ultrasound of carotid arteries

1. ULTRASOUND ASSESSMENT OF
CAROTID ARTERY

2. INTRODUCTION
• Stroke -third leading cause of death and is a major cause of morbidity.
• Thus, the identification of patients with ICA stenoses of 60% to 70% is
clearly important for patient management, allowing appropriate
referral for carotid endarterectomy.
• Risk factors for disease at the carotid bifurcation include
atherosclerosis, hypertension, diabetes mellitus, hyperlipidemia,
hypercholesterolemia, obesity, and smoking.

4. TECHNICAL REQUIREMENTS
• Doppler ultrasound examination of the carotid arteries requires an ultrasound
machine with high-resolution gray-scale imaging as well as color Doppler and
spectral Doppler capability.
• A high-frequency 5- to 7.5-MHz linear array transducer should be used to
optimize spatial resolution.
• However, if the carotid arteries are too deep to visualize with the linear array
transducer in a patient with a short, thick neck, a lower frequency curved array
transducer may be necessary for adequate penetration.

5. Technique
Indications for a carotid ultrasound examination include
1. carotid bruit,
2. stroke,
3. transient ischemic attack,
4. syncope,
5. risk factors for atherosclerosis,
6. preoperative evaluation before major surgery,
7. follow-up for carotid endarterectomy or carotid stent placement,
and trauma.

6. Technique Description
• A complete ultrasound evaluation of the carotid arteries has three
components:
• (1) evaluation of plaque,
• (2) estimation of ICA stenosis by velocity criteria, and
• (3) waveform analysis.

7. • The examination begins with evaluation of plaque burden. Plaque
echotexture should be characterized as hypoechoic, heterogeneous,
or echogenic .
• The surface contour of the plaque should be described as smooth or
irregular ,and the percentage reduction of the arterial diameter by
the plaque should be estimated.

10. Protocol
• Longitudinal gray-scale and color or power Doppler images of the
proximal and distal CCA, bifurcation, bulb extending into the ICA, and bulb
extending into the ECA.
• Transverse gray-scale and color or power Doppler images of the proximal
and distal CCA, bulb, bifurcation, proximal ICA, and proximal ECA.
• Spectral Doppler tracings from the proximal CCA, distal CCA, proximal ICA,
mid ICA, distal ICA, proximal ECA, and mid vertebral artery.

11. • PSV is recorded for each segment, and end-diastolic velocity (EDV) is noted if it
is more than 100 cm/sec.
• The PSVR is calculated by dividing the highest PSV in the proximal ICA or area
of stenosis by the PSV in the distal CCA.
• PSV in the distal CCA should always be measured 2 to 3 cm proximal to the
level of the carotid bulb.
• Several measurements, optimally three, of PSV should be obtained and the
highest velocity recorded.

12. Normal Findings
• The normal carotid arteries have a thin, regular echogenic wall
without focal areas of calcification, intraluminal plaque, or thrombus.
• Color should fill the vessel lumen homogeneously with a slight central
increase in color intensity consistent with normal parabolic or laminar
flow.
• Where the carotid bulb widens, a helical blood flow pattern or
reversal of peripheral flow is a normal finding, particularly in younger
patients, and is believed to be due to boundary layer separation.

13. • The CCA, ICA, and ECA demonstrate distinct characteristic waveform
patterns.
• All segments of the extracranial carotid arteries normally demonstrate a
sharp systolic upstroke and thin spectral envelope, the amount of
diastolic flow varies in each vessel.
• The ECA, which supplies the muscular bed of the scalp, typically
demonstrates completely absent or very low velocity end-diastolic flow.
Although the amount of diastolic flow in the ECA may vary from patient
to patient, it should be symmetric right to left and less than the diastolic
flow in the ICA or CCA.
• An early diastolic notch followed by a short reversal of flow in early
diastole is often seen in the ECA.

14. • The ICA, which supplies blood to the brain (high oxygen consumption),
has a low-resistance waveform pattern with continuous forward,
relatively high velocity diastolic flow.
• The waveform of the CCA demonstrates an intermediate amount of
diastolic flow and often demonstrates a brief reversal of flow in early
diastole.
• The vertebral artery has a waveform pattern similar to that of the ICA,
characterized by a sharp systolic upstroke and continuous forward
diastolic flow.

