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PubMed1994

Pulsatility improves hemodynamics during fetal bypass. Experimental comparative study of pulsatile versus steady flow.

BACKGROUND: The main advantage of pulsatile flow compared with steady flow during cardiopulmonary bypass is to prevent a rise in systemic vascular resistances. We hypothesized that pulsatile flow could overcome the progressive rise in peripheral and placental vascular resistances observed during fetal bypass and leading to progressive irreversible hypoxemia. METHODS AND RESULTS: A study was undertaken in 17 fetal lambs (110 to 140 days of gestation). Fetal bypass was established for a 30-minute period through right atrial and main pulmonary artery cannulation. The circuit had no oxygenator. Flow was delivered by a standard roller pump for the continuous study (group 1, n = 9) or by a centrifugal pulsatile pump for the pulsatile study (group 2, n = 8). Oxymetric and hemodynamic parameters, along with organ blood flow determined by radiolabeled microspheres counting, were recorded before (T1) and after 10 minutes (T2) and 30 minutes (T3) of bypass. SaO2 and PaO2 were significantly higher in group 2 than in group 1 at T2 but thereafter deteriorated similarly in both groups, whereas PCO2 remained unchanged. Pump flow in group 2 was significantly higher than in group 1 at T2 and T3 (957.6 +/- 49 and 1104 +/- 152 versus 437.6 +/- 23 and 467.8 +/- 43 mL/min, respectively). Systemic vascular resistances during pulsatile bypass were also significantly lower than in group 1 at T2 (402 +/- 12 versus 930 +/- 79 dynes/sec/cm-5) and T3 (374 +/- 60 versus 1017 +/- 192 dynes/sec/cm-5). At T2 and T3, all individual blood flows except the brain but including the placenta were statistically higher in group 2 than in group 1. Placental vascular resistances gradually increased during bypass in group 1 to reach 2.9 +/- 0.2 mm Hg.mL-1.min-1.kg-1 at T3 and remained approximately stable in group 2 during 30 minutes of pulsatile bypass, varying from 0.35 +/- 0.02 to 1.26 +/- 0.14 from T2 to T3 (P < .01). CONCLUSIONS: The data suggest that pulsatile flow for 30 minutes of bypass in a fetal lamb preparation temporarily prevents the progressive hypoxemia observed under steady-flow bypass. Pulsatile flow allows higher pump flow through a significant decrease in systemic vascular resistances. Individual organ blood flow, including placenta, was significantly higher under pulsatile bypass. With technical improvements in the design of pulsatile devices adapted to more physiological beat rates, pulsatility may become a valuable adjunct to overcome placental dysfunction observed during experimental fetal cardiac surgery.

Animals↗
PubMed2002

Temporal gradients in shear stimulate osteoblastic proliferation via ERK1/2 and retinoblastoma protein.

Bone cells are subject to interstitial fluid flow (IFF) driven by venous pressure and mechanical loading. Rapid dynamic changes in mechanical loading cause transient gradients in IFF. The effects of pulsatile flow (temporal gradients in fluid shear) on rat UMR106 cells and rat primary osteoblastic cells were studied. Pulsatile flow induced a 95% increase in S-phase UMR106 cells compared with static controls. In contrast, ramped steady flow stimulated only a 3% increase. Similar patterns of S-phase induction were also observed in rat primary osteoblastic cells. Pulsatile flow significantly increased relative UMR106 cell number by 37 and 62% at 1.5 and 24 h, respectively. Pulsatile flow also significantly increased extracellular signal-regulated kinase (ERK1/2) phosphorylation by 418%, whereas ramped steady flow reduced ERK1/2 activation to 17% of control. Correspondingly, retinoblastoma protein was significantly phosphorylated by pulsatile fluid flow. Inhibition of mitogen-activated protein (MAP)/ERK kinase (MEK)1/2 by U0126 (a specific MEK1/2 inhibitor) reduced shear-induced ERK1/2 phosphorylation and cell proliferation. These findings suggest that temporal gradients in fluid shear stress are potent stimuli of bone cell proliferation.

