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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