Ch 11 Extracranial Duplex Flashcards
What is a bruit?
-An abnormal “blowing” or “swishing” sound heard with a stethoscope while auscultating over an artery
-Due to vibrations transmitted through a stenotic artery
(bruits are a sign of arterial disease, although not all stenoses have bruits)
Where are baroreceptors assisting in reflex BP control located?
In the carotid bulb
Primary goal of performing a carotid exam?
To identify pt’s who are at risk for stroke due to atherosclerosis
Treatment for atherosclerosis?
-Carotid endarterectomy (CEA)
-Stenting
-Aggressive medical management of modifiable RFs
Secondary goal of performing a carotid exam?
To document progressive disease in pt’s who are already known to be at risk or have recurrent stenosis after intervention
List major indications for a duplex scan of the carotid + vertebral arteries?
-Asymptomatic neck bruit
-Hemispheric cerebral or ocular TIAs
-History of stroke
-Screening prior to major cardiac, vascular, or other srugery
-Follow up after carotid endarterectomy or stenting
List 3 symptoms of cerebrovascular disease?
-Emboli (travels to brain)
-Reduction of flow, due to high grade stenoses (stenosis in ICA does not typically cause symptoms due to circle of willis)
-Arterial thrombosis (carotid artery thrombosis is rare)
How long do symptoms from a TIA + RIND typically last?
TIA: minutes to a few hours, but NOT longer than 24 hours
RIND: b/w 24-72 hours
List symptoms of a TIA + RIND?
TIA (transient ischemic attack):
-mini stroke
-paralysis or numbness (paresthesia) of face, arm + leg only on 1 side of the body
-difficulty speaking (aphasia)
-symptoms occur on the side of the body OPPOSITE to the affected carotid artery + cerebral hemisphere
RIND (reversible ischemic neurologic deficit):
-same symptoms as a TIA
What is amaurosis fugax?
-TIA of the eye
-Painless temp loss of vision in 1 or both eyes
-Causes transient monocular blindness on the SAME side as the responsible carotid artery
What is a cerebrovascular accident?
-Stroke
-Permanent neurologic deficits
-Vertebrobasilar arterial insufficiency symptoms include dizziness, diplopia + ataxis
-Carotid circulation symptoms include paralysis or paresthesia of face, arm + leg on ONE side of body
Pt’s who had a TIA, RIND or AF are at an increase risk for what?
Stroke
List history questions we should obtain prior to a carotid exam?
-Hypertension
-Hypercholesterolemia (high cholesterol)
-Diabetes
-Heart attack, angina
-Relevant vascular surgery
-TIA’s or CVA’s
-Stroke like symptoms
How far should the pt turn their head away for a carotid exam?
30-45 degrees from midline
(common pitfall: rotating head too far, as this causes the SCM to tighten + make imaging harder)
Where is plaque m/c found?
-CCA bifurcation/bulb (distal CCA)
-Prox ICA
-Prox ECA
What should we set our CD scale to for this exam?
20-40 cm/s
Benefits of using CD + power doppler?
CD: rapid identification of flow disturbances
PD: detecting very low flow velocities, including “string sign” flow
How should we adjust our CD gains in order to know where to sample with PW?
Turn scale up until there is a few pixels of aliasing, this is highest velocity + we want to sample here
How can we perform a temporal tap?
-Palpate the pulse in the superficial artery anterior to the ear, then tap on the artery while insonating flow in the ECA
-An artifact from tapping should appear on waveform (looks like spikes in diastolic flow)
What does flow separation (recirculation) look like in the bulb?
-Small area of flow reversal, typically along the outer wall of the bulb on the opposite side to the flow divider
-No need to sample this, this is normal in the bulb
-As plaque forms + fills in the bulb, the flow separation will disappear
(small area of blue flow, instead of red)
Which part of the ICA is often hard to see + tortuous?
Distal
We must evaluate the distal ICA in pt’s at risk for ___ ___?
Fibromuscular dysplasia
How to angle probe to get the vertebral artery?
Identify CCA then slide/angle probe posteriorly to find it
(it is located b/w the TRV processes of the cervical vertebrae)
An abnormal vertebral artery waveform may indicate what?
Significant stenosis of the ipsilateral (same side) prox subclavian artery
How to angle probe to get the subclavian artery?
Place probe at base of neck + angle inferiorly
(place SVB as proximal as possible, then sweep distally to obtain highest PSV + most laminar waveform)
SF of the intimal-medial + adventitial layer?
Intimal-medial:
-Clearly visible as a thin gray/white line on the innermost part of the wall + is uniform throughout the length of the vessel
Adventitial:
-Visible outside the intimal-medial layer as a brighter white than adjacent tissues
List 3 carotid pathologies?
-Plaque
-Intraluminal defects
-Iatrogenic injury
SF of homogeneous + heterogeneous plaque?
Homo:
-Uniform appearance + low echogenicity
-Be sure gains aren’t set too low
Hetero:
-Mixed + brighter echogenicity
-Shadowing due to areas of calcium
What are intraluminal defects?
-Disruption of intima with blood from the lumen, blood flows b/w the layers of the vessel wall
-Separation of layers is called arterial dissection
What does arterial dissection create?
A second false lumen within the vessel
(reverberation can mimic this, use CD)
Why do intimal dissections occur?
