Mean Wall Shear Stress Values Research Articles

The Difference of Mean WSS Value on The Carotid Bifurcation and The Medial Segment of Common Carotid Artery Using Vector Flow Ultrasonography in Hypertensive Patients at Prof Dr. I.G.N.G Ngoerah General Hospital February-April 2022

Background : Hypertension is a risk factor for atherosclerosis which increases the risk of stroke. Transitions in blood vessels such as bifurcations are associated with changes in the velocity and pattern of blood flow that decrease wall shear stress (WSS) and is believed to be a risk factor for atherosclerosis. Shear stress on the common carotid artery also decreased with increasing blood pressure. This study aims to determine the difference of mean WSS value on the carotid bifurcation and the medial segment of common carotid artery using vector flow ultrasonography in hypertensive patients. Methods: This study used a cross-sectional design with the research location at the Radiology Installation of Prof. Dr. I.G.N.G Ngoerah Hospital Denpasar in February-April 2022. The sample of this study was hypertensive patients who came to the Radiology Installation of Prof. Dr. I.G.N.G Ngoerah Hospital and met the inclusion criteria as many as 32 people. The examination was carried out by a consultant of head and neck radiology, using an ultrasound device with a linear transducer probe that has a probe frequency range of 3-9 Mhz. Results: The average age of the sample in this study was 50 years, with 9 males (28.1%), 23 females (71.9%). The results showed that the average maximum WSS value on the carotid bifurcation (3.37±0.96) Pa, the mean value (1.15±0.45) Pa, while the average maximum WSS value on the medial segment of the common carotid artery (4 ,41±1.45)Pa, the mean value (1.78±0.54)Pa. The average maximal and mean WSS value on carotid bifurcation were lower than the medial segment of the common carotid artery in hypertensive patients (p<0,05). The results of multivariate analysis on WSS values after controlling for confounding variables, obtained the average maximal and mean WSS value on carotid bifurcation, remained lower than the medial segment of the common carotid artery (p<0,05). Conclusion: there were significant differences in the mean wall shear stress (WSS) of the carotid bifurcation and the medial segment of the common carotid artery in hypertensive patients. Suggestions that can be done next are in facilities that have vector flow ultrasonography facilities, it is recommended to measure the WSS value in hypertensive patients as additional information as a predictor of atherosclerosis

Characteristics and Correlations of Wall Shear Stress and Flow Turbulence in the Carotid Bifurcation Evaluated Using an Ultrasound Vector Flow Imaging

Introduction: The aim of the study was to evaluate characteristics and provide the normal values of wall shear stress (WSS) and flow turbulence (Tur), and the relationship between them in the carotid bifurcation based on an ultrasound vector flow imaging (V Flow) in healthy adults. Methods: Max and mean WSS and Tur values at three segments (initial segments of internal and external carotid arteries [IICA and IECA]; distal segment of common carotid artery [DCCA]), both in anterior and posterior walls, were successfully obtained in 56 healthy adults, using ultrasound V Flow function. Relationship between mean WSS and Tur was further explored. Results: The mean WSS value was 0.71 Pa, 0.86 Pa, and 0.96 Pa at IICA, IECA, and DCCA, respectively (IICA < IECA < DCCA, p < 0.05). The mean Tur value was 13.85%, 5.46%, and 4.17% at IICA, IECA, and DCCA, respectively (IICA > IECA > DCCA, p < 0.05). A cutoff value (WSS = 0.4 Pa) was selected and Tur values were significantly higher in group with WSS cutoff value <0.4 Pa than group with WSS cutoff value ≥0.4 Pa (p < 0.01). Conclusion: WSS and Tur are moderately negatively correlated, which can be used in the quantitative evaluation of carotid bifurcation and could be a potential dual-parameter tool in the clinical research for early detection of carotid atherosclerosis.

Feasibility study of combining wall shear stress and elastography to assess the vascular status of carotid artery.

