Non-invasive evaluation of the conduit function and the buffering function of large arteries in man

The purpose of this study was to validate a two-dimensional (2D) echography coupled range-gated Doppler system for the non-invasive measurement of internal diameter, blood flow velocity, and pulse wave velocity of peripheral arteries, such as the common carotid artery (CCA), femoral artery (FA), and brachial artery (BA) in man. The array of the ultrasonic system and the Doppler probe were attached and formed a fixed angle (38deg; 30′). The artery was firstly visualized using the echo-graphic array probe in order to position the Doppler beam. Then, the range-gated Doppler system was used to measure both internal diameter and blood flow velocity with the sample volume position covering the internal diameter. Using a hydraulic device, there was an obvious correlation between the calculated and the measured velocities (r = 0·98). Normal values of diameter, blood flow velocity and blood flow were measured in 18 healthy volunteers. The means (± 1 standard deviation) was as follows: diameter, CCA = 0·636 ± 0·027 cm, FA = 0·843 ± 0·074 cm, BA = 0·302 ± 0·052 cm; flow velocity, CCA = 19·5 ± 2·1 cm s¹, FA = 11·4 ± 1·2 cm s¹, BA = 6·7 ± 1·0 cm s¹. Blood flows were as follows: CCA, 370·6 ± 42·5 ml mn¹, FA 387·0 ± 75·0 ml mn¹ and BA (wrist occlusion) 29·8 ± 12·5 ml mn¹. The intra-observer reproducibilities for CCA, FA and BA were respectively: for diameter, 4·9%, 4·12% and 14·8%; for velocity, 8·9%, 10·6% and 10·2%. The inter-observer reproducibilities were respectively: for diameter, 5·6%, 5·4% and 11·3% for velocity, 6·5%, 5·7% and 6·3%. Simultaneous determinations of pulse wave velocity from blood flow velocity recording allowed estimations of the distensibility of these arteries. Finally, the coupled echo and range-gated Doppler system permitted non-invasive evaluation of blood flow calculated as the product of the vessel cross-sectional area and measured blood velocity and also of arterial compliance as the ratio of the cross-sectional area and the square of pulse wave velocity. Such estimations of the conduit and buffering functions of peripheral large arteries in man were shown to be more accurate for the common carotid and the femoral arteries than for the brachial artery.     

Volume blood flow estimation in the normal and growth-restricted fetus

The objective was to compare volume blood flow (VBF) in the descending aorta (DAo) of gestational age and weight-matched growth restricted (GR) and normal (N) fetuses. A longitudinal study of 20 N was compared with 11 GR in two analyses matched for weight and gestation. DAo dimensions and flow velocity were measured simultaneously using a new technique combining an ultrasonic phase-locked echo-tracking system synchronized with a pulsed Doppler velocimeter. Cardiac output was estimated using standard echocardiographic views. DAo and semilunar valve diameters increased linearly in N and indexed cardiac output was similar in N and GR, although GR showed reduced DAo relative pulse amplitude, mean flow velocity and VBF. This synchronized technique permits calculation of VBF in human fetuses. Growth restriction is associated with reduced aortic wall pulsations and lower mean blood flow velocities and VBF in DAo secondary to increased placental impedance.     

Umbilical venous volume flow in the normally developing and growth-restricted human fetus.

