Doppler ultrasound of blood flow in the hepatic veins

The blood flow in the hepatic veins can normally be studied easily by Doppler ultrasound. The pattern of blood flow in normal individuals is described, and its relation to the cardiac cycle and changing pressure in the right atrium. The blood flow shows variations in healthy persons, and may change in cases of heart disease and hepatic disease. Conditions such as atrial fibrillation, tricuspid regurgitation, abnormal relaxation, restrictive cardiomyopathy, constrictive pericarditis and cardiac tamponade are reflected in the hepatic veins, and the pattern of blood flow may help in diagnosis, and in grading the pathology. In cirrhosis and portal hypertension the heart-synchronous variation in velocity is reduced. This is due to increased resistance to blood flow across the liver and the pressure gradient becoming larger than the variations in pressure in the right atrium.     

Alveolar oxygen uptake and blood flow dynamics in knee extension ergometry

The relationship was studied between the increase in oxygen uptake (VO2) measured breath-by-breath at the mouth, and the increase in femoral artery blood flow measured continuously with pulsed and echo Doppler methods. Five men exercised at 50 W on a knee extension ergometer in both the supine and the upright posture. The kinetics of the responses were determined by curve fitting to obtain the mean response time (MRT = 63% of the time required to achieve steady state). In the upright position, the increase in blood flow (MRT = 12.4 +/- 9.4 s, mean +/- SD) was faster than the increase in VO2 (29.6 +/- 9.3 s). Likewise in the supine position, blood flow increased more rapidly (25.1 +/- 9.7 s vs. 36.7 +/- 9.6 s). It should be noted that the increase in blood flow appeared to be faster than VO2, yet when blood flow adapted more slowly in the supine posture, it had an impact on the adaptation of VO2. This suggests that blood flow might have important effects on metabolism at the onset of submaximal exercise.     

Noninvasive assessment of collateral blood flow of the cerebral hemisphere by Doppler ultrasound

Directional flow in the frontal artery, a terminal branch of the ophthalmic artery, was assessed nonivasively by Doppler ultrasound druing brief digital compression of the ipsilateral common carotid artery in 62 patients. Directional frontal artery flow during carotid compression was compared with mean distal internal carotid back pressure measured at subsequent carotid endarterectomy. Mean carotid back pressure in 28 patients with normal frontal artery flow direction during carotid compression, 68 +/- 14 millimeters of mercury, was significantly higher than that observed in 24 patients in whom frontal artery flow was completely obliterated and ten in whom frontal artery flow was reversed. Distal internal carotid back pressure exceeded 48 millimeters of mercury in all patients with normal frontal artery flow direction during carotid compression. Conversely, carotid back pressure was below 41 millimeters of mercury in all but one patient in whom frontal artery flow was obliterated or bliterated or reversed during carotid compression. The results of this study indicate that Doppler ultrasound assessment of frontal artery flow direction during simultaneous carotid compression provides a rapid, sale noninvasive estimate of the adequacy of collateral hemispheric circulation.     

Doppler ultrasound of blood flow velocities in ophthalmic and central retinal arteries during the early neonatal period

Dopamine has been implicated as a potential mediating factor in a variety of neurodegenerative disorders. Dopamine can be oxidized to form a reactive dopamine quinone that can covalently modify cellular macromolecules including protein and DNA. This oxidation can be enhanced through various enzymes including tyrosinase and/or prostaglandin H synthase. One of the potential targets in brain for dopamine quinone damage is tyrosine hydroxylase, the rate-limiting enzyme in catecholamine biosynthesis. The present studies demonstrated that dopamine quinone, the formation of which was enhanced through the activity of the melanin biosynthetic enzyme, tyrosinase, covalently modified and inactivated tyrosine hydroxylase. Dihydroxyphenylalanine (DOPA; the catechol-containing precursor of dopamine) also inactivated tyrosine hydroxylase under these conditions. Catecholamine-mediated inactivation occurred with both purified tyrosine hydroxylase as well as enzyme present in crude pheochromocytoma homogenates. Inactivation was associated with covalent incorporation of radiolabelled dopamine into the enzyme as assessed by immunoprecipitation, size exclusion chromatography, and denaturing sodium dodecylsulfate (SDS)-polyacrylamide gel electrophoresis. Furthermore, the covalent modification and inactivation of tyrosine hydroxylase was blocked by antioxidant compounds (dithiothreitol, reduced glutathione, or NADH). In addition to kinetic feedback inhibition and the formation of an inhibitory dopamine/Fe+3 complex, these findings suggest that a third mechanism exists by which dopamine (or DOPA) can inhibit tyrosine hydroxylase, adding further complexity to the regulation of catecholamine biosynthesis.     