15. > SHARP SYSYTOLIC UPSTROKE
> INTERMEDIATE AMOUNT
DIASTOLIC FLOW
> HIGH RESISTANCE
WAVEFORM
> SHARP SYSTOLIC
UPSTROKE
> LOW OR ABSENT
DIASTOLIC FLOW
> EARLY DIASTOLIC
NOTCH
> THIN SPECTRAL
ENVELOPE

16. > LOW RESISTENCE WAVEFORM
> BLUNTED SYSTOLIC PEAK
> HIGH DIASTOLIC FLOW
> WIDE SPECTRAL ENVELOPE
> WAVEFORM
PATTERN SIMILAR TO
ICA

21. • Differentiation of the ICA from the ECA is critically important to avoid
misinterpretation of a stenosis in the ECA as a more clinically significant ICA
stenosis.
• The best method of identifying the ECA is by visualization of branches arising
from the vessel .
• The ICA virtually never gives rise to branch vessels in the neck.
• Temporal tapping over the ophthalmic artery will generate sharp, spike-like
deflections in the waveform of the ECA during diastole

23. Grading Stenoses in the Internal Carotid Artery
• Because flow volume is a relative constant, PSV is inversely related to vessel
lumen diameter. Therefore, if the vessel diameter decreases, PSV must
increase to maintain flow volume.
• As demonstrated by the Spencer diagram, once the vessel diameter
decreases by more than 50%, PSV at the site of the stenosis rises
exponentially, and this compensatory increase in PSV maintains flow volume
until the stenosis reaches approximately 70%.

24. The SRU convened a multidisciplinary panel of experts, including both
radiologists and vascular surgeons, to develop a consensus for grading of ICA
stenoses by Doppler ultrasonography. The published recommendations of this
consensus conference are as follows:
• PSV < 125 cm/sec and PSVR < 2.0 suggest a stenosis < 50%
• PSV between 125 and 230 cm/sec and PSVR between 2.0 and 4.0 are most
consistent with a stenosis of 50% to 69%
• PSV > 230 cm/sec, PSVR > 4.0, and EDV > 100 cm/sec indicate a stenosis of
≥70% to 96%

25. PSV- 195 CM/SEC PSV-96CM/SEC

26. PSV-305 CM/SEC PSV-85 CM/SEC

28. Pitfalls: Technique
• Incorrect Choice of Doppler Angle
• Incorrect Gain

29. PSV-131CM/SEC PSV-190CM/SEC PSV-266CM/SEC

31. Pitfalls: Pathology
• Tortuous Carotid Artery
When the carotid arteries are tortuous, most commonly in elderly patients,
PSV can be elevated without an underlying stenosis.
This is due in part to a true increase in PSV as the blood accelerates around
the curves but is also likely due to difficulty in assigning a correct Doppler
angle along the curved vessel, which results in an overestimation of PSV
due to incorrect Doppler angle

33. Long-Segment or Synchronous Involvement
Coexistent disease in the carotid arteries will also make PSV Doppler criteria less
reliable.
Synchronous disease in the CCA, or tandem lesions, will result in a decrease in
PSV for a given percentage stenosis in the ICA.
Hence, the entire CCA and ICA must be evaluated, not just the carotid
bifurcation.
Most ICA stenoses are less than 2 cm in length. However, if a stenosis is
unusually long (>2 cm), PSV often drops (possibly because of increased in-flow
resistance), although diastolic velocity may remain high.

34. Prior radiation therapy, carotid dissection, arteritis, or fibromuscular dysplasia should be
considered when a long-segment stenosis is noted.

35. • Contralateral Carotid Disease
A high-grade carotid stenosis or occlusion will increase PSV in the
contralateral side, especially at the site of a stenosis.
Hence, if the PSV seems more elevated than one would expect given the
amount of visualized plaque and if the vessel is not tortuous, one should be
suspicious of contralateral disease.

37. ULTRASOUND ASSESSMENT OF PLAQUE
• Ultrasound evaluation of plaque requires gray-scale and color Doppler imaging in
both longitudinal and transverse planes.
• Such images can be used to estimate percentage diameter reduction by plaque and
correlated with PSV measurements.
• In addition, the echotexture and surface contour of the plaque should be
assessed.
• Plaque should be characterized as hypoechoic or echogenic with either a smooth
or irregular surface.
• Prospective studies have shown that hypoechoic, irregular plaque is associated
with an increased risk of neurologic events and increased rate of plaque
progression.

41. WAVEFORM ANALYSIS OF THE CAROTID ARTERIES
Abnormalities of the Systolic Peak:
1) Parvus Tardus Waveform:
The parvus tardus waveform is characterized by decreased PSV and a
delayed, more horizontal systolic upstroke with rounding or blunting of
the systolic peak.
The parvus tardus waveform phenomenon becomes more pronounced the
more distal to the stenosis that the vessel is sampled. Hence, it is
important to sample the ICA as distally as possible.

