ESC/EACTS guidelines for the management of valvular heart disease. Conclusion: Reduced LV systolic S and SR in children with TS may indicate . what does elevated peak systolic velocity mean. 1. 7.4 ). There is wide variability in the peak systolic velocities seen in normal patients, with a range of 20 to 60cm/s, with an even wider range noted at the vertebral artery origin (also called segment V0). A peak systolic velocity of 2.5 m/s or greater is indicative of a significant stenosis. Data from 202 patients showing changes in peak systolic velocity (PSV) sensitivity, specificity, and accuracy for the diagnosis of 70% or greater angiographically proven stenosis using NASCET grading system. Significantly increased vertebral artery peak systolic velocities can also be seen when one or both vertebral arteries are the compensatory mechanism for occlusive disease elsewhere in the cerebrovascular system ( Fig. 2. All rights reserved. The carotid ultrasound examination begins with the patient supine and neck slightly extended with the head turned to the opposite side if needed ( Fig. Circ Cardiovasc Imaging. , and peak TR velocity > 2.8 m/sec. In 20%-30% of patients, these parameters are discordant (usually AVA <1 cm and MPG <40 mmHg). Mitral E/A ratio The ratio between the E-wave and the A-wave is the E/A ratio. Frequent questions. Few validated velocity criteria are available to define the severity of a vertebral artery stenosis, but based on our experience with peripheral arterial disease (see Chapter 15 ) reliance on a focal doubling of the peak systolic velocity implies a greater than 50% diameter reduction. The normal PVAT is > 130 msec. 9.5 ]). Ideally, these parameters should be concordant, with severe AS being defined by a peak velocity >4 m/sec, an MPG >40 mmHg and an AVA <1 cm (Table 1). The ICA is usually posterior and lateral to the ECA. Specific cut-points based on the arteriographic correlative studies need to use the NASCET/ACAS measurement approach ( Fig. Peak systolic velocity of 269 cm/s detected with an angle of 53 indicates moderate renal artery stenosis. The acoustic window between the transverse processes of the vertebral bodies can be used to visualize the vertebral arteries (segment V2) and to acquire color Doppler images and Doppler waveforms. 2010). The scan may begin with either the longitudinal or transverse imaging of the CCA. Among patients with discordant grading (AVA <1 cm and MPG <40 mmHg), those with low flow are much less frequent than those with normal flow. Peak systolic velocity (Doppler ultrasound). The resistive indexes calculated from the peak-systolic and end- These few published studies reported on the potential source for errors when using the standard ultrasound criteria after carotid stenting since the reduced compliance of stented carotid arteries. Can you tell me what this could possibly mean? Duplex ultrasound has been shown to be an effective noninvasive technique for the evaluation of the extracranial segments of the vertebral arteries. The fact that discordant grading is common and that low flow is rare but impacts on prognosis is of no help in assessing whether these patients truly presented severe AS. 24 (2): 232. 4,5 In cats, the resultant increase in left ventricular (LV) afterload is associated with enlargement of the cardiac . With the advent of statin (HMG-CoA reductase inhibitors) therapy, studies demonstrated a decreased risk of major vascular events such as stroke and that more aggressive statin treatment further decreased that risk by an additional 16%. As expected, computed tomography and calcium scoring accurately classified patients with concordant grading, but more importantly 50% of the patients with discordant grading could be considered as having true severe AS, whereas 50% did not fulfil the criteria for severe AS, irrespective of flow calculation. B., Edvardsen T., Goldstein S., Lancellotti P., LeFevre M., Miller F. Jr., & Otto C.M. ADVERTISEMENT: Supporters see fewer/no ads. The most appropriate way of classifying patients is first to consider whether AVA and MPG are concordant, and secondly to consider the flow (stroke volume index). There are no consistently successful diagnostic or management techniques for vertebral artery disease. Because of tortuosity, nonlaminar blood flow is commonly seen in the proximal vertebral artery, and kinking of the vessel may occur, causing an elevated peak systolic velocity. In addition, results in symptomatic patients were conflicting with more studies arguing against CAS in patients with symptomatic stenosis and high medical risk. They are usually classified as having severe AS. The goal of this study is to determine the impact of 12 weeks of Lp299v supplementation (20 million cfu/day vs. placebo) on exercise capacity, circulating biomarkers of cardiac