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CAROTID DOPPLER STUDY

ULTRASOUND EVALUATION OF CAROTID DISEASES

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CAROTID DOPPLER STUDY

  1. 1. CAROTID DOPPLER STUDY Dr.I.Gurubharath MD PhD Dr.Pooja MD
  2. 2. Doppler US Carotid arteries • Anatomy of Carotid arteries • Normal Doppler US of carotid arteries • Causes of Carotid artery disease • Effect Extra carotid arteries
  3. 3. CAROTID ARTERY ANATOMY • The right and left CCAs ascend into the neck posterolateral to the thyroid gland and lie deep to the jugular vein and sternocleidomastoid muscle. • The CCAs have different proximal configurations, with the right originating at the bifurcation of the innominate (brachiocephalic) artery into the common carotid and subclavian arteries. • The left CCA usually originates directly from the aortic arch but often arises with the brachiocephalic trunk. This is known as a “bovine arch” configuration. • The CCA usually has no branches in its cervical region.
  4. 4. • Occasionally, however, it may give off the superior thyroid artery, vertebral artery, ascending pharyngeal artery, and occipital or inferior thyroid artery. • At the carotid bifurcation, the CCA divides into the external carotid artery (ECA) and the internal carotid artery (ICA). • The ICA usually has no branching vessels in the neck. • The ECA, which supplies the facial musculature, has multiple branches in the neck. • The ICA may demonstrate an ampullary region of mild dilation just beyond its origin.
  5. 5. Variants resulting due to elongation of ICA
  6. 6. Patient Position One is the overhead position, in which the examiner sits beyond the patient’s head beside the end of the examination table and use two hands for ultrasonography. Head hyperextended and 45* away from side being examined. High frequency linear tranducers
  7. 7. Transducer • Higher-frequency linear transducers (>7 MHz) are ideal for assessment of the intima-media thickness and plaque morphology • Lower frequency linear transducers (<7 MHz) are preferred for Doppler examination. • In a short muscular neck, if imaging with a linear transducer is impossible, a curved-array transducer (7 MHz)
  8. 8. All carotids artery examinesd should be performed with: • Grey scale US • Color Doppler • Power Doppler • Spectral doppler • Vessels should be imaged as completely as possible • Caudal angulation of the transducer in the supraclavicular region and cephalic angulation at the level of the mandible
  9. 9. Limitations  Short muscular neck  A high carotid bifurcation  Tortuous vessels  Calcified shadowing plaques
  10. 10. Avoid excess pressure on carotid bifurcation to avoid -Stimulate carotid sinus Bradycardia Syncope Ventricular systole -Compress carotid arteries high velocities
  11. 11. Optimal Scanning Techniques and Doppler Settings • Scan both in transverse and longitudinal plane. • Starting from proximal most CCA, bulb, ECA and ICA • Distal carotid ‐2 cm from the bulb
  12. 12. Color Doppler Sampling Window •Also known as the color box •The size is adjusted to include all regions of interest. •Adjustment of the angle‐by changing the box angles fro m left to center or right •Angling the transducer to ensure that the Doppler angl e is less than 60°to the direction of blood flow
  13. 13. Proper steering
  14. 14. Sample Volume Gate and Angle Correction • If the Doppler angle is small or more than 60 degree small error in the estimated velocity. • Preferred angle of incidence is 45°±4. • The optimal position of the sample volume gate in a normal artery is in the mid lumen parallel to the vessel wall in a diseased vessel, parallel to the direction of blood flow • Should not be placed on the sharp curves of a tortuo- us artery falsely high velocity reading • Should not be placed too close to the vessel wall‐spec tral broadening.
  15. 15. Spectral Broadening •Spectral broadening results from turbulence in the bloo d flow. Spurious spectral broadening •A large Doppler angle •A sample volume gate located close to the vessel wall •A high Doppler gain setting •The size of the gate is normally ‐between 2 and 3 mm. •Too small (1.5 mm) ‐the Doppler signal may be missed •Too large >3.5 ‐spectral broadening
  16. 16. Color velocity scale •If set belowthe mean velocity of blood flow, aliasing throughout the vessel lumen •set significantly higher than the mean velocity of b lood flow, aliasing may disappear resulting in a mi ssed stenosis •In a normal carotid US examination, the color velo city scale should be set between 30 and 40 cm/sec (mean velocity).