At present, early detection of the potential risk of atherosclerosis and prevention is of great significance to reduce the occurrence of stroke. This study aims to explore the value of combining the wall shear stress measured by ultrasound vector flow imaging technique and sound touch elastography of common carotid artery in normal adults using the Mindray Resona 7 ultrasound system. Forty volunteers (mean age 39.5 y, 23 females, 17 males) were divided into four groups according to their age. All volunteers underwent ultrasound carotid artery examination, and the values of wall shear stress and elasticity on the posterior wall of the common carotid artery were measured using advanced imaging functions, vector flow imaging technique, and sound touch elastography. Different cut-off values of wall shear stress were used to investigate the significance between two groups with corresponding sound touch elastography values. It can be seen that the statistical difference could be found when the mean wall shear stress was larger than 1.5 Pa approximately (statistical significance was defined when P < 0.05), and the sound touch elastography value was positively correlated with the wall shear stress value. This study reveals that the combination of wall shear stress and sound touch elastography is an effective and feasible method for assessing carotid artery health. When the mean wall shear stress value is over 1.5 Pa, the corresponding sound touch elastography value increases significantly. The risk of atherosclerosis increases with the stiffness of blood vessel walls.

Investigation on the differences of hemodynamics in normal common carotid, subclavian, and common femoral arteries using the vector flow technique.

To investigate the feasibility of the vector flow imaging (V Flow) technique to measure peripheral arterial hemodynamic parameters, including wall shear stress (WSS) and turbulence index (Tur) in healthy adults, and compare the results in different arteries. Fifty-two healthy adult volunteers were recruited in this study. The maximum and mean values of WSS, and the Tur values at early-systole, mid-systole, late-systole, and early diastole for total 156 normal peripheral arteries [common carotid arteries (CCA), subclavian arteries (SCA), and common femoral arteries (CFA)] were assessed using the V Flow technique. The mean WSS values for CCA, SCA, and CFA were (1.66 ± 0.68) Pa, (0.62 ± 0.30) Pa, and (0.56 ± 0.27) Pa, respectively. The mean Tur values for CCA, SCA, and CFA were (0.46 ± 1.09%), (20.7 ± 9.06%), and (24.63 ± 17.66%), respectively. The CCA and SCA, as well as the CCA and CFA, showed statistically significant differences in the mean WSS and the mean Tur (P < 0.01). The mean Tur values had a negative correlation with the mean WSS; the correlation coefficient between log(Tur) and WSS is -0.69 (P < 0.05). V Flow technique is a simple, practical, and feasible quantitative imaging approach for assessing WSS and Tur in peripheral arteries. It has the potential to be a useful tool for evaluating atherosclerotic plaques in peripheral arteries. The results provide a new quantitative foundation for future investigations into diverse arterial hemodynamic parameters.

Computational fluid dynamics simulation of hemodynamic changes in a hemodialysis patient with central venous stenosis treated with stent.

It has not been demonstrated that computational fluid dynamics (CFD) can be used to model central venous stenosis (CVS), nor that hemodynamic changes in CVS treated with stent placement can be anticipated. The purpose of this study was to demonstrate the hemodynamic performance of CVS patients treated with stent placement. Patient-specific geometric models were constructed using computed tomography images of veins from hemodialysis patients treated with stent placement. CFD simulation based on geometry was performed using ANSYS-15 to compare pressure quantitatively, wall shear stress (WSS), and flow velocity in the brachial vein before and after stent placement. Following a covered stent placement, the swelling of the left upper extremity was relieved. Prior to stent implantation, the maximum and mean brachial vein wall pressures were 465.2 Pa and 224.609 Pa, respectively. It was determined that the maximum WSS value was 8.449 Pa and that the mean WSS value was 0.743 Pa. The maximum and mean flow velocities were 1.16 and 0.173 m/s, respectively. After stent placement, the maximum wall pressure, maximum WSS, and maximum flow velocity dropped by 59.4%, 71.2%, and 57.8%, respectively. The mean wall pressure, mean WSS, and mean flow rate decreased by 43.5%, 52.7%, and 17.6%, respectively. Hemodynamics of CVS in hemodialysis patients exhibited turbulent, imbalances and disorders, which can be improved by stent placement.

A pilot study using a machine-learning approach of morphological and hemodynamic parameters for predicting aneurysms enhancement.