OBJECTIVE: To determine the reproducibility of measurement of umbilical venous volume flow components and to calculate umbilical venous volume flow in normal and growth-restricted (small-for-gestational age) fetuses in a cross-sectional study. METHOD: Using Labview and Imaq-vision software, the cross-sectional inner area of the umbilical vein was traced. Vessel area (mm2) and Doppler-derived time-averaged flow velocity (mm/s) were multiplied to calculate volume flow (mL/min) including flow per kg fetal weight. The coefficient of variation for vessel area and flow velocity scans and tracings were determined (n = 13; 26-35 weeks). Normal charts for components and volume flow were constructed (n = 100; 20-36 weeks) and related to data from growth restricted fetuses (birth weight < 5th centile) (n = 33; 22-36 weeks). In growth-restricted fetuses the umbilical artery pulsatility index was also obtained. RESULTS: Reproducibility: The coefficient of variation was 5.4% (vessel area) and 7.3% (time-averaged velocity) for scans and 6.6% and 10.5% for measurements, resulting in a coefficient of variation of 8.1% (scans) and 11.9% (measurements) for volume flow. A gestational age-related increase exists for vessel area, time-averaged flow velocity and umbilical venous volume flow from 33.2 (SD, 15.2) mL/min at 20 weeks to 221.0 (SD, 32.8) mL/min at 36 weeks of gestation, but there is a reduction from 117.5 (SD, 33.6) mL/min to 78.3 (SD, 12.4) mL/min for volume flow per kg fetal weight. In small-for-gestational age fetuses, the values were below the normal range in 31 of 33 cases for volume flow and in 21 of 33 cases for volume flow per kg fetal weight. Umbilical artery pulsatility index was significantly different between the subsets with normal and those with reduced volume flow per kg fetal weight. CONCLUSIONS: Measurements of umbilical venous vessel area and time-averaged velocity resulted in acceptable reproducibility of volume flow calculations, which show a seven-fold increase at 20-36 weeks of gestation. In growth-restricted fetuses, volume flow is significantly reduced. When calculated per kg/fetus, the values were reduced in 21 (63.6%) out of 33 cases.     

Evaluation of aortic geometries created by magnetic resonance imaging data in healthy volunteers

Introduction: The development of atherosclerotic plaques has been associated with the patterns of wall shear stress (WSS). However, much is still uncertain with the methods used to calculate WSS. Correct vessel geometries are mandatory to get reliable estimations, and the purpose of this study was to evaluate an in vivo method for creating aortic 3D geometry in human based on data from magnetic resonance imaging (MRI) with ultrasound as reference. Methods: The aortas of ten healthy men, 23·4 ± 1·6 years of age, were examined with a 1·5 T MRI system using a 3D gadolinium‐enhanced gradient‐echo sequence. Three‐dimensional geometries were created using manual segmentation of images. Lumen diameters (LD) were measured in the abdominal aorta (AA) and the thoracic aorta (TA) with non‐invasive B‐mode ultrasound as a reference. Results: The anteroposterior diameter of the AA was 13·6 ± 1·1 mm for the MRI and 13·8 ± 1·3 mm for the ultrasound (NS). Intraobserver variability (CV) for MRI and ultrasound was <0·92% and <0·40%, respectively. Interobserver variability for MRI and ultrasound was 0·96% and 0·56%, respectively. The diameter of the TA was 19·2 ± 1·4 mm for the MRI, and the intraobserver variability (CV) was <0·78% and interobserver variability (CV) was 0·92%. Conclusion: Specific arterial geometries can be constructed with a high degree of accuracy using MRI. This indicates that the MRI geometries may be used to create realistic and correct geometries in the calculation of WSS in the aorta of human.     

超声心动图对正常胎儿心脏结构的定量分析

目的对孕20～40周正常胎儿心脏结构及血流参数进行定量分析,评价其动态变化规律。方法测量2458例胎儿各房室内径、大血管内径及各瓣口血流速度。对其中854例正常胎儿心脏按不同孕周分为5组进行分析。结果在所观察的胎儿心脏各项参数中,其中各房室内径和主、肺动脉内径均与孕周呈直线相关(r值分别为0.69、0.68、0.70、0.68、0.73和0.72),而二尖瓣血流速度(E峰、A峰)、三尖瓣血流速度(E峰、A峰)、肺动脉瓣峰值血流速度和动脉导管血流速度(S峰、D峰)与孕周的相关关系较差(r值分别为0.33、0.06、0.35、0.04、0.22、0.23和0.09);并进行相关系数的显著性检验,均P<0.05。结论胎儿心脏发育以右心占优势;心脏各径线大小与孕周呈明显相关,据此可评价胎儿心脏发育情况,更好地对异常胎心进行筛查。     

Variation and reliability of ultrasonographic quantification of the architecture of the medial gastrocnemius muscle in young children

