J Vasc Surg. The vascular diagnostic community is divided into two groups: 1) those that perform duplex Doppler examinations using a 60 degree Doppler angle between the ultrasound beam and the vessel axis, and 2) those that use a convenient angle less than or equal to 60 degrees [ 28 ]. The degree of carotid stenosis was characterized by measuring the size of the residual lumen and comparing it with the size of the original vessel lumen ( Fig. Analysis of external carotid flow can be useful for determining lesions in neighboring vessels, such as internal or common carotid occlusion. Example of Sensitivity and Specificity for Internal Carotid Artery Peak Systolic Velocity Cut Points Corresponding to a 70% Diameter Stenosis. In a diseased artery, however, the color velocity scale should be shifted up or down according to the mean velocity of blood flow to demonstrate aliasing only in systole. The SRU consensus conference provided reasonable values that can be easily applied ( Table 7.1 ) and have been adopted by a large number of laboratories. It can make quite a difference to the patient if a stenotic lesion or a plaque is located in the internal or external carotid. Elevated velocities can be seen in normal carotid arteries that diverge from a straight line and become curved. FIGURE 7-2 Off-axis view of the carotid wall. Is the ICA high or low resistance? The CCA shares the appearance of both waveforms. These features are illustrated in Figure 7-6. Plaque with strong echolucent elements is generally termed heterogeneous plaque, which is considered unstable and more prone to embolize. d. demonstrate an alternating blood flow pattern. Locate it in transverse and rotate into longitudinal. Atlas of anatomy, Head and neuroanatomy. There is no obvious cut point to indicate an ideal threshold. showed that, in most patients, the systolic velocity decreases in the CCA as one goes from proximal to distal within the vessel. This longitudinal image of the common carotid artery demonstrates a sharp line (specular reflection) that emanates from the intimal surface (arrow). (2011) ISBN:0443066841. Lancet. For this reason, the carotid examination should be conducted after the patient has been at rest for 5 to 10 minutes. Doppler blood flow velocity measurements should be obtained from the proximal and distal CCA and the proximal, mid, and distal ICA. Carotid Ultrasound Case Series: What's the Diagnosis? The normal range of the ICA/CCA ratio was defined in 2966 symptomatic or contralateral carotid arteries with 0% to 49% stenosis. Assess in transverse and longitudinal for pathology. Secondary parameters such as elevated EDV in the ICA and elevated ICA/CCA PSV ratios further support the diagnosis of ICA stenosis. Arteries with 70% to 99% symptomatic stenosis and an ICA/CCA ratio below this range were categorized as narrowed. The ICA is usually posterior and lateral to the ECA. Homogeneous or echogenic plaques are believed to be stable and are unlikely to develop intraplaque hemorrhage or ulceration. Here are two examples. Arrows indicate the flow direction in a right sided subclavian steal syndrome. Begin the examination by assessing vessels in B-Mode, optimising factors such as frequency, depth, gain, TGC and focal zone. This is rarely acheivable but as we approach 0 degrees, our human inter-observer error error is diminishing. Quantitative evaluation of external carotid artery stenoses is likewise difficult, due to lack of published data and low clinical significance of disease in this vascular distribution. The vertebral artery also supplies the brain with blood. External carotid artery - normal Doppler waveform, Doppler waveform of normal external carotid artery (ECA). While this is not a major problem in peripheral arteries when the original lumen is visible on both sides of a stenosis, lesions at the origin of the ICA typically do not have a normal lumen on both sides. The CCA is readily visible. Ultrasound of the Shoulder Case Series: What is the Diagnosis? With ACAS and NASCET, the degree of stenosis is measured by relating the residual lumen diameter at the stenosis to the diameter of the distal ICA. Ideally an angle of 0 degrees provides least error and greatest doppler shift. Although ultrasound plaque can be visualized and qualitatively analyzed using duplex ultrasound, vessel diameter measurement can be subjective and may often underestimate degree of stenosis. 