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Vertebral Ultrasound:A Window to the Great Vessels

Mindy M. Horrow MD, FACR, FSRU, FAIUM

Vice Chairman Einstein Medical Center, Philadelphia PA

Professor of Radiology Sidney Kimmel Medical School, TJU

May 15, 2019

Course Objectives

1. Identify the anatomy of the vertebral arterial

circulation

2. Describe the spectrum of subclavian steal

syndrome

3. Describe the findings in the vertebral artery and

carotid circulation which indicate

brachiocephalic disease

I have no personal disclosures

Outline

• Vertebral artery

• Normal anatomy and variations

• Waveforms and velocities

• High resistance

• Parvus tardus

• Subclavian Steal

• Complete

• Partial/pre

• Brachiocephalic Disease

• Occlusion

• Stenosis

VV

Basilar

Subclavian

Subclavian

Brachiocephalic

CCA

ICA

CCA

ICA

Vertebral Artery Anatomy

• First branch of subclavian artery, in 6% may arise

directly from aortic arch

• Extends from origin (v1) to entry into transverse

foramen of C6 (v2), passing through to exit C1

(v3) to foramen magnum. Intracranial portion (v4)

gives rise to PICA then joins with contralateral VA

to form basilar artery

• Variations: hypoplastic, terminates in PICA, left

VA dominant in 50 – 60%

Doppler of Normal VA

• Routinely imaged between

vertebral foramina during

carotid US studies in 95%

• Origins imaged as needed

– Right visualized 92%, left

86%

• Low resistance monophasic

vessel (mean RI= .69),

waveform similar to ICA

• Average peak systolic/diastolic

velocities 56/17 cm/sec

Intrinsic VA DiseaseClinical Issues

• Posterior circulation strokes account for

approximately 1/5 all ischemic strokes

• High frequency of subsequent strokes with

higher mortality than those associated with

carotid disease

• Treatment most commonly is medical

• Surgical and endovascular strategies becoming

more common making detection of disease

more important

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Intrinsic VA DiseaseImaging

• Proximal stenoses: usually at origin – Inferred by parvus tardus waveforms

• Distal disease– Inferred by high resistance waveform (may also occur

with hypoplastic vessel, VA terminating in PICA)

• Other

– Dissection

• Absent or low velocity, sensitive but not specific

– Fibromuscular dysplasia

Proximal Vertebral Artery

Stenosis

• Accepted standard not established

– Peak systolic ratio V1/V2 > 2.2 had sensitivity

and specificity of 96 and 89 for ≥ 50%

stenosis

– PSV at origin for 50-69% and 70-99%

stenoses were 182.7±40.4 cm/sec and

280.5±75.9 cm/sec

High grade stenosis at origin

of left vertebral artery

Where is the

lesion?

Normal systolic upstroke

and direction

Parvus tardus waveform

Turbulent flow with spectral broadening

Bilateral vertebral artery

stenoses at origin

Where is the

lesion?

Turbulent flow with

spectral broadening

Bilaterally

Parvus tardus waveform Parvus tardus waveform

High Resistance Vertebral Artery

• Study of 79 patients with correlative

angiographic imaging

• Total 90 high resistance waveforms

• 18.9 % normal

• 38.9 % distal stenosis or occlusion

• 35.6 % congenitally diminutive

• 6.7 % other (tortuosity, FMD, basilar artery

hypoplasia)

Occluded left distal vertebral artery

Left cerebellar infarct

Where is the

lesion?

Normal systolic upstroke

and direction

Brisk systolic upstroke

but no forward diastolic flow

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Hypoplastic Left Vertebral Artery

Where is the

lesion?

Normal systolic upstroke

and direction

Brisk systolic upstroke

but no forward diastolic flow

Right vertebral artery Left ICA

Fibromuscular Dysplasia

Diagnosis?

