Elevated Blood Velocity Research Articles

Aggressive and Autoaggressive Behaviors in Patients with Autism Spectrum Disorder in Correlation with Middle Cerebral Artery Flow Velocity.

Background/Objectives The purpose of this study was to see whether there is a correlation between the behavior of autism spectrum disorder patients and brain abnormalities based on the velocity of blood flow in the MCA (middle cerebral artery). Methods: The use of HAP (High Altitude Protection) suits, which are used in aviation, to treat patients with ASD (autism spectrum disorder) causes significant changes in their functioning and physiological processes. These changes are not only noted in psychological tests but are observed in cerebral blood flow using transcranial Doppler ultrasound of the MCA. Results The results of this study made it possible to distinguish two groups with different flow velocities, which can be characterized as flows of less than 80 cm/s and flows of more than 80 cm/s. In addition, it was shown that in patients with elevated blood flow velocity, aggressive behaviors account for 86.96%, while self-aggressive behaviors account for 65.2%. On the other hand, in the case of patients with reduced flow velocity, i.e., less than 80 cm/s, the rate of aggressive behavior is 20% and that of self-aggressive behavior is 50%. The experiment showed that after therapy, there is a normalization of blood flow, which increased in the case of patients with a reduced flow rate below 80 cm/s and, in the case of elevated blood velocity after therapy, decreased towards normal levels. Conclusions The observed rate of normalization of flow velocities in the MCA translated into significant changes in the behavior and functioning of patients in the neurotypical direction, which was noticeable in the psychological tests conducted.

Sleep Fragmentation and Obstructive Sleep Apnea Are Associated with High Primary Stroke Risk in Children with Sickle Cell Disease

Background Children with sickle cell disease (SCD) are at elevated risk of developing sleep disorders, 1 which may contribute to the sequelae of their disease. One important sequela of SCD exacerbated by sleep disorders is cerebrovascular stroke. Transcranial Doppler (TCD) screening of large intracranial arteries can detect elevated blood velocity and strongly predict stroke in children with SCD. 2 However, the association between stroke risk, as assessed by TCD, and sleep disorders has not been sufficiently investigated. Main Objective To investigate the association between sleep disorders and abnormal TCD examinations in children with SCD. Design/Methods We evaluated associations between sleep disorder severity with TCD examinations in children with SCD. We selected all participants from the Sickle Cell Clinical Research and Intervention Program (SCCRIP), who underwent polysomnography between 2016 - 2020 and had at least one TCD examination. SCCRIP prospectively recruits patients diagnosed with SCD and includes retrospective and longitudinal collection of clinical, neurocognitive, geospatial, psychosocial, and health outcomes data. 3 The severity of sleep apnea was assessed using the apnea/hypopnea index, separated into total and obstructive apnea/hypopnea indices. The number of oxygen desaturation events per hour of sleep as well as the O2 saturation nadir were recorded. Sleep fragmentation was measured by the total arousal index (events per hour of sleep) and sub-categorized into spontaneous and respiratory-related arousal indices. Transcranial Doppler exams were reported as abnormal with timed average mean maximum velocities (TAMMV) of greater than 200 cm/s, high-conditional > 185 cm/s, low-conditional > 170 cm/s, and normal ≤ 170 cm/s. Exact Wilcoxon rank sum test was used to compare sleep outcomes between two groups. The false discovery rate adjusted p-values or q-values were calculated using Benjamini and Hochberg approach to control for multiple comparisons at a level of 0.05. Results Eighty-four patients met inclusion criteria (genotypes SS/SB0 81 (96%), median age 8.3, range 2.2-23.1, 42 male: 42 female). Six patients had abnormal, six high-conditional, 12 low-conditional velocities, while the remainder (60) had normal TCD exams. Patients with abnormal TCD exams exhibited more severe obstructive sleep apnea (mean AHI 25.0 + 9.1 vs. 5.3 + 8.3, p = 0.003), more severe respiratory related arousals (12.7 + 7.9 vs. 3.2 + 4.5, p = 0.008), and higher total arousals (22.9 + 7.7 vs. 12.9 + 5.8, p = 0.01) than those with normal TCD studies at p<0.05.The number of oxygen desaturation events per hour (mean 10.6 + 10.5 vs. 4.5 + 8.0, p = 0.05) was not significantly different among patients with abnormal and normal TCD exams at q<0.05 but the O2 saturation nadir was significantly less in patients with abnormal TCD exams (mean 74.0 + 5.0 vs. 86.8+9.9, p = 0.007) at q<0.05 (Figure 1). Conclusion In pediatric patients with SCD, a link exists between sleep apnea, O2 saturation nadir, sleep fragmentation, and stroke risk. While the findings of this study establish a correlation between sleep disorders and cerebrovascular complications in SCD, further research is still necessary to fully comprehend the exact role of sleep disorders on stroke risk. Nevertheless, this study underscores the importance of addressing sleep apnea and promoting healthy sleep patterns in pediatric patients with SCD to reduce the risk of stroke.

