Biomedical subjects

E M Pedersen

Publications and source records attributed to E M Pedersen.

At least 55 records · Page 3Linked to original sources

PubMed1999

Distribution of early atherosclerotic lesions in the human abdominal aorta correlates with wall shear stresses measured in vivo.

OBJECTIVES: to study the relationship between wall shear stresses measured in vivo and early atherosclerotic lesions in the abdominal aorta. MATERIALS: eight young volunteers for in vivo wall shear-stress measurements. Abdominal aortas from 10 young adults without signs or history of atherosclerotic disease were obtained by autopsy for histomorphometric measurements. METHODS: wall shear stresses were measured in the abdominal aorta above and below the renal arteries using a magnetic resonance technique with high resolution for imaging and blood velocity mapping. At identical abdominal aortic locations, intimal thickness was measured blindly using histomorphometric techniques and correlated to wall shear-stress variables using linear-regression analysis. RESULTS: intimal thickness showed a linear decrease with mean wall shear stress (r=-0.90, p<0.01) and with maximum wall shear stress (r=-0.86, p<0.01). CONCLUSIONS: intimal thickness in the normal abdominal aorta is associated with mean, maximum and oscillating wall shear stresses. These in vivo data corroborate previous in vitro studies suggesting that low and oscillating wall shear stresses are localising factors for intimal thickening and hence the early development of atherosclerosis.

Adolescent↗

PubMed1999

Development of velocity profiles and retrograde flow in the porcine abdominal aorta under different haemodynamic conditions.

Low and/or oscillating wall shear stresses are related to the development of atherosclerosis and this oscillation is influenced by changes in basic haemodynamics (exercise). The objective of this study was to provide in vivo data on the development of velocity profiles and oscillating blood velocities in the abdominal aorta under varying haemodynamic conditions. Six anaesthetized, 90-kg pigs were used in the study. Abdominal aortic velocity profiles across the anterior-posterior diameter were acquired at different axial positions using 10 MHz pulsed Doppler ultrasound. Measurements were obtained under normal conditions and during cardiac pacing up to 170 beats/min. Velocity profiles were obtained during heart rates ranging between 58 and 169 beats/min, and during flow rates ranging between 0.57 and 2.89 l/min. Main outcome measures included minimum velocities, frequency index, shape of velocity profiles (velocity distribution index), Reynolds' numbers, and Womersley's frequency parameter. Velocity profiles were blunted, with lowest velocities at the distal posterior vessel wall. Multiple regression analysis showed the development of velocity profiles to be inversely correlated with the pulsatility index, Womersley's frequency parameter and the mean Reynolds' number (r = 0.89, p < 0.0005). Minimum velocities were negatively correlated with the PI, Womersley's frequency parameter and positively with the mean Reynolds' number (r = 0.94, p < 10(-8)). Retrograde velocities (and hence oscillating wall shear stresses) were present at mean Reynolds' number < 1000. The oscillation of blood velocities at the wall in the porcine abdominal aorta was highly dependent on general haemodynamics (i.e. flow, heart rate and vessel diameter as expressed in the Reynolds' numbers and Womersley's frequency parameters). The velocity profiles in the abdominal aorta were found to be far from parabolic. These findings have important implications for the understanding and future modelling of the complex haemodynamics in the abdominal aorta and their relation to the development of atherosclerotic disease.

Animals↗

PubMed1999

A histomorphometric method for evaluating topographic differences in degree of early atherosclerosis within the human aorta.

