DISCLOSURES Advanced Carotid US

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Advanced Carotid US

Interpretation

Leslie M. Scoutt, MD, FACR, FSRU, FAIUMProf of Diagnostic Radiology , Surgery & Cardiology

Vice Chair, Dept of Radiology & Biomedical Imaging

Medical Director, Non-Inv asiv e Vascular Lab

Yale School of Medicine

DISCLOSURES

• Educational consultant for Philips Healthcare

• Will discuss the use of IV US contrast to evaluate plaque, not FDA approved for vascular imaging

OBJECTIVES

• Understand the pathophysiology of stroke

– most strokes are embolic

– 20% due to disease at the carotid bifurcation

– begin by evaluating the plaque

OBJECTIVES

• While the chart is important…..

• Know when the charts don’t work– tortuous vessels, contralateral stenoses/occlusions

– tandem, long segment, near occlusive lesions

– high and low output states

– post intervention

• ALWAYS correlate spectral Doppler w/ grayscale, color Doppler, and waveforms– explain any discordance

OBJECTIVES

• Discuss the significance of abnormal carotid waveforms

– tardus parv us w aveform

– high resistance w av eform

VULNERABLE PLAQUE

• Risk of rupture + embolization related to

– v ascularity in plaque

– intra-plaque hemorrhage

– inflammation

– lipid content

– necrotic core

– thinning of fibrous cap

Courtesy Dr Ed Bluth

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STABLE PLAQUE

• Hyalinized, fibrous, calcified plaque

– few er v essels

– less inflammation

– smooth surface

• Less likely to rupture

• Nothing for high velocity jet to knock off and embolize Courtesy Dr Ed Bluth

VULNERABLE PLAQUE:

What can you detect w/ US?

• Hemorrhagic plaque is typically hypoechoic• Irregularly surfaced plaque

– acts as a nidus for platelet aggregation

• The more plaque there is, the more likely it is to be friable

• Both ↑ vascularity and inflammation in plaque may be detectable with IV US contrast

PLAQUE: Echogenicity

• Hemorrhagic plaque is hypoechoic

– esp w orrisome if > 50%


• Extremely hypoechoic plaque may only be seen on color Doppler imaging

– signal v oid


• Hypoechoic plaque is a non-specific finding, esp if homogeneous

– hy alinized, fibrous, fatty plaque


• Extremely hypoechoic homogeneous plaque may represent thrombus/acute hemorrhage

– most unstable or “v ulnerable” plaque of all

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PLAQUE: Surface Characteristics

• Irregular, fissured, undermined, ulcerated

• Often best evaluated with color or power Doppler

PLAQUE: Surface Characteristics

• Ulcers: US findings are non-specific

– histologic rather than morphologic diagnosis

– deeper than 2 mm, confirm in tw o planes

STABLE PLAQUE

• Echogenic, smooth surface

PLAQUE: How Much?

• Large plaques often hemorrhagic

• > 90% stenosis may have ↑ risk of stroke

• Large amount of plaque as assessed by 3D US assoc w/ elevated coronary artery calcium score on cardiac CT

Sillesen, JACC: 2012

PLAQUE: How Much?

• Before you start the spectral Doppler exam

– know w here the plaque is

– hav e a good sense of the degree of stenosis

• Helps guide & Q/A the spectral Doppler exam

– spectral Doppler findings should be concordant w ith amount

of plaque

Q/A DOPPLER EXAM

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• Good for evaluation of plaque burden

– ov erestimate % stenosis c/w NASCET criteria

• Confirm findings on sagittal images

– make sure y ou are not off center, esp

if plaque is irregular

• Consider TRV cine clip of bulb

TRANSVERSE IMAGES TRANSVERSE IMAGES

• Incorrect gain– too low – plaque w ill look falsely hy poechoic

– too high – w ill miss hy poechoic areas

PLAQUE: Pitfalls PLAQUE: Pitfalls

• Color blooming may obscure plaque and underestimate stenosis

• Feinstein et al, J Am Coll Card: 2006

– early phase IV contrast enhanced US identified surface

ulcers and plaque neov ascularity

• Coli et al, J Am Coll Card: 2008

– CE of plaque correlated w / histologic density of

neov essels and hy poechoic plaque

• Giannoni et al, Eu J Vasc Endovasc Surg: 2008

– CE of plaque correlated w / Sx (acute neurologic ev ent)

PLAQUE: Vascularity

Copy right ©2006 Am eric an Col lege of Card io logy Foundation. Res tric tions m ay apply.