Optimizing the Frequency of Transcranial Doppler (TCD) Exams in Children with Sickle Cell Anemia

Background Transcranial Doppler (TCD) screening of the large intracranial arteries can detect elevated blood velocity and is a strong predictor of stroke risk in children with sickle cell anemia (SCA, HbSS and HbSβ0-thalassemia). Initiation of chronic blood transfusion for patients with confirmed abnormal TCD velocities (time-averaged mean velocity, TAMV≥200 cm/sec) is shown to effectively reduce primary stroke. Current guidelines recommend annual TCD screening for children with SCA ages 2-16 years. Screening intervals were developed following evidence from the STOP studies1 (Figure 1). The estimated prevalence of normal TCD velocities is 83%2 and these children will have received 15 TCD exams from ages 2 to 16 if all results remain within normal range. The cumulative incidence of conversion from normal to conditional TCD velocities is dependent on age, whereby the risk is four times lower in children >10 years, compared to those <10 years of age3. Although TCD screening is non-invasive and safe, it consumes time and requires specialized equipment and trained examiners. Identifying sub-populations for whom TCD screening frequency could be safely reduced could lessen time burden on patients and caregivers and could be cost saving. Main objective To estimate the risk of TAMV conversion from normal to conditional or abnormal categories among children with SCA relative to age. Design/Method We included all participants with SCA from the Sickle Cell Clinical Research and Intervention Program, a longitudinal lifetime cohort of patients with SCD with at least one TCD measurement available both before and after age 10 years. We classified participants into two groups based on TCD screening results before 10 years of age; one group with all normal TCDs, and the other group with at least one non-normal TCD. We then compared the time to first non-normal study after ten years of age between the two groups using the log rank test. Time to first conversion was defined as time from age 10, to time of conversion if conversion occurred, or time to last follow up if no conversion occurred. We correlated the number of TCD exams before age 10 with time to first conversion using the Cox proportional regression model. Exposure to chronic transfusion or hydroxyurea before age 10 and age at first TCD measurement were covariates and were correlated with the time to first conversion. Results Of the 614 patients with TCD screening, 297 had SCA and at least 1 screening before and after age 10 (Table 1). Of these, 174 patients had only normal TCD screening before age 10 and the remaining 123 patients had at least 1 non-normal TCD screening before age 10. During the time they were followed,no patients with only normal TCD screenings before age 10, regardless of exposure to hydroxyurea or transfusions, had a conditional or abnormal TCD exam. Conversely, 41.5% of patients with at least one non-normal TCD before age 10 had a conditional or abnormal TCD screening after age 10. Conclusion In a large retrospective cohort study analysis of children with SCA, patients with TCD exams consistently within the normal range under age 10 years were not at risk of conversion to conditional or abnormal TAMV. These results suggest that children with SCA with all normal TCD velocities before age 10 years may not require additional TCD screening exams after age 10. These results translate to 6 fewer TCD exams per each child with SCA over age 10 with all prior normal TCD exams, potentially conserving resources and reducing burden on patients, families, and the health system. De-implementation studies to reduce the use of TCD screening exams in low-risk cases are needed

Effect of Circulating Omentin-1 on the Retinal Circulation in Patients With Type 2 Diabetes Mellitus.