42. THIS 79-YEAR-OLD WOMAN HAS SEVERE AORTIC STENOSIS

43. 2) Pulsus Bisferiens Waveform:
Rarely, two systolic peaks of similar velocity with an interposed midsystolic
retraction or deceleration may be observed .
This has been termed pulsus bisferiens (Latin, “beat twice”).
Whereas this has been described in the literature as most commonly
associated with aortic regurgitation (particularly if it coexists with aortic
stenosis) and hypertrophic cardiomyopathy

45. 3) Pulsus Alternans Waveform:
Alternating systolic velocity peaks, pulsus alternans, may be very rarely
observed.
The cause of this phenomenon is not known. However, intrinsic myocardial
disease, hypocalcemia, and impairment of venous return have been
postulated as possible causes

46. THIS 69-YEAR-OLD MAN WITH HISTORY OF ATRIAL FIBRILLATION, GLOBAL
HYPOKINESIS, AND EJECTION FRACTION OF 30%.

47. Abnormalities of Diastolic Flow
• The normal ECA demonstrates a characteristic high-resistance waveform
pattern with little or no diastolic flow and an early diastolic notch.
• Although the amount of diastolic flow may vary from individual to individual,
the diastolic flow pattern should be symmetric right to left in the same
individual.
• When the ipsilateral ICA is occluded, “internalization” of the ECA may occur,
and a lower resistance waveform pattern with increased diastolic flow and
asymmetric to the contralateral ECA may be observed.

49. • A high-resistance waveform pattern with diminished, absent, or reversed
diastolic flow is an abnormal finding in the CCA or ICA suggestive of
increased peripheral vascular resistance or a distal vascular occlusion or
high-grade stenosis.
• When PSV is significantly reduced, this appearance has been described as a
“knocking” waveform pattern.
• Bilateral high-resistance waveform patterns in the ICAs may indicate
increased intracranial pressure, diffuse intracerebral vasospasm, or arteritis

51. Abnormal Waveform Patterns Involving the Entire
Cardiac Cycle
1) Carotid Dissection:
In patients with carotid dissection, an echogenic intraluminal flap may
be observed on longitudinal or transverse gray-scale images .
The spectral Doppler waveform pattern is highly variable, probably
related to the length of the dissection, diameter of the lumen,
fenestration of the dissection flap, coexisting involvement of aortic
dissection, and whether the true or false lumen is sampled

53. 2) Carotid Pseudoaneurysm:
• occur most commonly in the CCAs as a result of inadvertent needle sticks
during attempts to place an internal jugular central line.
• May also occur in the setting of other forms of penetrating trauma (including
drug abuse), blunt trauma, infection, cystic medial necrosis, invasion of the
carotid artery by malignant neoplasm, and after carotid endarterectomy.
• On gray-scale and color Doppler imaging, pseudoaneurysms are easily
recognized as an outpouching from the carotid artery.

54. 50-YEAR-OLD MAN WITH NECK SWELLING AFTER PLACEMENT OF A CENTRAL LINE
REPRESENTING A LARGELY THROMBOSED PSEUDOANEURYSM

55. 3) Arteriovenous Fistula:
Arteriovenous fistulas involving the carotid arteries typically occur secondary to
trauma or malignant invasion.
Color Doppler interrogation may demonstrate the connection between the
artery and the vein.
Color aliasing due to high-velocity flow within the arteriovenous fistula may be
observed, and a color bruit due to tissue reverberation secondary to the high-
velocity flow may be seen in the surrounding soft tissues.

56. 46-YEAR-OLD WOMAN WITH RIGHT UPPER EXTREMITY SWELLING AFTER
ATTEMPTED CENTRAL LINE PLACEMENT

57. CONCLUSION
• Highly accurate, readily accessible, inexpensive, and noninvasive method of
diagnosis of high-grade (>70%) stenosis of the ICA.
• Provide morphologic information similar to an angiogram unless the image is
degraded by shadowing from calcified plaque.
• Important for identification of hypoechoic or irregular plaque, which is believed to
progress more rapidly and to pose an increased risk of thromboembolic events.
• To avoid pitfalls in the estimation of ICA stenoses, PSV criteria should always be
correlated with the gray-scale images and analysis of the spectral waveforms

58. THANK YOU