Blood flow in free muscle flaps measured by color Doppler ultrasonography

Color Doppler ultrasonography, a noninvasive method for studying changes in blood flow, has been used to monitor 18 patients with free microvascular lower limb muscle flaps. The peak, mean, and minimum velocities, resistance indices, and diameters of the flap pedicle arteries and also of the limb recipient arteries proximal to the microvascular anastomoses were measured at 2 and 6 weeks and 3, 6, and 9 months after surgery. The peak velocities did not significantly differ from each other, but the mean velocity in the flap pedicle arteries was 12.5% higher than that in the recipient arteries throughout the study period. End diastolic velocity in the pedicle was positive (toward the ultrasound probe) at 2 weeks (mean, 2 cm/sec, SD 10), 6 weeks (mean, 5 cm/sec, SD 16), and 3 months (mean, 3 cm/sec, SD 13) after surgery and significantly higher (P < 0.05) than at 6 months (mean, 7 cm/sec, SD 11), when the pattern of blood flow was normal forward/backward flow during systole/diastole. The resistance indices of the pedicle at 2 weeks (Ri = 0.978), 6 weeks (Ri = 0.936), and 3 months (Ri = 1.001) were significantly lower (P < 0.05) than at 6 months (Ri = 1.108), when the pedicle and recipient artery indices were the same. The diameter of the pedicle arteries was 14% smaller than those of the recipient arteries, but did not change during follow-up. This prospective clinical study shows that blood flow in the pedicle of a free microvascular muscle flap is increased until 6 months after surgery, mainly due to the increased minimum velocity of the pedicle in diastole and decreased resistance index. These findings can be attributed to the loss of vessel tone after denervation and are in accordance with earlier studies showing that denervated muscles lose their autoregulation and that blood flow increases, but that these phenomena subside with time. Increased blood flow in free muscle flaps can explain the high success rate of microanastomoses and positive effect on wound healing.     

Strain gauge plethysmography and Doppler ultrasound in the measurement of limb blood flow

The maintenance of adequate oxygen delivery (DO2) and tissue uptake (VO2) has become central dogma in the management of the critically ill. However, these parameters are derived using gas tensions measured in mixed venous blood and may not reflect changes in regional blood flow. Therefore, it has become necessary to provide estimates of blood flow to specific organs and to evaluate the most adequate techniques available. In order to define the best means of assessing blood flow to the lower limb noninvasively in normal subjects, measurements of superficial femoral arterial blood flow using Doppler ultrasound (DU) and strain gauge plethysmography (SGP) were compared in 10 normal volunteers at rest and during exercise. To evaluate the effect of strain gauge positioning, results of measurements made under four different combinations of cuff/strain gauge placement were compared in 15 other volunteers. The correlation of the limb blood flow obtained using the two methods at rest and exercise was 0.57 and 0.62 and the limits of agreement (d +/- 2SD) were 0.40 +/- 2.49 and -0.86 +/- 5.22 ml 100 ml-1 tissue min-1 at rest and on exercise, respectively. Results obtained using SGP were more reproducible (Coef. repeat. 0.45 vs. 0.94 ml 100 ml-1 tissue min-1, for SGP and DU, respectively). The various combinations of cuff/strain gauge positioning showed a tendency to over-read when the latter was placed on the thigh, but were not significantly different (P > 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)     

Characterization of blood flow turbulence with pulsed-wave and power Doppler ultrasound imaging

Blood turbulence downstream of a concentric 86 percent area reduction stenosis was characterized using absolute and relative Doppler spectral broadening measurements, relative Doppler velocity fluctuation, and Doppler backscattered power. Bidimensional mappings of each Doppler index were obtained using a 10 MHz pulsed-wave Doppler system. Calf red cells suspended in a saline solution were used to scatter ultrasound and were circulated in an in vitro steady flow loop model. Results showed that the absolute spectral broadening was not a good index of turbulence because it was strongly affected by the deceleration of the jet and by the shear layer between the jet and the recirculation zones. Relative Doppler spectral broadening (absolute broadening divided by the frequency shift), velocity fluctuation, and Doppler power indices provided consistent mapping of the centerline axial variation of turbulence evaluated by hot-film anemometry. The best agreement between the hot-film and Doppler ultrasound methods was however obtained with the Doppler back-scattered power. The most consistent bidimensional mapping of the flow characteristics downstream of the stenosis was also observed with the Doppler power index. The relative broadening and the velocity fluctuation produced artifacts in the shear layer and in the recirculation zones. Power Doppler imaging is a new emerging technique that may provide reliable in vivo characterization of blood flow turbulence.     

