PPT Chapter 7: Extracranial Duplex Ultrasound Examination PDF

Chapter Chapter 77 The The Extracranial Extracranial Duplex Duplex Ultrasound Ultrasound Examination Examination Kari Kari A. A. Campbell Campbell R. R. Eugene Eugene Zierler Zierler ...

Chapter Chapter 77 The The Extracranial Extracranial Duplex Duplex Ultrasound Ultrasound Examination Examination Kari Kari A. A. Campbell Campbell R. R. Eugene Eugene Zierler Zierler Objectives List the essential components of a carotid duplex ultrasound examination Describe the normal waveform characteristics of the extracranial carotid vessels Define the common diagnostic criteria used to evaluate the extracranial carotid vessels Describe common pathology observed during a carotid duplex ultrasound examination Copyright © 2018 Wolters Kluwer · All Rights Reserved Goals of Extracranial Duplex Identify patients who are at risk for stroke Facilitate treatment Document disease progression Detection of nonatherosclerotic conditions Copyright © 2018 Wolters Kluwer · All Rights Reserved Indications for Extracranial Duplex Exam Asymptomatic neck bruit Hemispheric cerebral or ocular transient ischemic attacks (TIAs) History of stroke Screening prior to surgery Follow-up after carotid endarterectomy or stenting Copyright © 2018 Wolters Kluwer · All Rights Reserved Mechanisms of Cerebrovascular Symptoms Emboli from atherosclerotic plaques – Ulcerated plaque Reduction of flow due to high-grade stenoses Arterial thrombosis Copyright © 2018 Wolters Kluwer · All Rights Reserved TIA vs. Stroke TIA – Neurologic deficits that occur intermittently, lasting from several minutes to a few hours – Symptoms resolve within 24 hours Cerebrovascular accident (CVA or completed stroke) – Fixed or permanent neurologic deficits Reversible ischemic neurologic deficit (RIND) – Neurologic deficits that last between 24 and 72 hours Copyright © 2018 Wolters Kluwer · All Rights Reserved Symptoms of Carotid Artery Lesions Focal weakness (paralysis) or numbness (paresthesia) involving some combination of face, arm, and leg on one side of body (opposite to the affected cerebral hemisphere) Difficulty speaking (dysphasia or aphasia) Amaurosis fugax (same side as responsible carotid lesion) Copyright © 2018 Wolters Kluwer · All Rights Reserved Symptoms of Vertebrobasilar Insufficiency Less specific than carotid circulation Dizziness Diplopia Ataxia Copyright © 2018 Wolters Kluwer · All Rights Reserved Patient Preparation No specific preparation is needed prior to the exam. Patient should remove jewelry or clothing that may obstruct access to neck. Obtain patient history – Current signs or symptoms – Pertinent past medical history Physical exam – Bilateral brachial blood pressures – Palpation of pulses (carotid, axillary, brachial, radial) for strength and symmetry – Auscultation for bruits (high, middle, low neck, supraclavicular) Copyright © 2018 Wolters Kluwer · All Rights Reserved Patient Interview for Pertinent Medical History Copyright © 2018 Wolters Kluwer · All Rights Reserved Patient Positioning Patient should be in supine position. – Head of bed can be elevated and pillow can be placed under patient’s knees. Pillow can be placed under head and shoulders. – Or, towel can be placed under patient’s neck. Patient’s chin should be tilted up. Patient’s head should be turned away from the side to be examined. Copyright © 2018 Wolters Kluwer · All Rights Reserved Patient Positioning—(cont.) Figure 7-1, The correct patient position for performing a carotid artery duplex evaluation. The patient’s chin is elevated and the head is turned 45 degrees away from the side being examined, Copyright © 2018 Wolters Kluwer · All Rights Reserved Equipment 7-4 MHz linear array typically used – High frequency for image quality – Adequate “footprint” for access and visualization