Blood Flow Velocity Parameters Research Articles

Preeclampsia is Associated With Global Cerebral Hemodynamic Changes

To compare blood flow-velocity parameters in the anterior and posterior cerebral arteries between normotensive and preeclamptic pregnant women. Transcranial Doppler ultrasound was used to measure peak, end-diastolic, and mean velocities in the anterior cerebral artery (ACA) and posterior cerebral artery (PCA) of 22 normotensive and 12 preeclamptic women in the third trimester. All measurements were performed with the subject in the left lateral position. Blood pressure and heart rate were recorded with each Doppler measurement. The mean pulsatility index (PI), resistance index (RI), and cerebral perfusion pressure for each artery was averaged and compared. Statistical significance was set at P <.05. Preeclamptic women had higher cerebral perfusion pressure in both ACA and PCA (64.7 +/- 5.9 and 78.1 +/- 7.6 compared with 42.4 +/- 2.6 and 54.1 +/- 4.1 mmHg, P <.05), lower PI (0.83 +/- 0.05 and 0.71 +/- 0.04 compared with 0.96 +/- 0.04 and 0.84 +/- 0.02, P <.05), and lower RI (0.55 +/- 0.02 and 0.49 +/- 0.02 compared with 0.60 +/- 0.02 and 0.55 +/- 0.01, P <.05) than normotensive pregnant women. Preeclamptic patients have globally elevated cerebral perfusion pressure and lower resistance in the cerebral circulation than normotensive pregnant women.

Application of FFT-Analyzed Umbilical Artery Doppler Signals to Fuzzy Algorithm

Doppler signals, recorded from the umbilical artery of 60 women with pregnancy, were transferred to personal computer via a 16-bit sound card. The fast Fourier transform (FFT) method was applied to the recorded signal from each patient. Because FFT method inherently cannot offer a good spectral resolution at highly turbulent blood flows, it sometimes causes wrong interpretation of Doppler signals. In order to avoid this problem, umbilical artery Doppler blood flow velocity parameters were introduced to a fuzzy algorithm. It is observed that the fuzzy algorithm gives true results for interpretation of umbilical artery blood flow velocity parameters. Forty-five blood flow velocity parameters of 60 women with pregnancy and 15 parameters in training data have been used in a fuzzy system as testing data. The overall success ratio in training data and the testing data were 95.55 and 93.35% respectively.

Cerebrovascular Reactivity in Hypertensive and Healthy Adolescents: TCD With Vasodilatory Challenge

Adolescent hypertension predicts hypertension and increased cardiovascular morbidity in adulthood. The aim of the present work was to test whether cerebrovascular reactivity to CO2 is altered among hypertensive adolescents. From the population-based cohort of the Debrecen Hypertension Study, 113 hypertensive and 58 normotensive adolescents underwent transcranial Doppler measurements at rest and after 30 seconds of breath holding. Systolic, mean, and diastolic blood flow velocities were higher among hypertensive individuals at rest. Taking the absolute blood flow velocity parameters into account, after breath holding, only the pulsatility index was significantly higher in the hypertensive group. The percentage change of the different blood flow parameters showed less intensive change in hypertensive teenagers. Cerebral vasoreactivity is decreased among hypertensive individuals as compared to healthy controls.

Water-immersion wrinkling is due to vasoconstriction.

The underlying mechanism of the water-immersion skin wrinkling test, which is used as a test of sympathetic nerve function, remains elusive. We investigated changes of blood circulation in the hand occurring with water-immersion wrinkling by measuring the velocity of ulnar and digital artery blood flow, and of digit skin blood flow, in healthy subjects before and during wrinkling. Wrinkling was accompanied by significant reduction in blood flow velocity in all vessels, with a maximum in digital vessels. Our data show that water-immersion wrinkling is a function of digit pulp vasoconstriction. This test of sympathetic function can now be quantified using parameters of blood flow velocity, enabling its more widespread and accurate use.

Optimized stent implantation according to intracoronary Doppler-derived parameters