Lobulated vessel surface contour

Subclavian Steal

• Secondary to occlusion or near occlusion of

subclavian artery proximal to VA origin with

retrograde flow via contralateral antegrade VA

through basilar artery

• First described in 1961

• Causes: atherosclerosis, trauma, embolic,

inflammatory, ipsilateral hemodialysis graft

• Most common clinical finding: diminished BP

and pulses, vertebral-basilar insufficiency with

arm exerciseLeft Subclavian Steal

LVARVA

Where is the

lesion?

Opposing

direction of flow in

the CCA and LVA

Normal systolic upstroke

and direction

Normal systolic upstroke but

reversed direction

Low velocity parvus tardus waveforms Normal waveforms

Comparison of distal subclavian

arteries in same patient

Delayed phase aortic arch

injection

CTA

Subclavian artery occlusionproximal to vertebral artery origin

★

★

★

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Right Subclavian Steal

Antegrade flow in the Rt CCARetrograde flow in the Rt Vert

Where is the

lesion?

Left Subclavian

Stenosis distal to LVA

History: Lower BP left arm

Antegrade flow in the Lt. Vert a.

High velocity, high resistance

flow in the Lt. subclavian a.

Where is the

lesion?

Partial Steal Physiology

• Transient sharp deceleration in velocity in

mid/late systole

• Due to subclavian artery stenosis

• Typically progresses to more severe level with

induced hyperemia (may be induced by blood pressure

cuff compression/decompression)

• 4 types: nadir of systolic notch• > end diastole

• = end diastole

• = baseline

• Below baseline

Partial Steal Imaging

“Bunny”waveforms

Increasing

subclavian

stenosis

Partial Steal Physiology

1. Antegrade flow in ipsilateral VA in early systole

2. Systolic velocity rises, pressure gradient across

subclavian stenosis becomes hemodynamically

significant

3. Pressure in arm distal to subclavian stenosis becomes

lower than pressure in VA with resulting deceleration

and reversal of systolic flow in VA

4. In diastole velocity across subclavian stenosis is low,

gradient disappears, normal antegrade flow re-

established

Partial Steal: Left

Subclavian StenosisWhere is the lesion?

Early Systole: Antegrade flow

Late Systole: Retrograde flow

Diastole: Antegrade flow

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After L Subclavian artery angioplasty,

LVA waveform returns to normal

Pre Steal:

Left Subclavian Stenosis

Patient pre-op for CABG surgery with

decreased pulses left arm and history of

left subclavian artery stent

Early Systole: Antegrade Flow in VA

Mid/Late Systole: Pressure is SCA drops with

deceleration of flow in VA

Diastole: Return of Antegrade flow in VAWhere is the lesion?

Initial angiogram Post angioplasty

Repeat Doppler with near normal waveforms

Stenosis Stenosis relieved

Pre-steal waveform L vertebral2º mild L subclavian stenosis

Partial Steal: Right

Subclavian Stenosis

RCCA

Where is the

lesion?

“Bunny” waveform

Normal waveform

High resistance waveform

Recurrent left subclavian stenosis reflected in

subtle changes of vertebral artery waveform

Left subclavian steal

Post

stent

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Clinical Importance of Steal

Physiology in pre-CABG patients

• Small study of 13 patients showed 7 (54%) with abnormal flow in internal mammary artery ipsilateral to a VA with some degree of reversed flow

• With completely reversed VA flow, internal mammary artery always showed some degree of abnormality

• In patients with in situ internal mammary grafts can result in coronary – subclavian steal syndrome

Pre-op study before CABG surgery

Right subclavian partial steal causes parvus tardus

waveform in right IMA

Only use left IMA for bypass

Normal Waveform

Normal Waveform

“Bunny” Waveform

Parvus tardus waveform

Where is the lesion?

Innominate Disease

• Severe stenosis or occlusion of

innominate can cause steal physiology in

RVA, but will also effect carotid circulation

• Carotid vessels: decreased velocities,

( LCCA/RCCA ), mid-systolic

deceleration, parvus tardus.