Alternative transducers may include: – 8–5 MHz curvilinear – 4–1 MHz sector – 5–2 MHz curvilinear Copyright © 2018 Wolters Kluwer · All Rights Reserved Equipment—(cont.) Figure 7-2. Suitable transducers for performing a carotid artery duplex evaluation: linear 9–3 MHz (for average size necks), curvilinear 8–5 MHz (for short necks and small spaces), and curvilinear 5–2 MHz (for deeper depths). Copyright © 2018 Wolters Kluwer · All Rights Reserved Scanning Technique Carotid artery duplex evaluation generally includes examination of bilateral – Common carotid arteries (CCAs) – Internal carotid arteries (ICAs) – External carotid arteries (ECAs) – Vertebral arteries – Subclavian arteries Vessels should be evaluated in both transverse and longitudinal planes and with B-mode imaging, color, and spectral Doppler. Copyright © 2018 Wolters Kluwer · All Rights Reserved Scanning Technique Tips Sweep through carotid system in transverse and longitudinal planes with B-mode imaging – Begin above clavicle and sweep up to angle of jaw – Use multiple approaches to identify best image path Document any identified intraluminal echoes (plaque or other intimal defects) Document any other areas of interest Copyright © 2018 Wolters Kluwer · All Rights Reserved Scanning Technique Tips—(cont.) Color Doppler should be used to help identify – Areas of aliasing or mosaic flow patterns – Speckling that could indicate color bruit Pulsed wave spectral Doppler is used to – Measure flow velocities – Document waveform contours Copyright © 2018 Wolters Kluwer · All Rights Reserved ICA vs. ECA Differentiation ECA has multiple branches within the neck. ECA spectral waveform will oscillate with “temporal tap.” Additionally – ICA typically is larger (contains bulb). – ICA typically lies posterior to ECA. Copyright © 2018 Wolters Kluwer · All Rights Reserved ECA Temporal Tap Figure 7-3. Duplex image of the ECA. The Doppler flow signal is affected by oscillations on the ipsilateral temporal artery. Copyright © 2018 Wolters Kluwer · All Rights Reserved Carotid Bulb Sweep Doppler sample volume from CCA into proximal ICA Document flow separation in bulb – Flow reversal located along outer wall of bulb – Indicates normal flow in bulb – Velocity measurement is not needed on this signal. Copyright © 2018 Wolters Kluwer · All Rights Reserved Carotid Bulb—(cont.) Figure 7-4. Duplex image of normal Doppler flow separation in the proximal ICA (carotid bulb). Copyright © 2018 Wolters Kluwer · All Rights Reserved Scanning Technique—ICA Must evaluate the entire length of the ICA – Continue through carotid bulb – Insonate the proximal, mid, and distal segments of ICA – Measure peak systolic velocity (PSV) and end diastolic velocity (EDV) throughout – Distal segment may be difficult beyond the angle of the jaw Copyright © 2018 Wolters Kluwer · All Rights Reserved Scanning Technique—Vertebral Artery Evaluate vertebral artery – Place transducer at anteromedial aspect of midneck on long axis – Identify CCA and slide or angle posteriorly to identify vertebral artery between transverse processes of vertebrae – Take care to identify flow direction and waveform contour Copyright © 2018 Wolters Kluwer · All Rights Reserved Scanning Technique—Subclavian Artery Evaluate subclavian artery – Place transducer in transverse orientation at the base of the neck. – Obtain Doppler signal from subclavian artery as far proximally as possible. – Identify the highest PSV and most laminar Doppler waveform possible. Copyright © 2018 Wolters Kluwer · All Rights Reserved Pitfalls Identifying vessels either high in the neck or low in the neck Patients with short, thick necks Beam steering and angle correction when using alternative transducers Copyright © 2018 Wolters Kluwer · All Rights Reserved Diagnosis Normal B-mode characteristics – Smooth vessel