Flashcards in Carotid Stenosis Deck (44):
What normal flow abnormality can be found in the carotid bulb?
Related to diameter and angle of branch vessels
Which vessel has highest diastolic component on doppler? Highest pulsatility during systole and diastole and why?
ECA, due to reflect waves from branches
What are normal blood flow velocities in the ICA in >60yo? How does it changes in younger patients?
higher likely due to increased CO
How much does blood flow change between mid CCA and CCA near bifurcation? Where should peak CCA systolic velocity be measured?
It increases by 10-20cm/sec
2-4cm below the bulb
What are normal flow velocities in the ECA?
What are normal peak systolic velocities in the ICA?
usually <100 cm/sec
What things can cause elevated flow velocities? (4)
technical error (transducer error)
What features distinguish ICA from ECA? (6)
ICA usually bigger
ICA branches rare
ICA proceeds deep and post towards mastoid (ECA anteriorly)
ICA low resistance
ECA, oscillations with temporal tap
ICA less color variation from diastole to systole (ECA flickers)
What is normal intima-media thickness formula?
(0.009 x age in years) + 0.116
What is usually considered abnormal intima-media thickness?
What is the international classification for carotid plaque?
type I uniformly sonolucent (>90%)
type 2 predominantly sonolucent (>50%)
type 3 predominantly echogenic (>50%)
type 4 uniformly echogenic
type 5 unclassified (poor visualization)
What method of measuring stenosis did ECST use?
(residual lumen d - original lumen d)/ original lumen d *100%
What method of measuring stenosis did ACAS/NASCET use?
(residual lumen d - lumen d normal distal)/lumen d normal distal * 100%
What parameters can characterize ICA stenosis? (3)
peak systolic velocity
What can cause unexpected readings of the PSV?
What can alter readings of VICA/VCCA?
external or bulb disease
At what degree of stenosis do Doppler values begin to become abnormal?
What is the Washington criteria?
normal ICA PSV 125 EDV 125 EDV >140
For the SRU consensus, what cutoff values are use for PSV and ratio in carotid stenosis?
50-69% PSV 125-230, EDV 40-100, ratio 2-4
>70% to near occlusion PSV >230, EDV >100, ratio >4
near occlusion high/low/undectec
What is the incidence of stroke for an occluded ICA compared to gen pop?
What is the incidence of stroke for a nearly occluded ICA?
What are features of near occlusion on US?
distal ICA small beyond stenosis
ICA smaller then ECA
What is the issue with NASCET measurement of ICA stenosis?
because the distal ICA gets smaller in near occlusion the nascet method no longer applies.
What are features of carotid occlusion on doppler?
hypoechoic/anechoic region that occupies entire lumen
no spectral, color or power dopple in lumen
occluded vessel may not be identifiable
externalization of the CCA
What is CCA externalization?
when the CCA flow pattern resembles ECA when the ICA is occluded. may not occur if ECA is serving as a large collateral.
What features on doppler indicate siphon or distal ICA occlusion?
absent diastolic flow in ICA
What scenarios can eliminate diastolic flow in the ICA
distal lesion, increase ICP, ICA dissection
How should ICA with string sign be managed?
string signs are associated with diffuse stenosis and there may not be a lesion to endarterectomize. Ligation may be the best management if causing stroke/TIA.
What are issues with measuring CCA stenosis?
PSV is variable along the CCA
How to measure CCA stenosis?
doubling of PSV to indicat4ee moderate stenosis
quad for severe >70%
How to measure origin CCA stenosis?
difficult as not visualized
ipsi/contra ratio normal 0.7-1.3
parvus tardus waveform
Stenosis of the innominate artery can cause symptoms related distributions?
anterior circulation (stroke/TIA)
posterior circulation (cerebellar, brainstem strokes, dizziness)
What % of arch dissection include carotid arteries?
What % of carotid dissection resolve spontaneously? suffer disabling neuro? fatal?
What features does carotid dissection have on US?
long tapering stenosis
occluded artery with no calcified lesion
duplication of the carotid color flow
What features do you need to report on when assessing a carotid dissection with US?
flow direction in false lumen
What features are important to assess when examining a pseudoaneurysm with US
size and location
to and fro in the neck (confirm its a pseudoaneurysm)
length and d of neck
proportion of flow/thrombosis in pseudoaneurysm
What is the most common site for AV fistula?
What are clinical findings of AVF in carotid?
palpable or audible thrill
dilated, hyperdynamic draining vein
What can be the consequence of large AVF?
high output cardiac failure
What are US features of AVF carotid?
turbulent, pulsatile flow in jugular vein
high velocity jet between the two structures
What size and location of carotid body tumor?
1-1.5cm in adventitia at carotid bifurcation
What are US features of carotid body tumors?
can encase ECO or ICA