Pulsatile flow

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

Effect of flow diverter porosity on intraaneurysmal blood flow

Abstract: Background and Purpose: Growth and rupture, the two events that dominate the evolution of an intracranial aneurysm, are both dependent on intraaneurysmal flow. Decrease of intraaneurysmal flow is considered an attractive alternative for treating intracranial aneurysms by minimally invasive techniques. Such modification can be achieved by inserting stents or flow diverters alone. In the present paper, the effect of different commercial and innovative flow diverters’ porosity was studied in intracranial aneurysm models. Material and Methods: Single and stent-in-stent combination of Neuroform II as well as single and stent-in-stent combination of a new innovative, low-porosity, intracranial stent device (D1, D2, D1 + D2) were inserted in models of intracranial aneurysms under shear-driven flow and inertia-driven flow configurations. Steady and pulsating flow rates were applied using a blood-like fluid. Particle image velocimetry was used to measure velocity vector fields in the aneurysm midplane along the vessel axis. Flow and vorticity patterns, velocity and vorticity magnitudes were quantified and their value compared with the same flows in absence of the flow diverter. Results: In absence of flow diverters, a solid-like rotation could be observed in both shear-driven and inertia-driven models under steady and pulsatile flow conditions. The flow effects due to the insertion of low-porous devices such as D1 or D2 provoked a complete alteration of the flow patterns and massive reduction of velocity or vorticity magnitudes, whereas the introduction of clinically adopted high-porous devices provoked less effect in the aneurysm cavity. As expected, results showed that the lower the porosity the larger the reduction in velocity and vorticity within the aneurysm cavity. The lowest-porosity device combination (D1 and D2) reached an averaged reduction of flow parameters of 80% and 88% under steady and pulsatile flow conditions, respectively. The reduction in mean velocity and vorticity was much more significant in the shear-driven flows as compared to the inertia-driven flows. Conclusion: Although device porosity is the main parameter influencing flow reduction, other parameters such as device design and local flow conditions may influence the level of flow reduction within intracranial aneurysms.

Electrophysiological correlates of pulsatile gonadotropin release in rats.

Abstract: In order to reveal the electrophysiological correlates of pulsatile LH release in ovariectomized rats, changes in multiple unit activity (MUA) in the arcuate nucleus (ARC), the medial preoptic area, t

Effects of hypothalamic deafferentation on the pulsatile rhythm in plasma concentrations of luteinizing hormone in ovariectomized rats.

Abstract: Plasma LH concentrations were measured by radioimmunoassay in blood collected at 10-min intervals through atrial cannulas implanted in long-term ovariectomized rats. Regular fluctuating levels of the hormone were recorded in which plasma LH concentration rose rapidly to a peak every 20–40 min. Interruption of the anterior nerve projections to the medial basal hypothalamus (MBH) by deafferentation with a small stereotaxic knife rendered rats acyclic and resulted in a persistently cornified vaginal epithelium (constant estrus). Although these neural afferents were necessary for an ovulatory discharge of LH, the anterior deafferentation procedure did not block either the post-castration rise in plasma LH or the pulsatile discharge of hormone in the same rats when they were ovariectomized 4–6 weeks after deafferentation.Similarly, an extended frontal or an anterior-lateral cut resulted in constant estrus and permitted the pulsatile circulating levels of LH after ovariectomy. Posterior-lateral deafferentation ...

Flow Pulsatility Is a Critical Determinant of Oxidative Stress in Endothelial Cells

Abstract: Atherosclerotic plaques are found in regions exposed to disturbed flow, suggesting the active participation of the hemodynamic environment in atherogenesis. Indeed, unidirectional and oscillatory flow patterns (ie, bidirectional) have been shown to induce contrasting effects on endothelial function. The purpose of the present study was to evaluate the effect of these 2 flow patterns characterizing plaque-free and plaque-prone regions, respectively, on the oxidative stress of endothelial cells. NADH-dependent oxidase activity was shown to be equally induced (2- to 3-fold) in endothelial cells exposed to pulsatile unidirectional or oscillatory flow patterns. Under these flow conditions, an increase in endothelial cell oxidative state compared with static cultures was observed. Pulsatility of flow, but not cyclic stretch, was a critical determinant of flow-induced superoxide anion production. P22phox mRNA level increased in cells exposed to both unidirectional and oscillatory shear stress, suggesting that p22phox gene expression upregulation contributes to flow-induced increase in superoxide anion production in endothelial cells. In conclusion, we demonstrate a flow-induced increase in oxidative stress in endothelial cells. This chronic increase is dependent on the pulsatile nature of flow and is mediated in part by upregulation of an NADH-dependent oxidase expression.

Peripheral vascular resistance and angiotensin II levels during pulsatile and no-pulsatile cardiopulmonary bypass.

Abstract: The effects of pulsatile and non-pulsatile cardiopulmonary bypass (CPB) on levels of peripheral vascular resistance and plasma angiotensin II (AII) have been studied in 24 patients submitted to elective cardiac surgical procedures. Twelve patients had conventional non-pulsatile perfusion throughout the period of CPB (non-pulsatile group), while 12 had pulsatile perfusion during the central period of total CPB, using the Stockert pulsatile pump system (pulsatile group). There were no significant differences between the groups in respect of age, weight, bypass time, cross-clamp time, or in mean pump flow or mean perfusion pressure at the onset of CPB. Peripheral vascular resistance index (PVRI) and plasma AII levels were measured at the onset of total CPB and at the end of total CPB. In the non-pulsatile group PVRI rose from 19.6 units to 29.96 units during perfusion. In the pulsatile group PVRI showed little change from 20.89 units to 21.45 units during perfusion (P less than 0.001). Plasma AII levels (normal less than 35 pg/ml) rose during perfusion from 49 pg/ml to 226 pg/ml in the non-pulsatile group. The rise in the pulsatile group from 44 pg/ml to 98 pg/ml was significantly smaller than that in the non-pulsatile group (P less than 0.01). These results indicate that pulsatile cardiopulmonary bypass prevents the rise in PVRI associated with non-pulsatile perfusion, and that this effect may be achieved by preventing excessive activation of the renin-angiotensin system, thus producing significantly lower plasma concentrations of the vasoconstrictor angiotensin II.