The aim of the study was to develop an unbiased topographically oriented method of evaluating early atherosclerotic lesions in the aorta and to apply this to a series of human aortas from young adults. A systematic sampling procedure and histomorphometric analysis of intimal thickening is described. Results from a group of 15 young adults (aged 18-40 years) showed a characteristic pattern with increasing intimal thickening when moving distally from the thoracic to the upper and finally to the lower abdominal aorta, but also a shift in the localization of the most pronounced intimal thickening from the posterior to the anterior and back to the posterior aspect. This pattern was found in aortas both with minimal and with more pronounced atherosclerosis, and supports the view that the early intimal thickening precedes the atherosclerotic lesions and marks the sites of predilection for the more advanced disease processes. An increase in intimal thickness with age could be demonstrated in the aortas without overt atherosclerosis. The simple sampling procedure, well-defined sampling sites, and ability to demonstrate and quantitate differences in intimal thickening and plaque morphology make this method well suited for relating morphometric data to other parameters of interest when studying the etiology and dynamics of atherosclerotic disease.

Adolescent↗

PubMed1999

High-resolution assessment of velocity fields and shear stresses distal to prosthetic heart valves using high-field magnetic resonance imaging.

BACKGROUND AND AIM OF THE STUDY: Complications after replacement of diseased heart valves with mechanical prostheses have been shown to be related to the hemodynamics distal to the valve. For this reason, the velocity patterns have been disclosed in vitro with a variety of different techniques. This study introduces a magnetic resonance imaging (MRI) -based technique, which entails easy acquisition of fluid velocity field data with a high accuracy and spatial resolution. METHODS: A high-field magnetic resonance scanner equipped with short echo time phase-contrast velocity measurement software was applied in a detailed mapping of the axial velocity profile across the entire vessel area at two positions downstream of a bileaflet valve prosthesis inserted in a pulsatile flow system in vitro. The laminar shear forces were calculated from the fluid velocity field data. RESULTS: The velocity profiles very close to the valve reflected the bileaflet design as also shown in previous studies, but the extent and velocities of the jet emanating from the slit between the leaflets were clearly better visualized. However, one diameter downstream of the valve the central jet was completely dispersed and the hemodynamic complexity was significantly reduced. Recirculation and retrograde flow regions that might be relevant for understanding typical long-term complications after implantation were observed close to the valve. CONCLUSIONS: In one scan experiment the presented method provides information on flow characteristics that previously required application of different types of experiment. Thus, the method seems promising as a new technique for detailed and extensive mapping of the velocities and laminar shear stresses downstream of prosthetic heart valves in vitro.

Blood Flow Velocity↗

PubMed1998

Quantitation of circumferential subpixel vessel wall position and wall shear stress by multiple sectored three-dimensional paraboloid modeling of velocity encoded cine MR.

Methods are lacking for accurate, noninvasive circumferential edge detection and wall shear stress calculation. Using standard MR phase contrast sequences, parts of the velocity profiles were fitted to a multiple sectored three-dimensional paraboloid model enabling exact calculation of vessel wall position and wall shear stress in 24 locations evenly distributed around the luminal vessel wall. The model was evaluated by in vitro scans and computer simulations and applied to the common carotid artery of humans. In vitro, the luminal area of a glass tube was assessed with an error of 0.9%. Computer simulations of peak systolic data revealed errors of +/-0.9% (vessel area) and +/-3.25% (wall shear stress). The in vivo results showed substantial difference between anterior and posterior wall shear stress values due to skewed velocity profiles. A new noninvasive method for highly accurate measurement of circumferential subpixel vessel wall position and wall shear stress has been developed.

Adult↗

PubMed1998

Accurate noninvasive quantitation of blood flow, cross-sectional lumen vessel area and wall shear stress by three-dimensional paraboloid modeling of magnetic resonance imaging velocity data.