The aim of this study was to evaluate the suitability of ultrasonography for the quantification of gastrocnemius muscle architecture in healthy young children. The variation and reliability of measurement of muscle thickness, pennation angle and fibre length of the medial gastrocnemius were determined, using stationary and portable ultrasound machines, in 13 boys and eight girls aged 4–10. Ultrasound images were obtained from each leg, in duplicate, with the ankle at 90°, then at maximal plantar flexion, with the two machines within the same session. The same set of 16 scans was repeated in four children 4–6 weeks later. The mean muscle thickness, pennation angle and fibre length differed between ankle positions and between legs. Measurements obtained using the two machines established similar values with no significant differences in absolute values and coefficients of variation (CV). For duplicate images taken during the same session for the same leg, ankle position and machine, the CV and intraclass correlation coefficients (ICC) ranged, respectively, from 2·1% to 3·1% and 0·94–0·98 for muscle thickness, from 4·1% to 6·0% and 0·85–0·96 for pennation angle and from 4·5% to 6·3% and 0·87–0·96 for fibre length. Corresponding values for variables for the same child measured on two separate occasions were within the same ranges, all being similar to reliability data reported previously for adult muscle. Muscle thickness, pennation angle and fibre length of the medial gastrocnemius can therefore be quantified reliably, using either a stationary or portable ultrasound machine, in healthy young children.     

Whole‐body vibration dosage alters leg blood flow

The effect of whole‐body vibration dosage on leg blood flow was investigated. Nine healthy young adult males completed a set of 14 random vibration and non‐vibration exercise bouts whilst squatting on a Galileo 900 plate. Six vibration frequencies ranging from 5 to 30 Hz (5 Hz increments) were used in combination with a 2·5 mm and 4·5 mm amplitude to produce twelve 1‐min vibration bouts. Subjects also completed two 1‐min bouts where no vibration was applied. Systolic and diastolic diameters of the common femoral artery and blood cell velocity were measured by an echo Doppler ultrasound in a standing or rest condition prior to the bouts and during and after each bout. Repeated measures MANOVAs were used in the statistical analysis. Compared with the standing condition, the exercise bouts produced a four‐fold increase in mean blood cell velocity (P<0·001) and a two‐fold increase in peak blood cell velocity (P<0·001). Compared to the non‐vibration bouts, frequencies of 10–30 Hz increased mean blood cell velocity by approximately 33% (P<0·01) whereas 20–30 Hz increased peak blood cell velocity by approximately 27% (P<0·01). Amplitude was additive to frequency but only achieved significance at 30 Hz (P<0·05). Compared with the standing condition, squatting alone produced significant increases in mean and peak blood cell velocity (P<0·001). The results show leg blood flow increased during the squat or non‐vibration bouts and systematically increased with frequency in the vibration bouts.     

A methodological study of arterial wall function using ultrasound technique

We aimed to establish reference values for three important properties of the arterial wall using a conventional ultrasound scanner. We measured: (1) intima–media thickness (IMT) of the carotid arteries with the internal trace function of the ultrasound system; (2) wall stiffness by pulsatile diameter changes in the right common carotid artery assessed by M-mode; and (3) endothelial function expressed as flow-mediated dilatation (FMD) of the brachial artery. IMT and wall stiffness measurements and reproducibility were compared with those obtained by external analysing systems. All variables were obtained in healthy subjects (n = 20), 29–53 years old. IMT increased with age (P<0·01). There was no difference in IMT between men and women. The inter-operator variability for measuring IMT was 6–9%. The same order of reproducibility was obtained with an external PC-based analysing system. Regarding wall stiffness, no correlation was found with age, nor any difference between men and women. A low intra-operator variability (CV < 10%) was found for measurements of wall stiffness with both M-mode and an external wall tracking system. FMD of the brachial artery diminished with age (P<0·01). There was a relation between FMD and brachial artery size (P<0·01) and, therefore, as men have larger arterial diameters (P<0·01), smaller FMD in men. We conclude that it is possible to characterize arterial wall function non-invasively in an adequately reproducible manner using a conventional ultrasound system in healthy middle-aged men and women.     