The introduction of guidewires equipped with sensors for measurement of intracoronary Doppler flow and pressure allows direct evaluation of the result of percutaneous transluminal coronary angioplasty (PTCA) on coronary hemodynamics. Single-center studies have shown that stent implantation can be optimized using intracoronary-measured blood flow velocity (coronary flow reserve [CFR]) and pressure (fractional flow reserve [FFR]) parameters. 1,2 Furthermore, recent studies have shown that an optimized stent implantation according to Doppler flow parameters (CFR and relative CFR) yields an excellent clinical outcome. 3,4 In the Doppler Endpoints Balloon Angioplasty Trial Europe (DEBATE) II study, optimized balloon angioplasty using angiographic and Doppler flow parameters was followed by stent implantation in a subset of patients. 5 This post hoc analysis examines optimal cutoff values for angiographic and Doppler flow parameters to predict long-term (12 months) clinical outcome after stent implantation. ••• The study population of this post hoc analysis consisted of 187 patients with stable or unstable angina pectoris undergoing Doppler-guided stent implantation in the setting of a multicenter study for the treatment of a single de novo coronary stenosis (DEBATE II). 5 Briefly, patients with 1 major native coronary artery and normal left ventricular function that were eligible for PTCA were included in this study. In the DEBATE II study, 620 patients were first randomized to guided balloon angioplasty (n 523) or direct stent implantation (n 97). In the guided balloon angioplasty arm, the operators were urged to obtain an optimal result predefined as a diameter stenosis 35% and a CFR 2.5. Bailout stenting was performed in 129 patients, and 15 patients were excluded because of technical reasons. The patient population of this substudy consisted of 187 of the remaining 379 patients who underwent stent implantation after a second randomization, irrespective of the result after balloon angioplasty. Coronary cineangiography was performed using standard procedures. All cine films were analyzed by an independent core laboratory without

Surgically induced menopause and blood flow in cerebral arteries

The relationship between hormone replacement therapy (HRT) and Doppler-derived parameters of blood flow velocity in the arterial vessels of nonatherosclerotic, nonhypercholesterolemic postmenopausal women has been widely studied (1–4). These studies have generally used the pulsatilty index, which is believed to represent flow resistance downstream of the point of measurement, but only cross-sectional data are available concerning the relationship between pulsatilty index and menopause. The aim of this prospective clinical study was to elucidate this correlation by evaluating the effect of surgical castration on blood flow velocity in the cerebral arteries of premenopausal women.

Hypoxic-Ischaemic Encephalopathy Is Associated with Regional Changes in Cerebral Blood Flow Velocity and Alterations in Cardiovascular Function

Doppler-derived indices of cerebral blood flow velocity (CBFV) and echocardiographic parameters of left ventricular function were measured in 18 patients with hypoxic-ischaemic encephalopathy HIE (group I) and in 28 normal controls (group II). Group-I infants had a subnormal distribution of CBFV values increasing over the first 85 h postnatally. CBFV values were constantly higher in the internal carotid than in the anterior cerebral artery. During the first 24 h postnatally, pulsatility and resistance indices of cerebral blood flow were significantly higher in group-I patients. From 30 to 85 h after birth, resistance indices were lower in group-I infants with severe HIE. Depressed left ventricular function and/or hypotension was documented in 50% of group-I patients.

Middle cerebral artery blood flow velocity in patients with cirrhosis

Brain dysfunction is common in patients with advanced liver disease; it is often manifested as hepatic encephalopathy, but its cause is not clearly understood. Intracranial blood flow velocity parameters, including peak systolic velocity, end diastolic velocity and mean velocity of both middle cerebral arteries were measured by transcranial Doppler ultrasonography in 37 patients with cirrhosis without encephalopathy (16 Child's A, 10 Child's B and 11 Child's C) and 12 normal controls. The cause was alcohol-related in 24 and non-alcohol-related in 13. No significant differences in any of the Doppler parameters were detected in Child's group A when compared with controls. However, a statistically significant decrease in middle cerebral artery blood flow velocity was evident when Child's B and C patients without clinically apparent encephalopathy were compared with controls irrespective of the cause. Our results demonstrate that intracranial blood flow is abnormal in patients with advanced liver disease without clinically apparent encephalopathy.

Intracranial pressure and cerebral arterial flow velocity indices in childhood hydrocephalus: current review.

Because of its noninvasive and repeatable nature, Doppler ultrasound has been increasingly used to assess changes in cerebral haemodynamics in infants and children with hydrocephalus. There is general agreement that a direct correlation exists between the intracranial pressure (from experimental, fontanometric and direct measurement evidence) and the resistance index. In addition, this increasing index has been predominantly due to a reduction in the end-diastolic velocity. Stable ventriculomegaly is associated with normal pulsatility. The cerebral blood flow velocity parameters change significantly following CSF drainage by tapping or shunting. The measurement of intracranial pressure and cerebral blood flow velocity are currently the best ways of assessing the need for CSF diversion and monitoring subsequent shunt function.

