Color doppler examination of subclavian steal:our experience

Color doppler examination of subclavian steal:our experience Poster No.: C-2202 Congress: ECR 2014 Type: Educational Exhibit Authors: W. Severino Rondón, A. Carreres, S. Peris, M. C. Senís Sayas, J. Forner, M. L. Vernetta; Valencia/ES Keywords: Arteriosclerosis, Diagnostic procedure, Ultrasound-Colour Doppler, Vascular DOI: 10.1594/ecr2014/C-2202 Any information contained in this pdf file is automatically generated from digital material submitted to EPOS by third parties in the form of scientific presentations. References to any names, marks, products, or services of third parties or hypertext links to thirdparty sites or information are provided solely as a convenience to you and do not in any way constitute or imply ECR's endorsement, sponsorship or recommendation of the third party, information, product or service. ECR is not responsible for the content of these pages and does not make any representations regarding the content or accuracy of material in this file. As per copyright regulations, any unauthorised use of the material or parts thereof as well as commercial reproduction or multiple distribution by any traditional or electronically based reproduction/publication method ist strictly prohibited. You agree to defend, indemnify, and hold ECR harmless from and against any and all claims, damages, costs, and expenses, including attorneys' fees, arising from or related to your use of these pages. Please note: Links to movies, ppt slideshows and any other multimedia files are not available in the pdf version of presentations. www.myesr.org Page 1 of 25

Learning objectives To analyze the value of Doppler sonography in the diagnosis of patients with subclavian steal syndrome (SSS). Background The subclavian steal syndrome (SSS) refers to a vascular disorder in which occlusion or stenosis of the subclavian artery proximal to the vertebral artery origin causes altered vascular hemodynamics. The end result is a retrograde blood flow in the ipsilateral vertebral artery toward the upper arm, distal to the subclavian artery narrowing, where decreased blood pressure had been established (Fig.1). It has been estimated by multiple authors that the prevalence of SSS is between 0.6% and 6%, but this data comes from smaller single center studies and the true prevalence 1-2 of this syndrome is still unknown. It usually affects patients older than 50 years of age, with a male to female ratio of 2:1 and the left side is affected four times more often than the 1 right side. The reason of this is because the left subclavian artery has a more prominent 3 angle at its origin, and turbulent flow will accelerate atherosclerosis in this location. 3 Atherosclerosis is the most common cause and represents 90% of cases of SSS and up to 10% of patients with cardiovascular disease have concomitant subclavian artery 4 stenosis. Takayasu arteritis, neurofibromatosis, aberrant subclavian artery, traumatic subclavian artery occlusion, hemodialysis fistula, radiation, complications after vascular surgery or intravascular catheter procedure, critical contralateral internal carotid artery stenosis can be recited among the other causes. Risk factors like advanced age, smoking, hypertension, diabetes, family history, and dislypidemia particularly low high 4 density lipoprotein cholesterol known to atherosclerosis also, have been associated to SSS. The pathophysiology of SSS involves a proximal subclavian stenosis or occlusion in which appears subsequent retrograde blood flow in the ipsilateral vertebral artery because existence of a negative pressure gradient between the vertebral basilar and vertebro-subclavian region permitting the supply of arterial inflow to the ipsilateral subclavian artery (Fig. 1). Page 2 of 25

The retrogade flow can be classified as complete or incomplete, meaning the flow 3 reversal is continuous or intermittent. The latter will reproduce the subclavian steal phenomen, but it is the continuous flow reversal that will be responsible for the majory 5 of the true syndromes. Because the vertebral artery serves as an important collateral circulation to the upper extremety, this same mechanism that may lead to arterial 3 insufficiency and symtomatology from the arm. Most patients are asymptomatic, and diagnose incidentally through routine carotid Doppler examination. When patients present symptoms, they can be divided between neurological symptoms related to posterior and vertebrobasilar cerebral circulation ischaemia and those due to diminished perfusion to affected arm. Patients refer that when they exercise, symptoms like numbness, diminish pulse or claudication worsen. Among the neurological symptoms we include: visual loss, which may range from total blindness to unilateral visual field loss or amaurosis fugax, dysarthria, perioral numbness, hearing loss, light- headedness or vertigo. Most of typical SSS cases, a difference greater than 1 20mmHg in blood pressure can be found in the affected arm. In rarer cases, SSS can manifest as refractary unstable angina, often during coronary 1 revascularization after the CABG surgery or as cerebellar infarction due to an acute 2 thrombus that appears secondarily to the subclavian stenosis. Images for this section: Page 3 of 25