The development of straightforward classification methods is needed to identify unstable aneurysms and rupture risk for clinical use. In this study, we aim to investigate the relative importance of geometrical, hemodynamic and clinical risk factors represented by the PHASES score for predicting aneurysm wall enhancement using several machine-learning (ML) models. Nine different ML models were applied to 65 aneurysm cases with 24 predictor variables. ML models were optimized with the training set using tenfold cross-validation with five repeats with the area under the curve (AUC) as cost parameter. Models were validated using the test set. Accuracy being significantly higher (p < 0.05) than the non-information rate (NIR) was used as measure of performance. The relative importance of the predictor variables was determined from a subset of five ML models in which this information was available. Best-performing ML model was based on gradient boosting (AUC = 0.98). Second best-performing model was based on generalized linear modeling (AUC = 0.80). The size ratio was determined as the dominant predictor for wall enhancement followed by the PHASES score and mean wall shear stress value at the aneurysm wall. Four ML models exhibited a statistically significant higher accuracy (0.79) than the NIR (0.58): random forests, generalized linear modeling, gradient boosting and linear discriminant analysis. ML models are capable of predicting the relative importance of geometrical, hemodynamic and clinical parameters for aneurysm wall enhancement. Size ratio, PHASES score and mean wall shear stress value at the aneurysm wall are of highest importance when predicting wall enhancement in cerebral aneurysms.

V Flow technology in measurement of wall shear stress of common carotid arteries in healthy adults: Feasibility and normal values.

To evaluate the feasibility of vector flow imaging technique (V Flow) in measurement of wall shear stress (WSS) of common carotid arteries (CCA) in healthy adults and to provide the normal WSS values assessed by V Flow. This prospective study was approved by the Ethics Committee of our University. Eighty healthy adult volunteers were included (mean age 43.3 y, 47 females, 33 males). The volunteers were classified into three groups according to their age: group I (age 20 - 39 y), group II (age 40 - 59 y) and group III (age 60 - 80 y). Mindray Resona 8 ultrasound machine and a linear array transducer (3-9 MHz) was used, equipped with the updated V Flow function. Common carotid arteries of both sides were evaluated in three segments (initial segment, middle segment and near bifurcation segment). The WSS values of CCA were measured by two independent radiologists. The intraclass correlation coefficient (ICC) of observer reliability in WSS measurement was calculated. Inter-observer reproducibility was also evaluated with the 95% Bland-Altman limits of agreement (LOA). V Flow measurements were performed successfully in 79 volunteers (98.8 %, 79/80). The mean value of WSS in right CCA was (0.66±0.24) Pa, in left CCA was (0.66±0.18) Pa (P > 0.05). Mean WSS value had a moderately negative correlation with age group (P < 0.05). The mean WSS value of group I(mean±SD, 0.75±0.25 Pa) is larger than group II (mean±SD, 0.62±0.13 Pa) and group III (mean±SD, 0.49±0.11 Pa) (P < 0.05). The ICC of observer reliability of group I, II and III was 0.96 (95% confidence interval (95% CI) 0.92-0.98), 0.94 (95% CI 0.88-0.97), 0.93 (95% CI 0.76-0.98) respectively. The Bland-Altman plots showed that the 95% LOA were -0.17-0.12 (Pa) for group I, -0.09-0.13 (Pa) for group II and -0.08-0.10 (Pa) for group III. V Flow measurement is a simple, rapid and feasible imaging method for the WSS assessment of CCA in healthy volunteers, which will probably be an important tool for assessing CCA function.

Optimal Site for Proximal Optimization Technique in Complex Coronary Bifurcation Stenting: A Computational Fluid Dynamics Study