walls – Intimal-medial layer clearly visible and uniform (thin, gray-white line on innermost part of vessel wall) – Lumen is anechoic. Copyright © 2018 Wolters Kluwer · All Rights Reserved B-Mode Characteristics Figure 7-5. B-mode image of the common carotid artery, with the intimal-medial layer clearly visible. Copyright © 2018 Wolters Kluwer · All Rights Reserved Diagnosis—Plaque Most commonly occurs at the CCA bifurcation Early stages – Plaque appears as thickened areas of the intimal- medial layers. – Fibrous cap may form between plaque and lumen. Copyright © 2018 Wolters Kluwer · All Rights Reserved Plaque Figure 7-6. B-mode and color Doppler images demonstrating smooth homogenous plaque in the carotid arteries. A: Homogenous plaque ICA. B: Homogenous plaque in the CCA. The fibrous cap is visible as a brighter line along the intraluminal aspect of the plaque. Copyright © 2018 Wolters Kluwer · All Rights Reserved Diagnosis—Plaque By ultrasound, plaque is usually classified as – Smooth vs. irregular “Ulcerated” is usually discouraged – Homogenous vs. heterogeneous Extensive characterization of plaque by B-mode imaging is controversial. Copyright © 2018 Wolters Kluwer · All Rights Reserved Diagnosis—Plaque—(cont.) Figure 7-7. B-mode and color images of heterogeneous irregular plaque in the proximal internal carotid artery. Note the color Doppler flow eddy at the area of apparent plaque compromise, which indicates possible ulceration. Copyright © 2018 Wolters Kluwer · All Rights Reserved Diagnosis—Plaque—(cont.) Figure 7-8. B-mode image of the carotid bifurcation demonstrating heterogeneous plaque with mixed echogenicity, calcification, and acoustic shadowing. Copyright © 2018 Wolters Kluwer · All Rights Reserved Diagnosis—Plaque—(cont.) Figure 7-9. B-mode and color image of the proximal ICA demonstrating plaque with echolucency (arrow). These findings may represent lipid core versus intraplaque hemorrhage. Copyright © 2018 Wolters Kluwer · All Rights Reserved Diagnosis—Intraluminal Defects Other intraluminal defects identified by B-mode imaging include – Arterial dissection – Carotid artery thrombosis – Iatrogenic injury Copyright © 2018 Wolters Kluwer · All Rights Reserved Diagnosis—Intraluminal Defects—(cont.) Figure 7-10. A: A common carotid artery dissection illustrating color- flow variations within both the true and false lumens. Copyright © 2018 Wolters Kluwer · All Rights Reserved Diagnosis—Intraluminal Defects—(cont.) B: Sagittal B-mode image of the distal CCA illustrating an intraluminal defect (arrow). Copyright © 2018 Wolters Kluwer · All Rights Reserved Diagnosis—Intraluminal Defects—(cont.) C: Transverse B-mode image across the carotid bifurcation with the dissected lumen (arrow) visible within the ICA. Copyright © 2018 Wolters Kluwer · All Rights Reserved Diagnosis—Intraluminal Defects—(cont.) Figure 7-11 B-mode and color Doppler images of softly echogenic material within the lumen of the carotid artery. A: Duplex ultrasound findings in conjunction with patient history indicated carotid artery partial thrombosis. B: Findings indicated soft homogenous plaque. Copyright © 2018 Wolters Kluwer · All Rights Reserved Diagnosis—Iatrogenic Injury Figure 7-12 CCA pseudoaneurysm following internal jugular vein line placement attempt. A: Duplex ultrasound demonstration of to-and-fro flow in the neck of the pseudoaneurysm, arising from the CCA. B: Duplex image of the pseudoaneurysm, which is mostly thrombosed. Copyright © 2018 Wolters Kluwer · All Rights Reserved Diagnosis—Spectral Doppler Spectral Doppler provides the most reliable means for assessing vessel patency and classifying degree of stenosis. Doppler waveform contour is related to – Cardiac output – Vessel compliance – Status of distal vascular bed Copyright © 2018 Wolters Kluwer · All Rights Reserved