To identify any significant correlations between retinal circulatory parameters and serum concentrations of omentin-1, a novel adipokine produced by adipocytes, in patients suffering from type 2 diabetes mellitus. Eighty-seven patients suffering from type 2 diabetes and incipient diabetic retinopathy (DR) were analyzed and further divided into two groups according to sex. We compared the patients' retinal circulatory parameters measured with laser Doppler velocimetry and serum omentin-1 concentrations. The plasma omentin-1 concentrations were related positively to the retinal blood flow (RBF) (r = 0.212; P = 0.048) and primarily with female sex (r = 0.288; P = 0.06) and negatively to the retinal arterial vascular resistance (RVR) (r = -0.218; P = 0.043). Moreover, the plasma omentin-1 concentration was modestly but not significantly positively related to the blood velocity. Multiple regression analysis showed that the serum omentin-1 level contributed independently and negatively to the RVR. Increased concentrations of plasma omentin-1 might be linked to elevated RBF levels probably through elevated blood velocity in patients suffering from type 2 diabetes with incipient DR, especially in female patients, which warrants further investigation.

Original Research: Sickle cell anemia and pediatric strokes: Computational fluid dynamics analysis in the middle cerebral artery.

Children with sickle cell anemia (SCA) have a high incidence of strokes, and transcranial Doppler (TCD) identifies at-risk patients by measuring blood velocities in large intracerebral arteries; time-averaged mean velocities greater than 200 cm/s confer high stroke risk and warrant therapeutic intervention with blood transfusions. Our objective was to use computational fluid dynamics to alter fluid and artery wall properties, to simulate scenarios causative of significantly elevated arterial blood velocities. Two-dimensional simulations were created and increasing percent stenoses were created in silico, with their locations varied among middle cerebral artery (MCA), internal carotid artery (ICA), and anterior cerebral artery (ACA). Stenoses placed in the MCA, ICA, or ACA generated local increases in velocity, but not sufficient to reach magnitudes > 200 cm/s, even up to 75% stenosis. Three-dimensional reconstructions of the MCA, ICA, and ACA from children with SCA were generated from magnetic resonance angiograms. Using finite element method, blood flow was simulated with realistic velocity waveforms to the ICA inlet. Three-dimensional reconstructions revealed an uneven, internal arterial wall surface in children with SCA and higher mean velocities in the MCA up to 145 cm/s compared to non-SCA reconstructions. There were also greater areas of flow recirculation and larger regions of low wall shear stress. Taken together, these bumps on the internal wall of the cerebral arteries could create local flow disturbances that, in aggregate, could elevate blood velocities in SCA. Identifying cellular causes of these microstructures as adhered blood cells or luminal narrowing due to endothelial hyperplasia induced by disturbed flow would provide new targets to treat children with SCA. The preliminary qualitative results provided here point out the critical role of 3D reconstruction of patient-specific vascular geometries and provide qualitative insight to complex interplay between vascular geometry and rheological properties possibly altered by SCA.

Cerebral Tissue Transit Time in Patients with Sickle Cell Anemia

Introduction Accurate characterization of cerebral blood flow (CBF) in patients with sickle cell anemia (SCA) is imperative given the occurrence of neurovascular sequelae in this population. Arterial Spin Labeling (ASL) is a promising MRI modality that has been used to quantify CBF in SCA by several groups. Unfortunately, ASL quantification has proven challenging in SCA given the unique phenotype found in these patients including decreased hematocrit, elevated blood velocity an abnormal rheologic properties. As a result, there are conflicting accounts of ASL perfusion in this population. One of the key parameters of ASL quantification is the time between the labeling of spins in the neck and the downstream diffusion of those spins into parenchymal tissue, termed tissue transit time (TT). Delayed tissue TT is a known consequence of many neurovascular pathologies, including stroke. Given the elevated cerebral blood velocity and flow in response to anemia, however it is generally assumed that tissue TT is shorter in SCA but has yet to be studied. In order to improve ASL quantification and characterize this neurovascular biomarker we measured ASL derived tissue TT in healthy patients with SCA and ethnicity matched controls.Methods All patients were recruited with informed consent or assent and this study was approved by the Children's HospitalLos Angeles institutional review board. Exclusion criteria included pregnancy, previous stroke, acute chest, pain crisis or hospitalization within one month. All MRI scans were performed on an Achieva 3T scanner with an 8 channel head coil. Tissue TT was measured using two single shot, GRASE, ASL acquisitions, one with velocity spoiling gradients (venc 5 cm/s) and one without. Pseudo continuous ASL had a label duration of 1150ms and delay of 1500ms. Single slice phase contrast MRI of the carotids and vertebral arteries measured arterial blood velocity and global CBF. Hemoglobin level was determined on the day of the study.Results Eight patients with SCA (7 SS, 1 SC; 15.8 + 4.4yo; 5F, 3M) and nine ethnicity matched healthy controls (36.4 + 4.1yo; 6 F, 3M) were recruited. Patients with SCA had a lower hemoglobin levels (SCA, 10.1 + 0.64 g/dl, CTRL 13.7 + 0.58) and elevated CBF (SCA, 76.6 + 5.8 ml/100g/min, CTRL 49.0 + 4.4 ml/100g/min). Regional ASL perfusion asymmetries were observed in several SCA subjects. These asymmetries were not present in corresponding tissue TT maps (Figure 1). There was a trending difference in tissue TT between the two groups (SCA 1588 + 49.8, CTRL 1696 + 46.9 ms, p=.1). After multivariate analysis, sex and global CBF were the only predictors of tissue TT, r2=.54 (Figure 2).Discussion Our data is the first of our knowledge to measure the tissue TT in patients with SCA. Tissue TT is distinct from the bolus arrival time or arterial TT which corresponds to the arrival time of tracer at the imaging region. Tissue transit time is more sensitive to microvascular flow and diffusion effects and may reflect microvascular health and blood brain barrier integrity. Our measurement of tissue TT is congruent with other findings in separate neurovascular pathologies and suggests that gender and global CBF must be considered when quantifying ASL perfusion. These preliminary results also offer insight into the perfusion asymmetries observed in the ASL SCA literature. We found that perfusion asymmetries do not correlate with tissue TT suggesting either 1) tissue TT is conserved despite differences in regional flow or 2) a separate source of error is leading to spurious regional perfusion quantification, ie labeling efficiency. [Display omitted] DisclosuresNo relevant conflicts of interest to declare.

