Topic
Pulsatile flow
About: Pulsatile flow is a research topic. Over the lifetime, 6278 publications have been published within this topic receiving 149638 citations.
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TL;DR: Age differences in vascular response and ventricular output were abolished by beta blockade and the young had a greater increase in external left ventricular power than the old across exercise, demonstrating a profound difference in the response of young and old vasculature to exercise.
Abstract: The diminished cardiac output response to exercise with advancing age may be attributable to intrinsic inability of the old ventricle to respond appropriately and/or to an additional loading imposed upon the ventricle by the aged vascular system. The steady (resistance) and pulsatile (characteristic impedance) load components together comprise the vascular load faced by the ejecting ventricle. To study the effect of exercise on both vascular components of load, the aortic input impedance was measured in chronically instrumented young and old beagle dogs during graded treadmill exercise before and after beta blockade. Ascending aortic flow was measured by a cuff electromagnetic flow probe, and pressure was measured by a high-fidelity semiconductor transducer. At low levels of exercise the old animals demonstrated a striking 20% increase in characteristic impedance and a 28% decrease in peripheral resistance with no increase in stroke volume. This vascular loading and limitation in stroke volume persisted across the higher exercise levels. In contrast, the young group demonstrated no increase in characteristic impedence, a progressive decrease in peripheral resistance, and a progressive increase in stroke volume across the same exercise levels. These age differences in vascular response and ventricular output were abolished by beta blockade. The groups did not demonstrate a difference in heart rate response, but the young had a greater increase in external left ventricular power than the old across exercise. These data demonstrated a profound difference in the response of young and old vasculature to exercise. At low and intermediate exercise levels the pulsatile vascular load appeared to be a major factor in the limitation of stroke volume in old dogs. At high levels of exercise, the limited exercise response in the old dog may be caused in part by a diminished inotropic responsiveness as well as by the vascular loading.
111 citations
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TL;DR: In this paper, a collection of fluid-structure interaction (FSI) computational techniques are presented to enable realistic simulation of pulsatile VADs, which involve dynamic interaction of air, blood, and a thin membrane separating the two fluids.
Abstract: In this paper we present a collection of fluid---structure interaction (FSI) computational techniques that enable realistic simulation of pulsatile Ventricular Assist Devices (VADs). The simulations involve dynamic interaction of air, blood, and a thin membrane separating the two fluids. The computational challenges addressed in this work include large, buckling motions of the membrane, the need for periodic remeshing of the fluid mechanics domain, and the necessity to employ tightly coupled FSI solution strategies due to the very strong added mass effect present in the problem. FSI simulation of a pulsatile VAD at realistic operating conditions is presented for the first time. The FSI methods prove to be robust, and may be employed in the assessment of current, and the development of future, pulsatile VAD designs.
111 citations
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TL;DR: A novel perfusion bioreactor capable of providing pulsatile fluid flow at physiologically relevant shear stresses and flow rates was constructed and the enhanced hypertrophy index observed for the PP‐LF group was consistent with the highest cellular length and diameter in this group.
Abstract: Cardiovascular disease is the number one cause of mortality in North America. Cardiac tissue engineering aims to engineer a contractile patch of physiological thickness to use in surgical repair of diseased heart tissue. We previously reported that perfusion of engineered cardiac constructs resulted in improved tissue assembly. Because heart tissues respond to mechanical stimuli in vitro and experience rhythmic mechanical forces during contraction in vivo, we hypothesized that provision of pulsatile interstitial medium flow to an engineered cardiac patch would result in enhanced tissue assembly by way of mechanical conditioning and improved mass transport. Thus, we constructed a novel perfusion bioreactor capable of providing pulsatile fluid flow at physiologically relevant shear stresses and flow rates. Pulsatile perfusion (PP) was achieved by incorporation of a normally closed solenoid pinch valve into the perfusion loop and was carried out at a frequency of 1 Hz and a flow rate of 1.50 mL/min (PP) or 0.32 mL/min (PP-LF). Nonpulsatile flow at 1.50 mL/min (NP) or 0.32 mL/min (NP-LF) served as controls. Static controls were cultivated in well plates. The main experimental groups were seeded with cells enriched for cardiomyocytes by one preplating step (64% cardiac Troponin I+, 34% prolyl-4-hydroxylase+), whereas pure cardiac fibroblasts and cells enriched for cardiomyocytes by two preplating steps (81% cardiac Troponin I+, 16% prolyl-4-hydroxylase+) served as controls. Cultivation under pulsatile flow had beneficial effects on contractile properties. Specifically, the excitation threshold was significantly lower in the PP condition (pulsatile perfusion at 1.50 mL/min) than in the Static control, and the contraction amplitude was the highest; whereas high maximum capture rate was observed for the PP-LF conditions (pulsatile perfusion at 0.32 mL/min). The enhanced hypertrophy index observed for the PP-LF group was consistent with the highest cellular length and diameter in this group. Within the same cultivation groups (Static, NP-LF, PP-LF, PP, and NP) there were no significant differences in the diameter between fibroblasts and cardiomyocytes, although cardiomyocytes were significantly more elongated than fibroblasts under PP-LF conditions. Cultivation of control cell populations resulted in noncontractile constructs when cardiac fibroblasts were used (as expected) and no overall improvement in functional properties when two steps of preplating were used to enrich for cardiomyocytes in comparison with only one step of preplating.
111 citations
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TL;DR: In the otoscopically normal patient, there is a range of possible imaging approaches, however, combined CT angiography and venography is particularly useful.
110 citations
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TL;DR: Pulsatile flow significantly alters prostacyclin and thromboxane profiles during cardiopulmonary bypass and favors production of the coronary vasodilator and platelet disaggregant prostacy Clin.
110 citations