  17. 17. Color Gain Control •The color gain should be set so that color just reaches the intimal surface of the vessel. •If the color gain setting is too low, trickle flow may go undetected. •If a color gain setting is high, “bleeding” of the color into the wall and surrounding tissues limit visualizatio n of the plaque surface
  18. 18. Color Gain Control •The color gain should be set so that color just reaches the intimal surface of the vessel. •If the color gain setting is too low, trickle flow may go undetected. •If a color gain setting is high, “bleeding” of the color in to the wall and surrounding tissues limit visualization o f the plaque surface
  19. 19. Role of power doppler PDI may provide increased sensitivity to visualize the continuity of blood flow in arterial stenoses
  20. 20. Advantages of power doppler •Angle independent •No aliasing •Very sensitive to low velocity and low amplitude flow •Helps in differentiating critical stenosis from occlusion Disadvantages: Motion sensitive Does not give direction and velocity of flow
  21. 21. Technique and Waveform Analysis Normal Carotid Artery
  22. 22. CCA • Begin proximally in transverse and follow distally to the bifurcation. • Assess the course (i.e. if tortuous) and the presence of any intimal thickening or plaque. • Repeat in longitudinal plane. • Use colour to assess patency of vessel and the direction of flow. • Use 'Heel/Toe' technique to optimize insonation of vessel, apply colour box and Doppler sample gate with appropriate steering and angle correction. • Measure the Peak Systolic (PSV) and end diastolic velocities (EDV).
  23. 23. CCA • Combination of ICA and ECA patterns, • Intermediate amount of continuous forward diastolic flow • A sharp systolic upstroke and thin spectral envelope flow below the baseline or filling in of the spectral window normally should not be seen
  24. 24. BIFURCATION • Assess in transverse and longitudinal for pathology. • Identify the origins of the ICA and ECA arteries. • Measure the Peak Systolic (PSV) and end diastolic velocities (EDV) of the ECA.
  25. 25. • A low‐resistance waveform pattern • Systolic peak should be sharp and the spectral en velope thin continuous forward diastolic flow • The systolic peak may be slightly blunter than the systolic peak of the ECA ICA
  26. 26. ECA • The systolic upstroke is sharp • The spectral envelope is thin. • Reduced to no diastolic flow • Diastolic flow should be symmetrical bilaterally transient reversal in early diastole (characteristic ear ly diastolic notch ) ‐a normal finding
  27. 27. Temporal tap maneuver
  28. 28. Temporal tapping of ECA “Saw-tooth” appearnce
  29. 29. Normal flow reversal in ICA Velocity is highest near the flow divider Flow reversal on opposite side to flow divider Flow reversal zone Opposite to the origin of ECA
  30. 30. VERTEBRAL ARTERIES Return to a longitudinal plane of the CCA and angle the beam postero-laterally to visualise the vertebral artery. Ensure suitable PRF and gain for these smaller, deeper vessels. The flow should be low resistance flow ( presence of forward diastolic flow). Confirm the flow is antegrade i.e. towards the head - (normal) or retrograde (suggesting subclavian steal syndrome).
  31. 31. VERTEBRAL ARTERY • Low resistance wave pattern • forward diastolic flow • no systolic or diastolic notch • similar to carotid in flow (colour) • No reversal of wave form
  32. 32. SCA
  33. 33. Intima –Media complex Normal <0.8mm
  34. 34. Look At •Pattern •Systolic contour •Diastolic pattern •PSV •DV •ICA PSVs / CCA PSVs ratio •Compare Right and Left side
  35. 35. Causes for unilateral low PSVs • Proximal stenosis (brachiocephalic) • Parvus tardus waveform or normal pattern but asymmetrical PSVs. • Distal stenosis (carotid bulb level) • High resistance wave form
  36. 36. Indications for Carotid Ultrasound • Evaluation of patients with hemispheric neurologic symptoms, including stroke, transient ischemic attack, and amaurosis fugax • Evaluation of patients with a carotid bruit • Evaluation of pulsatile neck masses • Evaluation of patients scheduled for major cardiovascular surgical procedures • Evaluation of nonhemispheric or unexplained neurologic symptoms Follow-up of patients with proven carotid disease Evaluation of patients after carotid revascularization, including stenting Intraoperative monitoring of vascular surgery • Evaluation of suspected subclavian steal syndrome • Evaluation of a potential source of retinal emboli • Follow-up of carotid dissection • Follow-up of radiation therapy to the neck in select patients
  37. 37. Causes of carotid artery diseases Arteriosclerotic disease NonArteriosclerotic disease Fibromuscular dysplasia Dissection Vasospasm Aneurysm and pseudoaneurysm A-V Fistula Arteritis Carotid body tumor
  38. 38. Common sites for extracranial arterial disease Most common site at carotid bifurcation with plaque extending into ICA
  39. 39. Carotid plaque •Defined as a localized protrusion from the wall into the lumen with an area 50% greater than the intima media thickness of neighboring sites. Parameters and properties of plaques (a) Plaque extent , Location ,size including the maximally thick area and the elevated area (b) Texture, Surface morphology (c) Internal properties, (d) Mobility. (e) Luminal stenosis.