Feinstein et al, J Am Coll Cardiol

2006; 48: 236-243

Unenhanced (A) & contrast enhanced (B) US images of the carotid artery

Ulceration only seen on CE

image

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Feinstein et al, J Am Coll Cardiol 2006; 48: 236-243


Photomicrograph: ↑ number of endothelial cells in carotid plaque

Feinstein et al, J Am Coll Cardiol 2006; 48: 236-243

• Microbubbles adhere to damaged epithelium and taken up by inflammatory cells

– monocy tes, macrophages

• Owen et al, Radiology: 2010

– ↑ late phase CE of plaque correlated w / Sx and

hy poechoic plaque

– believ e they are identify ing inflammatory plaque

PLAQUE: Inflammation

Non-CE image: Carotid lumen (white arrowhead), Carotid plaque (green arrowhead)

©2010 by Radio log ic a l Soc iety of North Am eric a

Owen DR et al, Radiology 2010; 255: 638-644

Late-phase CE image shows a lower density of contrast agent microbubbles in

the carotid lumen (white arrowhead) compared with that inside the carotid

plaque (green arrowhead)

Owen DR et al, Radiology 2010; 255: 638-644©2010 by Radio log ic a l Soc iety of North Am eric a

• Has been accepted as a good measure of CVD risk

• However, the jury is still out….

• New studies suggest that IMT assessment w/ US does not improve CVD risk stratification enough to be clinically significant

• Current thought is that MR might be better

– includes assessment of adv ential lay er and v asa v asorum

INTIMA-MEDIA THICKNESS

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WHY DO WE GRADE CAROTID STENOSES?

• Patients with carotid stenosis derive a clear benefit, ↓ incidence of stroke, from carotid endarterectomy (CEA)– North American Sy mptomatic CEA Trial

(NASCET, 1991)

– Asy mptomatic Carotid Atherosclerosis Study (ACAS, 1995)

– European Carotid Surgery Trial (ECST, 1991)

– Asy mptomatic Carotid Surgery Trial (ACST, 2004)

SRU 2002 CONSENSUS CONFERENCE

Grant et al, Radiology: 2003

DISCORDANCE BTWN GRAYSCALE

& DOPPLER FINDINGS

• PSV elevated

• But no plaque!

– tortuous v essel

– contralateral occlusion/stenosis

TORTUOUS VESSEL

PSV = 163 cm/s

50-69% stenosis?

TORTUOUS VESSEL

• Velocity increases around a curve

• Difficult to assign correct Doppler angle as direction of blood flow changes rapidly

CONTRALATERAL HI-GRADE

STENOSIS/OCCLUSION

PSV = 260 cm/s< 50% stenosis

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CONTRALATERAL HI-GRADE

STENOSIS/OCCLUSION

• ↑ PSV in CCA and ICA, esp at a stenosis

• Variable, unpredictable

• Correlation ↓ as contralateral stenosis ↑

• Use of PSVR may not compensate, but probably better than using PSV alone

Beckett, AJNR: 1990

AbuRahma, J Vasc Surg: 1995

Busuttil, Am J Surg: 1996

DISCORDANCE BTWN GRAYSCALE &

DOPPLER FINDINGS

• Plaque – LOTS!

• But velocity not as elevated as one would expect

– tandem lesions

– long segment stenosis

– > 95% stenosis

TANDEM LESIONS

• PSV < expected for a given % stenosis

LONG SEGMENT STENOSIS

LONG SEGMENT STENOSIS

• If plaque extends over more than 2 cm

– PSV w ill , diastolic v elocity usu remains high

• Likely due to increased in-flow resistance

– proportional to length of stenosis

TIGHT STENOSIS

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Spencer and Reid, Stroke: 1979

CLUES TO A TIGHT STENOSIS

• diameter of lumen on grayscale and/or color images

• “Knocking”, “Thump”, or “Staccato” waveform proximally

• Tardus parvus waveform distally

TIGHT STENOSIS

Proximal CCA Distal ICA

TARDUS PARVUS WAVEFORM

• Delayed systolic upstroke

• Decreased PSV

• Rounded systolic peak

• Occurs distal to a high grade stenosis

• Pattern of distribution can help localize stenosis

• Rt CCA, Lt CCA & both VAs


• Note: ↓ PSV

• Seen in SEVERE Aortic Stenosis


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TP in Rt CCA & ICA, Reversed flow Rt VA

Normal sharp upstroke in Lt CCA

Stenosis of Innominate Artery

TP in Lt CCA & Lt ICASharp upstroke on Rt and in both VAs

Stenosis at Origin of Lt CCA

• Low PSV

• Decreased, absent or reversed diastolic flow

• Occurs prox imal to an occlusion or high grade stenosis

“KNOCKING” WAVEFORM

• Asymmetry of Rt & Lt CCA waveforms

• ↓ diastolic flow in Lt CCA

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• More pronounced in Lt ICA↓ PSV & EDV: RT CCA

