Pulsatile flow

About: Pulsatile flow is a research topic. Over the lifetime, 6278 publications have been published within this topic receiving 149638 citations.

Finite element modelling of pulsatile blood flow in idealized model of human aortic arch: study of hypotension and hypertension.

Abstract: A three-dimensional computer model of human aortic arch with three branches is reproduced to study the pulsatile blood flow with Finite Element Method. In specific, the focus is on variation of wall shear stress, which plays an important role in the localization and development of atherosclerotic plaques. Pulsatile pressure pulse is used as boundary condition to avoid flow entry development, and the aorta walls are considered rigid. The aorta model along with boundary conditions is altered to study the effect of hypotension and hypertension. The results illustrated low and fluctuating shear stress at outer and inner wall of aortic arch, proximal wall of branches, and entry region. Despite the simplification of aorta model, rigid walls and other assumptions results displayed that hypertension causes lowered local wall shear stresses. It is the sign of an increased risk of atherosclerosis. The assessment of hemodynamics shows that under the flow regimes of hypotension and hypertension, the risk of atherosclerosis localization in human aorta may increase.

Importance of pulsatility in hypertensive carotid artery growth and remodeling.

Abstract: Arteries experience marked variations in blood pressure and flow during the cardiac cycle that can intensify during exercise, in disease, or with aging. Diverse observations increasingly suggest the importance of such pulsatility in arterial homeostasis and adaptations. We used a transverse aortic arch banding model to quantify chronic effects of increased pulsatile pressure and flow on wall morphology, composition, and biaxial mechanical properties in paired mouse arteries: the highly pulsatile right common carotid artery proximal to the band (RCCA-B) and the nearly normal left common carotid artery distal to the band (LCCA-B). Increased pulsatile mechanical stimuli in RCCA-B increased wall thickness compared with LCCA-B, which correlated more strongly with pulse (r* = 0.632; P < 0.01) than mean (r* = 0.020; P = 0.47) or systolic (r* = 0.466; P < 0.05) pressure. Similarly, inner diameter at mean pressure increased in RCCA-B and correlated slightly more strongly with a normalized index of blood velocity pulsatility (r* = 0.915; P < <0.001) than mean flow (r* = 0.834; P < 0.001). Increased wall thickness and luminal diameter in RCCA-B resulted from significant increases in cell number per cross-sectional area (P < 0.001) and collagen-to-elastin ratio (P < 0.05) as well as a moderate (1.7-fold) increase in glycosaminoglycan content, which appears to have contributed to the significant decrease (P < 0.001) in the in-vivo axial stretch in RCCA-B compared with LCCA-B. Changes in RCCA-B also associated with a signficant increase in monocyte chemoattractant protein-1 (P < 0.05) whereas LCCA-B did not. Pulsatile pressure and flow are thus important stimuli in the observed three-dimensional arterial adaptations, and there is a need for increased attention to the roles of both axial wall stress and adventitial remodeling.

Alkaline phosphatase in osteoblasts is down-regulated by pulsatile fluid flow

Abstract: It is our hypothesis that interstitial fluid flow plays a role in the bone remodeling response to mechanical loading The fluid flow-induced expression of three proteins (collagen, osteopontin, and alkaline phosphatase) involved in bone remodeling was investigated Rat calvarial osteoblasts subjected to pulsatile fluid flow at an average shear stress of 5 dyne/cm2 showed decreased alkaline phosphatase (AP) mRNA expression after only 1 hour of flow After 3 hours of flow, AP mRNA levels had decreased to 30% of stationary control levels and remained at this level for an additional 5 hours of flow Steady flow (4 dyne/cm2 fluid shear stress), in contrast, resulted in a delayed and less dramatic decrease in AP mRNA expression to 63% of control levels after 8 hours of flow The reduced AP mRNA expression under pulsatile flow conditions was followed by reduced AP enzyme activity after 24 hours No changes in collagen or osteopontin mRNA expression were detected over 8 hours of pulsatile flow This is the first time fluid flow has been shown to affect gene expression in osteoblasts

Hypothalamic and extrahypothalamic mediation of pulsatile discharges of luteinizing hormone in the ovariectomized rat

Abstract: Various hypothalamic lesions were placed in long term ovariectomized rats, and their effects on pulsatile discharges of LH were noted in order to determine which neural regions are involved in the control of this mode of LH secretion. Complete hypothalamic deafferentiation did not affect pulsatile patterns of LH secretion unless the anterior portion of the cut also lesioned the anterior portion of the arcuate nuclei, in which case pulsatile LH discharges were completely blocked. Pulsatile LH secretion was not blocked by bilateral electrolytic lesions placed in ventromedial, paraventricular, or suprachiasmatic nuclei or anterior or posterior portions of the arcuate nuclei, although the nuclei were not completely destroyed by the lesions. When bilateral electrolytic lesions of the anterior portions of the arcuate nuclei were combined with anterior hypothalamic deafferentation, however, pulsatile discharges of LH were completely blocked. These results suggest that two pathways can stimulate the pulsatile mode of LH secretion independently of each other. One of these pathways involves the arcuate nuclei and possibly nearby structures, while the other appears to include extrahypothalamic structures and to enter the hypothalamus anteriorly.