Animals↗
PubMed1986

Bio-medico-mechanical behavior of natural artery blood vessel under constant and variable internal pulsatile pressure flow test in vitro.

Studies have been carried out on the bio-medico-mechanical behavior in vitro of natural blood vessel (dogs) under constant and variable internal pulsatile pressure flow. The apparatus designed by us well simulated the arterial system. The studies were made for the case of pressure amplitude kept as constant, of the two-step-multi-duplicated pulsatile pressure and of the fluctuating pressure. For the case of the fluctuating pressure, the strength of the artery becomes considerably lower than those under constant amplitude and two-step-multi-duplicated pulsatile pressure. SEM observations of the inner walls of the artery shows that collagen fibers are more elongated under fluctuating pulsatile pressure flow. In conclusion, in order to avoid the mechanical deterioration of the artery strength, it is useful to keep the pulsatile blood pressure at constant amplitude. Even for the case of the blood pressure fluctuation, it is necessary to manage to keep the blood pressure as near a regular wave as possible, the total number of repeated pulse being equal.

Animals↗
PubMed1998

Testing neonate-infant membrane oxygenators with the University of Texas neonatal pulsatile cardiopulmonary bypass system in vitro.

Neurologic complications are already well documented after cardiopulmonary bypass (CPB) procedures in neonates and infants. Physiologic pulsatile flow CPB systems may be the alternative to the currently used steady-flow CPB circuits. In addition to the pulsatile pump, a membrane oxygenator should be chosen carefully, because only a few membrane oxygenators are suitable for physiologic pulsatile flow. We have tested four different types of neonate-infant membrane oxygenators for physiologic pulsatility with The University of Texas neonate-infant pulsatile CPB system in vitro. Evaluation criteria were based on mean ejection time, extracorporeal circuit (ECC) pressure, and upstroke of dp/dt. The results suggested that the Capiox 308 hollow-fibre membrane oxygenator produced the best physiologic pulsatile waveform according to the ejection time, ECC pressure, and the upstroke of dp/dt. The Minimax Plus and Masterflo Infant hollow-fibre membrane oxygenators also produced adequate pulsatile flow. Only the Variable Prime Cobe Membrane Lung (VPCML) Plus flat-sheet membrane oxygenator failed to reach the criteria for physiologic pulsatility. Depending on the oxygenator used, the lowest priming volume of the infant CPB circuit was 415 ml and the highest 520 ml.

Brain Diseases↗
PubMed1989

A new algorithm for deriving pulsatile blood flow waveforms tested using stimulated dynamic angiographic data.

In vascular pathology the assessment of disease severity and monitoring of treatment requires quantitative and reproducible measurements of arterial blood flow. We have developed a new technique for processing sequences of dynamic digital X-ray angiographic images. We have tested it using computer simulated angiographic data which includes the effect of pulsatile blood flow and X-ray quantum noise. A parametric image was formed in which the image grey-level represents dye concentration as a function of time and distance along a vessel segment. Adjacent concentration--distance profiles in the parametric image were re-registered along the vessel axis until a match occurred. A match was defined as the point where the sum of squares of the differences in the two profiles was a minimum. The distance translated per frame interval is equal to the bolus velocity. We have tested several contrast medium injection methods including constant flow and a range of discrete pulses per second. The technique proved to be robust and independent of injection technique. Average blood flow was measured for simulated pulsatile waveforms with mean flows of up to 650 ml/min (peak velocities up to 186 cm/s) in a range of diameters from 2 mm to 6 mm. The standard deviation of the error in the mean flow estimates over the whole range of velocities and vessel sizes was +/- 1.4 cm/s.

Algorithms↗
PubMed1999

A fluid--structure interaction finite element analysis of pulsatile blood flow through a compliant stenotic artery.