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Fig. 1: Schematic drawing showing a left-side subclavian steal syndrome. Stenotic lesion just proximal left vertebral artery (small arrow). The blood flow in the ipsilateral VA is reverse, stealing the blood from the contralateral VA (large arrows). (Image courtesy of Rebeca Mirón Mombiela, General University Hospital of Valencia). Page 5 of 25

Findings and procedure details Anatomy: The vertebral artery (VA) is usually the first branch which arises from the subclavian. In 90% of people the proximal vertebral artery follows an upward, superomedial trajectory, and passes in front of the transverse process of C7 and penetrates into the transverse hole at C6. The rest of the vertebral arteries penetrate in the transverse level C5 or C7 holes and rarely at the level of C4. Typically, the vertebral arteries come together to form the basilar artery. Thus, the vertebral arteries supply blood to most of the posterior cerebral circulation through the circle of Willis, providing also collateral circulation to other 6 regions of the brain in case of occlusive carotid disorder. The VA is divided into four segments. Segment 1-3 represent the extracranial VA. The first vertebral segment, or pre-transverse segment, extends from the origin of the subclavian 7 artery (SCA) to its entry into the foramen of the transverse process. Visualization by ultrasound of the first segment is variable, but in the most patients it can be adequately 8 visualize. The significance of the V1 segment of the VA is that is the most prone to atherosclerotic change at its origin. The second segment extents from the transverse process of C6 to where the VA exits 8 the axis. The V2 segment is visible in aproximately 95% of patients. The third segment 7 extends from the point of exit from the axis to its entry into the spinal canal. The second segment and the third segment are difficult to visualize, and cannot always be insonated. Technique: Doppler ultrasound has been used as a screning tool because of its accessibility, low costs, non-invasiveness, allowing to quickly identify the vertebral arteries. Moreover patients do not requie any preparation before examination. In most cases it is possible to visualize the vertebral artery by Doppler flow analysis. The patient may lie down in o the supine or semi-supine position with the head slightly hyperextended and rotated 45 away from the side being examined (Fig. 2). We use a 7,5 MHz linear or 3,5 MHz convex transducer (Fig. 3), depending on the depth of the VA and patient constitution. To explore the vertebral arteries, the Common Carotid Artery (CCA) is located first in the longitudinal plane. It is necessary to determine the flow direction of the CCA by Page 6 of 25

performing a lateral and gradual sweep with the transducer, identifing vertebral arteries and vein that run between the transverse processes of C2-C6, which are identified by their posterior acoustic shadow. The examiner can simultaneously display the carotid artery and vertebral artery, as a reference to determine the direction of flow in the vertebral 6 artery (Fig.4) by color Doppler imaging with a suitably low pulse repetition frequency/ high color gain. The measured angle of insonation should be less than 60º 9. VA flow is cephalad throughout the cardiac cycle, and any deviation from this pattern is abnormal. It can semi quantify subclavian stenosis and diagnoses other extracraneal carotid occlusive disease. Occasionally, transcranial ultrasound is utilized to evaluate the 10-11. direction of the basilar artery blood flow To confirm flow presence of the vertebral arteries, a pattern of low resistance flow has to be found, similar to those of the CCA. The Doppler waveform is monophasic with prominent diastolic flow and spectral broadening (Fig. 5). Spectral broadening in normal vessels can be seen as a result of a large sample volume relative to the small diameter of the vessel, which averages 4-4.6mm 12. 13-14. Normal peak systolic velocity (PSV) for the VA is approximately 20-60 cm/s This range is poorly defined in the literature, but a PSV if <10cm/s is probably abnormal and a focal PSV >100cm/s probably indictive of a significant stenosis 14. Findings of SSS: Haemodynamically significant abnormalities of the SCA proximal to the VA origin may cause characteristic changes in the ipsilateral VA. A reduction in diameter of the proximal SCA which produces a pressure gradient between the cerebral circulation (donor) and left SCA recipient) will alter VA flow (Fig. 1). This ultrasonographic finding are known as 8 the vertebral-subclavian steal syndrome. Depending of the side affected we can find: on the left side, the subclavian steal can be caused only by occlusion or near occlusion of the left suclclavian artery. On the right side, the SSS can be caused by occlusive desease of the subclavian artery or branchiocephalic artery 12. These two right-sided lesions can be differentiated by the appearece of the right common carotid artery waveform. If the lesion involves the subclavian artery, the common carotid Page 7 of 25