Background/purposeThe optimal position of the balloon distal radio-opaque marker during the post optimization technique (POT) remains debated. We analyzed three potential different balloon positions for the final POT in two different two-stenting techniques, to compare the hemodynamic effects in terms of wall shear stress (WSS) in patients with complex left main (LM) coronary bifurcation. Methods/materialsWe reconstructed the patient-specific coronary bifurcation anatomy using the coronary computed tomography angiography (CCTA) data of 8 consecutive patients (6 males, mean age 68.2± 18.6 years) affected by complex LM bifurcation disease. Subsequently a virtual bench test was performed in each patient using two different double stenting techniques represented by the DK and Nano crush using the reconstruction of Orsiro stents (Biotronik IC, Bulack, Switzerland). ResultsA significant reduction in the mean WSS values in all the lesion's sites was observed when the final POT was performed 1 mm distally the carina cut plane in both techniques. Moreover, a significant improvement in the mean WSS values of the entire SB (e.g. LCX) was obtained performing the POT 1 mm distally to the carina cut plane. The proximal POT resulted in larger area of lower WSS values at the carina using both the Nano crush and the DK crush techniques. ConclusionsIn patients with complex LM bifurcation disease the use of a final POT performed 1 mm distally to the carina cut plane might results in more favorable WSS patterns (i.e. higher WSS values) along all stented segments and, especially, along the entire LCX lesions.

P1824Aortic wall shear stress in bicuspid aortic valve disease - 10-year follow-up

Abstract Introduction Bicuspid aortic valve (BAV) disease leads to deviant complex helical flow patterns in the aorta - especially in the mid-ascending (AoA) part. In association with congenital BAV, aortic wall alterations such as aortic dilatation and dissection may occur. Among others, wall shear stress (WSS) could be one parameter to contribute to the prediction of the long-term outcome of patients with BAV. 4D-flow in cardiovascular magnetic resonance has been established as a valid method to estimate WSS. Purpose The aim of this study is to reevaluate WSS and comparing it to values generated in the same patient cohort with bicuspid aortic valve disease in 2008. No one of the above had aortic dilation in 2008 but proven helical flow pattern. The long term follow-up study might show changes in WSS over the period of ten years. Methods Ten complete 4D flow datasets of patients (age at follow-up: median 34.5 years; range 19–41 years) with bicuspid aortic valve disease without enlargement of the aorta were obtained in 2008 and reevaluated in 2018/2019 in the same patient collective. Mean WSS values were calculated with identical specific software tools. All data were analyzed by two experienced investigators. Results Aortic diameters at the level of the mid AoA did not change significantly in the 10-year period. The WSS values were lower in 2018 at all levels of the ascending aorta (Table 1). Indexed aortic diameters at the level of the mid ascending aorta did not change, median difference 0.06 cm/m2 (range −0.1 cm/m2 to 0.2 cm/m2; p=0.28), absolute values of indexed AoA diameters in 2018/2019 ranged from 1.27 cm/m2 to 2.2 cm/m2 (median 1.76 cm/m2). Table 1 WSS magnitudinal [N/m2] 2008 (n=10) 2018 (n=10) Median difference p-value median range median range Level aortic bulb 0.95 0.80–1.46 0.42 0.34–0.82 −0.53 &lt;0.01 Level mid ascending aorta 0.72 0.40–0.98 0.39 0.34–0.59 −0.33 &lt;0.01 Level brachiocephalic trunc (BCT) 0.71 0.38–1.03 0.40 0.37–0.61 −0.31 &lt;0.01 Conclusions Indexed AoA diameters in BAV disease did not change significantly over a 10-year period. WSS of AoA was less compared to values generated in 2008. This might be explained by a slight alteration in hemodynamic flow patterns by the aging aorta, but not by changes of the aortic diameters. Possibly a drop of WSS in BAV could serve as a marker for a benign long term course.

Time-dependent flow velocity measurement using two-dimensional color Doppler flow imaging and evaluation by Hagen-Poiseuille equation.