Retinal Venous Oxygen Saturation Increases by Flicker Light Stimulation

Luminance flicker stimulation of the photoreceptors is known to increase retinal blood flow. Elevated blood velocity was determined using laser Doppler velocimetry, and increased vascular diameters during flicker were observed by measurements with a retinal vessel analyzer. Oxygen supply may be the target of the regulation of retinal blood flow. Thus, the oxygen saturation (SO(2)) in retinal arterioles and venules was investigated along with their diameters. Dual-wavelength (548 nm and 610 nm) fundus images were taken in 19 healthy volunteers (mean age, 26 ± 2.5 years) before (baseline) and during luminance flicker stimulation (12.5 Hz; modulation depth, 1:25). Retinal vessel SO(2) (dual-wavelength optical oximetry) and diameters (central retinal arterial and venous equivalents [CRAE and CRVE]) were determined. CRAEs and CRVEs of 193 ± 20 μm and 228 ± 20 μm at baseline increased statistically significant to a maximum of 202 ± 19 μm (P < 0.0005) and 242 ± 17 μm (P < 0.0005), respectively, under flicker stimulation. Although the arterial SO(2) remained unchanged at 98%-99%, an increase of the venous saturation from 60% ± 5.7% to 64% ± 5.9% (P < 0.0005) was found. In agreement with earlier investigations, the vessel dilation found here indicates an elevation of retinal blood flow by luminance flicker stimulation. This increase of the flow should meet the enhanced metabolic need of the neural retina under a physiological stimulus. The augmentation of venous oxygenation may indicate a higher capillary oxygen concentration, necessary to provide a sufficient diffusion rate of oxygen from the capillaries to the inner retinal tissue.

Retinal hemodynamic changes in diabetic macular edema

Abstract Purpose To report the 1 year prospective hemodynamic results in a cohort of patients with varying levels of risk for the development of diabetic macular edema (DME) and to correlate these parameters to systemic changes in blood pressure and diabetes control. Methods The sample comprised 4 groups. Group 1: 37 non‐diabetic controls; Group 2: 42 patients with no diabetic retinopathy (DR); Group 3: 38 patients with DR but no DME; Group 4: 27 patients with DME. Retinal arteriolar diameter, velocity, maximum‐to‐minimum (max:min) velocity ratio and flow were measured using the Canon Laser Blood Flowmeter. Blood pressure, blood and urine tests were taken and correlated to changes in retinal hemodynamics. A sub‐group of patients with progressive DR was analyzed separately. Results There was a trend for elevation of the max:min velocity ratio (p=0.060) with increasing risk of DME at baseline which was significant on follow‐up (p=0.020). Diameter decreased for all groups (p&lt;0.056) except for patients with DME. Changes in retinal blood velocity, max:min velocity ratio and flow were correlated to blood pressure mostly in patients with DR and DME. Blood albumin level was negatively correlated to retinal blood velocity and flow in the DME group. Patients with progressive DME had elevated blood velocity and flow. Conclusion Patients with DME have a higher max:min velocity ratio. Changes in retinal hemodynamics were correlated to changes in blood pressure and were negatively correlated to changes in blood albumin. The results indicate a loss of vascular compliance with diabetes, particularly in patients with DME, and elevated retinal perfusion in patients with progressive DME.

