URR Carotid Disease Flashcards
as area of vessel decreases what happens to velocity?
increases
flow changes direction as it enters and leaves stenosed portion causing what?
turbulence and spectral broadening
most common reason for underestimation is what?
improper sample volume location
what happens in the pre stenotic zone?
-increase resistance and RI
-flow velocity may be dampened with loss of diastolic
-short acceleration time
what happens in the stenotic zone?
-increase PSV
-increase diastolic
-decrease pressure
-spectral broadening
-highest velocity detected within stenosis or just distal
what happens in the post stenotic zone?
-turbulence
-decreased resistance
-increase diastolic
what happens distal to critical ICA stenosis?
-diastolic and systolic flow will be low velocity with blunted waveform
-slow acceleration time
-tardus parvus
normal waveform of CCA?
low resistive
-more than 30 cm/s difference in PSV between rt and lt CCA can indicate issue
CCA with reduced velocity, slow upstroke and holodiastolic flow means what?
stenosis prox
CCA with reduced velocity, quick upstroke and minimal diastolic flow reversal means what?
occlusion distal
CCA with elevated velocity means what?
tortuosity on that side or compensatory flow due to obstruction in other CCA
increased velocity in bilat CCAs means what?
-overestimated carotid stenosis
-systemic HTN
-increased cardiac output
-decreased hematocrit
-mild to moderate AO stenosis
decreased velocity in bilat CCAs means what?
-underestimated carotid stenosis
-CHF
-decreased cardiac ejection fraction\
-severe AO valve stenosis
-increased hematocrit
-polycythemia vera
bilat CCA with increased diastolic flow reversal can indicate what?
significant Ao valv regurg
intra AO balloon pump (IABP)
-have 2 systolic peaks
-1st peak = lt vent contraction
-2nd peak = balloon inflation
-EDV cannot be determined
-flow reversal commonly seen
-if possible, turn off for CCA eval
lt vent assist device (LVAD)
-have decreased velocity flow
-CCA waveforms vary due to device
-waveform cant be evaled
high resistance
-minimal to mild antegrade diastolic flow
-may have flow reversal at end of systole
-PSV normal <150 cm/sec
ECA
ipsilat ICA occlusion can cause what to happen to ECA flow?
can become low resistive
ipsilat CCA occlusion can cause what to ECA flow?
can cause ECA flow to reverse so it can supply flow to the ICA
most accurate doppler predictor of the ICA stenosis is the what?
EDV
nomal psv <125 cm/s and EDV < 40 cm/s
-as stenosis increases = PSV + EDV will increase
ICA
highest ICA velocity is where in the vessel?
first 3 cm
highest CCA velocity is where in the vessel?
first 3 cm
compares the highest ICA to the distal CCA
systolic velocity ratio (SVR)
-higher ratios indicate stenosis
-when stenosis is present in the CCA, use highest normal CCA in the ratios
compares highest end diastolic velocity to the end diastolic velocity in the distal CCA?
diastolic velocity ratio (DVR)
-higher ratios indicate stenosis
-when stenosis is present in the CCA, use highest normal CCA in the ratios
indirect doppler criteria for significant ICA stenosis
-internalization of the ECA (becomes low resistive) w/ flow reversal in opthal A
-collat flow noted in TCD exam such as cross filling in anterior or posterior communicating a
-decreased blunted flow in one MCA
critical stenosis
-near occlusion that should be treated
-significant stenosis that demonstrates small amount of flow through narrowed segment
-string flow sign
-flow velocity very low with decreased pulsatility
-bruit not usually present
vertebral artery waveform
-low to medium velocity, low resistance
-variations in flow velocity between left and right is normal, left usually dominant
-stenosis usually occurs in prox A
-loss of diastolic flow indicates a dist occlusion
early systolic deceleration in the vert a is a sign of what?
subclavian a stenosis
subclavian artery waveform?
-normal high resistive
-right and left should be compared for expected similarity
-biphasic or monophasic waveform are associated with stenosis or occlusion
ulceration of plaque
-very difficult to identify
-formation of a crevice within the atheroma deposit
-leads to the formation of a protruding edge of the atheroma that could be sheared off by blood flow becoming an embolism
soft plaque has the greatest risk of what?
embolization
-complex and calcific plaque becomes increased in fibrous tissue and more easily adheres to vessel walls
when an artery is occluded the risk of what drops?
risk of future stroke drops significantly when what?
horizontal motion of vessel wall instead of wall pulsation and no flow indicates what?
carotid occlusion
what happens to resistance prox to occlusion
increase
-flow velocity decreases too (thump flow, stump flow, or thud flow)
diagnostic criteria for carotid occlusion?
-absent flow in dist ICA
-increase resistance, peaked waveform with absent diastolic flow or reversal prox
-decreased blunted flow in ipsilat MCA
-decreased resistance with increased diastolic flow in ipsilat ECA
-evidence of collats
-during occlusion or stenosis, flow velocities in contralat carotid will be increased
-if also occluded on ipsilat, stenosis may be overestimated
-can look like CCA velocities, are increased on side with stenosis and diminished on side with occlusion
-the ICA/ CCA ratio indicates lower level of stenosis than velocity criteria
compensatory flow
what is a carotid compression test?
-performed by physician only
-used to eval presence of collat formation
-compress unilat CCA for about 5 mon, if no symptoms occur, cerebral collats are present
what are the false positives for stenosis?
-increased cardiac output
-vessel tortuosity
-inappropriate angle of insonation
-compensatory flow
false negatives for occlusion?
-improper sample location
-low cardiac output
-stenosis at bulb
-inappropriate angle of insonation
-doppler angle > 60degrees
-incorrect placement
-collat formation