• Variations in Doppler abnormalities may

reflect type and extent of collateral

pathwaysBrachiocephalic

Occlusion

Where is the

lesion?

Reversed flow

Parvus tardus

Brachiocephalic

StenosisStenosis confirmed on

angiogram

Where is the

lesion?

Normal flow in left CCA and VA

Parvus tardus in Rt CCA, VA and SA

References

• Bendick PJ et al. Evaluation of the vertebral arteries with duplex sonography. J Vasc Surg1986; 3:523-530

• Chen SP et al. Bidirectional flow in VA not always indicative of steal phenomenon. JUM 2013; 32: 1945-50

• Colquhoun. I et al. The assessment of carotid and vertebral arteries. Br J Radiol 1992;65:1069-74

• De Bray JM et al. Accuracy of color-Doppler in quantification of proximal vertebral artery stenoses. Cerebrovasc

Dis 2001; 11:335-50

• Grant EG, et al. Innominate artery occlusive disease: sonogroaphic findings. AJR 2006; 186: 394-400

• Hua Y et al. Color Doppler imaging evaluation of proximal vertebral artery stenosis. AJR 2009; 193: 1434-8

• Horrow MM, Stassi J. Pictorial Essay: Sonography of the vertebral arteries. AJR 2001;177:53-59

• Kim ES et al. High Resistive Vertebral artery Doppler waveform. JUM 2010; 29: 1161-65

• Kliewer MA , Hertzberg BS, et al. Vertebral artery Doppler waveform changes indicating subclavian steal

physiology AJR 2000; 174: 815-9

• Kotval PS. Doppler waveform parvus and tardus. A sign of proximal flow obstruction. JUM 1989; 8: 697-700

• Kotval PA et al. Doppler Dx of partial vertebral/subclavian steals convertible to full steals with physiologic

maneuvers.JUM 1990; 9: 207-13

• Lu CJ et al. Imaging I diagnosis and follow-up vertebral artery dissection. JUM 2000; 19: 263-70

• Ozbek SS et al. Hemodynamic disorders in internal thoracic artery. JUM 1998; 17: 147

• Reivich M, et al. Reversal of blood flow through the vertebral artery and its effect on cerebral circulation. NEJM

1961: 265: 878-885

• Tay KY et al. Imaging the vertebral artery. Eur Radiol 2005; 15:1329-43

• Trattnig S, et al. Color-coded Doppler imaging of normal vertebral arteries. Stroke 1990; 21:1222-5

• Vicenzini E et al. Extracranial and intracranial Sonographic findings in VA Diseases. JUM 2010; 29:1811-13

• Yip PK et al. Subclavian steal phenomenon: correlation between duplex sonographic and angiographic findings.

Neuroradiology 1992; 34: 279-282

• Yudakul M et al. Doppler Criteria for Proximal Vertebral Artery Stenosis of 50% of More. JUM 2011; 30: 163-8

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SAM Questions

What normal anatomic feature allows for the

subclavian steal phenomenon to occur?

a. Bovine type aortic arch

b. Intact circle of Willis

c. Basilar artery formed from vertebral arteries

d. Right aortic arch

What normal anatomic feature allows for the

subclavian steal phenomenon to occur?

a. Bovine type aortic arch

b. Intact circle of Willis

c. Basilar artery formed from vertebral arteries

d. Right aortic arch

The combination of reversed flow in the right

vertebral artery and parvus tardus flow in the right

common and internal carotid arteries suggests

disease in which artery?

a. Middle cerebral

b. Right subclavian

c. Basilar

d. Brachiocephalic

The combination of reversed flow in the right

vertebral artery and parvus tardus flow in the right

common and internal carotid arteries suggests

disease in which artery?

a. Middle cerebral

b. Right subclavian

c. Basilar

d. Brachiocephalic