Differential characterization of blood flow, velocity, and vascular resistance between proximal and distal normal epicardial human coronary arteries: Analysis by intracoronary Doppler spectral flow velocity

To characterize coronary blood flow velocity parameters and to determine the relation among velocity, volumetric flow, and vascular resistance in awake human beings, we performed paired proximal and distal velocity measurements in 28 angiographically normal coronary arteries. Mean velocity, peak velocity, diastolic-to-systolic velocity ratio, and diameter and cross-sectional area of proximal and distal arteries were determined and coronary flow and vascular resistance computed. Mean velocity and coronary vasodilator reserve were similar for all three native arteries and were preserved from proximal to distal segments. Volumetric flow decreased from proximal to distal segments. The demonstrated inverse and curvilinear (polynomial) relation between volumetric flow and vascular resistance agrees with theoretical and animal models of coronary physiologic characteristics and suggests a nadir of coronary vascular resistance below which coronary flow no longer increases.

Duplex ultrasonographic assessment of gut blood flow velocity: effect of meal composition in normal full-term newborns after first feed.

We used transcutaneous duplex Doppler ultrasound to measure superior mesenteric artery and celiac artery blood flow velocity in 45 normal healthy newborn infants. Doppler indices of PSV, TAMV, EDV, and PI were measured immediately before and after feeding at 15 minute intervals up to 75 minutes. Maximal changes were compared with preprandial baseline values. There were no significant differences between the preprandial and postprandial blood pressures and heart rates. In the superior mesenteric artery the PSV, TAMV, and EDV rose progressively and peaked 30 minutes after feeding in both the milk-fed group and the 5% glucose, water-fed group over baseline (73 versus 41% and 110 versus 63%, 130 versus 100%) (P < 0.05). The PI decreased significantly in the milk-fed group only. There were no significant changes in any blood flow velocity parameters derived from the celiac artery. We conclude that duplex ultrasonography provides a noninvasive means of studying the reactivity of the splanchnic arterial circulation to different stimuli. The chemical composition of the meal is a significant factor determining postprandial mesenteric hyperemia.

Laser Doppler Flowmetry in Lower Extremity Ischemia: Application and Interpretation

The present study was undertaken in order to develop numerical criteria for the parameters of laser Doppler flowmetry-skin blood flow velocity and pulse wave amplitude in the evaluation of lower extremity ischemia. Fifty limbs of young healthy volunteers were examined in order to obtain baseline normal values. Patient population was divided into moderately ischemic (52 limbs) and severely ischemic (22 limbs), based on patients' complaints, physical examination, ankle-brachial indices, pulse volume recordings and arteriographies. Univariate comparison between the three groups of skin blood flow velocity and pulse wave amplitude at each time point were done by analysis of variance. Power of discrimination between degrees of ischemia was evaluated by computing sensitivity and specificity, based on skin blood flow velocity and pulse wave amplitude values at time points best for predicting the severity of disease by multiple regression analysis. Using cutoff points of < 31 for skin blood flow velocity and < 9 for pulse wave amplitude, a 96% sensitivity and 96% specificity were obtained in separating normal from ischemic limbs. Cutoff points of < 9 for skin blood flow velocity and < 4 for pulse wave amplitude discriminated with a 100% sensitivity and specificity between the moderately and severely ischemic limbs. We propose the use of laser Doppler flowmetry with local heating and reactive hyperemia, and the cutoff points stated above as an additional tool to evaluate lower extremity ischemia through assessment of cutaneous microcirculation.

Thrombolytic effects of a novel modified tissue plasminogen activator, E6010, on coronary thrombosis in the pig.

This study was conducted to compare the thrombolytic effect of a novel modified tissue plasminogen activator, E6010, with that of recombinant human tissue plasminogen activator (t-PA), administered by single intravenous bolus injection in pigs with occlusive coronary thrombosis. Thrombosis was induced by electrical stimulation of the intimal surface of the left circumflex coronary artery. Coronary blood flow velocity and hemodynamic parameters were observed for 1 hr after complete cessation of coronary flow. Ten minutes after heparin injection (300 U/kg), E6010, t-PA or placebo was intravenously administered as a bolus. E6010 at 0.2 and 0.4 mg/kg caused recanalization of the occluded coronary artery in 1 of 6 and 5 of 5 pigs, respectively. The time to recanalization after 0.4 mg/kg of E6010 was 22 +/- 11 min (mean +/- S.E.M.). t-PA (0.4 mg/kg) caused recanalization in only 1 of 5 pigs. Recanalization did not occur in any of the 6 animals administered placebo. Plasma clearance of E6010 was smaller than that of t-PA (4.9 +/- 0.3 vs. 9.4 +/- 3.8 ml/min/kg). There were no significant differences in plasma levels of fibrinogen, alpha 2-plasmin inhibitor and plasminogen among the placebo, E6010 and t-PA groups. These results suggest that the slower clearance of E6010 from plasma contributes to the effective thrombolytic action of E6010 following single intravenous bolus injection.