Congenital aortico-left ventricular tunnel in fetuses and infants

Congenital aortico-left ventricular tunnel (ALVT) is a rare congenital heart disease. A 27-year-old woman was referred to us at 37 weeks gestation with fetal cardiac enlargement. The left ventricle (LV) of the fetus was enlarged. Fetal aortic valve (AoV) ring diameter spread was observed. Back flow from the AoV margins to the LV was observed. The prenatal diagnosis of the fetus was aortic regurgitation (AR). A male neonate was delivered by cesarean section at 40 weeks gestation. We made the diagnosis of ALVT because the aorta and the LV of the neonate showed a tunnel with blood flow on echocardiography. We took another look at the fetal echocardiography. The neonate underwent surgery for exacerbation of heart failure on the 7th day after birth. Trivial flow from the tunnel and mild AR were observed after surgery.     

Test–retest reliability of skeletal muscle oxygenation measurements during submaximal cycling exercise in patients with chronic heart failure

The potential purpose of near-infrared spectroscopy (NIRS) as a clinical application in patients with chronic heart failure (CHF) is the identification of limitations in O₂ delivery or utilization during exercise. The objective of this study was to evaluate absolute and relative test–retest reliability of skeletal muscle oxygenation measurements in patients with CHF. Thirty patients with systolic heart failure (left ventricular ejection fraction 31 ± 8%) performed 6-min constant-load cycling tests at 80% of the anaerobic threshold (AT) with tissue saturation index (TSI) measurement at the vastus lateralis. Tests were repeated after 10 ± 5 days to evaluate reliability. Absolute reliability was assessed with limits of agreement (LoA, expressed as bias ± random error) and coefficients of variation (CV) for absolute values (LoA range: 0·4 ± 6·2% to 0·6 ± 7·9%; CV range: 4·7–7·1%), amplitudes (LoA range −0·5 ± 5·8% to −0·7 ± 6·8%; CV range: 26·2–42·1%), onset and recovery kinetics (mean response times; LoA 0·4 ± 9·5 s, CV 23·5% and LoA −5·8 ± 50·8 s, CV 67·4% respectively) and overshoot characteristics (CV range 45·7–208·6%). Relative reliability was assessed with intraclass correlation coefficients for absolute values (range 0·74–0·90), amplitudes (range 0·85–0·92), onset and recovery kinetics (0·53 and 0·51, respectively) and overshoot characteristics (range 0·17–0·74). In conclusion, absolute reliability of absolute values and onset kinetics seems acceptable for serial within-subject comparison, and as such, for evaluation of treatment effects. Absolute reliability of amplitudes and recovery kinetics is considered unsatisfactory. Relative reliability of absolute values and amplitudes is sufficient for purposes of physiological distinction between patients with CHF. Despite lower relative reliability, kinetics may still be useful for clinical application.     

Diameter and velocity changes in the femoral vein during thermal stress in humans

Summary. Unlike most studies on deep veins performed with simultaneous suppression of cutaneous blood flow, a sonographic study of femoral diameter and blood flow velocity changes in response to thermal stress was performed while cutaneous flow was preserved. In 11 normal subjects, mean peak blood flow velocity and diameter of the femoral vein were measured at rest and during indirect whole body heating and cooling. Mean peak venous blood flow velocity was 0–12 0–06 m s^-1 at rest, 0–35 0–23 m s^-1(P < 0–001) during heat stress, and 0–13 0–07 m s^-1 during cold stress (NS). Femoral venous diameter was 5-3 0–9 mm at rest, 5-l l-0 mm (P < 0–05) during warming, and 5-4 81-0 mm (NS) during cooling. This study showed a decrease in diameter during thermal stress. However, as mean femoral venous blood-flow velocity was doubled during heat stress, femoral venous blood flow was increased. Thus, it is suggested that during heat stress part of the increase in cutaneous flow is returned through deep veins.,     