remodeling, quality of life, and vascular endothelial function in humans with heart failure and reduced ejection fraction (HFrEF) who have evidence of residual inflammation based on an elevated C-reactive protein level. The SRU criteria were derived from multiple studies reflecting different velocity parameters including the PSV, the ratio of PSV in the ICA to that in the ipsilateral distal CCA (i.e., the ICA PSV/CCA PSV ratio), and end-diastolic velocity (EDV). These vessels exhibit high diastolic flow and EDV 4. If significant plaque is present in the ICA, the degree of luminal narrowing can be estimated in the transverse plane by comparing the main luminal diameter and residual lumen diameter (the diameter that excludes plaque) and using it as a qualitative adjunct to the measurement of stenosis severity based in the peak systolic velocity (PSV). [12] Importantly, these thresholds are not valid for rheumatic disease and deserve specific validation in the bicuspid aortic valve. Your measurement is Multiples of Median The risk of anemia is highest in fetuses with a pre-transfusion peak systolic velocity of 1.5 times the median or higher. The last decade has seen this apparently easy and straightforward classification shaken up by the observation that up to one-third of patients present with discordant AS grading, and by the identification of a subset with paradoxical low-flow, low-gradient severe aortic stenosis despite preserved ejection fraction. This is our usual practice and our personal recommendation. In addition to the fact that thresholds are different in males and females (approximately 2,000 and 1,250 AU, respectively), these results show that AS pathophysiology is different in males and females and, indeed, female leaflets are more fibrotic than those of males. The first two parameters are directly measured using continuous wave Doppler, while the last one is calculated based on the continuity equation and measurement of the left ventricular outflow tract (LVOT) diameter, LVOT time-velocity integral (TVI) and aortic TVI. Systolic BP of 140 or higher is Stage 2 hypertension, which can drastically increase the risk of stroke or heart attack, may require a prolonged regimen of medication. At the aortic valve, peak velocities of up to 500 cm/sec may be possible. Is 50 blockage in carotid artery bad? The important points discussed in the present paper can be summarised as follows: Discordant grading is common in clinical practice. This is why some have suggested combining CT (for the measurement of the LVOT area) and echocardiography for LVOT and aortic TVI in the calculation of the AVA. Elevated blood flow velocities in the ECA are not considered clinically important except that they can explain the presence of a clinically detected carotid bruit. The content of this article reflects the personal opinion of the author/s and is not necessarily the official position of the European Society of Cardiology. In these same studies, after repetitive dosing, the half-life increased to a range from 4.5 to 12.0 hours (after less than 10 consecutive doses given 6 hours apart . Typically, a 9-MHz linear transducer (or transducer range of 5 to 12MHz) is used. A tardus-parvus waveform is indicative of a significant proximal vertebral artery stenosis. Circulation, 2007, June 5. steal is the earliest change which manifests as a mid-systolic notch also known as a "bunny waveform" (12) (Figures 2,3), flow remains antegrade throughout the cardiac cycle. Trials combining CEA with statin therapy started on hospital admission for surgery showed a decrease in neurologic events such as ischemic stroke and decreased mortality after CEA. The arteries of the hand have many anatomic variants and their evaluation may require a high level of technical expertise. Thus, it is expected that the AVA will increase and the number of patients with MPG <40 mmHg and AVA <1 cm will mathematically decrease. Transversely, the CCA is imaged from its proximal to distal aspects with gray-scale and color Doppler imaging. This can be quantified using the pulmonary velocity acceleration time (PVAT). Methods Echocardiographic images were collected and post processed in 227 ACS patients. Heart failure patients with low cardiac output are known to have poor cardiovascular outcomes. Our mission: To reduce the burden of cardiovascular disease. Up to 30% of all major hemispheric events (stroke, transient ischemic attacks [TIA], or amaurosis fugax) are thought to originate from disease at the carotid bifurcation. Given that the two velocity values are taken from the same vessel involved by the stenosis, Hathout etal. Arterial duplex is utilized by most centers as a second line of testing. Note that peak systole is mildly exaggerated relative to end diastole (compare with, Effect of origin stenosis on distal vertebral artery waveform. 