A new model is used to analyze the fully coupled problem of pulsatile blood flow through a compliant, axisymmetric stenotic artery using the finite element method. The model uses large displacement and large strain theory for the solid, and the full Navier-Stokes equations for the fluid. The effect of increasing area reduction on fluid dynamic and structural stresses is presented. Results show that pressure drop, peak wall shear stress, and maximum principal stress in the lesion all increase dramatically as the area reduction in the stenosis is increased from 51 to 89 percent. Further reductions in stenosis cross-sectional area, however, produce relatively little additional change in these parameters due to a concomitant reduction in flow rate caused by the losses in the constriction. Inner wall hoop stretch amplitude just distal to the stenosis also increases with increasing stenosis severity, as downstream pressures are reduced to a physiological minimum. The contraction of the artery distal to the stenosis generates a significant compressive stress on the downstream shoulder of the lesion. Dynamic narrowing of the stenosis is also seen, further augmenting area constriction at times of peak flow. Pressure drop results are found to compare well to an experimentally based theoretical curve, despite the assumption of laminar flow.

Arteries↗
PubMed2006

Critical oxygen delivery during cardiopulmonary bypass in dogs: pulsatile vs. non-pulsatile blood flow.

BACKGROUND AND OBJECTIVE: To determine the minimal oxygen delivery and pump flow that can maintain systemic oxygen uptake during normothermic (37 degrees C) pulsatile and non-pulsatile cardiopulmonary bypass in dogs. METHODS: Eighteen anaesthetized dogs were randomly assigned to receive either non-pulsatile (Group C; n = 9) or pulsatile bypass flow (Group P; n = 9). Oxygen delivery was reduced by a progressive decrease in pump flow, while arterial oxygen content was maintained constant. In each animal, critical oxygen delivery was determined from plots of oxygen uptake vs. oxygen delivery and from plots of blood lactate vs. oxygen delivery using a least sum of squares technique. Critical pump flow was determined from plots of lactate vs. pump flow. RESULTS: At the critical point, oxygen delivery obtained from oxygen uptake was 7.7 +/- 1.1 mL min(-1) kg(-1) in Group C and 6.8 +/- 1.8 mL min(-1) kg(-1) in Group P (n.s.). These values were similar to those obtained from lactate measurements (Group C: 7.8 +/- 1.6 mL min(-1) kg(-1); Group P: 7.6 +/- 2.0 mL min(-1) kg(-1)). Critical pump flows determined from lactate measurements were 55.6 +/- 13.8 mL min(-1) kg(-1) in Group C and 60.8 +/- 13.9 mL min(-1) kg(-1) in Group P (n.s.). CONCLUSIONS: Oxygen delivery values greater than 7-8 mL min(-1) kg(-1) were required to maintain oxygen uptake during normothermic cardiopulmonary bypass with either pulsatile or non-pulsatile blood flow. Elevation of blood lactate levels during bypass helps to identify inadequate tissue oxygen delivery related to insufficient pump flow.

Algorithms↗
PubMed2003

Modeling and simulation of pulsatile blood flow with a physiologic wave pattern.

This article presents a computational fluid dynamics (CFD) model to analyze pulsatile blood flow in a human artery. The model assumes the vessel as being a straight wall tube, and the blood flow is considered to be incompressible, Newtonian, and axisymmetric. Physiologically realistic resting conditions were adopted for the simulation tests. The main objective was to identify regions where pulsatile effects were significant. Velocity profiles were obtained for both normal and stenosed vessels. The results have shown that, for normal vessels, pulsatile effects prevail close to the vessel wall. The presence of stenosed sections resulted in flow alterations, with flow recirculation areas changing both size and location during the cardiac cycle. These results are especially important in the design of artificial organs. The knowledge of the flow pattern in complex geometries such as artificial hearts, prosthetic valves, and ventricular assist devices can help avoid or minimize thrombogenesis and hemolysis.