↓ PSV & EDV: RT ICA RT MCA OCCLUSION

BILATERAL ↓ PSV & EDV in ICAs INCREASED INTRACRANIAL PRESSURE

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74 YO FEMALE W/ STROKE BILATERAL DISTAL OCCLUSIONS

BILATERAL ↓ EDV in CCAs

• ↑ PSV

Severe Aortic Regurgitation

WATER HAMMER PULSE

• Severe aortic regurgitation

–sharp systolic upstroke

–normal to PSV

– reversed diastolic flow

–bilateral

–waveform normalizes distally

CCA PSV < 60 cm/s

• Low output states

– ↓ ejection fraction

cardiomyopathies, LV dysfunction, LV aneurysm, AS

– hy potension

– thoracic aortic aneury sm

LOW CARDIAC OUTPUT

• PSV in CCA = 35 cm/s

• When ICA PSV = 230 cm/s, PSVR will be > 6.5

• Relying on PSV will result in underestimation of ICA stenosis

• Grayscale, color Doppler, PSVR more reliable EF = 15%

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CCA PSV > 100 cm/s

• High output states

– hy pertension

– hy perdy namic state

– aortic regurgitation

– thy rotox icosis

HIGH CARDIAC OUTPUT

• PSV will overestimate % stenosis

• Grayscale, color Doppler & PSVR more reliable

INTRA-AORTIC BALLOON PUMP

• Inflation of balloon causes 2nd peak of forw ard flow during

early diastole

• Flow rev ersal at end of diastole corresponds to deflation of

balloon



• PSV Lt ICA = 222 cm/s, but PSVR only 2.2

• What % stenosis?


• Choose 1st OR 2nd peak to measure PSV and be consistent

• PSVR may be a better Doppler criterion

• Look at grayscale and color Doppler

• May have to turn balloon off or decrease firing ratio

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WEANING FROM IABP (1:2) LEFT VENTRICULAR ASSIST DEVICE

• Rx of severe heart failure, refractory to medical management

– bridge to my ocardial recov ery or cardiac transplantation

– final Rx for pts w ho are not candidates for cardiac transplant

• Blood diverted from Lt ventricular apex and propelled via pump through Dacron graft into aorta

LVAD

• Marked tardus parvus waveforms in all vessels

• ↓ PSV

– av erage = 32 cm/s

• Monophasic flow – no flow below the baseline

– rarely , nonpulsatile monophasic w av eform w /o perceptible

sy stolic peak

• Similar waveforms in subclavian, mesenteric, femoral arteries

LVAD: US Findings

Cervini, US Quarterly: 2010

LVAD

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CONCLUSIONS

• Ev aluate plaque carefully

• Hy poechoic, irregularly surfaced plaque ↑ risk for

cerebrov ascular ev ents & more rapid progression

• Estimate % stenosis on gray scale and color Doppler before

the spectral Doppler ex am

– large plaques more often hemorrhagic and friable

– will help you interpret the PSV measurements & Q/A exam

• New techniques: CE, elastography, arterial w all stiffness,

v ector flow

• Standard charts don’t work for

- tortuous v essels, contralateral stenosis/occlusion

- tandem, long segment, near occlusiv e lesions

- high or low output states

- s/p interv ention

• ALWAYS correlate velocity measurements w/

grayscale/color Doppler images & waveforms

CONCLUSIONS CONCLUSIONS

• Waveforms should be symmetric Rt to Lt

• “Knocking” waveform pattern– distal occlusion/high grade stenosis

• Bilateral ↓ EDV but normal to ↑ PSV → AR• Tardus Parvus Waveform

– consider prox imal stenosis

– distribution w ill tell y ou w here bilateral, all v essels → severe AS

CONCLUSIONS

• Use a pattern recognition approach for complex waveform patterns

– often due to iatrogenic conditions

– w av eforms frequently bizarre, quite v ariable

– correlate w / gray scale and color Doppler imaging

DOPPLER CRITERIA

• Whatever criteria you choose,

– the closer y ou are to the cut off v alue, the more likely y ou

are to be w rong

– the farther aw ay you are, the more likely y ou are to be right

• F+ vs F- dependent on sens vs. spec of cut off value

• Consider correlative imaging if close to discriminatory thresholds

• As management algorithms change, so must the chart

Documents

DISCLOSURES Advanced Carotid US