artery waveform will be unaffected. When the lesion is in the brachiocephalic artery, retrograde flow in the vertebral artery will supply not only the distal subclavian, but also the right common carotid artery (Fig. 6). Because the right common carotid artery flow is via colleterals, the waveform is parvus tardus with a slower-than-normal upstroke an disminshed peak systolic velocity 15. Based on hemodynamic changes of the vertebral artery flow, we can identify complete steal, manifested as complete flow reversal, and partial steal, showing bifasic or antegrade flow at rest and reversed flow or abnormal waveform with ipsilateral arm exercise. 8 In reference to the waveform, depending on the author, the SSS can be clasify in four or 1 three grades that correlates with severity of the syndrome. In our Radiology Department we prefer to use the thee grades classification (Fig. 7). Grade I (pre-subclavian steal): reduced antegrade vertebral flow. The wave present mid of bunny pattern, (end deceleration of the diastolic flow). The flow direction was entirely anterograde in the vertebral artery waveform. Converted in a steal partial if provocation manoeuvering are made. It is observed in the case of mild stenosis of the proximal subclavian. When the stenosis is 45% or less it shows a sharp mid-systolic deceleration, with a sharp first systolic peak and more rounded lower second systolic peak. Grade II (intermittent/partial/latent): alternating flow-antegrade flow in the diastolic phase and retrograde flow in the systolic phase. Converted into a grade III if provocation manoeuvering are made. It indicates the existence of a non-occlusive stenotic lesion. Stenosis of more 50% but les than 80% produces a deeper cleft between the two systolic peaks, where the nadir of the cleft is at approximately the same level at the end of diastole. When stenosis is significant (80% or grater) stenosis of the pre-verterbral subclavian artery produces a VA waveform with initial antegrade flow and subsequent retrograde flow. Grade III (permanent/advanced): Refers to the complete occlusion or high grade preverterbral subclavia artery stenosis. The flow direction is entirely retrograde in the vertebral artery. Our sample of patients: Page 8 of 25

We review 26 patients with clinical symptoms of SSS, to whom Doppler sonography was performed. In 12 patients, US-Doppler showed complete SSS with complete reversal of the blood flow through the ipsilateral vertebral artery. Fig. 8 y 10. In 8 patients, the vertebral waveform was biphasic (Fig. 12 y 14) when the study was performed at rest, whereas the flow became reversed with arm movement Fig. 13. In 5 patients, US-Doppler showed no alterations either at rest or with arm movement. All 20 cases with hemodynamic alterations where confirmed by TC angiography or by conventional arteriography. Fig. 9, 11 y 15. Images for this section: Page 9 of 25

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Fig. 3: 7,5MHz linear transducer and 3,5MHz covex transducer. Page 12 of 25

Fig. 4: This imagen show simultaneously display the carotid artery and vertebral artery. Both vessels with the same color indicared the direction correct flow in the vertebral artery. Fig. 5: Confirmed tha flow presence of the VA, we can see the pattern of waveform (monophasic and low resistance flow). Page 13 of 25

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Fig. 6: Schematic drawing showing stenotic lesion is in the brachiocephalic artery, retrograde flow in the VA which supply the distal subclavian, and the right CCA. (Image courtesy of Rebeca Mirón Mombiela, General University Hospital of Valencia). Page 15 of 25

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Fig. 7: Normal VA Doppler waterform. Grade I the wave present bunny pattern (deceleration of the diastolic flow). The flow direction is anterograde. Grade II bidirectional VA Doppler waveform and Grade III reverse VA Doppler waterform. (Image courtesy of Rebeca Mirón Mombiela, General University Hospital of Valencia). Fig. 8: 69 year-old man with complete reversal flow direction (covering systole and diastole of the curve). Complete steal syndrome subclavian with suspected right subclavian oclussion at origin. Page 17 of 25

Fig. 9: The same patient as the fig.8 arteriograghy was performed, which show the confirmation of the occlusion in the right VA. Page 18 of 25