Arteries↗
PubMed1995

Influence of different flow modi during extracorporeal circulation on endothelial-derived vasoactive substances.

Influences of shear stress on endothelin (ET) as well as prostacyclin (PGF) levels are common findings in different experimental settings. Thus, plasma levels of both substances seem to be a good tool to verify if different flow modi can be produced in blood vessels by generating pulsatile flow with a roller pump. In the present study, 20 patients scheduled for elective aortocoronary bypass operation were divided into two groups at random. One group was perfused with nonpulsatile (CON-group) and the other with pulsatile flow (PULS-group) during extracorporeal circulation. ET and PGF plasma levels were monitored perioperatively together with parameters of renal function and haemodynamic data. ET values were only slightly elevated at the end of extracorporeal circulation (mean baseline value; CON 3.1 pg/ml and PULS 3.2 pg/ml; mean maximal values at the end of cardiopulmonary bypass (CPB) 4.0 pg/ml and 3.9 pg/ml respectively). Prostacylin values (median baseline values: CON 56.7 pg/ml and PULS 57.1 pg/ml) peaked at the end of operation (median CON 117.8 pg/ml and PULS 137.5 pg/ml respectively) with a subsequent small decrease. No differences between the groups could be observed at any time point with respect to vasoactive substances, urine output (CON 6.5 ml/min and PULS 6.2 ml/min) or haemodynamics during CPB. This confirms studies emphasizing that no effective microvascular pulsatile flow is generated by conventional pulsatile flow-generating devices. In the present study, normothermia and a constant flow rate were maintained during CPB. Aortic cannulae (body-surface-related not maximal large diameters) were inserted. Altering these procedures may have led to more pronounced differences between the groups. All patients had an uneventful course after the operation. Similar to other reports, the present study was not able to demonstrate any benefit of pulsatile perfusion during extracorporeal circulation.

Aged↗
PubMed2001

In vivo measurement of fine and coarse aerosol deposition in the nasal airways of female Long-Evans rats.

Experimental data on fine and coarse aerosol deposition in the nasal airways of animals are essential in appropriately using toxicological studies to assess the potential risk to human health from exposure to airborne pollutants. However, such data are scarce. The objective of this study was to determine aerosol deposition efficiencies for the nasal airways in Long-Evans rats for particles with diameters ranging from 0.5 to 4 microm. Polystyrene latex (PSL) microspheres in steady-state and pulsatile flows were passed through the nasal airways for simulated inspiratory and expiratory scenarios. Average flow rates ranged from 220 to 640 ml/min. Deposition increased sharply with increasing particle inertia for all exposure scenarios. Expiratory deposition efficiency appeared to be somewhat higher than inspiratory deposition efficiency for both steady-state and pulsatile flow conditions. Pulsatile flow yielded significantly higher deposition than steady-state flow. This result emphasizes the importance of considering fluid accelerations inherent in normal breathing when determining aerosol deposition that is dominated by inertial impaction. Variability in the data, which was suspected to result primarily from the difficult surgical procedure, was in excess of expected intersubject variability. The results of this study will be incorporated into extrapolation-modeling and risk-assessment activities for inhaled pollutants.

Aerosols↗
PubMedDate not supplied

The vasoregulatory role of endothelium derived nitric oxide during pulsatile cardiopulmonary bypass.