6), while an end-diastolic velocity greater than 150 cm/s suggests a degree of stenosis greater than 80%. FESC. Second, the prognostic value of the AVA has been established using echocardiographic evaluation, while the prognostic value of combined AVA calculation is uncertain. The NASCET (North American Symptomatic Carotid Endarterectomy Trial) demonstrated that CEA resulted in an absolute reduction of 17% in stroke at 2 years when compared with medical therapy in symptomatic patients with 70% or greater stenosis. Adequate Doppler evaluation of the vertebral artery V1 segment may not be possible due to vessel tortuosity and proximity to the clavicle. Guy Lloyd: speaking engagements and advisory boards, Edwards, Philips, GE. Quantitative Doppler waveforms and velocity estimates can be obtained from the middle portion of the extracranial vertebral arteries in more than 98% of patients and vessels. Figure 1. The SRU panel concluded that elevated PSV in the ICA and the presence of flow-limiting plaque are the primary parameters determining the severity of ICA stenosis. Therefore, if the CCA velocity for the ratio is obtained from the proximal portion of the artery, the ratio may be low, potentially causing an underestimation of the degree of stenosis based on this parameter. In the coronal plane, a heel-toe maneuver is used to image the CCA from the supraclavicular notch to the angle of the mandible. Doppler blood flow velocity measurements should be obtained from the proximal and distal CCA and the proximal, mid, and distal ICA. The vertebral artery is readily identified by the prominent anatomic landmarks of the transverse processes of the cervical spine, which appear as bright echogenic lines that obscure imaging of deeper-lying tissues because of acoustic shadowing ( Fig. Plaque that contains an anechoic or hypoechoic focus may represent intraplaque hemorrhage or deposits of lipid or cholesterol. In contrast, if positioned too close, within the flow acceleration, it will be responsible for an underestimation of AS severity. This vertebral artery segment does not have any adjacent blood vessels except for the vertebral vein ( Fig. Several studies showed that the average PSV and ICA/CCA PSV ratio rise in direct proportion to the severity of stenosis as determined by angiography. It has been shown that peak systolic velocity decreases as the distance from the circle of Willis increases. However, carotid stenting was associated with a higher incidence of periprocedural stroke, while CEA patients had a higher risk of perioperative myocardial infarction. The typical phenotype initially proposed of an old lady often in AF with preserved ejection fraction but important left ventricular hypertrophy responsible for the low flow is thus more the exception than the rule. Its maximum velocity is in the range of 0.8 -1.2 m/sec. The former study used the traditional method of grading stenosis, whereas the latter used the NASCET/ACAS approach. Normal human peak systolic blood flow velocities vary with age, cardiac output, and anatomic site. An icon used to represent a menu that can be toggled by interacting with this icon. It is the interval between the onset of flow and peak flow. The ascending aorta has the highest average peak velocities of the major vessels; typical values are 150-175 cm/sec. To get the best experience using our website we recommend that you upgrade to a newer version. NB: If the stenosis is short, there can be a return to triphasic flow dependant on the ingoing flow and quality of the vessels. Modified from Grant EG, Benson CB, Moneta GL, etal. These values were determined by consensus without specific reference being available. The ultrasound criteria for estimating ICA stenosis severity are largely based on the results of the NASCET and ECST. The more reliable approach to assessing the vertebral artery is to visualize it near the mid portion of the cervical spine, at the V2 segment of the vertebral artery, as it courses cranially through the foramina to the transverse processes of C 6 to C 2 ( Fig. Additional intrarenal scanning permits the diagnosis of RAS without direct imaging of the main renal artery. First, it is well established that echocardiography underestimates the measurement of the LVOT annulus by 1 to 2 millimetres. Symptoms of posterior circulation ischemia are typically varied, making it difficult to determine the potential contribution of vertebral-basilar insufficiency ( Table 9.1 ). What does CM's mean on ultrasound? Leye M., Brochet E., Lepage L., Cueff C., Boutron I., Detaint D., Hyafil F., Lung B., Vahanian A., & Messika-Zeitoun D. de Monchy C. C., Lepage L., Boutron I., Leye M., Detaint D., Hyafil F., Brochet E., Lung B., Vahanian A., & Messika-Zeitoun D. Hachicha Z., Dumesnil J. G., Bogaty P., & Pibarot