OBJECTIVES: We present a new method in which a priori knowledge of the blood velocity fields within the boundary layer at the vessel wall, combined with acquisition of high resolution magnetic resonance imaging (MRI) blood velocity data, allow exact modeling at the subpixel level. BACKGROUND: Methods are lacking for accurate, noninvasive estimation of blood flow, dynamic cross-sectional lumen vessel area and wall shear stress. METHODS: Using standard acquisition of MRI blood flow velocity data, we fitted all data points (n = 69) within the boundary layer of the velocity profile to a three-dimensional paraboloid, which enabled calculation of absolute volume blood flow, circumferential vessel wall position, lumen vessel area and wall shear stress. The method was tested in a 8.00 +/ 0.01-mm diameter glass tube model and applied in vivo to the common carotid artery of seven volunteers. RESULTS: In vitro the lumen area was assessed with a mean error of 0.6%. The 95% confidence interval included the specified tube dimensions. Common carotid mean blood flow was 7.42 ml/s, and mean (standard error) diastolic/systolic vessel area was 33.25 (0.72 [2.2%])/43.46 (0.65 [1.5%]) mm2. Mean/peak wall shear stress was 0.95 (0.04 [4.2%])/2.56 (0.08 [3.1%]) N/m2. CONCLUSIONS: We describe a new noninvasive method for highly accurate estimation of blood flow, cross-sectional lumen vessel area and wall shear stress. In vitro results and statistical analysis demonstrate the feasibility of the method, and the first in vivo results are comparable to published data.

Adult↗

PubMed1998

Automatic accurate non-invasive quantitation of blood flow, cross-sectional vessel area, and wall shear stress by modelling of magnetic resonance velocity data.

OBJECTIVES: To apply a new, automatic and non-invasive method for quantification of blood flow, dynamic cross-sectional vessel area, and wall shear stress (WSS) by in vivo magnetic resonance velocity mapping of normal subjects. DESIGN: Prospective, open study. MATERIALS: Six young volunteers. METHODS: A three-dimensional paraboloid model enabling automatic determination of blood flow, vessel distensibility and WSS was applied to blood velocity determinations in the common carotid artery. Blood flow was also determined by a manual edge detection method. RESULTS: Using the new method, the common carotid mean blood flow was 7.28 (5.61-9.63) (mean (range)) ml/s. By the manual-method blood flow was 7.21 (5.55-9.60) ml/s. Mean luminal vessel area was 26% larger in peak systole than in diastole. Mean/peak WSS was 0.82/2.28 N/m2. Manually and automatically determined flows correlated (r2 = 0.998, p < 0.0001). WSS and peak centre velocity were associated (r2 = 0.805, p < 0.0001). CONCLUSIONS: Blood flow, luminal vessel area dilatation, and WSS can be determined by the automatic three-dimensional paraboloid method. The hypothesis of association between peak centre velocity and WSS was not contradicted by the results of the present study.

Adult↗

PubMed1998

Permethrin-impregnated bednet effects on resting and feeding behaviour of lymphatic filariasis vector mosquitoes in Kenya.

The impact of permethrin-impregnated bednets on resting and feeding behaviour of mosquito vectors of Wuchereria bancrofti, causing human lymphatic filariasis was studied in six pairs of villages (treated and untreated) before and after intervention. The study villages were in Kwale District, near the coast of Kenya, where Bancroftian filariasis is highly endemic, transmitted by a combination of both anopheline and culicine mosquito vectors. Mosquitoes were collected weekly in each village, indoors (using pyrethrum spray catches) and outdoors (using pit traps) during 3-4 months following the long rainy season. Of the filariasis vector species of mosquitoes collected in 1994 before intervention. 33.6% were members of the Anopheles gambiae complex, 30% were An. funestus and 36.4% were Culex quinquefasciatus. PCR analysis of the An. gambiae complex species collected in 1995 demonstrated that 98.5% were An. gambiae sensu stricto. 1% An. arabiensis and 0.5% An. merus. Introduction of impregnated bednets in 1995 significantly reduced the number of indoor-resting An. gambiae s.l. by 94.6% and An. funestus by 96.7%, but there was no change in the number of Cx quinquefasciatus collected indoors. The number of outdoor-resting An. gambiae s.l. was significantly reduced, whereas densities of An. funestus and Cx quinquefasciatus remained unaffected outdoors. ELISA analysis of mosquito bloodmeals showed a shift from human to animal feeding after the introduction of treated nets. The human blood index (HBI) for indoor resting Cx quinquefasciatus was reduced from 93.1% to 14.4%. Vector potential based on the HBI and mosquito density was estimated to be reduced by 99% for An. gambiae s.l., 98% for An. funestus and 97% for Cx quinquefasciatus and vectorial capacity would be suppressed even more by the impact on the vector survival rates (not measured). These results suggest that permethrin-impregnated bednets give effective personal protection against transmission of W. bancrofti by An. gambiae, An. funestus and Cx quinquefasciatus in East Africa.