Diagnosis—Spectral Doppler—(cont.) Normal Doppler waveform contours (CCA, ICA, ECA) – Brisk systolic acceleration – Sharp systolic peak – Clear spectral waveform ICA has highest diastolic velocities (lowest peripheral resistance). ECA has lowest diastolic velocities (highest peripheral resistance). CCA has intermediate diastolic velocities. – Has characteristics of both ICA and ECA Copyright © 2018 Wolters Kluwer · All Rights Reserved Diagnosis—Spectral Doppler—(cont.) Figure 7-13. Normal Doppler arterial flow through the CCA. Copyright © 2018 Wolters Kluwer · All Rights Reserved Diagnosis—Spectral Doppler—(cont.) Figure 7-14. Duplex imaging of normal Doppler arterial flow through the CCA, ICA, and ECA. Copyright © 2018 Wolters Kluwer · All Rights Reserved Carotid Bulb Carotid bulb or sinus is a slight focal dilation in the carotid artery. Contains baroreceptors that assist in blood pressure control Carotid bodies located nearby – Chemoreceptors involved in control of respiratory rate Bulb typically involves proximal ICA but can also include distal CCA, proximal ECA, or all vessels Copyright © 2018 Wolters Kluwer · All Rights Reserved Carotid Bulb—Doppler Waveform Normal flow separation located along outer wall More laminar flow near flow divider Flow separation usually correlates with minimal to no plaque in bulb. As plaque develops, it can fill in the bulb, reducing flow separation. Absence of flow reversal can be considered abnormal. Copyright © 2018 Wolters Kluwer · All Rights Reserved  Carotid Bulb Figure 7-15. Duplex image of normal Doppler arterial flow characteristics through the carotid bulb and ICA. Copyright © 2018 Wolters Kluwer · All Rights Reserved Diagnosis—Spectral Doppler Abnormal Doppler waveform contours – High-velocity jet in the stenosis – Poststenotic turbulence – Distal to stenosis Dampened, decreased flow velocity Delayed acceleration, rounded peak “Tardus-parvus” Copyright © 2018 Wolters Kluwer · All Rights Reserved Diagnosis—Spectral Doppler—(cont.) Figure 7-16. Abnormal dampened Doppler arterial waveform contour in the ICA, described as “tardus and parvus.” Copyright © 2018 Wolters Kluwer · All Rights Reserved Diagnosis—Spectral Doppler—(cont.) Abnormal Doppler waveform contours – Proximal to stenosis Varies with disease severity and amount of collateral vessels May be relatively normal With very significant stenosis, proximal waveform will display a more high-resistance pattern (decreased diastolic flow) Copyright © 2018 Wolters Kluwer · All Rights Reserved Diagnosis—Spectral Doppler—(cont.) Figure 7-17. Abnormal, resistive Doppler arterial flow through the CCA in the setting of an internal carotid artery occlusion. Copyright © 2018 Wolters Kluwer · All Rights Reserved “Steal” Waveform Contours Steal is a situation where one vascular bed draws blood away or steals from another. Degree of steal depends on – Severity of stenosis – Resistance offered by the various downstream vascular beds Copyright © 2018 Wolters Kluwer · All Rights Reserved “Steal” Waveform Contours—(cont.) Latent steal – Flow that is beginning to show signs of reversal but not completely retrograde – Waveform characteristics can be Hesitant (deep flow reversal notch) Alternating or bidirectional Copyright © 2018 Wolters Kluwer · All Rights Reserved “Steal” Waveform Contours—(cont.) Figure 7-18. Duplex images of abnormal “hesitant” Doppler vertebral artery flow, indicating latent subclavian steal phenomenon. Copyright © 2018 Wolters Kluwer · All Rights Reserved “Steal” Waveform Contours—(cont.) Complete steal – Complete retrograde flow of vessel involved – For example, with severe subclavian artery stenosis, the vertebral artery will reverse in order to provide blood flow to the arm Copyright © 2018 Wolters Kluwer · All Rights Reserved  “Steal” Waveform Contours—(cont.) Figure 7-19. A: Abnormal Doppler arterial flow through the carotid distribution. Copyright © 2018 Wolters Kluwer · All Rights Reserved “Steal” Waveform Contours—(cont.) Figure 7-19. B: Abnormal Doppler flow through the subclavian and vertebral distribution. Copyright © 2018 Wolters Kluwer · All Rights Reserved String Sign Blunted, somewhat resistive waveforms that precede complete occlusion Most commonly found in ICA To detect – Image in both transverse and longitudinal plane – Use low scale and high gain Doppler settings – Use power Doppler – Carefully evaluate distal for any flow Copyright © 2018 Wolters Kluwer · All Rights Reserved String Sign—(cont.) Figure 7-20. Duplex images of a functionally occluded ICA with “string sign” Doppler flow. A: Use of color Doppler and spectral Doppler modalities. B: Use of color power angio modality. Copyright © 2018 Wolters Kluwer · All Rights Reserved Distal ICA Stenosis or Occlusion Associated with following findings in extracranial ICA – Decreased diastolic flow or resistive component – Overall “blunted” appearing waveform Same abnormalities in the CCA Important to compare bilaterally ICA end diastolic velocities Copyright © 2018 Wolters Kluwer · All Rights Reserved Distal ICA Stenosis or Occlusion—(cont.) Figure 7-21. Duplex images of a patent proximal internal carotid artery and abnormal, blunted, and resistive Doppler arterial flow. Findings indicate distal extracranial versus intracranial severe stenosis or occlusion of the ICA. Copyright © 2018 Wolters Kluwer · All Rights Reserved  Proximal ICA Occlusion Figure 7-25. Duplex images of an ICA occlusion, no obtainable Doppler flow. A: Use of color Doppler and spectral Doppler modalities. Copyright © 2018 Wolters Kluwer · All Rights Reserved Proximal ICA Occlusion—(cont.) Figure 7-25. Duplex images of an internal carotid artery occlusion, no obtainable Doppler flow. B: Use of color power angio modality. Copyright © 2018 Wolters Kluwer · All Rights Reserved ECA Stenosis Lesions tend to involve origin and proximal segments Associated with – Focal velocity increase – Poststenotic turbulence – Dampened distal waveform Watch for diffuse increase in velocity as a result of collateralization Copyright © 2018 Wolters Kluwer · All Rights Reserved CCA Stenosis Can occur in the proximal, mid, or distal segments Significant stenosis associated with – Focal velocity increases – Poststenotic turbulence – Dampened distal waveforms in both the ICA and ECA “Choke lesion” may result in retrograde ECA to supply ICA Copyright © 2018 Wolters Kluwer · All Rights Reserved CCA Stenosis—(cont.) Figure 7-23. B-mode and color Doppler images of a distal CCA stenosis, or “choke lesion.” Copyright © 2018 Wolters Kluwer · All Rights Reserved CCA Stenosis—(cont.) Figure 7-24. Duplex images demonstrating distal CCA occlusion with retrograde Doppler flow through the ECA and dampened antegrade flow through the proximal ICA. Copyright © 2018 Wolters Kluwer · All Rights Reserved Aortic Valve or Root Stenosis Will generate symmetrically abnormal Doppler waveform contour in the bilateral carotid systems – Dampened waveforms throughout both carotid artery systems May also cause bilateral low brachial systolic pressures Brachiocephalic stenosis will only affect the right carotid system. Copyright © 2018 Wolters Kluwer · All Rights Reserved Aortic Valve or Root Stenosis—(cont.) Figure 7-22. Duplex images demonstrating symmetrically abnormal Doppler arterial flow in the presence of known aortic stenosis, demonstrated in the right and left (A) carotid arteries. Copyright © 2018 Wolters Kluwer · All Rights Reserved Aortic Valve or Root Stenosis—(cont.) Figure 7-22. Duplex images demonstrating symmetrically abnormal Doppler arterial flow in the presence of know aortic stenosis, demonstrated in the right and left (B) vertebral arteries. Copyright © 2018 Wolters Kluwer · All Rights Reserved Aortic Valve or Root Stenosis—(cont.) Figure 7-22. Duplex images demonstrating symmetrically abnormal Doppler arterial flow in the presence of know aortic stenosis, demonstrated in the right and left (C) subclavian arteries. Copyright © 2018 Wolters Kluwer · All Rights Reserved Special Considerations Low cardiac output and poor ejection fraction Aortic valvular disease Hypertrophic obstructive cardiomyopathy Cardiac arrhythmias Cardiac assist devices (ventricular assist device [VAD], intra-aortic balloon pump [IABP]) Copyright © 2018 Wolters Kluwer · All Rights Reserved  Special Considerations—(cont.) Figure 7-26. Doppler flow signal obtained in the CCA, with arrhythmia. Copyright © 2018 Wolters Kluwer · All Rights Reserved Special Considerations—(cont.) Figure 7-27. Carotid artery Doppler flow affected by cardiac assist devices: IABP and left VAD (LVAD). Copyright © 2018 Wolters Kluwer · All Rights Reserved Doppler Flow Velocity Primary criterion for classification of stenosis severity Depends on correct Doppler angle – 60 degrees or less – Parallel to vessel walls May require Doppler beam steering and/or heel-toe transducer maneuver in order to obtain proper alignment Pulsed wave Doppler sample volume should be “swept” through all vessels. Copyright © 2018 Wolters Kluwer · All Rights Reserved Doppler Flow Velocity—(cont.) Collateralization – Posterior-to-anterior – Side-to-side – Extracranial-to-intracranial – May result in increased velocities contralaterally to severe stenosis or occlusion Copyright © 2018 Wolters Kluwer · All Rights Reserved Criteria for Classification of Disease Classification has validated for the ICA ONLY. – Criteria cannot be applied to CCA or ECA Criteria were developed by comparing duplex results with “gold standard” imaging modalities or surgical findings. Copyright © 2018 Wolters Kluwer · All Rights Reserved Criteria for Classification of Disease— (cont.) Copyright © 2018 Wolters Kluwer · All Rights Reserved Criteria for Classification of Disease— (cont.) NASCET criteria – >70% stenosis defined as PSV >230 cm/s ICA/CCA ratio >4.0 Highest PSV from stenotic ICA CCA PSV from normal mid-to-distal segment Copyright © 2018 Wolters Kluwer · All Rights Reserved Criteria for Classification of Disease— (cont.) Figure 7-28. Duplex images demonstrating high-grade stenosis of the ICA. A: A stenosis of 80% to 99% of the proximal ICA with poststenotic turbulence. Copyright © 2018 Wolters Kluwer · All Rights Reserved Criteria for Classification of Disease— (cont.) Figure 7-28. B: Calculation of the ICA to the CCA ratio. Copyright © 2018 Wolters Kluwer · All Rights Reserved Criteria for Classification of Disease— (cont.) Copyright © 2018 Wolters Kluwer · All Rights Reserved Criteria for Classification of Disease— (cont.) Preceding tables only apply to the ICA For CCA and ECA stenosis, general criteria can be applied. – Focal velocity increase – Poststenotic turbulence – Distal waveform changes These changes correlate with a >50% stenosis in these vessels. Copyright © 2018 Wolters Kluwer · All Rights Reserved Color and Power Doppler Findings Diagnostic relevance secondary to Doppler velocities Advantages – Rapid identification of flow disturbances – Rapid determination of location and direction of high velocity jets – Demonstration of poststenotic turbulence Copyright © 2018 Wolters Kluwer · All Rights Reserved Color and Power Doppler Findings—(cont.) Smooth, single color in the low to medium tone range indicates laminar flow. Aliasing occurs with higher flow velocities. Turbulent flow produces a “mosaic” color Doppler pattern. Always use pulsed wave spectral Doppler waveforms to classify severity of disease Copyright © 2018 Wolters Kluwer · All Rights Reserved Color and Power Doppler Findings—(cont.) Figure 