P. Paradoxical low-flow, low-gradient severe aortic stenosis despite preserved ejection fraction is associated with higher afterload and reduced survival. This approach mimics the method of measurement used in the NASCET. Kamperidis V., van Rosendael P. J., Katsanos S., van der Kley F., Regeer M., Al Amri I., Sianos G., Marsan N. A., Delgado V., & Bax J. J. Messika-Zeitoun D., Aubry M. C., Detaint D., Bielak L. F., Peyser P. A., Sheedy P. F., Turner S. T., Breen J. F., Scott C., Tajik A. J., & Enriquez-Sarano M. Cueff C., Serfaty J. M., Cimadevilla C., Laissy J P., Himbert D., Tubach F., Duval X., Lung B., Enriquez-Sarano M., Vahanian A., & Messika-Zeitoun D. Aggarwal S. R., Clavel M. A., Messika-Zeitoun D., Cueff C., Malouf J., Araoz P. A., Mankad R., Michelena H., Vahanian A., & Enriquez-Sarano M. Simard L., Cote N., Dagenais F., Mathieu P., Couture C., Trahan S., Bosse Y., Mohammadi S., Page S., Joubert P., & Clavel M. A. Clavel M. A., Messika-Zeitoun D., Pibarot P., Aggarwal S. R., Malouf J., Araoz P. A., Michelena H. I., Cueff C., Larose E., Capoulade R., Vahanian A., & Enriquez-Sarano M. Baumgartner H., Falk V., Bax J. J., De Bonis M., Hamm C., Holm P. J., Lung B., Lancellotti P., Lansac E., Munoz D. R., Rosenhek R., Sjogren J., Tornos Mas P., Vahanian A., Walther T., Wendler O., Windecker S., & Zamorano J. L. Bichat Hospital and University Paris VII, Paris, France; Barts Heart Centre, St. Bartholomews Hospital, West Smithfield, London,United Kingdom. 7.3 ). Aortic-valve stenosis--from patients at risk to severe valve obstruction. 8 . In addition, the course of the V1 segment of the vertebral artery can be markedly tortuous thereby limiting proper Doppler angle correction and velocity measurements. Fulfilling the precise and rigorous methodology presented above, the rate of patients with discordant grading is still between 20% and 30%, thus representing a common clinical problem. The peak systolic phase jet flow impacts the aortic valve flaps, leading to harm, scarring, excess flaps, . The E/A ratio is age-dependent. Circulation, 2011, Mar 1. 7.5 and 7.6 ). In diseased arteries, PSV increased proportionally with increasing stenosis and decreased to 0 cm/s at occlusion. Mean ratio peak systolic velocity in the DA-to-peak velocity across the pulmonary valve was 1.35 (SD 0.27). This is confirmed by a high-velocity measurement made on an angle-corrected Doppler waveform. [13] Confirming the findings of other papers, a discordant grading (AVA <1 cm and MPG <40 mmHg) was observed in 27% of the population; most of them (85%) presented with normal flow. The Doppler waveform should have a well-defined systolic peak with sustained blood flow signals throughout diastole as shown in Fig. All three parameters are consistent with a 70% or greater stenosis according to the Society of Radiologists in Ultrasound (SRU) consensus criteria. Vol. [3] If the crystal probe is unavailable, the regular two-dimensional probe can be used in the right parasternal view, providing similar results to the crystal probe in our experience. Normal human peak systolic blood flow velocities vary with age, cardiac output, and anatomic site. Thresholds adjusted to height are currently missing. Left ventricular outflow tract velocity time integral (LVOT VTI) is a measure of cardiac systolic function and cardiac output. In addition, ulcerated plaque that demonstrates a focal depression or break within the plaque is also more prone to plaque rupture and subsequent embolic event ( Fig. The proposed threshold of 35 ml/m is now widely accepted, even if its validation has never been carried out properly. The first step is to look for error measurements. When traveling with their greatest velocity in a vessel (i.e. Peak systolic velocity ranged from 1.2 to 3.3 cm/s, and peak diastolic velocity ranged from 1.6 to 4.5 cm/s. Prof. Messika-Zeitoun: consultant for Edwards, Valtech, Mardil and Cardiawave. In the vast majority (21% of the overall population), the flow was normal, while low flow was observed in only 3% of the total population. However, the standard deviations around each of these average velocity values are quite large, suggesting that Doppler velocity measurements cannot predict the exact degree of vessel narrowing ( Fig. 1-3 Its -agonist effect is responsible for arterioconstriction, which is reflected clinically in a transiently increased arterial blood pressure. Doppler waveforms can be consistently obtained at both vertebral artery intervertebral segments and the right vertebral origin. CCA , Common carotid artery . 7.2 ). The ECA waveform has a higher resistance pattern than the ICA. No external carotid artery stenosis is demonstrated. 