Carotid Stenosis Flashcards
What normal flow abnormality can be found in the carotid bulb?
Why?
Flow reversal
Related to diameter and angle of branch vessels
Which vessel has highest diastolic component on doppler? Highest pulsatility during systole and diastole and why?
ICA
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?
60-90cm/sec
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?
80-115 cm/sec
What are normal peak systolic velocities in the ICA?
usually <100 cm/sec
What things can cause elevated flow velocities? (4)
Stenosis
kinking, coiling
elevated CO
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?
> 0.9mm
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
VICA/VCCA
end-diastolic velocity
What can cause unexpected readings of the PSV?
low CO hypertension tandem lesions contra occlusion tortuous vessel
What can alter readings of VICA/VCCA?
external or bulb disease
At what degree of stenosis do Doppler values begin to become abnormal?
50%
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?
same
What is the incidence of stroke for a nearly occluded ICA?
11%/year
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