Animals↗

PubMed1998

Validation of a new transit time ultrasound flowmeter for measuring blood flow in colonic mesenteric arteries.

OBJECTIVE: To validate a transit time ultrasound flowmeter (CardioMed CM 4000) for measuring blood flow in isolated colonic mesenteric arteries. DESIGN: Experimental and clinical study. SETTING: Teaching hospital, Denmark. ANIMALS AND SUBJECTS: One female pig, and 6 patients being operated on for carcinoma of the sigmoid colon and rectum. INTERVENTIONS: Volume blood flow measured by Cardiomed CM 4000 and pump withdrawal flow recordings. MAIN OUTCOME MEASURES: Correlation between the two methods. RESULTS: There was good agreement between transit time flow recordings and pump withdrawal flow recordings (correlation coefficient of 1.0). Of the differences between the two methods, 95% were between -0.16 ml min(-1) and 1.29 ml min(-1), mean 0.57 ml min(-1), or (in percentages) 105, 95% lying between 97-115. There was also good reproducibility in transit time flow recordings, the mean difference between repeated measurements being 0.06 ml min(-1), 95% lying between -0.66 ml min(-1) and 0.78 ml min(-1). CONCLUSION: Ultrasound transit time flow recordings gave precise measurements of blood flow in isolated colonic mesenteric arteries.

Aged↗

PubMed1997

Where to place the Doppler sample volume in the human main pulmonary artery: evaluated from magnetic resonance phase velocity maps.

OBJECTIVE: To give recommendations for the placement of Doppler sample volumes for blood flow assessment in the human main pulmonary artery. METHODS: In 10 healthy volunteers MR-phase velocity measurements were obtained and computing of the mean temporal blood velocity data was performed to guide single point Doppler velocity recordings. RESULTS: The mean temporal blood velocity profiles were consistently skewed with the lowest blood velocities towards the inferior/right vessel wall. Blood velocity indices (ratio of point to mean velocities, where a point equals a square of 4 pixels) varied considerably with the lowest indices located towards the inferior/right vessel wall. A centrally located fictive sample volume revealed an average blood velocity index value (average of all 10 subjects) of 1.08 (range 0.99-1.25; s.d. 0.08) where the central point was defined at maximum systole, and a value of 1.13 (range 0.97-1.34; s.d. 0.11) when the central point was defined in end-diastole. The mean of multiple sample volumes along the inferior/right to superior/left diameter revealed a blood velocity index of 1.01 (range 0.87-1.21; s.d. 0.09) in systole and 1.03 (range 0.87-1.19; s.d. 0.09) in diastole. CONCLUSIONS: For practical clinical purposes, single point estimation of the mean blood velocity in the pulmonary artery should be performed centrally. The use of multiple sample volumes placed along the inferior/right to superior/left diameter improves the mean velocity estimate in healthy volunteers. Further studies should be conducted to reinforce the basis for Doppler velocity recording in the diseased human pulmonary artery as well as to investigate other important determinants of Doppler-derived CO, namely angle of insonation and assessment of the cross-sectional area.

Adult↗

PubMed1997

Transesophageal multiplane imaging of the human pulmonary artery: a comparison of MRI and multiplane transesophageal two-dimensional echocardiography.