Fig. 10: 62 year old woman with complete reversal flow direction, full subclavian steal syndrome by occlusion of the subclavian artery. Page 19 of 25

Fig. 11: CT angiography of same patient as fig.10 was performed. It showed findings compatible with artery thrombosis of the left subclavian artery, confirming the findings of complete subclavian steal by doppler ultrasaound. Page 20 of 25

Fig. 12: 65 year old man with SSS simptoms, ultrosound Doppler show the vertebral waveform was biphasic when the study was performed at rest. Page 21 of 25

Fig. 13: The same patient as fig. 12 the ultrasound was performed whereas the flow became reversed with arm movement. Page 22 of 25

Fig. 14: 70 year old woman with partial reversal of flow during systole, findings consistent with the phenomenon of partial steal of the subclavian artery, through of the stenosis. Fig. 15: CT Angiography of the same patient as fig. 14., confirmed the presence of calcifications at the origen of the subclavia artery causing partial stenosis. Page 23 of 25

Conclusion Doppler ultrasonography is a widely accepted technique non-invasive for screening patients with extracranial arterial stenosis. Based on hemodynamic changes of the vertebral artery flow, we can identify complete steal, manifested as complete flow reversal, and partial steal, showing bifasic or antegrade flow at rest and reversed flow or abnormal waveform with ipsilateral arm exercise. Personal information References 1. Osiro S, Zurada A. A review of subclavian steal syndrome with clinical correlation. Med Sci Monit, 2012: 18(5): RA57-63. 2. Park H, Kim H, Jin Cha M, Lee J, Koh I, Nam H. A Case of Cerebellar Infartion Caused by Acute Subclavian Thrombus Following Minor Trauma. Yonsei Med J 2013; 54(6): 1538-1541. 3. Alcocer F, David M. A forgotten vascular disease with important clinical implications. Subclavian steal syndrome. Am J Case Rep, 2013; 14: 58-62. 4. Dieter R, Darki A, Nanjundappa A, Lopez J. Subclavian Steal Syndrome Successfully Treated with a Novel Application of Embolic Capture Angioplasty. Int J Angiol 2012; 21:121-124. 5. Berger R, Sidd J, Ramaswamy K: Retrograde Vertebral-Artery Flow Produced by Correction of Subclavia-Steal Syndrome.N EnglJ Med, 1967; 277:64-69. 6. Rumack CM. Diagnostic Ultrasound. Third edition. Elsevier. Spain, 2006. Page 24 of 25

7. Roberts LH, Demetriades D. Vertebral artery injuries. Surg Clon North Am 2001; 81:1345-56. 8- Buckenham TM, Wright IA. Ultrasound of the extracranial vertebral artery. The British Journal of Radiology 2004; 77: 15-20. 9. Kliewer MA. Vertebral Artery Doppler Waveform Changes Indicating Subclavian Steal Physiology. AJR Am J Roetngenol 2000;174:815-819. 10. Labropoulos N, Nandivada P, Bekelis K. Prevalence and Impact of the Subclavian Steal Síndrome. Ann surg 2010; 252: 166. 11. klingelhöfer J, Conrad B, Benecke R, Frank B. Transcranial Doppler ultrasonography of carotid-basilar collateral circulation in subclaian steal. Stroke, 1998; 19: 103. 12. Horrow M, Stassi J,. Sonography of the Vertebral Arteries: A Window to Disease of the Proximal Great Vessels. Pitorial Essay 2001. 13. Siedel E, Eicke BM, Tettenborn B, Krummenauer F. Reference values for vertebral artery flow volume by Duplex sonography in young and elderly adults. Stroke 1999; 30: 2692-6. 14. Sidhu PS. Ultrasound of the carotid and vertebral arteries. Br Med Bull 2000; 56:346-66. 15. Kotval PS. Doppler waveform parvus and tardus: a sign of proximal flow obstruction. J Ultrasound Med 1989;435-440. 16. Kawahara I, Nakamoto. Subclavian steal phenomenon associated with hypervascular thyroid tumor. Neurological Surgery. 2010; 38(5): 473-476. 17. Kizilkilic O, Oguzkurt L, Tercan F, Yalcin O, Tan M, Yildirim T. Subclavian Steal Syndrome from the Ipsilateral Vertebral Artery. Am J Neuroradiol 2004; 25: 1089-91. Page 25 of 25