Call-Fleming Postpartum Angiopathy in the Puerperium

The postpartum angiopathy (Call-Fleming syndrome) is a rare, reversible cerebral vasoconstriction syndrome. Unlike in eclampsia, neither proteinuria nor hypertension have been observed in the Call-Fleming syndrome. A 17-year-old woman developed headache, seizures, confusion, cortical blindness, and denial of visual loss (optic anosognosia, Anton syndrome) on the first postpartum day. Transcranial Doppler demonstrated severely elevated blood velocities. Magnetic resonance angiography showed multifocal segmental narrowing of cerebral arteries. Magnetic resonance imaging revealed occipitotemporal edema. After symptomatic treatment, the clinical deficits disappeared completely within 2 weeks. The follow-up neuroimaging performed after 3 months was unremarkable. The case shows that the Call-Fleming syndrome is a reversible condition with excellent prognosis representing an important differential diagnosis of eclampsia, dural sinus thrombosis, and intracranial bleeding in puerperium.

Lessons from the Stroke Prevention Trial in Sickle Cell Anemia (STOP) study.

Stroke is generally uncommon in children, but sickle cell disease is associated with a high risk of stroke in the early years of childhood. Large cerebral arteries, especially the middle cerebral and intracranial internal carotid, develop stenosis that predisposes to ischemic stroke. Noninvasive prediction of risk using transcranial Doppler ultrasonography made it possible to test primary stroke prevention in a clinical trial comparing chronic blood transfusion with standard care. A consortium of 14 clinical centers conducted a randomized clinical trial (Stroke Prevention in Sickle Cell Anemia--the "STOP" study) to test a strategy to prevent first stroke in children with sickle cell disease. Over 2000 children were screened with transcranial Doppler ultrasonography and of these, 130 with elevated blood velocity indicating high risk were enrolled in the trial. Regular red cell transfusions sufficient to reduce the percentage of Hb S gene product from over 90 to less than 30 of total hemoglobin was associated with a marked reduction in stroke. The untreated risk of 10% per year was reduced over 90% with treatment, an effect sufficient to cause early termination of the trial. Although treatment was unblinded, the design included blinded adjudication of possible stroke by a panel of neurologists remote from the study sites. The study led to a Clinical Alert, issued by the National Heart, Lung, and Blood Institute, recommending screening and consideration of treatment in children with sickle cell disease and 2 to 16 years of age who are at risk based on transcranial Doppler ultrasonography, and who have not had stroke.

The role of transcranial Doppler in the management of patients with subarachnoid haemorrhage--a review.

Introduced 15 years ago, transcranial Doppler (TCD) recordings of blood-velocity in patients with recent subarachnoid haemorrhage (SAH) have two objectives: to detect elevated blood velocities suggesting cerebral vasospasm (VSP) and to identify patients at risk for delayed cerebral ischemic deficits (DID). The pathophysiological cascade causing DID is complex. Discrepancies between blood velocities and DID (presuming that there actually is an "ischemic threshold" for blood velocity in absolute terms, which seems most unlikely) have been demonstrated, particularly in patients with elevated intracranial pressure (ICP) levels. Furthermore, the vessel showing the highest blood velocity is not always the one perfusing the area where ischemic symptoms arise, nor does the site of the greatest subarachnoid blood clot always relate to the ischemic brain region. Moreover, it is probable that the complex haemodynamic changes following SAH and the subsequent development of VSP may be underestimated if only considering the crude intracranial artery blood velocities. Cerebral blood flow measurements combined with TCD to assess both flow and velocity have emphasised this point. Despite these findings and ignoring the basic principles of cerebral haemodynamics, cerebral vasospasm is still being assessed from the intracranial velocity measurement alone. The addition of at least a careful measurement from the extracranial internal carotid artery--using the same TCD equipment and taking only a few short minutes to perform--allows a much more accurate assessment of the degree and the effects of vasospasm. This probably explains why the clinical value of TCD is still debated. There is still uncertainty as to the best method to prevent and to treat VSP, and the overall outcome after SAH depends on so many factors besides VSP. Conclusive evidence may therefore be hard to obtain, and it appears sound to conclude that even with advanced investigation technology available, proper selection, pre- peri- and postoperative care and timing of surgery remain cornerstones in the management of these patients,--equal in importance to their treatment in the operating room or in the interventional angiography suite.