The role of pulsatile flow as a physiologic stimulus for endothelium mediated vasoregulation is poorly understood. Furthermore, non pulsatile flow, which is associated with increased vascular resistance and end-organ failure, has been demonstrated to lead to a decrease in nitric oxide (NO) production in vitro. Anesthetized pigs (23.4 +/- 0.3 kg) were placed on cardiopulmonary bypass using either non pulsatile or pulsatile perfusion for 60 min. In both groups, animals were maintained with a constant mean aortic flow (1.0-1.3 L/min). Serum samples obtained during bypass were assayed for the stable end-products of NO (nitrate [NO3-] and nitrite [NO2-]) by a method based on the Greiss reaction. Systemic vascular resistance was higher after 60 min in the non pulsatile (3712.5 +/- 481.2 dyne sec cm(-5)) vs the pulsatile group (2672.6 +/- 427.0 dyne sec cm(-5)), but not statistically significant (p > .05). However, NO production was decreased in the non pulsatile flow group (27 +/- 6%) vs the pulsatile flow group (14 +/- 5%) at a statistically significant level (p < .005). The results suggest that non pulsatile flow is associated with diminished endothelial shear stress and a reduction in endothelial nitric oxide production. This may contribute to the detrimental physiologic effects observed in prolonged non pulsatile flow states.

Animals↗
PubMed2000

Tissue engineering of heart valves: in vitro experiences.

BACKGROUND: Tissue engineering is a new approach, whereby techniques are being developed to transplant autologous cells onto biodegradable scaffolds to ultimately form new functional tissue in vitro and in vivo. Our laboratory has focused on the tissue engineering of heart valves, and we have fabricated a trileaflet heart valve scaffold from a biodegradable polymer, a polyhydroxyalkanoate. In this experiment we evaluated the suitability of this scaffold material as well as in vitro conditioning to create viable tissue for tissue engineering of a trileaflet heart valve. METHODS: We constructed a biodegradable and biocompatible trileaflet heart valve scaffold from a porous polyhydroxyalkanoate (Meatabolix Inc, Cambridge, MA). The scaffold consisted of a cylindrical stent (1 x 15 x 20 mm inner diameter) and leaflets (0.3 mm thick), which were attached to the stent by thermal processing techniques. The porous heart valve scaffold (pore size 100 to 240 microm) was seeded with vascular cells grown and expanded from an ovine carotid artery and placed into a pulsatile flow bioreactor for 1, 4, and 8 days. Analysis of the engineered tissue included biochemical examination, enviromental scanning electron microscopy, and histology. RESULTS: It was possible to create a trileaflet heart valve scaffold from polyhydroxyalkanoate, which opened and closed synchronously in a pulsatile flow bioreactor. The cells grew into the pores and formed a confluent layer after incubation and pulsatile flow exposure. The cells were mostly viable and formed connective tissue between the inside and the outside of the porous heart valve scaffold. Additionally, we demonstrated cell proliferation (DNA assay) and the capacity to generate collagen as measured by hydroxyproline assay and movat-stained glycosaminoglycans under in vitro pulsatile flow conditions. CONCLUSIONS: Polyhydroxyalkanoates can be used to fabricate a porous, biodegradable heart valve scaffold. The cells appear to be viable and extracellular matrix formation was induced after pulsatile flow exposure.

Animals↗
PubMed1996

Color Doppler ultrasound signals of thoracic lesions. Correlation with resected histologic specimens.

Sixty-eight patients with thoracic lesions (48 with lung cancer and 20 with benign lesions) underwent color Doppler ultrasound (US) examinations. Of those, 21 patients (13 with lung cancer and eight with benign lesions) also received resections, and the correlation between color Doppler US signals and resected histologic specimens was evaluated. Our results showed that three patterns of color Doppler US signals could be detected and confirmed: pulsatile flow (artery), constant flow, and triphasic flow (pulmonary vein). Among the 48 patients with lung cancer, pulsatile flow, constant flow, and/or triphasic flow were detected in 34 (71%), 24 (50%), and 14 (29%), respectively. Among the 20 patients with benign lesions, only pulsatile flow and/or triphasic flow were detected in nine (45%) and eight (40%), respectively. From the correlation between color Doppler US signals and histologic specimens, constant flow was representative of the true neovascularity of lung cancers, and it was valuable for differentiating lung cancers from benign lesions (p = 0.00008, sensitivity = 0.50, and specificity = 1.0). Although color Doppler US still had some limitations in detecting blood vessels in thoracic lesions, the correlation between the vascularity represented by color Doppler US signals and histologic specimens was excellent. We conclude that color Doppler US is a valuable method for assessing blood flow in thoracic lesions and differentiating lung cancers from intrapulmonary benign lesions.

