Lecture 5: Carotid Artery Duplex Imaging Flashcards
patient history that can indicate a carotid artery scan? (6)
- neurological symptoms
- myocardial infarction
- HTN
- diabetes
- smoking
- vascular surgeries
3 scanning positions when scanning carotid
- anterolateral
- lateral
- posterolateral
the CCA waveform has elements of both ___ & ___
ICA & ECA
what is interpretive criteria for carotid stenosis primarily based on?
velocities taken with PW Doppler waveform & waveform analysis
this vessel is low resistance, has continuous forward flow, and no branches in the cervical region
ICA
this vessel is high resistance, contains branches in the cervical portion, and responds to the temporal tap
ECA
at the posterolateral approach, which branch of the CCA is in the near field and which is in the far field?
ICA is in the near field; ECA in far field
this waveform has elements of both ICA & ECA with a sharp upstroke, moderate diastolic flow, and a well-defined dicrotic notch
CCA waveform
the waveform of this branch of the carotid is low resistance with broad systolic peaks, substantial diastolic flow, and a dicrotic notch that isn’t well visualized
ICA waveform
what is the typical range for PSV for the ICA?
54-88 cm/sec
what is considered the abnormal PSV for the ICA?
> 100cm/sec
MAX FOR NL <125cm/sec
the waveform for this branch of the CCA is high resistance with a sharp systolic upstroke, little flow in diastole, and a well-visualized dicrotic notch
ECA waveform
what is the normal range for PSV in the ECA?
77-115 cm/sec
MAX FOR NL <125cm/sec
how does plaque formation start?
lipids start infiltrating the tunica intima
progressive accumulation of plaque affects which layers of the arterial walls?
initially affects intima; later intima & media
what 3 types of deposits can be found with progressive build up of plaque?
- fibrotic material
- hemorrhagic products
- calcifications
how does fibrotic material in plaque show up on ultrasound?
hyperechoic but without shadowing
how do hemorrhagic products in plaque show up on ultrasound?
depends on age of the blood
how do calcifications in plaque show up on ultrasound?
hyperechoic with shadowing
which type of plaque presents with more risk: smooth or irregular?
irregular
another name for irregular plaque?
ulcerated plaque
why is there an increased risk for ulcerated plaque?
there is an increased chance of rupture & erosion of intima
what happens if there is an erosion of the intima?
it can break off and be swept away into the brain, leading to a stroke
which type of plaque echogenicity is less cellular in content?
low level echogenicity
what risk does low level echogenic plaque pose?
there’s an increased risk for ulceration with cerebral ischemic symptoms
which type of plaque echogenicity contains fibrous plaque with collagen?
medium level echogenicity
medium level plaque echogenicity poses less risk for cerebral ischemic symptoms if plaque is ____
homogenous
why does high level echogenic plaque pose less risk for cerebral ischemic symptoms?
plaque is calcified and attached very well to the arterial wall
a normal spectral waveform has a ___ range of velocities in systole & diastole
narrow
a normal spectral waveform has an ___ spectral window
open
PSV of normal spectral waveforms are ___
< 125 cm/sec
what is the percentage of diameter reduction for a hemodynamically significant stenosis?
50-60% diameter reduction
a ___ diameter reduction correlates with __ area reduction
50% DR; 75% AR
what happens to PSV & EDV when there is a 50-60% DR?
both increase
the pre-stenotic area is considered the area distal to stenosis. T/F?
false; it’s the area proximal to stenosis
is PSV of a pre-stenotic area normal or abnormal?
normal
at the stenotic site, what happens to PSV & EDV?
both velocities increase
spectral broadening doesn’t occur at the stenotic site. T/F?
false; it does occur
what happens to PSV & EDV at the post-stenotic site?
both velocities decrease
what type of flow can you expect to see at the post-stenotic site?
turbulent
what 3 factors influence carotid velocities?
- cardiac output
- blood pressure
- obstruction in contralateral CCA
what is cardiac output?
the amount of blood the left ventricle is ejecting per minute
how do you calculate the diameter reduction of a stenosis?
go in transverse
DR % = (residual lumen/original lumen)(100)
6 categories of stenotic disease?
- normal
- mild
- moderate
- moderately severe
- severe
- totally occluded
PSV of a normal carotid?
< 125 cm/sec
what % is considered mild stenosis?
1-15%
PSV, EDV, and sonic window of mild stenosis?
PSV <125 cm/sec
EDV slightly increased
sonic window open
what % is considered moderate stenosis?
16-49%
PSV and sonic window of moderate stenosis?
PSV <125 cm/sec
sonic window may or may not be open
what is normal ICA/CCA ratio?
< 1.5
ICA/CCA ratio of moderate stenosis?
normal <1.5
what % is considered moderately severe stenosis?
49-80%
PSV of moderately severe stenosis?
> 125 cm/sec
EDV of moderately severe stenosis?
increase but < 105 cm/sec
sonic window of moderately severe stenosis?
spectral broadening & window filling
ICA/CCA ratio of moderately severe stenosis?
2.0+
what % is considered severe stenosis?
80-99%
PSV of severe stenosis?
80% stenosis = 250+ cm/sec
99% stenosis = 400 cm/sec
EDV of severe stensois?
> 110 cm/sec
ICA/CCA ratio of severe stenosis?
5.6+
how should you adjust PRF to look for trickle flow/string sign in severe stenosis?
lower PRF/scale to increase sensitivity
how should you adjust wall filter to look for string sign in severe stenosis?
lower wall filter
how should you adjust doppler gain to look for trickle flow in severe stenosis?
increase doppler gain
how should you adjust sample size to look for trickle flow in severe stenosis?
increase sample size
where should you image in ICA to prove flow with severe stenosis?
go as distal as possible
use ___ doppler to search for trickle flow in severe stenosis
power doppler
how can systole & diastole appear in the CCA with total occlusion?
systole is shorter with rounded peak
diastole has no flow
the CCA waveform with severe proximal stenosis will have a ___ systolic component
dampened
the CCA waveform with severe proximal stenosis will have ___ flow in diastole
forward
the CCA waveform with severe proximal stenosis will have ___ pulsatility
decreased
the CCA waveform with severe distal stenosis will have a ___ systolic portion
blunted
the CCA waveform with severe distal stenosis will have a ___ diastole
absent or decreased