OBJECTIVE: To evaluate the anatomical relationship between the esophagus and pulmonary artery including assessment of the correct transesophageal Doppler insonation angle into the mid-pulmonary artery trunk. METHODS: We evaluated the anatomical relationship between the esophagus and pulmonary artery (PA) from comparable magnetic resonance (MR) and transesophageal echocardiographic (TEE) multiple two-dimensional images (0 degree, 45 degrees, 90 degrees and 135 degrees clockwise rotation of the standard transverse scanning plane when seen bearfrom the esophagus) obtained in 10 healthy, young volunteers. RESULTS: The main PA could be visualized with both techniques in all 10 volunteers and provided highly identical images of good quality. A mean insonation angle of 35 degrees (range 26 degrees-46 degrees) for a fictive esophageal Doppler beam into the main PA was disclosed. The PA trunk was short with a mean length of 23.4 mm (range 17-30 mm). CONCLUSIONS: These anatomical data contradict the general assumption of alignment of the pulmonary artery and the transesophageal Doppler beam. Angle correction should be applied in the clinical setting using MTEE by rotation of the scanning plane to approximately 45 degrees. Ignoring the insonation angle of approximately 35 degrees may cause 20% underestimation of blood flow velocity and cardiac output in the PA.

Adult↗

PubMed1997

The impact of ischemic heart disease on main pulmonary artery blood flow patterns: a comparison between magnetic resonance phase velocity mapping and transesophageal color Doppler.

OBJECTIVE: To give a detailed evaluation on main pulmonary artery blood velocity patterns, in patients with ischemic heart disease and to provide recommendations for pulsed Doppler sample volume placement, in order to optimize cardiac output estimation. METHODS: Using magnetic resonance phase and esophageal color Doppler velocity mapping in 12 patients with ischemic heart disease and undergoing coronary artery by-pass grafting, very similar data on pulmonary artery blood velocity patterns were provided for comparison with each other. RESULTS: Peak blood velocities were located in the inferior half of the main pulmonary artery cross-sectional area. Early after peak systole the highest velocities shifted towards the superior/left (major curvature) with a simultaneous decrease in velocities inferiorly. The velocity decrease further evolved into retrograde flow to the inferior/right (minor curvature). This feature was significantly enhanced compared to earlier findings in healthy volunteers. The mean temporal blood velocity profiles were asymmetrically skewed, thereby giving unreliable cardiac output estimates based on single point Doppler blood velocity recordings. The error incurred may amount to more than 100% in extreme cases. According to our data, optimal assessment of cardiac output should be based on multiple sample volumes placed along the inferior/right to superior/left diameter. CONCLUSIONS: MR-phase velocity mapping and multiplane transesophageal color Doppler recordings provided similar blood velocity patterns in patients with ischemic heart disease. The skewness of the mean temporal blood velocity profile is enhanced compared with healthy subjects, resulting in error in the assessment of CO by means of pulsed Doppler echocardiography. By using multiple Doppler sample volumes, the error can be minimized.

Aged↗

PubMed1997

In vivo wall shear stress measured by magnetic resonance velocity mapping in the normal human abdominal aorta.

OBJECTIVE: To apply a new non-invasive method for quantification of in vivo wall shear stress (WSS) by magnetic resonance (MR) FAcE velocity mapping and measure WSS in the human abdominal aorta. DESIGN: Prospective, open study. MATERIAL: Six volunteers. METHODS: MR FAcE velocity method was developed for measurements of mean, maximum, minimum WSS and oscillating shear index (OSI) values at the anterior and posterior walls of suprarenal and infrarenal abdominal aorta. RESULTS: The mean, maximum and minimum WSS values were 0.63/0.28, 4.07/2.72 and -0.71/-1.00 N/m2, respectively, in the suprarenal/infrarenal aorta. The mean WSS was 0.35 N/m2 (p < 0.001) and the maximum WSS was 1.36 N/m2 (p < 0.0001) lower in the infrarenal aorta than in the suprarenal aorta. Mean, maximum minimum WSS and OSI values in the infrarenal position differed (p < 0.01) between the anterior and posterior walls. CONCLUSION: WSS can be determined in vivo by MR FAcE velocity technique. Since the lowest WSS values were measured in the infrarenal, posterior blood-to-wall interface, the theory of more pronounced atherosclerosis development in low and oscillating WSS domains was not contradicted by the results of the present study.

