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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: The initial in vitro testing of the CFTAH with a single, valveless, continuous-flow pump demonstrated its passive self-regulation of flows and atrial pressures and a new automatic control mode.
Abstract: The clinical use of left ventricular assist devices (LVADs) is becoming more widely accepted, due in large part to the introduction of continuous-flow blood pumps.1-6 These newer devices show significant improvements in size, simplicity, reliability, durability, and clinical results. However, 20-50% of patients undergoing LVAD implantation also have significant right ventricular failure, which limits the utility of implantable LVAD therapy.7-11 Existing total artificial hearts (TAHs) are either a temporary pneumatic system (CardioWest™, SynCardia, Tucson, AZ) with an externalized pneumatic driver or a permanent pulsatile implantable system (AbioCor™, Abiomed®, Danvers, MA). To date, they have demonstrated significant limitations in initial clinical trials because of their large size, limited durability, and incidence of thrombus formation and embolization.12 The inherent design characteristics of these pulsatile systems prevent significant reductions in size.
The feasibility of native heart replacement with two separate continuous-flow pumps has recently been demonstrated at the Texas Heart Institute (Houston, TX)13 and Tohoku University (Sendai, Japan).14 These systems require duplication of pump components, increasing the potential for component failure and necessitating the development of complex algorithms to appropriately coordinate the outputs of the two pumps. We are developing a continuous-flow TAH (CFTAH) that is extremely innovative, exploring radical new concepts in TAH design. The proposed concept involves the use of a valveless, sensorless, continuous-flow pump and automatic control system. This double-pump concept comprises a single, continuously rotating, brushless DC motor and a pump assembly with a centrifugal pump on both ends. Pump speed will be modulated to create pulsatile flow and pressure. This report details the CFTAH design concept and our initial in vitro data in a mock circulatory loop.
84 citations
TL;DR: The results are consistent with the conclusion that the acute negative feedback action of estradiol on circhoral LH release in the monkey is at the level of the pituitary gland, whereas the inhibitory action of phentolamine on this mode of LH secretion is at a neural site.
Abstract: Pulsatile LH secretion was re-established in ovariectomized monkeys bearing hypothalamic lesions by an intermittent infusion of LHRH. The administration of estradiol to such animals resulted in a prompt cessation of these pulsatile discharges of LH and a resultant decline in the mean plasma concentration of the gonadotropin. The time course of this inhibition of LH secretion was indistinguishable from that observed after estrogen administration to ovariectomized animals with intact nervous systems. In contrast, phentolamine did not interrupt the pulsatile LH discharges occasioned by the hourly administration of exogenous LHRH to the lesioned animals. These results are consistent with the conclusion that the acute negative feedback action of estradiol on circhoral LH release in the monkey is at the level of the pituitary gland, whereas the inhibitory action of phentolamine on this mode of LH secretion is at a neural site. (Endocrinology 102: 1015, 1978)
84 citations
TL;DR: Results are consistent with the hypothesis that the pulsatile release of LH in the long-term ovariectomized rat is caused by the stimulating activity of adrenergic and cholinergic, probably nicotinic, systems and the inhibitory activity of a dopaminergic system.
Abstract: In the long-term ovariectomized rat the secretion of LH has a pulsatile character. In such rats no difference was observed between morning and afternoon LH secretion. The administration of phenoxybenz
84 citations
TL;DR: The findings of this study show that peak wall stress and maximum shear stress are highest in the media layer and the presence of aortic intramural hematoma is found to have a significant effect on the peak wall Stress acting on the inner layer.
83 citations
TL;DR: It is found that perfusion protocol can influence mucosal blood flow, but other overriding factors that operate during and after CPB act to cause mucosal hypoxia.
83 citations