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%. The other terminal branch is the internal carotid (ICA), which is somewhat larger than the ECA, which supplies the intracranial structures. IMPORTANTLY, this angle may not correspond to the course of the vessel. Your CME credits are available at any time in your Online CME Control Panel. Positioning for the carotid examination. Internal carotid artery (ICA). Hence, if the ICA is extremely tortuous, caution is required when making the diagnosis of a stenosis on the basis of increased Doppler velocities alone without observing narrowing of the vessel lumen on gray-scale and/or color flow imaging and showing poststenotic turbulence on the Doppler spectral tracing. The flow velocity at the nadir of the notch was greater than the flow velocity at end diastole for type 1 waveforms (Fig. Ultrasound of the ECA waveform is high resistance and may have retrograde flow in diastole. External carotid artery (ECA). The ultrasound criteria for estimating ICA stenosis severity are largely based on the results of the NASCET and ECST. 7.3 ). In others, magnetic resonance angiography (MRA) or computed tomographic angiography (CTA) may be performed in combination with sonography in cases where significant luminal narrowing is identified on the ultrasound examination or when the sonographic results are equivocal. Be aware of the possibility of a Carotid bulb tumour which whilst relatively rare, is a clinically significant finding. Wiley-Blackwell. The ultrasound criteria for estimating ICA stenosis severity are largely based on the results of the NASCET and European Carotid Surgery Trials (ECST). Rotate on the ECA origin to sample it longitudinally. The external carotid artery suppliesa high resistance vascular bed, while the internal carotid artery supplies the brain which has a low resistance vascular bed. The external carotid artery (ECA) displays many of the characteristics of a high resistance vessel, including a high pulsatility waveform. Unless the vessel is tortuous, you should see a low resistance waveform with a clean spectral window beneath the trace in the ultrasound. This blends into the also echogenic periadventitial region. velocity ratio (ICA peak systolic velocity/CCA peak systolic velocity; see Chapter 9) will depend on the location where velocities are sampled in the CCA. A, This diagram shows the key landmarks of the carotid artery bifurcation. Moderate (50% to 69%) internal carotid artery (, Receiver Operating Characteristic (ROC) curves for three Doppler velocity measurements to detect 70% or greater internal carotid artery (ICA) stenosis: peak systolic velocity (PSV =, Click to share on Twitter (Opens in new window), Click to share on Facebook (Opens in new window), Click to share on Google+ (Opens in new window), on Ultrasound Assessment of Carotid Stenosis, Ultrasound Assessment of Carotid Stenosis, Carotid Sonography: Protocol and Technical Considerations, Normal Findings and Technical Aspects of Carotid Sonography, Ultrasound Assessment of Lower Extremity Arteries, Ultrasound Assessment of the Vertebral Arteries. Usually the widening is slight, but some normal individuals have capacious carotid bulbs that may harbor large plaques in the absence of significant carotid stenosis. Variations of the origin and branches of the external carotid artery in a human cadaver. If there is the suggestion of retrograde vertebral artery flow, examine the subclavian artery for a tight stenosis or occlusion that could result in subclavian steal syndrome. 7.1 ). You will see reverberations in the trace corresponding to your tapping. Use a linear, mid frequency range probe (5-8MHZ). Executive Committee for the Asymptomatic Carotid Atherosclerosis Study. Therefore it is a low resistance artery. ECA lies on these structures), variations in origin arise from the anomalous bifurcation of the, common occipito-auricular trunk (incidence ~12.5%):common origin occipital and posterior auricular arteries. Angiography was the initial diagnostic test of choice for cerebrovascular atherosclerotic disease. CCA = common carotid artery. The Asymptomatic Carotid Surgery Trial 1 (ACST-1) demonstrated a 10-year benefit in stroke reduction in asymptomatic patients who underwent CEA for severe stenosis between 70% and 89%. As discussed in Chapter 3, the Doppler spectral waveforms are almost always altered in the region of the bulb (see Figure 7-4), a reflection of the complex flow dynamics that occur at this location.6, Peak systolic ICA velocities as high as 120 cm/sec have been reported in some normal adults, but these values are exceptional, and an ICA velocity exceeding 100 cm/sec should be viewed as potentially abnormal in older individuals. THere will always be a degree of variation. . The majority of stenotic lesions occur in the proximal internal carotid artery (ICA); however, other sites of involvement in the carotid system may or may not contribute to significant neurologic events. The CCA is an elastic artery, whereas the ICA is a muscular artery.4 The region of the ICA sinus is of mixed characteristics between a muscular and an elastic artery.5. Whitaker RH, Borley NR. The younger patient has higher blood flow velocities 100 cm/sec? 