Adult↗
PubMed2002

Modelling of flow and wall behaviour in a mildly stenosed tube.

In the present computational analysis, pulsatile flow and vessel wall behaviour in a simplified model of a stenosed vessel were investigated. Geometry of a 45% axisymmetrically stenosed (by area) cylindrical tube and a sinusoidal inflow waveform were simulated, with the fluid being assumed to be incompressible and Newtonian. The vessel wall was treated as a thick-walled, incompressible and isotropic material with uniform mechanical properties across the normal as well as the constricted segment. The study of fluid flow and wall motion was initially carried out separately using two commercial codes CFX4.2 and ABAQUS7 respectively. Their combined effects and interactions were later investigated through an iteratively coupled algorithm. Model validations on the rigid-wall fluid and static no-flow solid models were satisfactory, with Root Mean Square deviations of around 7% in centreline axial velocity between the prediction and measurement values for the rigid wall stenosis model, and 5% in circumferential stress for a cylindrical tube model under static loading when compared with the analytical solution. Results on velocity profiles, wall shear stress, intramural strain and stress for the rigid and compliant cases were all presented. Comparison between the rigid and compliant models revealed that, the flow separation layer distal to the stenosis was thicker and longer, and wall shear stress was slightly lower in the compliant model by less than 7.2%. Results obtained from the static wall model (with uniform pressure loading) and coupled fluid/wall interaction modelling of pulsatile flow showed qualitatively similar wall strain and stress patterns but considerable differences in magnitude. The radial and axial stresses were reduced by 31 and 8%, while the circumferential stress was increased by 13% due to the presence of pulsatile flow. Under the flow and structural conditions investigated, the effects of wall compliance were small, and did not change the flow and solid behaviours qualitatively in this case.

Arterial Occlusive Diseases↗
PubMed1999

Sequentially combined hormone replacement therapy reduces impedance to flow within the uterine and central retinal arteries in healthy postmenopausal women.

OBJECTIVE: The purpose of this study was to investigate the long-term effects of combined hormone replacement therapy on the impedances of the uterine, central retinal, and ophthalmic arteries in healthy postmenopausal women. STUDY DESIGN: In a prospective controlled study we randomly assigned 30 healthy postmenopausal women (mean age, 52 +/- 3 years) to 2 groups. Women in the hormone replacement therapy group (n = 15) received 1 mg micronized 17beta-estradiol daily sequentially combined with 5 or 10 mg dydrogesterone for 14 days of each 28-day cycle during 12 months and 2 mg 17beta-estradiol combined with 10 mg dydrogesterone thereafter for a period of 3 months. The control group (n = 15) received no treatment. Color Doppler ultrasonography was used to measure the impedance to flow (pulsatility index) within the uterine, central retinal, and ophthalmic arteries in the 17beta-estradiol phase at baseline and after 3, 12, and 15 months. RESULTS: With respect to values in the control group, 12 months of hormone replacement therapy was associated with a significantly lower (by 39%) mean pulsatility index of the uterine artery (decrease from baseline of 25% in hormone replacement therapy group and increase of 14% in control group) and a significantly lower (by 29%) mean pulsatility index of the central retinal artery (decrease of 9% in hormone replacement therapy group and increase of 20% in control group). After 3 months this effect was already evident. During hormone replacement therapy the reductions in mean pulsatility index values of the uterine and central retinal arteries with respect to baseline were larger (both P =.002) in the women with high pretreatment pulsatility index values than in those with low pretreatment values. The baseline pulsatility index of the uterine artery correlated positively with age and with duration of amenorrhea (r = 0.42, P =. 01; r = 0.48, P =.008; respectively). CONCLUSION: These results suggest that 12 months of sequentially combined hormone replacement therapy with a low dose of estradiol (1 mg) lowers arterial impedance in specific vascular territories. These data may help in understanding the effects of hormone replacement therapy on the cerebral circulation.