9.9 ). The ascending aorta has the highest average peak velocities of the major vessels; typical values are 150-175 cm/sec. At the time the article was created Patrick O'Shea had no recorded disclosures. Peak plasma concentrations are reached between 1 and 2 hours after oral administration. Aortic valve calcium scoring is a quantitative and flow-independent method of assessing AS severity (recommended thresholds are 2,000 in men and 1,250 in women). Since the trigonometric ratio that relates these values is the cosine function, it follows that the angle of insonation should be maintained at 60o1,2. On the left, there is no elevation of peak systolic velocity with a normal ICA/CCA ratio of 0.84. 7.1 ). Thus, extremely low LVOT VTI may predict heart failure patients at highest risk for mortality. With the use of computed tomography in the workup evaluation before TAVI, the anatomy of the aortic annulus has been well described. [4] The Mayo Clinic group has provided us with important data regarding the prevalence of the different subsets. Within the evaluated physiological range, there was no association between peak systolic velocity and fetal heart rate (P 0.64). It is a cylindrical mechanical device which is placed over the penis and pumped; consequently, it creates a negative pressure vacuum to draw blood into the penis. John Pellerito, Joseph F. Polak. Subjects with MMSE score of 24 (25th percentile) was defined as low MMSE. The minimum and maximum flow rates for the temporal window of interest were based on the cycle-averaged mean velocity in the Middle Cerebral Artery (MCA), and the peak systolic flow velocity in the MCA as predicted by a 30% damped older-adult flow waveform (Hoi et al. If the diagnosis of severe AS is established (and if the patient is symptomatic), intervention should be promptly considered. Gated computed tomography is performed from the apex to the base of the heart, including the aortic valve. (A) The approximate locations of the V1 and V2 segments of the vertebral artery are shown. . Baumgartner H., Hung J., Bermejo J., Chambers J. In complete occlusion, PSV and EDV are absent 4. This study confirms the high prevalence of patients with discordant grading and also shows that most often these patients presented with normal flow. THere will always be a degree of variation. Subsequent data from the NASCET reported improvement in outcome with CEA in patients with 50% to 69% stenosis, although the amount of improvement was far less than was the case with higher grade stenosis. The ratio on the right is 1.6 between the renal artery and the aorta and the left is 1.8. Symptoms associated with atherosclerotic disease of the vertebral-basilar arterial system are diverse and often vague. S: peak systolic tissue doppler velocity; PECS: peak endocardial circumferential strain; PWWCS: peak whole . In these circumstances, AVA should be adjusted for BSA, with the threshold being 0.6 cm/m. be assessed by phase-contrast determination of peak systolic velocity combined with the modified Bernoulli equation [85]. Patients on the left part of the figure are easily classified as severe AS, whereas rest echocardiography remains inconclusive in the other two groups, namely patients with low gradient and normal or low flow. Dr. Jahan Zeb answered 26 years experience Peak velocity: Sometimes what is being recorded is not the velocity in the internal carotid but an adjacent artery such as external carotid . However, this approach can be difficult, if not technically impossible, in as many as one-third of patients because the clavicle interferes with the probe position necessary to see the origin of the vertebral artery and the V1 segment in the longitudinal plane. 10 Jan 2018, Association for Acute CardioVascular Care, European Association of Preventive Cardiology, European Association of Cardiovascular Imaging, European Association of Percutaneous Cardiovascular Interventions, Association of Cardiovascular Nursing & Allied Professions, Working Group on Atherosclerosis and Vascular Biology, Working Group on Cardiac Cellular Electrophysiology, Working Group on Pulmonary Circulation & Right Ventricular Function, Working Group on Aorta and Peripheral Vascular Diseases, Working Group on Myocardial & Pericardial Diseases, Working Group on Adult Congenital Heart Disease, Working Group on Development, Anatomy & Pathology, Working Group on Coronary Pathophysiology & Microcirculation, Working Group on Cellular Biology of the Heart, Working Group on Cardiovascular Pharmacotherapy, Working Group on Cardiovascular Regenerative and Reparative Medicine, E-Journal of Cardiology Practice - Volume 15, e-Journal of Cardiology Practice - Volume 22, Previous volumes - e-Journal of Cardiology Practice, e-Journal of Cardiology Practice - Articles by Theme. The difficulty in estimating the exact location of the plaque-free lumen of the proximal ICA introduced a great degree of interobserver error in estimating the degree of ICA stenosis. In most cases, these patients present with a normal flow (stroke volume index 35/ml/m), but low flow provides important prognostic information. 