Adult↗

PubMed1997

Wall shear stress and early atherosclerotic lesions in the abdominal aorta in young adults.

OBJECTIVES: To study the correlation between wall shear stress and early atherosclerotic lesions in the abdominal aorta. DESIGN: Blinded histomorphometric studies. Comparison with in vitro data. MATERIALS: Abdominal aortic haemodynamics were simulated in a realistic pulsatile flow model. Abdominal aortas from 10 young adults with no signs of atherosclerotic disease were obtained during autopsy. METHODS: Quantitative wall shear stresses were measured at rest and exercise in one suprarenal and two infrarenal positions using laser Doppler anemometry. Intimal thickening indices were measured blindly at the corresponding locations using histomorphometric methods, and compared to wall shear stress variables using linear regression analysis. RESULTS: Intimal thickness index increased significantly with age. Intimal thickness index was significantly lower in the suprarenal than the infrarenal aorta, and higher at the distal posterior vessel wall compared to the anterior wall. Intimal thickness index correlated significantly with mean, minimum and oscillating wall shear stresses measured at rest. CONCLUSION: Intimal thickness in the undiseased abdominal aorta correlated significantly with mean, minimum and oscillating wall shear stresses at rest measured in a pulsatile flow model. No correlations were found with maximum shear stress parameters. Exercise changed the local wall shear stresses away from the characteristics associated with intimal thickness index.

Adolescent↗

PubMed1997

Measurement of renal vein blood flow in rats by high-field magnetic resonance.

The aim of the present study was to examine whether magnetic resonance imaging (MRI) based method for non-invasive in vivo measurement of vein blood flow in rats could be used to estimate renal blood flow (RBF). Measurements were performed using a high-field (7 Tesla) MRI scanner with a short echo time phase contrast velocity measurement pulse sequence. The method was evaluated in vitro by flow measurements in an acrylic pipe and in vivo by recording left renal vein blood flow in normal and unilaterally nephrectomized rats. In a subset of animals RBF was measured by a direct method using 14C-tetraethylammoniumbromide. In vitro a high accuracy was found between applied and MRI measured flow rates in the range from 0.5 to 33 ml/min (r = 0.997; P < 0.001). In vivo the MRI measured left renal vein blood flow was 70% higher in unilaterally nephrectomized animals compared to control animals (3.4 +/- 0.4 ml/min/ 100 g body wt vs. 2.0 +/- 0.1 ml/min/100 g body wt, P < 0.001). Direct measurements of RBF revealed comparable values (3.4 +/- 0.3 ml/min/100 g body wt vs. 2.3 +/- 0.4 ml/min/100 g body wt, P = 0.05). In addition, the left kidney volume was recorded by MRI with an increase amounting to 40% (1.18 +/- 0.05 ml vs. 0.84 +/- 0.02 ml; P < 0.001) in the nephrectomized group compared to controls. Finally, a positive correlation was seen between left renal vein blood flow and MRI measured renal volume (r = 0.91; P < 0.001). In summary, MRI is a non-invasive tool by which measurement of renal vein blood flow can be performed, and it is concluded that MRI-based renal vein flow measurements can be used to estimate RBF in small rodents.

Animals↗

PubMed1997

Quantitative evaluation of flow patterns in perfusion cannulae by a new magnetic resonance imaging method.