Drug Administration Schedule↗
PubMedDate not supplied

Ultrasound backscattering from non-aggregating and aggregating erythrocytes--a review.

The objective of the present paper is to provide a detailed review of theoretical, experimental and clinical works aimed at understanding the scattering of ultrasound by red blood cells (RBC). The paper focuses on the role of biofluid mechanics and blood biorheology on the scattering mechanisms. The influence of RBC aggregation on the ultrasound backscattered power is specifically addressed. After a short introduction, the paper presents the theory of Rayleigh scattering and summarizes theoretical models on ultrasound backscattering by RBC. The particle, continuum and hybrid models are presented along with reported packing factors used to consider the orderliness in the spatial arrangement of RBC. Computer models of ultrasound backscattering by RBC are also presented in this section. In the second section, experimental factors affecting the ultrasound backscattered power from blood are presented. The influence of the volume of the scatterers, ultrasound frequency, hematocrit, orientation of the scatterers, flow turbulence, flow pulsatility, and concentration of fibrinogen and dextran is discussed. The third section focuses on the use of ultrasound to characterize RBC aggregation. Three aspects are reported: the shear rate dependence of the backscattered power, the "black hole" phenomenon, and the kinetics of RBC rouleau formation. The fourth section reports in vivo observations of the "smoke like" echo in mitral valve disease, and blood echogenicity and backscattered power in veins and arteries. In the last section, new areas of research, clinical applications of ultrasound backscattering, and areas of potential future developments are presented.

Blood Vessels↗
PubMed2001

Two types of umbilical venous pulsations and outcome of high-risk pregnancy.

Normally, blood flows evenly in the umbilical vein, without fluctuation. A pulsating pattern has been reported during fetal heart failure and asphyxia. Recently we have noticed two types of pulsating pattern; its relationship to adverse outcome is unclear. In a prospective multicenter study, recording of umbilical cord venous blood flow was conducted in high-risk pregnancies admitted for routine artery Doppler. In cases of pulsating flow or signs of vascular resistance in the umbilical artery, the examination was extended to the intra-abdominal part of the umbilical vein. Venous pulsation, single or double, were noted and correlated to perinatal outcome. Venous flow pulsatility was noted in 83 fetuses during 2 years, 26 had a double pulsating pattern, which was closely related to increased vascular resistance in the umbilical artery and perinatal mortality. A single pulsating venous pattern in one location had a good prognosis. In conclusion a double pulsating venous pattern, especially if extending to the cord, is an ominous finding in high-risk pregnancy associated with poor perinatal outcome. A single pulsating pattern predicted a much better outcome and might be an indication for delivery in the high-risk case.

Female↗
PubMed1990

Doppler color-flow images from a stenosed arterial model: interpretation of flow patterns.

The capability of the recently introduced Doppler color-flow mapping devices to accurately detect flow patterns in the region of an arterial stenosis was evaluated by use of an in vitro flow model. Pulsatile flow simulating that in a low-resistance vessel was induced through a straight acrylic tube, which alternatively contained axisymmetric stenoses of 0%, 20%, 40%, 60%, and 80% diameter reduction. Doppler color-flow mapper images were taken in realtime along the tube midplane from 0 to 8 diameters downstream of each stenosis. Comparison of the Doppler color-flow mapping results with similarly recorded flow visualization (hydrogen bubble) images showed a close correspondence of key features of the flow, including detection of a high-velocity, centerline jet and near-wall separated flow zones. Distinctive flow patterns exist with each stenotic case, and these should be of considerable value in diagnosing clinical disease conditions.

Arterial Occlusive Diseases↗