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. ICA = internal carotid artery. (2000) ISBN:0632054034. Most of the large carotid stenosis studies compared ultrasound with angiography as the gold standard while using the traditional non-NASCET method of grading carotid stenosis. In the 1990s, many large, well-controlled, multicenter trials both in North America and Europe confirmed the effectiveness of CEA in preventing stroke in patients with ICA stenoses as compared with optimized medical therapy. The common carotid artery (CCA) lies deep to the sternocleidomastoid and jugular vein. The other terminal branch is the internal carotid (ICA), which is somewhat larger than the ECA, which supplies the intracranial structures. Patients with peak systolic velocities between 175 and 260 cm/s may represent a group at higher risk for future neurologic event, but this has not yet been definitively shown [7]. ), have velocities that fall outside the expected norm for either PSV or EDV. The ICA and the ECA are then imaged. 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). SRU Consensus Conference Criteria for the Diagnosis of ICA Stenosis. (2007) ISBN:3131421215. In a normal carotid US examination, the color velocity scale should be set between 30 and 40 cm/sec (mean velocity). Identify the origins of the ICA and ECA arteries. Modified from Grant EG, Benson CB, Moneta GL, etal. There is wide variability in the peak systolic velocities seen in normal patients, with a range of 20 to 60 cm/s, with an even wider range noted at the vertebral artery origin (also called segment V0). 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. The carotid sinus originates along the medial wall of the proximal ICA where it is adjacent to the external carotid artery (ECA). B, This diagram shows a more typical anatomic definition of the carotid bifurcation. 4. The degree to which the carotid arteries widen at the carotid bulb varies from one individual to another. Any cardiac arhythmia or significant left heart valvular problems may be relected in the wave form (eg via a audible and visible flutter). (Reprinted with permission from the Radiological Society of North America: Grant EG, Duerinckx AJ, El Saden S, etal. The temporal tap maneuver is used to identify the external carotid artery. Conversely, blood flow velocities in the ICA contralateral to a high-grade stenosis or occlusion may be higher than expected if the vessel is the major supplier of collateral blood flow around the circle of Willis. 3.5B) (14,15). Ensure suitable PRF and gain for these smaller, deeper vessels. The blue area in the carotid bulb and proximal internal carotid artery represents the normal flow reversal zone. towards the head (normal) or retrograde (suggesting subclavian steal syndrome). Large, multicenter trials both in North America and Europe confirmed the effectiveness of CEA in preventing stroke in patients with ICA stenoses compared with optimized medical therapy. ANS: B. Tortuous segments, kinks, or areas of branching disrupt the normal laminar flow pattern. There are several observations that will help you identify the arteries. 8.3 How can color Doppler help to distinguish the internal from the external artery. Color Doppler also allows you to identify the internal carotid artery by detecting the area of recirculation of the internal carotid bulb. The ratios of of blood flow velocities in the internal carotid artery (ICA) to those in the common carotid artery (CCA) (V ICA /V CCA) are used to identify patients with critical ICA narrowing, but their normal reference values have not been established.We provide reference data for the V ICA /V CCA ratios for the peak systolic velocity (PSV), mean velocity (MV), and end-diastolic . Saunders, Philadelphia, PA. 2012. 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. This invasive study provided anatomic definition of any lesions but required selective catheterization of the great vessels and predisposed patients to risks of periprocedural stroke, contrast nephropathy, and access site complications. In such situations try imaging the more distal segments of the arteries. Duplex ultrasonography is able to provide both anatomic and hemodynamic information about the state of a vessel, allowing health care providers to make informed decisions regarding intervention for stroke prevention. Note: There is a certain variation in the characteristics of the internal and external carotid artery and the patterns can sometimes look quite similar, making it difficult to differentiate the vessels. In one study, PSV and ICA/CCA PSV ratios performed almost identically with regard to the identification of ICA stenoses greater than 70% when compared with angiography ( Fig. The benefit of surveillance of patients with asymptomatic stenosis also remains uncertain as data on risk and progression of those with varying degrees of stenosis determined by ultrasound remain limited. These elevated velocities are also associated with different degrees of coiling of the artery ultimately leading to kinking. Usually the widening is slight, but some normal individuals have capacious carotid bulbs that may harbor large plaques in the absence of significant carotid stenosis. 