This paper aims to develop a technique to assess velocity flow profile and wall shear stress (WSS) spatial distribution across a vessel phantom representing an artery. Upon confirming the reliability of the technique, it was then used on a set of carotid arteries from a cohort of human subjects. We implemented color Doppler flow imaging (CDFI) for measurement of velocity profile in the artery cross section. Two dimensional instantaneous and time-dependent flow velocity and WSS vector fields were measured and their waveforms of peak velocities based on the technique were compared with WSS values generated by Hagen-Poiseuille equation. Seventy-five patients with intima-media thickening were prospectively enrolled and were divided into an IMT group. At the same time, another 75 healthy volunteers were enrolled as the control group. All the subjects were scanned and the DICOM files were imported into our in-house program. Next, we determine the velocity profile of carotid arteries in a set of 150 human subjects and compared them again. The peak velocities by the CDFI and Hagen-Poiseuille equation techniques were compared and statistically evaluated. The amounts of deviation for the two measured WSS profiles were performed and we demonstrated that they are not significantly different. At two different flow settings with peak flow velocity of 0.1, 0.5 (×10(-11)) m/s, the obtained WSS were 0.021 ± 0.04, 0.038 ± 0.05 m/s, respectively. For the patient population study, the mean WSS value calculated by Hagen-Poiseuille equation was 2.98 ± 0.15 dyne/cm(2), while it was 2.31 ± 0.14 dyne/cm(2) by our CDFI analysis program. The difference was not statistically significant (t = -1.057, P = 0.259). Similar to the Hagen-Poiseuille equation, a negative linear correlation was also found between the calculated WSS and intima-media thickness (P = 0.000). Using CDFI analysis, we found that the WSS distribution at the middle of the proximal plaque shoulder was larger than the top of the shoulder. CDFI can assess the velocity and WSS profile accurately and efficiently and may be used for clinical diagnosis of cardiovascular conditions.

Spatial distribution of wall shear stress in the common carotid artery of type 2 diabetes mellitus patients

Objective To investigate the wall shear stress(WSS) in the common carotid artery of type 2 diabetes mellitus(DM) patients,and analyzed the spatial distribution of WSS by using quantitative visualization of blood flow shear stress analysis software.Methods Eighteen male type 2 DM subjects were enrolled as DM group and 18 age-matched healthy subjects were selected as control group.None of the participants was hypertensive,hyperlipidemic or a cigarette smoker.Intimal-medial thickness (IMT),number and size of plaques in the common carotid artery were evaluated by high-resolution echo-Doppler.Color Doppler flow images of common carotid arteries in the two groups were extracted from DICOM files.WSS in the common carotid arteries was calculated by shear stress visualization quantitative analysis software,and the corresponding spatial distribution maps of WSS were designed.Results WSS of the common carotid arteries in the control group were ranged from 4 to 14 dyne/cm2.WSS of the common carotid arteries in the DM group were ranged from 2 to 8 dyne/cm2.Compared to mean WSS value [(6.96 ± 1.17)dyne/cm2] of common carotid arteries in the control group,mean WSS value [(3.14 ± 0.79)dyne/cm2] of common carotid arteries in the DM group was significantly lower (t =9.380,P =0.000).Six diabetic participants had a plaque in one carotid artery and no lesions in the contralateral carotid.Among these subjects,mean WSS was significantly lower in the side with lesion (t =7.324,P =0.000).Therefore,IMT of common carotid arteries in participants was significantly inversely related to WSS (r =-0.76,P ＜0.01).Conclusions The common carotid arteries of DM patients are more prone to atherosclerosis which is associated with reduction of WSS.The hemodynamic profile might represent an additional factor contributing to the increased prevalence and severity of carotid atherosclerosis in diabetic patients compared with general population. Key words: Ultrasonography; Diabetes mellitus,type 2; Carotid artery,common; Wall shear stress

Periodontal disease and carotid atherosclerosis: Are hemodynamic forces a link?

Objective The link between periodontal disease and atherosclerosis has not yet been clarified, though systemic inflammation seems to be the common soil for both conditions. Inflammation influences also hemodynamic forces, that act as local risk factors for carotid plaques. It is not known if the link between periodontitis and carotid atherosclerosis is mediated, at least in part, by physical forces. Therefore, aim of the present study was to evaluate the association between carotid shear stress force and periodontal disease. Methods Thirty-three subjects underwent complete cardiovascular screening, carotid hemodynamic evaluation and dental inspection. Presence of classical risk factors for atherosclerosis, common carotid peak and mean wall shear stress values and periodontal indices of disease (plaque index, gingival index and pocket deep) have been evaluated. Results Worse periodontal health was associated to the presence of carotid atherosclerosis. Patients with carotid plaques ( n = 19) had higher periodontal indices compared with subjects without plaques ( n = 14) (gingival index: 1.40 ± 0.71 vs. 0.69 ± 0.64, p = 0.006). These relations were independent of the presence of cardiovascular risk factors in multiple logistic regression analysis. In the 66 examined common carotids, wall shear stress was inversely related to all periodontal indices ( r = 0.54, p < 0.00001 for peak wall shear stress and gingival index). These relations remained significant also in multiple regression analysis, after correction for cardiovascular risk factors, gender and age. Conclusions The present study identifies for the first time a link between periodontal indices and wall shear stress, suggesting that an alteration of hemodynamic profile might contribute to atherosclerosis in subjects with periodontal disease.

