be used for hemodynamics study conveniently and effectively. One of the most important hemodynamic mechanisms that lead to EECP’s good clinical effect may lie in its promotion to WSS level under physiological state, but the effect of OSI on endothelial function of the artery might much smaller than WSS itself; therefore, OSI may not be an ideal hemodynamic index for predicting the lesion of atherosclerosis.
ABSTRACT
The objectives of this investigation were to evaluate biomechanical factors in the atherosclerotic process using human in vivo hemodynamic parameters and computed numerical simulation qualitatively and quantitatively. The three-dimensional spatial patterns of steady and pulsatile flows in the left coronary artery were simulated, using a finite volume method. Coronary angiogram and Doppler ultrasound measurement of the proximal left coronary flow velocity were performed in humans. Inlet wave velocity distribution obtained from in vivo data of the intravascular Doppler study allowed for input of in vitro numerical simulation. Hemodynamic variables, such as flow velocity, pressure and shear stress of the left anterior descending coronary bifurcation site were calculated. We found that there were spatial fluctuation of flow-velocity and recirculation areas at the curved outer wall of the left anterior descending coronary artery, which were due to the differences of flow-velocity and shear stress, especially during the declaration phase of pulsatile flow. This study suggests that rheologic properties may be a part of the atherogenic process in the coronary bifurcated and curved areas.