Cardiorespiratory kinetics and femoral artery blood velocity during dynamic knee extension exercise

The kinetics of femoral artery mean blood velocity (MBV; measured by pulsed Doppler) and whole body oxygen uptake (VO2; measured breath by breath) were assessed from the time constant during the on (tau on) and off (tau off) transients to step changes in work rate between complete rest and dynamic knee extension (KE) exercise. Six healthy men performed 5 min of seated KE exercise, with each leg alternately raising and lowering a weight (10% maximum voluntary contraction) over a 2-s duty cycle. Because kinetic analysis of VO2 kinetics during KE exercise is a new approach, the VO2 responses were also evaluated during the on and off transitions to the more familiar upright cycling exercise in which the magnitude of increase in VO2 and cardiac output was similar to that during KE exercise. During KE exercise, VO2 tau on [mean 72.2 +/- 11.2 (SE) s] was slower than VO2 tau off (33.3 +/- 1.8 s; P < 0.01). Cardiac output, measured with impedance cardiography, was not different for tau on (67.1 +/- 20.0 s) compared with that for tau off (52.9 +/- 7.6 s). Likewise, MBV tau on (34.5 +/- 3.9 s) was not different from tau off (35.3 +/- 3.2 s). During cycling, the VO2 tau on (18.0 +/- 2.4 s) and tau off (30.7 +/- 1.2 s) were both faster than KE VO2 tau on (P < 0.01). Even though the MBV kinetics indicated a rapid adaptation of blood flow during KE exercise, there was a slow adaptation of VO2. A transient hyperemia immediately on cessation of KE exercise, indicated by both MBV and calculated systemic vascular conductance responses, suggested that blood flow might have been inadequate and could have contributed to the delayed adaptation of VO2 at the onset of exercise, although other explanations are possible.     

Doppler ultrasound investigation of uterine and ovarian blood flow in infertility and early pregnancy

This review describes the current use of Doppler ultrasound to examine blood flow in the uterus and ovaries in infertile patients and during early pregnancy. The basics of Doppler ultrasound and the different methods of measuring blood flow are discussed from the viewpoint of the clinician who may be unfamiliar with Doppler physics and terminology. Normal values in the menstrual cycle and the relationship of uterine and ovarian blood flow to infertility and to implantation following in-vitro fertilization are presented. Normal values for uterine blood flow in the first 16 weeks of pregnancy and the effect of sex steroids and ovulation induction on their values are described. The possible relationship of defective uterine blood flow to recurrent abortion is examined. New areas of investigation, such as the effect of standing on blood flow, and the effect of drugs are explored. The findings of this review indicate that Doppler blood flow studies may provide significant information about possible causes of some disorders of infertility and early pregnancy and methods of treatment for the same.     

Doppler echocardiographic assessment of fetal blood flow redistribution during maternal hyperoxygenation

In a retrospective analysis of the standard protocols for fetal echocardiographic examination, 27 fetuses (mean gestational age 29 +/- 5.4 weeks) with ascites were evaluated. Fetal cardiomegaly (increased heart area/chest area ratio), the presence or absence of atrioventricular valve regurgitation, inferior vena cava and ductus venosus Doppler flow velocity and umbilical vein pulsation were evaluated quantitatively in a group of survivors and non-survivors. A statistically significant difference between the two groups was found for the presence of atrioventricular valve regurgitation (p = 0.003), and for cardiomegaly (p = 0.009). There was no statistical difference for the presence of abnormal venous flow and umbilical pulsation (p > 0.05). Abnormal venous Doppler flow velocities in the inferior vena cava and ductus venosus were observed more frequently than umbilical vein pulsation. The mean heart area/chest area ratios in the group of survivors and in the group of non-survivors were 0.34 +/- 0.09 and 0.48 +/- 0.08, respectively (p < 0.001). The mean gestational ages at the time of diagnosis of ascites in the groups of survivors and non-survivors were 33 +/- 3.3 weeks and 28 +/- 5.1 weeks, respectively (p < 0.05); the mean gestational ages at the time of delivery were 35.6 +/- 2.3 weeks and 33.3 +/- 4.9 weeks, respectively (p = 0.33). In terms of different echocardiographic features as well as the gestational age of the unborn patient with ascites, there is apparently no single indicator of a poor prognosis. Our results suggest that the prognosis is usually poor in a fetus with ascites, when cardiomegaly is detected, as well as the presence of tricuspid and mitral valve regurgitation. This is regardless of the type of venous flow and regardless of the etiology of the ascites.     