Noninvasive determination of spatial distribution and temporal gradient of wall shear stress at common carotid artery

Wall shear stress (WSS) has been proved to play a critical role in formation and development of atherosclerotic plaques. Our objective was to quantify local WSS in vivo in normal subjects, and to analyze spatial distribution patterns and determine the temporal gradient of WSS. Seventy-eight CCAs of 42 healthy volunteers at common carotid arteries (CCAs) were studied. Cine phase-contrast MR sequence was used to acquire the flow velocity information. Three-dimensional paraboloid modeling was applied to fit the velocity profiles and WSS values were calculated. Mean WSS value for CCAs was 0.783±0.209, with the range of WSS value from −0.541 to 3.464 N/m 2. The 95% confidence interval for mean WSS value in CCA was (0.736–0.830) N/m 2. Different WSS spatial distribution patterns were classified into three types according to the location of low WSS values during a cardiac cycle. Mean value of maximum temporal gradient of WSS was 14.12±5.46, with the range from 5.87 to 33.23 N/m 2 s −1. Skewed velocity profiles were displayed in most CCAs, indicating the flow patterns in CCA were more complicated than commonly assumed. Obvious inter-subject variation were found in magnitude, spatial distribution and the temporal gradient of WSS in CCAs, and the blood flow patterns as well.

In-vivo measurements of wall shear stress in human coronary arteries.

Wall shear stress (WSS) is closely associated with arteriosclerosis. WSS values for various vessels and species are available, but fully in-vivo measurements in human coronary arteries have not yet been reported. To measure WSS in undiseased coronary arteries of adult patients at rest. We recorded the temporal average value (APV) of the instantaneous maximal blood velocity in the three vessel segments of angiographically normal coronary artery bifurcations in 21 patients undergoing cardiac catheterization to treat various diseases by means of a 0.036 cm Doppler wire (FloWire). In total, 36 bifurcations were examined. The 36 x 3 cross-sectional areas (CSA) were determined by means of a three-dimensional angiographic technique. The three flows, Q1 (inflow), Q2, and Q3 of each bifurcation were calculated according to Q=0.5 x APV x CSA. For each segment, WSS was calculated as WSS=32 eta Q/(pi D3) (where blood viscosity eta=3.5 mPa s and D is vessel diameter). Only the 54 WSS values obtained from the 18 flow triplets which satisfied the equation Q1/(Q2+Q3)=1 better than did the 18 other ones were retained. The 54 WSS values ranged from 0.33 to 1.24 Pa (mean 0.68 Pa, SEM, 0.027 Pa). They did not depend significantly on Q (r=0.07; P=0.60) and the CSA (r=0.24, P=0.08) but the second relationship approached significance. The obtained mean WSS value (0.68 Pa) is half the value predicted for coronary arteries from optimality principles. It is also smaller than many values reported for human carotid, renal, and femoral arteries.

Accuracy of the inverse Womersley method for the calculation of hemodynamic variables.

We have studied the accuracy of the inverse Womersley method, a linear theory for the calculation of hemodynamic variables from measured volumetric flow rate or centerline velocity, for two canine arteries with different degrees of arterial wall motion and taper. The results from the linear theory are compared with the estimates from the nonlinear theory of Ling and Atabek for a canine thoracic aorta and femoral artery. For the thoracic aorta, the linear theory underestimates the mean wall shear stress by as much as 77%, when compared with the nonlinear theory. For the femoral artery, on the other hand, the mean wall shear stress value is underestimated by as much as 23%. Estimates of other hemodynamic variables show similar discrepancies between the nonlinear and linear theories. Thus, the inverse Womersley method does not give accurate estimates of hemodynamic quantities. This failure results from the neglect of convective accelerations due to arterial wall motion and taper, with the neglect of arterial taper leading to the largest errors.