Technical achievement: transthoracic Doppler echocardiography can be used to detect LAD restenosis after coronary angioplasty

We investigated the capability of transthoracic Doppler echocardiography (TTE) to detect and quantify the severity of restenosis in the left anterior descending coronary artery (LAD) after percutaneous transluminal coronary angioplasty (PTCA). We studied 10 consecutive patients assigned for quantitative coronary angiography (qCA) due to a recurrent angina pectoris after PTCA of the LAD. The LAD was visualized by TTE, and the presence of local turbulence and an increase in the blood flow velocity was regarded to indicate coronary stenosis. To assess the severity of the stenosis, the increase of blood flow velocity was measured. Angiography showed stenoses of various degrees (27–100%) in all patients. All stenoses were detectable using TTE. Moreover, the ratio of maximal blood flow velocity at the site of stenosis to the pre‐stenotic blood flow velocity (M/P‐ratio) correlated significantly with the reduction of the luminal diameter of LAD (r=0·85, P<0·003). A M/P‐ratio higher than 3·0 predicted a diameter reduction of 50% or higher with sensitivity and specificity of 100% in patients with a subtotal stenosis (n=9). Our results indicate that stenoses in the LAD could be found and the severity of the stenoses could be quantified reliably with TTE. This approach is totally non‐invasive and less expensive than coronary angiography and can be used clinically in clarifying restenosis after coronary angioplasty.     

Aortic Doppler velocity measurement and cardiac function in the fetal lamb

Aortic haemodynamic parameters, and Doppler waveforms in particular, were investigated in acute experiments with fetal lambs. Cardiovascular changes were produced by central infusion of the drugs esmolol and dopamine. Pulsed Doppler waveforms were obtained from the descending thoracic aorta, simultaneous with recordings of pulsatile aortic volume flow rate, diameter and blood pressure. The relation between Doppler-derived velocities and the corresponding full vessel lumen velocities was shown to be fairly linear and consistent across different animals. The aortic volume flow per beat decreased with esmolol (p < 0.003, repeated measures ANOVA); the Doppler and vessel lumen mean velocities also decreased, whether measured only at peak systole or over the full cardiac cycle (at most p < 0.003). With dopamine the aortic flow per beat increased (p < 0.001), as did the Doppler and vessel lumen mean velocities (at most p < 0.02). An inverse relation between the aortic flow per beat and the peripheral resistance was observed. To identify inotropic changes in the presence of vascular effects, a theoretical model based on cardiac power output changes was implemented. The data were divided into three groups, according to whether the model did or did not identify a definite inotropic effect (positive or negative). The Doppler velocity changes for these three groups were different (p < 0.0001). The mean Doppler velocity increased by 7 cm s⁻¹ in the positive inotropic effect group, and decreased by 4 cm s⁻¹ in the negative group. The aortic flow parameters of the human fetus are very similar to those of the fetal lamb. Decreased aortic velocities have been reported in human fetal compromise, and the results of this study support the hypothesis that this can be evidence of impaired fetal cardiac function.     

Changes in inferior vena cava blood flow velocity and diameter during breathing movements in the human fetus.

Breathing movements in the human fetus cause distinct changes in Doppler flow velocity measurements at arterial, venous and cardiac levels. In adults, breathing movements result in a momentary inspiratory collapse of the inferior vena cava vessel wall. The study objective was to quantify the inferior vena cava flow velocity modulation during fetal breathing movements and to evaluate possible inferior vena cava vessel diameter changes in normal third-trimester pregnancies.We studied 57 women after oral administration of dextrose (50 g). In 40 fetuses (n = 19, 27-32 weeks and n = 21, 36-39 weeks), fetal inferior vena cava waveforms were obtained during apnea and fetal breathing activity. In 30 fetuses (27-39 weeks) inferior vena cava vessel diameter changes were studied using the M-mode during apnea and breathing movements. Peak and time-averaged velocities of inferior vena cava flow velocity waveforms showed a gestational age-independent increase of 60-160% during breathing activity. A temporary inferior vena cava vessel wall collapse (range, 50-83%) was recorded, which was significantly different from vessel diameter changes during apnea (range, 11-19%). The marked increase of inferior vena cava flow velocities is due to a raised thoraco-abdominal pressure gradient, which may cause a reduction in vessel size and additional volume flow into the right atrium. The significance of the caval index for recognition of elevated right atrial pressure in abnormal human fetal development needs further investigation.     

