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
Objective To explore the effect of long-term enhanced external counterpulsation(EECP)on endothelium-dependent and endothelium-independent vasorelaxation in the carotid arteries of atherosclerotic piss. Method Totally 18 20-day-old male infant pigs were randomly divided into 3 groups according to feeding given: the normal[control group(n=6),the hypercholesterolemic control group(n=6)and the hypereholesterolemic +EECP group(n=6).Porcine model of hypercholesterolemia was made by feeding high-cholesterol diet.After EECP for 36 hours in the hypercholesterolemic+EECP group(n=6),carotid arterial rings were harvested from all animals and their vaso-relaxation response to different dose of Acetylchofine(Ach)and Sodium nitroprusside (SNP)were detected,respectively.Results As the dose of Ach varying between 10-8 mol/L and 10-5mol/L, endothelium-dependent vasorelaxation ratio of hypereholesterolemic piss with or without EECP treatment was significantly lower than that of the normal control group(P＜0.05),however,endothehum-dependent vasorelax- ation ratio in pigs with EECP treatment was obviously higher compared with hypereholesterolemic pigs without EECP treatment(P＜0.05)as the Ach ranged from 10-7 mol/L to 10-5mol/L.Similarly,as the concentration of SNP ranged fiun 10-8 mol/L to 10-5 mol/L.endothelium-independent vasorelaxafion ratio of both the hypercholesterolemic control group and the hypercholesterolemic+EECP group were significantly lower than that of the normal control group(P＜0.05),and end othelium-independent vasorelaxation ratio of the hypercholesterolemic+EECP group was significantly higher than that of the hypercholesterolemic control group (P＜0.05).Condusions Long-term EECP improves the impaired endothelium-dependent and endothelium independent vasorelaxalion function resulting from atherosclerosis.