9.5 ), using combined gray-scale and color Doppler imaging, to assess blood flow hemodynamics in the proximal artery segment. Recommendations on the Echocardiographic Assessment of Aortic Valve Stenosis: A Focused Update from the European Association of Cardiovascular Imaging and the American Society of Echocardiography. Peak systolic velocity (PSV)is an index measured in spectral Doppler ultrasound. 2023 European Society of Cardiology. Magnetic resonance angiography (MRA) and computed tomographic angiography (CTA) have shown high accuracy, with duplex ultrasound having moderate accuracy, for the diagnosis of vertebral-basilar disease. Although the surgical treatment of vertebral artery disease can be successful and relatively safe, patient selection may require consideration of internal carotid artery disease because symptoms of posterior circulation ischemia frequently improve following carotid artery endarterectomy or reconstruction. From these, the ICA/CCA ratio can be automatically calculated, typically with the PSV measurement from the distal CCA in the ratio, because velocity measurements in the proximal CCA may be slightly elevated because of the proximity of the thoracic aorta. The normal peak systolic velocity (PSV) in peripheral lower limb arteries varies from 45-180 cm/s (30). (A) Normal upstroke and velocity in the mid left vertebral artery. We identified 622 patients with isolated, asymptomatic AS and peak systolic velocity > or =4 m/s by Doppler echocardiography who did not undergo surgery at the initial evaluation and obtained . Once this image has been obtained, a slight lateral rocking motion of the probe will bring the vertebral artery into view. The second source of error is the measurement of the aortic valve TVI obtained using continuous Doppler. Echocardiographic assessment of the severity of aortic valve stenosis (AS) usually relies on peak velocity, mean pressure gradient (MPG) and aortic valve area (AVA), which should ideally be concordant. The peak-systolic and end-diastolic velocities ranged from 36 to 74 cdsec (mean, 55 cmlsec) and 10 to 25 cdsec (mean, 16 cm/sec), respectively (Table 1). Secondary parameters such as elevated EDV in the ICA and elevated ICA/CCA PSV ratios further support the diagnosis of ICA stenosis if present. Secondary parameters such as elevated EDV in the ICA and elevated ICA/CCA PSV ratios further support the diagnosis of ICA stenosis. It would therefore seem logical to begin the duplex ultrasound examination in this segment. The estimation of the original lumen is further complicated by the presence of a normal, but highly variable, region of dilatation, the carotid bulb. Table 1. What are the symptoms of a blocked renal artery? This is more often seen on the left side. 9.1 ). The systolic pressure falls between 10 and 30 mmHg, and the diastolic pressure falls between 5 and 10 mmHg. This can reflect: (1) occlusion or near occlusion of the ICA; (2) contralateral vertebral artery occlusion; or (3) compensatory blood flow because of a subclavian steal in the contralateral vertebral artery. Calcium scoring measurements and the above-mentioned thresholds have recently been implemented in the latest version of the ESC/EACTS guidelines on valvular heart disease. revisited an interesting approach to ICA ratio measurements where the ratio of the highest PSV at the site of the stenosis was compared with the normalized velocity in the distal ICA. Introduction. (2010) Australasian journal of ultrasound in medicine. In addition, when statins were started on asymptomatic patients prior to CEA, the incidence of perioperative stroke and early cognitive decline also decreased. Sickle cell disease is a disorder of the blood caused by abnormal hemoglobin which causes distorted (sickled) red blood cells.It is associated with a high risk of stroke, particularly in the early years of childhood. This should be less than 3.5:1. Once an image of the vertebral artery has been obtained, the Doppler sample volume can be placed in the artery segment ( Fig. Note the dropout of color Doppler flow signals in the regions of acoustic shadowing (, Normal Doppler velocity waveform from the midsegment (V2) of a vertebral artery (, (A) This magnetic resonance angiogram of the right side of the neck shows a relatively small right vertebral artery (, (A) Color and spectral Doppler image at the origin of a normal vertebral artery. 9.10 ). The overall waveform has a sharp systolic upstroke and is characteristic of low-resistance flow. during systole), red blood cells exhibit their greatest magnitude of Doppler shift. Normal human peak systolic blood flow velocities vary with age, cardiac output, and anatomic site.