Methodology and basic problems related to blood flow studies in the human fetus

A method was developed for non-invasive measurement of human fetal blood flow. The method combines real-time ultrasonography with 2 MHz pulsed Doppler technique. The blood flow is calculated from the blood velocity, estimated from the Doppler spectrum, and the vessel diameter, measured in the real-time image. Time-distance recording was applied for measurements of the pulsatile diameter changes in the fetal aorta. The method proved to possess a good accuracy and reproducibility when tested in vitro experiments and in a comparison with electromagnetic flow measurements in animals. Possible sources of error were analysed and recommendations for minimizing the risk of errors are presented.     

Assessment of the reproducibility of the indirect ultrasound method of measuring diaphragm mobility

The aim of this study was to assess the reproducibility of the ultrasound (US) measurement of craniocaudal displacement of the left branch of the portal vein as an indirect method of measuring right hemidiaphragm mobility in healthy young adults. Forty‐one healthy participants were selected, ranging from 20 to 30 years of age. The US tests were conducted and interpreted by two observers (A and B) on two separate occasions (Test 1 and Test 2). Intra‐observer and interobserver reproducibility and repeatability of US measurements were determined by the intraclass correlation coefficient (ICC_[2,1]) using a 95% confidence interval (CI). Interobserver reproducibility assessment showed ‘high correlation’ for Test 1 and Test 2 (ICC_[2,1] = 0·83, 95% CI = 0·70–0·91, and ICC_[2,1]  = 0·79, 95% CI = 0·61–0·89, respectively). Intra‐observer reproducibility assessment showed ‘moderate correlation’ for observer A (ICC_[2,1]  = 0·69, 95% CI = 0·45–0·84) and for observer B (ICC_[2,1]  = 0·65, 95% CI = 0·39–0·81). Repeatability assessment showed ‘high correlation’ for all tests performed (ICC_[2,1]  = 0·86, 0·80, 0·74, 0·79, P<0·001). In conclusion, US measurement of craniocaudal displacement of the left branch of the portal vein is a reproducible method of measuring right hemidiaphragm mobility in healthy young adults.     

The fetal portal vein: normal blood flow development during the second half of human pregnancy.

OBJECTIVES: The umbilical vein is the major source of blood for the fetal liver, but portal blood, which has not been measured directly in human fetuses, probably constitutes a physiologically important contribution. We aimed to establish a method for measuring blood flow in the fetal portal vein and to produce longitudinal reference ranges for diameter, blood flow velocities and volume blood flow during the second half of pregnancy. METHODS: After a pilot project to develop the measuring technique, 160 low-risk pregnant women were recruited to a longitudinal study that included ultrasound examinations at 4-5-week intervals starting at 20-22 weeks of gestation. The inner diameter (D) of the vessel was measured with a perpendicular insonation angle, and the time-averaged maximum blood velocity (TAMXV) and weighted mean velocity (VWMEAN) were recorded with an insonation directed along the long axis of the vessel. Portal flow was calculated as: Q = pi(D/2)(2) x h x TAMXV (where h is a velocity profile parameter and equals 0.5). Portal flow was normalized for estimated fetal weight based on birth-weight percentiles. RESULTS: The portal vein could be visualized and measured in 558/593 (94%) cases. Blood flow was pulsatile. D and TAMXV doubled during the second half of pregnancy (21-39 weeks), from 1.5 to 3.4 mm and from 8.4 to 14.9 cm/s, respectively. Correspondingly, the portal flow increased from 5 to 41 mL/min, and from 10 to 13 mL/min/kg when normalized for fetal weight. Similar results were achieved for VWMEAN. CONCLUSION: Portal flow can be measured with a standardized technique. It increases during the second half of pregnancy, even when normalized for fetal weight, suggesting that it has increasing importance in the fetal liver circulation.     

