Pulsatile flow

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

Aging Impairs Myogenic Adaptation to Pulsatile Pressure in Mouse Cerebral Arteries

Abstract: Stability of myogenic tone in middle cerebral arteries (MCA) is essential for adequate control over penetration of pressure waves into the distal portion of the cerebral microcirculation. Because the increased pulse pressure observed in advanced aging is associated with cerebromicrovascular injury, the effect of aging on myogenic response of mouse MCAs was determined. Aging did not affect the myogenic constriction in response to static increases in pressure, whereas it significantly impaired pulsatile pressure-induced myogenic tone. Impaired myogenic adaptation of MCAs to pulsatile pressure may allow high pressure to penetrate the distal portion of the cerebral microcirculation, contributing to microvascular damage.

Pathogenesis of Elevated Peripheral Pulse Pressure: Some Reflections and Thinking Forward

Abstract: “Ashes to ashes, dust to dust, if the cancer don’t get us, the arteriosclerosis must” — —Richard Gordon in The Alarming History of Medicine, 1993 Substantial evidence suggests that arterial remodeling evolves over a life course under the conjoint influence of genes, environmental factors (including vascular risk factors), and lifestyle characteristics (such as diet and physical activity).1 Such arterial remodeling involves multiple vascular territories and is panarterial, ie, it involves all layers of the arterial wall.1 More recently, considerable attention has focused on the physiological aspects of propagation of blood within the aorta, and several important concepts have evolved. First, the aorta is no longer regarded as just a passive conduit that transports blood to the vital organs. Rather, it is a complex organ that remodels in dynamic fashion in response to biomechanical stresses that accumulate over the life course.1 The different segments of the aorta vary in their relations to risk factors, underscoring the heterogeneity in remodeling characteristics across the arterial tree.2 Second, age-associated changes in the aortic wall include fragmentation of the elastin fibers, increased synthesis of collagen, and calcification. The molecular epidemiology of these vascular remodeling changes have been well characterized, and are complex, being mediated via the interaction of vascular smooth muscle cells, integrins, metalloproteinases, endothelial function, and the renin-angiotensin axis, inflammation, and other pathways.1 Third, vascular flow propagation is the combination of steady flow (mean arterial pressure) and pulsatile (pulse pressure) components. The proximal (central) aorta stiffens with age, and these changes are associated with an increase in the pulsatile component (increased central pulse pressure), which in turn places a burden of increased afterload on the left ventricle. There is widespread agreement that elevated pulsatile load is associated with increased risk of cardiovascular disease, including myocardial infarction, stroke, and heart …

Estimation of volume flow rate by surface integration of velocity vectors from color Doppler images

Abstract: A new Doppler echocardiographically based method has been developed to quantify volume flow rate by surface integration of velocity vectors (SIVV). Electrocardiographic-gated color Doppler images acquired in two orthogonal planes were used to estimate volume flow rate through a bowl-shaped surface at a given time and distance from the probe. To provide in vitro validation, the method was tested in a hydraulic model representing a pulsatile flow system with a restrictive orifice. Accurate estimates of stroke volume (±10%) were obtained in a window between 1.2 and 1.6 cm proximal to the orifice, just before the region of prestenotic acceleration. By use of the Bernoulli's equation, the estimated flows were used to generate pressure gradient waveforms across the orifice, which agreed well with the measured flows. To demonstrate in vivo applicability, the SIVV method was applied retrospectively to the determination of stroke volume and subaortic flow from the apical three-chamber and five-chamber views in two patients. Stroke volume estimates along the left ventricular outflow tract showed a characteristic similar to that in the in vitro study and agreed well with those obtained by the Fick oxygen method. The region where accurate measurements can be obtained is affected by instrumental factors including Nyquist velocity limit, wall motion filter cutoff, and color flow sector angle. The SIVV principle should be useful for quantitative assessment of the severity of valvular abnormalities and noninvasive measurement of pulsatile volume flows in general.

Pulsatile flow Studies of Prosthetic Aortic Valves

Abstract: A pulse duplicator system, used for studying prosthetic heart valves, is described. It provides a pulsatile flow resembling that produced by the heart, and permits a quantitative estimation of fluid flow resistance, regurgitation and energy loss in the valves. A technique for visualization of flow pattern is presented. The hydrodynamic performance of five prosthetic aortic valves, Starr-Edwards, Smeloff-Cutter, Kay-Shiley, Wada-Cutter and Bjork-Shiley, were studied in the pulse duplicator and compared on the basis of their external (tissue) diameters. For a given tissue diameter, the Bjork-Shiley valve had the best performance, resulting in a significantly lower flow resistance and energy loss than in the other prostheses investigated. All valves had acceptably low degrees of regurgitation with the exception of the Wada-Cutter prosthesis (16 to 20% of stroke volume). Flow visualization demonstrated a more or less turbulent flow pattern in all the valves with the exception of the Bjork-Shiley valve. In thi...