  40. 40. Homogeneous (stable) plaque Homogeneous uniform echo pattern with smooth surface (acoustic impedance similar to blood) Heterogeneous (unstable) plaque Mixture of high, medium, and low-level echoes with smooth / irregular surface; Texture of Carotid Plaque
  41. 41. Ultrasound Types of Plaque Morphology Type 1: Predominantly echolucent, with a thin echogenic cap (A) Sagittal and (B) transverse images show plaque (arrows) virtually completely sonolucent, consistent with heterogeneous plaque (type 1). Note smooth plaque surface
  42. 42. Type 2: Substantially echolucent with small areas of echogenicity (>50% sonolucent)
  43. 43. Type 3: Predominantly echogenic with small areas of echolucency (<50% sonolucent)
  44. 44. Type 4: Uniformly echogenic
  45. 45. Plaque types 1 and 2 • Intraplaque hemorrhage and ulceration, Unstable • Abrupt increases in plaque size after hemorrhage or embolization. • Symptomatic patients with stenoses greater than 70% of diameter. Plaque types 3 and 4 • Fibrous tissue and calcification. • Homogeneous plaque. • Benign, • Stable plaques • Asymptomatic individuals
  46. 46. Surface Characteristics of Carotid Plaque US unreliable due to poor visualization of intima 4 Categories: • Smooth • Mildly irregular • Markedly irregular • Ulcerated
  47. 47. Intimal thickening wavy / irregular line paralleling vessel wall extending > 1 mm into vessel lumen Early I-M hyperplasia with loss of the hypoechoic component of the I-M complex and thickening (arrows
  48. 48. Plaque ulceration Ultrasound Features Suggestive of Plaque Ulceration • Focal depression or break in plaque surface • Anechoic region within plaque extending to vessel lumen • Eddies of color within plaque
  49. 49. Plaque Ulceration and Abnormal Flow. (A) Longitudinal image of the proximal right internal carotid artery (ICA) demonstrates heterogeneous plaque with an associated area of reversed low-velocity eddy flow within an ulcer (arrow). (B) Pulsed Doppler waveforms in this ulcer crater demonstrate the extremely dampened low- velocity reversed flow, not characteristic of that seen within the main vessel lumen of the ICA. A
  50. 50. Gray-Scale Evaluation of Stenosis Measurements of carotid diameter and area stenosis should be made in the transverse plane, perpendicular to the long axis of the vessel, using gray- scale, B-flow, or power Doppler sonographic imaging (A) Power Doppler transverse image shows a less than 50% diameter stenosis (cursors). (B) Transverse B-mode flow image of the right carotid bifurcation shows measurement of stenosis (B) in area of internal carotid artery (ICA). A, Outer ICA area.
  51. 51. Circumferential calcified plaque in the proximal ICA. (a) PW Doppler image of the right ICA obtained immediately distal to a circumferential shadowing plaque shows no sign of turbulence, and the PSV is within normal limits. Therefore, there is unlikely to be a significant stenosis behind the calcified plaque. (b) PW Doppler image of the proximal right ICA shows a tardus-parvus waveform. A severe proximal stenosis behind the shadowing plaque is suspected; therefore, evaluation with another imaging modality is required.
  52. 52. Abnormal CCA Either low or high psvs. Abnormally high‐resistance waveform, An abnormally low‐resistance waveform,
  53. 53. Abnormally low PSVs A normal CCA PSV should be in the range of approxi mately 60 –100 Cm/s •IF less than this, examine opposite side Symmetric Asymmetric (near normal) Low cardiac output Evaluate further •A velocity difference of >20 cm/sec between the righ t and left is abnormal
  54. 54. Causes for unilateral low PSVs •Proximal stenosis (brachiocephalic) Parvus ‐tardus waveform or normal pattern but asymmetrical PSVs. •Distal stenosis (carotid bulb level) High resistance wave form
  55. 55. Focal stenosis of the CCA •The ratio of the highest PSV at the CCA stenosis divided by the PSV 2 cm proximal to the stenosis should be calculated. PSV CCA at stenosis/PSV CCA prox. •If the ratio is 2 or more and less than 2.99 ‐stenosis of 50% or more. •If the ratio is 3 or more stenosis of 75% or more. •also used if there are tandem stenosis.
  56. 56. Unusual finding in Case of CCA occlusion • Reversal of flow in ECA and low resistance and low PSVs in ICA as it is fed by collaterals. • This is to maintain the antegrade flow in ICA
  57. 57. CCA -mildly elevated resistance High-velocity flow 627 cm/s, turbulenc
  58. 58. ICA stenosis • Most common site is ICA origin plaque extending fro m the bulb. • High resistance pattern in the ICA‐Stenosis distally. • PSVs raises ‐Significant stenosis
  59. 59. Sonographic features of a severe ICA or CCA stenosis may include the following: • PSV greater than 230 cm/sec, a significant amount of visible plaque (50% lumen diameter reduction on a gray-scale image), • Color aliasing despite a high color velocity scale setting (100 cm/sec), Spectral broadening, • Poststenosis turbulence at color Doppler and • PW Doppler imaging, color bruit artifact in the surrounding tissue of the stenotic artery, end- diastolic velocity of greater than 100 cm/sec, • ICA/CCA PSV ratio of 4.0 or greater. • A high-pitched sound at PW Doppler imaging .