24. Prior to the 1990s, the degree of carotid stenosis was measured by angiography and estimated where the artery wall should be so that the local or relative degree of stenosis can be estimated. In addition, the Doppler blood flow velocities should always be compared with the degree of plaque, if present. 7.5 and 7.6 ). In this case, the ICA/CCA ratio was approximately 7, The internal carotid PSV may be falsely elevated in tortuous vessels. The artery and vein can be differentiated by direction of flow on color Doppler as well as by the tendency of the vein to collapse with external ultrasound probe compression. The further distal you record the Doppler signal in the internal carotid artery the higher the diastolic component will become (decrease in the S/D ratio) and the easier it will be to differentiate it from the external carotid artery. The multicenter, prospective, noninterventional Evaluation of Ultrasound's Role in Patients Suspected of Having Extracranial and Cranial Giant Cell Arteritis (EUREKA) cohort study was conducted at 3 Danish hospitals. Emergency and Critical Care US Essentials, Emergency and Critical Care Ultrasound Essentials, MSK Ultrasound Foot & Ankle BachelorClass, MSK Ultrasound Guided Injections MasterClass, Neonatal and Pediatric Ultrasound BachelorClass, 8. The branches of the external carotid artery can be subdivided into groups: Memorable mnemonics for these branches include: Please Note: You can also scroll through stacks with your mouse wheel or the keyboard arrow keys. The younger patient has higher blood flow velocities 100 cm/sec? The transverse position enables the sonographer to follow the carotid artery in a transverse plane along its entire course in the neck, which is useful for initial identification of the carotid, its branch points, and position relative to the jugular vein. Benefit of Carotid Endarterectomy in Patients with Symptomatic Moderate or Severe Stenosis. Imaging conventions stipulate positioning of the probe such that the head of the patient is at image left for longitudinal views, and the patients right is at image left on transverse views as if viewed standing at the foot of the patient. Many other significant diagnoses can be made based upon lower-than-normal velocities. Others have advocated for the use of a peak systolic velocity of greater than 182 cm/s, developed in a study comparing duplex to CT angiography, although these criteria have not been externally validated [4]. The pathology will usually be located between the CCA origin and vertebral origin. It takes a slightly curved course upwards and anteriorly before inclining backwards to the space behind the neck of the mandible. The carotid sinus originates along the medial wall of the proximal ICA where it is adjacent to the external carotid artery (ECA). Previous studies have shown the importance of internal carotid plaque characterization (see Chapter 6 ). Carotid coils are likely due to genetic factors.13, Click to share on Twitter (Opens in new window), Click to share on Facebook (Opens in new window), Click to share on Google+ (Opens in new window), on Normal Findings and Technical Aspects of Carotid Sonography, Ultrasound Appearance of the Normal Carotid Artery Walls, The wall of every artery is composed of three layers: intima, media, and adventitia. B, This transverse video shows the zone of flow reversal (blue; arrow) in the proximal ICA at end diastole. The true ICA has parallel walls above (distal to) the sinus. What is normal ECA velocity? Since the ultrasound transducer typically measures 4 cm, it can be used to help locate this point by placing one end at the level of the bulb and sampling at the mid transducer, or approximately 2 cm below the beginning of the bulb. Similarly, the CCA waveform is a combination of both ICA and ECA waveforms. A, This transverse video shows the zone of flow reversal (blue; arrow) in the proximal internal carotid artery (ICA) at peak systole. 2. FIGURE 7-5 Flow reversal. They are automatically transferred to the ARDMS/APCA CME Bank and RSNA's CME Gateway (when you include your credentials). Criteria for duplex diagnosis of internal carotid stenosis [6]. EDV was slightly less accurate. Screening has been advocated as a tool for early detection of carotid stenosis and identification of patients who may be at high risk, with potential benefit from carotid intervention. A temporal-tap (TT) was employed here to confirm it was the ECA. Other positions of the probe either in more anterior or posterior positions can help with visualization in patients with very distal disease or with large or thick necks. Specific cut-points based on the arteriographic correlative studies need to use the NASCET/ACAS measurement approach ( Fig. A plaque or stenosis of the external carotid artery usually has little consequence (unless the external carotid artery provides collateral flow). Internal carotid artery stenosis. The utility of duplex as a mass screening tool is dependent on the identification of thresholds that increase the sensitivity of the test for severe stenoses, resulting in fewer false negatives. The wall of every artery