Spontaneously or due to trauma
What is iatrogenic injury?
-Any adverse pt condition that is caused inadvertently by a health care provider during a medical procedure or intervention
-Uncommon
(ex. iatrogenic injury to CCA from catheter interventions or venous line placement)
Why does the CCA typically have a low resistance pattern with forward flow?
B/c 70% of the normal CCA flow passes through the ICA, so it takes on similar characteristics as it
Is flow separation in the bulb normal?
Yes! Occurs along outer wall farthest from the ECCA. The waveform shows flow above + below baseline.
(correlates with min or no plaque in bulb)
How does a normal vertebral artery waveform appear?
-Same as ICA, with a low resistance pattern + forward flow
-Normal PSV is from 30-50 cm/s
How does a normal brachiocephalic artery waveform appear?
Higher resistance flow pattern, it has a triphasic waveform when normal:
-Arm (high resistance)
-Face (high resistance)
-Brain (low resistance)
How would a pre-stenotic waveform appear?
-If there are abundant collateral vessels it may appear normal
-If collateral flow is limited + the stenosis is severe, it will appear high resistance with lower/absent diastolic flow
How would a stenotic waveform appear?
High velocity jet
How would a post-stenotic waveform appear?
-Turbulence will be present distal to the stenosis, causing spectral broadening
-Waveform will be dampened, with decreased flow velocity, delayed acceleration + have a rounded peak (tardus-parvus pattern)
What is the “steal” phenomenon?
-A situation where 1 vascular bed draws blood away/steals from another
-Occurs when 2 runoff beds with different resistances are supplied by a limited source of inflow
What is subclavian steal?
-Severe stenosis of the subclavian artery (or RT BCA) prox to the origin of the vertebral artery
3 stages of a steal waveform?
Stage 1: Latent or Hesitant
-Antegrade flow with a deep flow reversal notch
Stage 2: Alternating or Bidirectional
-When the deep notch extends below the baseline
Stage 3: Complete
-A progressing stenosis where the ratio of antegrade + retrograde flow is altered
or
-A complete steal where the flow is entirely retrograde
How does string flow appear on b-mode, CD + spectral doppler?
B-Mode: extensive plaque, often with shadowing
CD: severely narrowed lumen (power doppler may show small lumen)
Spectral doppler: non-specific. Variable velocity + possibly decreased diastolic flow in ipsilateral CCA
What is the “string sign” or “trickle flow”?
-Low velocity flow with a somewhat resistive waveform
-Occurs before complete occlusion of vessel
-M/c found in a severely diseased ICA where only a small string like lumen remains
How can we differentiate b/w the string sign + complete occlusion?
CT angiography is useful to confirm occlusions
(note: direct intervention is not possible once the ICA has been fully occluded)
What is a choke lesion?
A severe distal CCA obstruction with continued patency of the carotid bifurcation
What happens when there is stenosis in the CCA?
-It will affect the ICA + ECA too
-Flow may reverse in the ECA to help supply the ICA
How does an ICA stenosis waveform appear?
-Highly resistive
-Decreased or no end diastolic flow
-Blunted appearance
How does a stenosis or occlusion in the ICA affect the CCA?
Stenosis: highly resistive + blunted flow in ICA will be reflected in CCA waveform
Occlusion: CCA waveform will take on features of the patent ECA
How does a prox ECA stenosis waveform appear?
-Focal velocity increase
-Post stenotic turbulence, due to spectral broadening
-Dampened waveform distally
Is complete ECA occlusion common?
No, b/c it has multiple branches + abundant collateral pathways
Besides with a stenosis, when would there be a diffuse increase in ECA velocity?
When the ipsilateral ICA is completely occluded (due to collateral pathways via the circle of willis)
How does a vertebral artery stenosis waveform appear?
-Dampened distally
-Delayed acceleration
-Rounded peal
-Post stenotic turbulence
(typically occur at origin of vessel from subclavian)
How would waveforms appear if the pt has a low CO + poor EF?
Dampened with delayed acceleration in every artery, yet no stenosis or turbulence seen
How would waveforms appear if the pt has Ao valvular disease + hypertrophic obstructive cardiomyopathy?
It will have 2 prominent systolic peaks separated by a mid-systolic retraction known as “pulsus bisferiens”
How would waveforms appear if the pt has a cardiac arrhythmia?
Standard velocity criteria may not apply + the waveform contour is altered
How would waveforms appear if the pt has a cardiac assist device?
-Can be unrecognizable as arterial flow
-They are used when pt’s have heart failure (ex. a LVAD + IABP)
How to calculate ICA/CCA ratio?
-Pick the highest PSV from the stenotic site for ICA value
-Pick the PSV in a normal mid-distal CCA segment for the CCA value
In what scenario would the ICA/CCA ratio not be valid?
In presence of significant CCA disease
How can CCA + ECA stenoses be diagnosed?
By a focal increase in PSV followed by post-stenotic turbulence
(PSV of >200 cm/s indicates suspicion for a 50-99% stenosis)
When there is a significant stenosis at the origin of the CCA, the more distal CCA waveforms will appear ___?
Dampened with low PSV + slow systolic acceleration
How can we identify a vertebray artery stenosis of >50%?
- Velocity ratio:
-Max PSV in prox vertebral / PSV in normal distal vertebral = >2.2 - Focal vertebral artery PSV of >150 cm/s