Doppler ultrasound determination of average blood flow velocity and flow volume in transjugular intrahepatic portosystemic shunt (TIPS)

We evaluated the acute and chronic experimental toxicity of a water extract of saponins from Argania spinosa following oral and intraperitoneal (i.p.) administration in mice (Iops Ofa) and rats (Wistar). The DL50 obtained were 79 mg/kg for the i.p. route and 1,300 mg/kg for the oral route. For the chronic toxicity studies, we administred 100 and 200 mg/kg orally once a day during a 3 month period. There was a decrease in blood sugar in the third month of each therapy. Blood creatinine levels increased, thus evoking a renal pathology. A slight increase in transaminases levels was not significatif. Hematologic parameters were unchanged during the treatment and the histopathologic study showed hepatic glycogen decrease and a focal renal tube deterioration.     

Local cerebral blood flow measured by xenon-enhanced CT during cryogenic brain edema and intracranial hypertension in monkeys

We developed a closed-skull model of freeze injury-induced brain edema, a model classically thought to produce vasogenic edema, and observed the natural course of changes in edema and blood flow using xenon-enhanced computed tomography (CT) in five rhesus monkeys before and for up to 6 h post insult. Intracranial pressure (ICP) gradually rose throughout the duration of the experiment. CT scans and CBF images permitted direct observation of the evolution of the lesion and revealed early ischemia in the periphery of the injury zone that progressed over time in association with edema. Frequency histogram analysis of local CBF (ICBF) demonstrated subtle but potentially important changes in distribution of ICBF between and within hemispheres at various times post insult. Changes in ICBF distribution were phasic and dissociated from increases in ICP in the latter stages of injury. The Xe/CT CBF method can be used to evaluate the effects of injury and therapy on CBF in this and other models of acute brain injury.     

Intrasplenic venous flow patterns demonstrated by Doppler ultrasound in patients with portal hypertension

The flow pattern in the splenic vein has been previously reported in patients with portal hypertension, but with no reference to the flow within the intrasplenic venous radicles. Using Doppler ultrasound, this study describes the intrasplenic venous flow direction in 176 adult patients with intrahepatic portal hypertension. In our series, a normal flow pattern was maintained in all except four patients (2.3%) who had either reversed or dual venous drainage patterns resulting in trans-splenic portosystemic shunts. These abnormal patterns are Doppler signs of portal hypertension which might be associated with a higher risk of oesophageal variceal bleeding. It is recommended that the intrasplenic venous flow pattern should be assessed before surgical intervention involving the spleen in patients with portal hypertension.     

Oxygen consumption by and blood flow across the portal-drained viscera and liver of pregnant ewes

The energy requirement of ewes increases during pregnancy. In late pregnancy, approximately 40% of the increase in heat production can be attributed to increases in heat production by nonreproductive tissues. The objective of this study was to determine the pattern of oxygen consumption by the portal-drained viscera (PDV) and liver during pregnancy to allow for an estimation of the extent to which these tissues contribute to the increase in energy requirement. Nineteen multiparous ewes were individually penned and allowed ad libitum access to an alfalfa hay-based diet. Catheters were surgically placed in the portal vein, a branch of the hepatic vein, a mesenteric vein, and the abdominal aorta. Oxygen consumption by the PDV and liver were subsequently measured before breeding and at 6, 19, 39, 61, 82, and, 103 d before lambing. Hepatic arterial blood flow was not influenced by litter size (P = .89) or stage of pregnancy (P = .28). Portal and hepatic venous blood flow peaked 19 d before lambing. Oxygen consumption by the PDV and liver increased with increased ad libitum feed intake. The increase in hepatic oxygen consumption occurred approximately 63 d earlier in ewes with twins than in ewes with a single fetus independent of changes in feed intake. Hepatic oxygen consumption increased with duration of gestation and was estimated to account for 40% of the heat production not associated with the gravid uterus.     