Prenatal sonographic diagnosis of short umbilical cord in a dichorionic twin with normal fetal anatomy

Short umbilical cords are associated with fetal anomalies, often including those with decreased or absent fetal movement, fetal akinesia/hypokinesia sequence, and restrictive dermopathies and aneuploidy. In normal fetuses, abnormally short umbilical cords have been associated with an increased risk of umbilical vessel hematomas, thrombosis, rupture, thrombocytopenia, cord compression, variable fetal heart rate decelerations, instrumental and operative deliveries, and fetal demise. We report a 24‐year‐old gravida 2, para 0 with a concordant dichorionic twin gestation, at 26 weeks' gestation, in whom sonography depicted fetuses with normal‐appearing anatomy as well as short umbilical cord of the 1st twin. Increased fetal surveillance was conducted. Following delivery at 36 weeks' gestation, the presence of a short umbilical cord of the 1st twin measuring 19 cm was confirmed. Systematic review of the literature confirms that this is the first report of prenatal diagnosis of a short umbilical cord in an otherwise normal fetus. © 2009 Wiley Periodicals, Inc. J Clin Ultrasound 2010     

Time domain ultrasonography – a reliable method of percutaneousvolume flow measurement in large arteries

The estimation of blood flow inarteries is important in the study of the (patho)physiology of the circulatory system. However,non-invasive techniques using pulsed Doppler ultrasound have so far shown potentially largeerrors. The aim of this study was to evaluate the precision and variability of a newly developednon-invasive ultrasonic system based on time domain processing, CVI (Philips). In vitro measurement of blood flow was conducted on a phantom with an elastic silicon tube.Both constant and pulsatile flow were tested at increasing flow levels, and pulsatile flowmeasurements were performed at three different pulse rates at each flow level. Furthermore,fixed and hand-held probes were compared. In vivo measurements of blood flowwere conducted on the common carotid artery of seven volunteers. The intra- and inter-observer variability was evaluated. In vitro measurements with fixed transducer andcontinuous flow showed an inaccuracy of 3·5%. Pulsatile flow showed nodifference between measurements at the three different pulse rates (P=0·69), and the overall inaccuracy of pulsatile measurements was2·5%. Pulsatile flow was more accurately measured than continuous flow (P<0·01). No difference was seen between fixed and hand-heldtransducers (P=0·26). In vivo, the intra-observervariability was 25 ml min^?1 (CV 7·8%), and theinterobserver variability was 35 ml min^?1 (CV 10·9%).CVI is a promising non-invasive new technique for flow measurements in arteries that givescorrect data with good reproducibility in vitro, as well as in healthy common carotidarteries in vivo.     

Brachial artery hyperemic blood flow velocities are related to carotid atherosclerosis

Objective: Cardiovascular (CV) risk relates to the blood flow velocity pattern in the brachial artery during hyperemia, especially to the hyperaemic systolic to diastolic mean blood flow velocity (SDFV) ratio. Here, we investigated the relations between SDFV in the brachial artery and different characteristics of carotid atherosclerosis. Material and methods: Data were collected from 1016 70‐year‐olds participating in the Prospective Investigation of Uppsala Seniors study. Doppler recordings of blood flow velocity during hyperemia were analysed in the brachial artery. In the carotid artery, intima‐media thickness (IMT) was recorded together with an assessment of echogenicity by the Grey scale median (GSM) method in both overt plaques and in the intima‐media complex (IM‐GSM). Results: The SDFV ratio was related to the number of carotid arteries affected by plaque (P = 0·018) and inversely to plaque echogenicity (P = 0·0003). The SDFV ratio was also related to IMT (P = 0·0022) and inversely to IM‐GSM (P = 0·0001). These relations were statistically significant also after adjusting for major CV risk factors, individually as well as summarised as the Framingham risk score. Conclusion: Our results indicate that the hyperemic systolic to diastolic blood flow velocity ratio in the brachial artery is related to atherosclerosis in the carotid artery.