Is routine transcranial Doppler ultrasound useful in the management of subarachnoid hemorrhage?

In this prospective observational study, the authors assess the impact of routine transcranial Doppler (TCD) ultrasound monitoring on the diagnosis, management, and outcome of delayed ischemic neurological deficit complicating subarachnoid hemorrhage (SAH). Over a 10-month period 186 patients admitted to a regional neurosciences center were included in the study. Three times a week, routine TCD examinations performed by neuroradiographers made an important positive contribution to the diagnosis of delayed ischemic neurological deficit in 72% of patients with this complication and altered management for the benefit of the patient in 43%. In 9% of patients with recent SAH, it was believed that the outcome might have been better if the TCD result had been acted upon appropriately. The TCD results did not adversely influence management or outcome and were accurate when compared with those obtained on angiography. The authors conclude that a routine TCD service provided by neuroradiographers is accurate and useful in diagnosing and managing elevated blood velocities and ischemic neurological deficit following SAH. In addition, it is possible that if the information gleened from TCD findings was used more often in patient management, outcome might be improved; however, a randomized controlled trial is necessary to assess this definitively.

Interleukin-1 beta enhances spinal cord blood flow after intrathecal administration in the normal rat

The effects of acute intrathecal recombinant human interleukin-1 beta (rhIL-1 beta) administration on spinal cord blood flow (SCBF), volume, and velocity were determined by laser-Doppler flowmetry in normal anesthetized rats with the use of a randomized and blinded protocol. The intrathecal administration of rhIL-1 beta (0.16-16 ng) produced a dose-dependent increase in SCBF that was not related to changes in blood pressure; arterial pH, PO2, PCO2; or spinal cord temperature. The IL-1 beta-induced enhancement of SCBF was directly proportional to the resultant elevation of spinal cord rhIL-1 beta content and was significantly correlated with an elevated blood velocity. The IL-1 receptor antagonist (IL-1ra) in concentrations 50- and 200-fold higher than IL-1 beta completely blocked the IL-1 beta-induced increase in SCBF when both compounds were administered concomitantly, but when administered alone, IL-1ra did not affect SCBF or other parameters. This suggests that IL-1 beta action was mediated by a specific interaction with an IL-1 membrane receptor site. The results suggest a role of IL-1 beta in the regulation of spinal cord hemodynamics. A potential pharmacological approach using IL-1 agonists for the treatment of the delayed appearance of posttraumatic spinal ischemia is proposed.

Inverse effect of chronically elevated blood flow on atherogenesis in miniature swine

The effect of chronically elevated blood flow on the development of atherosclerosis in miniature swine was studied. Fistulas connecting the right external iliac artery and vein were surgically created in four swine, while three were not fistulated. Pulsed Doppler velocity detection cuffs placed around the abdominal aorta and both iliac arteries of all pigs permitted chronic measurements of blood velocity, blood velocity distributions, and blood flow. All swine were fed an atherogenic diet consisting of 20% beef tallow, 3% cholesterol, and 5% cholic acid for 6 months. This diet elevated the serum cholesterol to values exceeding 500 mg/100 ml. Creation of the arteriovenous fistula (AVF) markedly elevated blood velocity and flow in the abdominal aorta and in the shunted iliac artery. In the shunted animals the aortic blood flow was 42.1 ± 2.0 ml/sec compared with 17.3 ± 1.4 ml/sec in the unshunted swine. The velocity distribution pattern across the vessel was also indicative of an elevated wall shear stress. After 6 months, the animals were killed and the arterial vessels examined macroscopically and microscopically for the presence of atherosclerotic lesions. In the shunted pigs, 17 15% of the lumenal surface was occupied by sudanophilic lesions, whereas 80 8% of the surface was covered by lesions in the unshunted (control) pigs. From these studies, it is apparent that mechanical factors related to blood flow rates can influence the development of atherosclerotic lesions in swine.