7-29. Turbulent arterial flow demonstrated with mosaic color Doppler pattern. Copyright © 2018 Wolters Kluwer · All Rights Reserved Color and Power Doppler Findings—(cont.) Figure 7-30. Color Doppler scale settings: appropriate, too high, and too low. Copyright © 2018 Wolters Kluwer · All Rights Reserved Color and Power Doppler Findings—(cont.) Figure 7-31. Color Doppler images comparing laminar color Doppler flow and abnormal turbulent color Doppler flow (mosaic pattern). Copyright © 2018 Wolters Kluwer · All Rights Reserved Color and Power Doppler Findings—(cont.) Power Doppler displays flow based on amplitude rather than frequency shift. – No direction information – Relatively independent of angle Power Doppler helpful in detecting extremely low flow velocities Copyright © 2018 Wolters Kluwer · All Rights Reserved Vertebral Artery Stenosis Proximal vertebral artery usually evaluated during routine carotid duplex scan Normal vertebral artery flow has same pattern as ICA – Low resistance – Antegrade flow throughout cardiac cycle – Brisk systolic acceleration, sharp peak, and relatively high diastolic flow Copyright © 2018 Wolters Kluwer · All Rights Reserved Vertebral Artery Stenosis—(cont.) Figure 7-32. Duplex images demonstrating various normal vertebral artery Doppler waveform contours. Copyright © 2018 Wolters Kluwer · All Rights Reserved Vertebral Artery Stenosis—(cont.) Proximal vertebral artery stenosis will produce – Abnormal dampened waveforms distally with delayed acceleration and rounded peaks – Possible poststenotic turbulence – No specific criteria should be suspected if focal velocity increase in PSV is >150 cm/s Generally occurs at origin from subclavian artery Resistive or blunted waveforms indicate distal stenosis or occlusion Copyright © 2018 Wolters Kluwer · All Rights Reserved Vertebral Artery Stenosis—(cont.) Figure 7-33. Abnormal, resistive, and blunted vertebral artery Doppler waveform contour, which indicates distal (versus intracranial) severe stenosis or occlusion. Copyright © 2018 Wolters Kluwer · All Rights Reserved Subclavian Steal Hemodynamically significant stenosis in the proximal subclavian artery causing changes to vertebral artery flow Results in brachial blood pressure decrease on affected side (more than 15 to 20 mm Hg lower than contralateral arm) Causes decreased pressure at the origin of ipsilateral vertebral artery that can lead to reversed flow Copyright © 2018 Wolters Kluwer · All Rights Reserved Subclavian Steal—(cont.) Vertebral artery flow changes as obstruction progresses – Normal antegrade flow – Antegrade flow with deep notch midcardiac cycle – Alternating or bidirectional (to-and-fro) flow – Complete reversal (fully retrograde) flow Copyright © 2018 Wolters Kluwer · All Rights Reserved Reactive Hyperemia Provocative test used to augment a subclavian steam from “latent” to “complete” Procedure – Blood pressure cuff is inflated to suprasystolic blood pressure on affected side – Left inflated for 3 to 5 minutes while vertebral artery is monitored – Cuff is rapidly deflated while ipsilateral vertebral artery is observed. – Positive when vertebral artery completely reverses Copyright © 2018 Wolters Kluwer · All Rights Reserved Subclavian Steal Figure 7-34. Abnormal vertebral artery Doppler flow signals. A: Progression from normal waveform contour to reversed vertebral artery flow. Copyright © 2018 Wolters Kluwer · All Rights Reserved Vertebral Artery Stenosis Figure 7-34. Abnormal vertebral artery Doppler flow signals. B: Vertebral artery stenosis. Copyright © 2018 Wolters Kluwer · All Rights Reserved Vertebral Artery Occlusion Figure 7-34. Abnormal vertebral artery Doppler flow signals. C: Proximal extracranial vertebral artery occlusion with collateral artery reconstitution. Copyright © 2018 Wolters Kluwer · All Rights Reserved