The blood flow characteristics in borderline ovarian tumors based on both color Doppler ultrasound and histopathological analyses

We previously reported that a macrophage response that increased binding to 125I-radiolabeled soluble denatured collagen (gelatin) was induced by preincubation of macrophage with a 70-kDa amino-terminal fibronectin fragment and soluble nonlabeled gelatin [S. F. Penc, F. A. Blumenstock, J. E. Kaplan (1995) J. Leukoc. Biol. 58, 501-509]. We now report that neither protein synthesis nor recycling of receptors between the cell surface and interior were required for this response. However, removal of cell surface components with trypsin demonstrated that induced gelatin binding required native cell surface constituents. It was found that in the presence of the 70-kDa fibronectin fragment and gelatin, matrix metalloprotease-2 (MMP-2) and matrix metalloprotease-9 (MMP-9) activity in the cell layers was significantly decreased or undetectable, respectively. Similar levels of increased gelatin binding could be reproduced after inhibition of matrix-degrading metalloprotease activity with 1'10-phenanthroline. These results demonstrate that a macrophage specific response that decreased gelatinase activity and increased gelatin binding was initiated by interaction with a 70-kDa fibronectin fragment and gelatin.     

Color flow pulsed Doppler ultrasound in diagnosing luteal phase defect

Actin-crosslinking proteins link F-actin into the bundles and networks that constitute the cytoskeleton. Dystrophin, beta-spectrin, alpha-actinin, ABP-120, ABP-280, and fimbrin share homologous actin-binding domains and comprise an actin crosslinker superfamily. We have identified a novel member of this superfamily (ACF7) using a degenerate primer-mediated PCR strategy that was optimized to resolve less-abundant superfamily sequences. The ACF7 gene is on human chromosome 1 and hybridizes to high molecular weight bands on northern blots. Sequence comparisons argue that ACF7 does not fit into one of the existing families, but represents a new class within the superfamily.     

Measurement of rectal blood flow by laser Doppler flowmetry in inflammatory bowel disease

BACKGROUND/AIMS: Vascular alterations have been suggested as pathogenic factors in inflammatory bowel disease, particularly Crohn's disease. The aim of our study was to assess rectal blood flow in patients with active inflammatory bowel disease involving the rectum. METHODOLOGY: Endoscopic measurement of rectal blood flow was performed by laser Doppler flowmetry in 45 subjects divided into three groups: healthy controls, ulcerative colitis and rectal Crohn's disease. RESULTS: Rectal perfusion was found to be significantly impaired in patients with ulcerative colitis, but not in those with Crohn's colitis. CONCLUSIONS: Our results confirm the role of local ischemia in ulcerative colitis, but do not support the theory that vascular factors play a key role in the pathogenesis of Crohn's disease.     

Regional cerebral blood flow measured by 99mTc-HMPAO SPECT differs in subgroups of Alzheimer's disease

Alzheimer's disease (AD) is a heterogeneous entity. Identifying AD subtypes might have impact in patients' response to different treatment strategies. We designed a study to examine regional cerebral blood flow (rCBF) in AD subtypes. To identify AD subtypes, we performed a cluster analysis including performance on memory, language, visuospatial, praxic, and executive functions. The rCBF measured by 99mTc-HMPAO SPECT was referred to the cerebellum. We examined 35 patients fulfilling the NINCDS-ADRDA criteria of probable AD and 13 age and sex-matched healthy cognitively intact controls. AD patients were at the early stage of the disease, their mean Mini-Mental Status (MMS) score (S.D.) was 22.5 (3.6). The cluster analysis revealed two AD subgroups: AD1 (N = 12) and AD2 (N = 23). The subgroups did not differ in age, sex, or global clinical severity as assessed by MMS and Brief Cognitive Rating Scale (BCRS). Both subgroups had equally impaired memory. The AD2 group was inferior to the AD1 group on verbal, visuospatial, praxic, and executive functions. The AD1 group showed reduced rCBF ratios in the temporal and parietal cortices and the amygdala compared to controls. The AD2 group differed from controls in the rCBF ratios of frontal, temporal, parietal, occipital, basal ganglia, and amygdaloid regions bilateral and from AD1 in the rCBF ratios of frontal and temporal cortices. In AD patients, the rCBF ratios did not correlate with MMS or BCRS scores. In contrast, several significant correlations were found between decreases rCBF ratios and impairment of memory and other cognitive functions. In conclusion, a cluster analysis on neuropsychological test performance identified two AD subgroups that differed on the neuropsychological profile and on the rCBF in spite of similar global clinical severity.