  60. 60. Severe stenosis (70% to near occlusion) of the ICA. Duplex US image of the left ICA shows a high PSV (366 cm/ sec), a significant amount of visible plaque, the presence of aliasing despite a high color scale setting (114 cm/sec), color flow turbulence immediately distal to the stenotic segment, broadening of the PW Doppler spectrum, and a high end-diastolic velocity (182 cm/sec
  61. 61. String sign -Near Total Occlusion
  62. 62. Total Occlusion
  63. 63. ECA • Confirm the ECA • Is there any reversal of flow • Is there any internalization
  64. 64. VERTEBRAL ARTERY LOOK AT Normal or hypoplastic or not seen Waveform pattern Direction of flow PSVs
  65. 65. Reversal of flow– stenosis or occlusion at subclavian or brachiocephalic ar tery •Transient systolic reversal–in lesser digree stenosis •High resistance wave pattern–distalocclusion or stenosis •Low resistance wave pattern–more proximal stenosis
  66. 66. Stenosis at vertebral origin-high PSV
  67. 67. SUBCLAVIAN STEAL SYNDROME •Subclavian artery steno‐occlusive disease proximal to the origin of the vertebral artery. •Resulting in decreased blood pressure in the arm distal to the steno‐occlusive disease. •Causes ipsilateral vertebral artery blood flow alteration •Severe stenoses, flow reversal occurs in the ipsilateral vertebral artery as compensatory collateral to the vascular territory beyond the subclavian steno‐occlusive lesion.
  68. 68. Abnormal Vertebral Artery Waveforms COMPLETE SUBCLAVIAN STEAL Reversal of flow within vertebral artery ipsilateral to stenotic or occluded subclavian or innominate artery INCOMPLETE OR PARTIAL SUBCLAVIAN STEAL Transient reversal of vertebral artery flow during systole May be converted into a complete steal using provocative maneuvers Suggests stenotic, not occlusive, lesion PRESTEAL PHENOMENON “Bunny” waveform: systolic deceleration less than diastolic flow May be converted into partial steal by provocative maneuvers Seen with proximal subclavian stenosis TARDUS-PARVUS (DAMPENED) WAVEFORM Seen with vertebral artery stenosis
  69. 69. Other wave patterns
  70. 70. PULSUS BISFERIENCE ‘‘Beat twice,’’ •Characterized by two systolic peaks with an interposed midsystolic retraction •Seen in AR with or without concomitant AS Hypertophic obstructive cardiomyopathy •Occasionally, may be seen in healthy, athletic, young in dividuals or in older patients.
  71. 71. PULSUS ALTERNANS •Alternating peak systolic heights on sequential beats in a regular normal sinus rhythm Clinical conditions Intrinsic myocardial disease • Ischemia • Cardiomyopathies • Valvularheart disease
  72. 72. ‘Water hammer pulse’’ •In aortic reagurgitation – reversed early diastolic flow in both CCAs with elevation of PSV and a sharp systolic upstroke
  73. 73. CAROTID DISSECTION • Trauma ‐seat belt injury or repetitive trauma. •Occasionally, spontaneous and isolated to the carotid a rteries in Marfan syndrome, Ehlers‐Danlos syndrome, fibromuscular dysplasia, hypertension, or drug abuse •Also ‐direct extension of an aortic dissection. •Rare but, dissection of the ICA is the most common ca use of stroke in young patients. •Most ICA dissections occur at the level of the carotid b ifurcation.
  74. 74. Internal Carotid Artery Dissection: Spectrum of Findings INTERNAL CAROTID ARTERY Absent flow or occlusion Echogenic intimal flap, with or without thrombus Hypoechoic thrombus, with or without luminal narrowing Normal appearance COMMON CAROTID ARTERY High-resistance waveform Dampened flow Normal appearance
  75. 75. Abnormal high-resistance waveforms (arrow) at the origin of the right ICA with no evidence of flow distal to this point (curved arrow).
  76. 76. REFERENCE: 1. Rumack CM, Levine D. Diagnostic Ultrasound E-Book. Elsevier Health Sciences; 2017 Aug 8. 2. Pozniak MA, Allan PL. Clinical Doppler Ultrasound E-Book: Expert Consult: Online. Elsevier Health Sciences; 2013 Oct 24. 3. http://www.ultrasoundpaedia.com/

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