is composed of three layers: intima, media, and adventitia. Appearance of plaques Ulcerated (will see flow within plaque) - very dangerous Soft Calcified (hyperechoic) Hypoechoic (isoechoic to lumen on grayscale, seen only on color doppler) 4. The two transition zones between the lumen and the intima and between the media and adventitia produce two parallel echogenic lines, with an intervening zone of low echoes that corresponds to the media. The arrows indicate the dicrotic notch, the transition from systole to diastole. You may only be able to see a few cm of the ICA if there is a high bifurcation. The lines define the location where IMT measurements are made in one of the protocols used in epidemiologic studies. As such, Doppler thresholds taken from studies that did not use the NASCET method of measurement should not be used. The external carotid artery (ECA) is one of the two terminal branches of the common carotid arterythat has many branches that supplies the structures of the neck, face and head. From the mid-distal CCA slide and angle posteriorly to visualise the cervical transverse processes and the vertebral artery. Values up to 150 cm/sec can be seen without a significant lesion being present (Figure 7-8). This test is done as the first step to look at arteries and veins. On transverse sections, clear visualization of the lumen-intima interface indicates that the image plane is perpendicular to the vessel axis. The flow should be low resistance flow ( presence of forward diastolic flow). What does ICA CCA mean? Stenoses of the external carotid artery (ECA) are not considered clinically important but should be reported because they may explain the presence of a bruit on clinical examination and need to be considered by the surgeon at the time of carotid endarterectomy (CEA). Warlow C, Farrell B, Fraser a., Sandercock P, Slattery J. Randomised trial of endarterectomy for recently symptomatic carotid stenosis: Final results of the MRC European Carotid Surgery Trial (ECST). Common carotid occlusion is simple to detect using duplex ultrasound; however, no consensus on stenosis criteria exists due to the lack of published data and its uncommon occurrence compared to the internal carotid distribution. 3. The maneuver is not always easy to perform. Check for errors and try again. The average PSV in normal volunteers is between 30 and 40 cm/s. 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. Arteriosclerosis. The scan may begin with either the longitudinal or transverse imaging of the CCA. Figure 3.3 Arterial Duplex examination (Doppler velocity and B-mode ultrasound) patterns in normal and diseased peripheral arteries. 8.1 Why is it important to differentiate the internal- from the external carotid artery with ultrasound? Just $79.99! After endarterectomy, the lumen-intima interface is less prominent at the surgical site because the intima has been removed. 8.5 How does the spectrum of the vertebral arteries and the common carotid artery look? high CCA: Waveforms in the common carotid artery close to the bifurcation show moderately broad systolic peaks and a moderate amount of blood flow throughout diastole. Examples of a classification of carotid kinks, Carotid Sonography: Protocol and Technical Considerations, Ultrasound Assessment of the Abdominal Aorta, Ultrasound Assessment of Carotid Stenosis, Hemodynamic Considerations in Peripheral Vascular and Cerebrovascular Disease, Introduction to Vascular Ultrasonography Expert Consult - Online. The flow . The common carotid artery supplies both a high and a low resistance bed (via the external and internal carotid artery). Anatomy of the carotid bifurcation; intima-media thickness (IMT) protocol. Although the so-called NASCET method may not truly reflect the degree of luminal narrowing at the site of stenosis, this method has the advantage of minimizing interobserver error. The internal carotid artery (ICA) is a lower resistance vessel and displays low to medium pulsatility on spectral imaging with no or minimal reversal of flow. The original studies validating intervention in asymptomatic patients showed absolute risk reductions at 5 years of 5-6%, but this number remains in question with continuing improvements in medical management of asymptomatic patients and the lack of recent data [5,6]. Cerebrovascular duplex ultrasound for carotid disease is a powerful tool that has become an invaluable resource in the decision making process. The external carotid artery (ECA) is one of the two terminal branches of the common carotid artery that has many branches that supplies the structures of the neck, face and head. This is probably related to both a true increase in velocity as blood accelerates around a curve and difficulty in assigning a correct Doppler angle. Lesions should be analyzed using duplex as part of a comprehensive examination but results reported qualitatively. meeting all three criteria for a severe (>70%) stenosis. 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