Thrombolytic Effects of a Novel Modified Tissue Plasminogen Activator, E6010, on Coronary Thrombosis in the Pig

This study Was conducted to compare the thrombolytic effect of a novel modified tissue plasminogen activator, E6010, with that of recombinant human tissue plasminogen activator (t-PA), administered by single intravenous bolus injection in pigs with occlusive coronary thrombosis. Thrombosis was induced by electrical stimulation of the intimal Surface of the left circumflex coronary artery. Coronary blood flow velocity and hemodynamic parameters were observed for 1 hr after complete cessation of coronary flow. Ten minutes after heparin injection (300 U/kg), E6010, t-PA or placebo was intravenously administered as a bolus. E6010 at 0.2 and 0.4 mg/kg caused recanalization of the occluded coronary artery in 1 of 6 and 5 of 5 pigs, respectively. The time to recanalization after 0.4 mg/kg of E6010 was 22 ± 11 min (mean ± S.E.M.). t-PA (0.4 mg/kg) caused recanalization in only 1 of 5 Pigs. Recanalization did not occur in any of the 6 animals administered plasma clearance of E6010 was smaller than that of t-PA (4.9 ± 0.3 vs. 9.4 ± 3.8 ml/min/kg). There were no significant differences in plasma levels of fibrinogen, α2-plasmin inhibitor and plasminogen among the placebo, E6010 and t-PA groups. These results suggest that the slower clearance of E6010 from plasma contributes to the effective thrombolytic action of E6010 following single intravenous bolus injection.

Orthostatic changes of cerebral blood flow velocity in patients with autonomic dysfunction

Simultaneous registrations of intracranial blood flow velocity parameters achieved by transcranial Doppler sonography and basic cardiovascular parameters were carried out during orthostatic changes in normal controls, diabetic patients and patients with pandysautonomia. Normal subjects had a rapid increase in heart rate at a constant blood pressure and a slight decrease in cerebral blood flow velocities associated with a mild increase of the pulsatility index (PI) after being tilted from a horizontal to a vertical position. Diabetics showed a fixed heart rate reflecting the disturbed autonomic innervation but only minor changes of cerebral blood flow velocity, which is similar to normal cerebrovascular autonomic regulation. Patients with pandysautonomia had a fixed heart rate associated with a decrease of systemic blood pressure but a failure of compensatory cerebral autoregulation to maintain normal flow velocity values after standing up. The results suggest that in diabetics cerebrovascular autonomic regulation is intact in contrast to cardiac autonomic function, while in patients with pandysautonomia both functions are disturbed. Criteria for the interpretation of autonomic regulatory mechanisms involved in cerebrovascular flow measurements are discussed.

Evaluation of dilated cardiomyopathy by pulsed Doppler echocardiography

The ability of pulsed Doppler echocardiography to identify patients with left ventricular systolic dysfunction was evaluated in 12 patients with dilated (congestive) cardiomyopathy. A range-gated, spectrum analyzer-based Doppler velocimeter was used to record blood flow velocity in the ascending aorta and main pulmonary artery. The following blood flow velocity parameters were measured or derived: peak flow velocity, acceleration time, average acceleration, deceleration time, average deceleration, ejection time, and aortic flow velocity integral. Doppler blood flow velocity data in the cardiomyopathy patients were compared to data from 20 normal subjects. Measurements from the ascending aorta revealed that peak aortic flow velocity discriminated between cardiomyopathy patients (mean 47 cm/sec, range 35 to 62) and normal subjects (mean 92 cm/sec, range 72 to 120) with no overlap in data ( p < 0.001). Aortic flow velocity integral was also able to separate the patients with dilated cardiomyopathy (mean 6.7 cm, range 3.5 to 9.1) from normal subjects (mean 15.7 cm, range 12.6 to 22.5) with no overlap in data ( p < 0.001). Although mean values for average aortic acceleration and aortic ejection time were also significantly different (both p < 0.005), there was some overlap between the two groups. Pulmonary artery blood flow studies demonstrated significantly increased average acceleration, as well as decreased ejection time (both p < 0.05), but no difference in average deceleration or peak flow velocity in cardiomyopathy patients compared to normals. Compared to pulmonary flow measurements, aortic Doppler flow velocity measurements allowed better separation of cardiomyopathy and normal groups. In addition, aortic peak flow velocity appeared to correlate well ( r = 0.83) with M-mode echocardiographic measurement of left ventricular percent fractional shortening; both parameters were equally useful in discriminating patients with normal left ventricular function from those with global dysfunction (dilated cardiomyopathy). Thus pulsed Doppler echocardiography appears to be a useful addition to M-mode and two-dimensional echocardiography in the quantitative noninvasive assessment of left ventricular systolic function.