The arterial cannula is a critical part of any extracorporeal circulation system due to the high flow rates which must pass a small cross-sectional area, resulting in high blood velocities. The aim of this study was to examine whether high-field magnetic resonance scanning is applicable for detailed mapping of velocity fields around the tip of such arterial cannulae in vitro. The investigated cannula was an angled, open-tip traditional design aortic cannula with an internal tip diameter of 5.5 mm. The velocity fields were measured at two different flow rates (2 and 4 l/min) at various positions in the lumen and outside the cannula using magnetic resonance imaging (MRI). All three components of the velocity vectors were measured. The study showed that MRI can provide a clear quantitative visualization of the velocity field around the tip of arterial cannulae at lower flow rates. At higher flow rates it can provide information about localization of regions with turbulent or disturbed flow.

Catheterization↗

PubMed1996

Arteriovenous fistulas aggravate the hemodynamic effect of vein bypass stenoses: an in vitro study.

PURPOSE: The purpose of this study was to assess the impact of arteriovenous fistulas combined with varying degrees of stenosis on distal bypass hemodynamics and Doppler spectral parameters. METHODS: In an in vitro flow model bypass stenoses causing 30%, 55%, and 70% diameter reduction were induced 10 cm upstream of a fistula with low outflow resistance. Flow and intraluminal pressure were measured proximal to the stenosis and downstream of the fistula. The waveform parameters peak systolic velocity, end-diastolic velocity, pulsatility index, and pulse rise time were determined from midstream Doppler spectra obtained 10 cm downstream of the fistula. All measurements were carried out with open and clamped fistula. RESULTS: At 30% diameter reducing stenosis opening of the fistula induced a 12% systolic pressure drop across the stenosis but had no adverse effect on the Doppler waveform parameters. At 55% stenosis the pressure drop increased from 16% to 31% after fistula opening. This increased pressure drop was associated with a further reduction in peak systolic velocity, a decrease in pulsatility index, and an enhanced pulse rise time prolongation. Fistula opening at 70% stenosis increased the systolic pressure drop from 31% to 48% and had significant impact on all waveform parameters. CONCLUSIONS: Distal arteriovenous fistulas enhance pressure loss across stenoses and affect downstream velocity waveform configuration. The presence of a combined fistula and a stenosis mimics the distal hemodynamic conditions of a more severe stenosis. Assessment of the hemodynamic impact of fistulas must be undertaken in the evaluation of in situ vein bypass stenoses.

Arteriovenous Fistula↗

PubMed1996

Validation of a new transit time ultrasound flowmeter in man.

OBJECTIVES: To validate the new CardioMed CM 4000 transit time ultrasound apparatus for intraoperative measurement of volume blood flow in vivo in man. DESIGN: Open, prospective series. MATERIALS: Thirteen patients undergoing in situ saphenous vein grafting for chronic critical leg ischaemia and 12 patients subjected to myocardial revascularisation with the internal thoracic artery as coronary bypass. METHODS: During operations, volume blood flows were measured simultaneously by exsanguination from the cut distal end of the in situ saphenous vein graft or the internal thoracic artery and by the transit time flowmeter equipment. In addition, the feasibility to detect arteriovenous fistula during in situ saphenous vein grafting was examined. RESULTS: Within the examined blood flow range, the volume blood flow determined by the transit time method corresponded to the directly measured blood flow. For in situ saphenous vein grafts: y = -2.4 + 0.95.x (r = 0.99; 35 measurements in 13 patients), and for internal thoracic artery grafts: y = -9.6 + 1.1.x (r = 0.99; 21 measurements in 12 patients), where y is blood flow determined by transit time, and x is directly measured blood flow by exsanguination (r = correlation coefficient) as calculated by the least squares regression method. Fistula detection was easy and swift. CONCLUSIONS: The transit time apparatus was simple to use during intraoperative settings and gave fast, precise measurements of volume blood flow.

Adult↗