Lesson 17 - Carotid Tech Difficult Flashcards
What method is used to measure plaque is <60% stenosis?
why?
2-D
No hemodynamic effects when <60%
How does color doppler help with clacification?
- Provides visualization of flow
- around hypoechoic plaque (see it going around)
- Jets and direction (velocity highest in stenosis)
What information does spectral doppler provide about flow?
- Velocity (PSV, EDV)
- Flow characteristics: resistance, evidence of proximal or distal obstruction
- Spectral broadening
What do you look at when low cardiac output or proximal stenosis makes the charts inaccurate?
Compare CCA & ICA velocity
What are the 2 methods for determining % stenosis?
- Hemodynamic criteria
- 2D
What do standardized velocity charts assume that can cause problems if they are not true?
What criteria should be used in the place?
- normal cardiac output
- no proximal stenosis
- short stenotic segment
- ICA/CCA Ratio
- Ratio = stenosis/proximal
How does the velocity ratio evaluate stenosis?
Same as lower extremity
- 2 x increase = 50% Stenosis
*Reference chart for further breakdown
*Remember: Ratio is for abnormal = poor cardiac output or proximal stenosis
Describe the waveforms of the CCA, ICA and ECA when there is stenosis of the proximal CCA
ICA, ECA, CCA = tardus parvus
There is stenosis in the proximal CCA: How might this effect the velocity in an ICA stenosis?
ICA stenosis may not reach target velocity on chart
*use ratio, compare to other side (proximal stenosis affects everything up the vessel)
(tardus parvus CCA, ICA and ECA)
Waveforms in the ____________ artieries appear ____________ as a result of poor cardiac output
- CCA, ICA, ECA, Vertebral
- tardus parvus
Poor cardiac output creates __________ waveforms in the ICA, ECA, CCA, Vertebral on the _____________ side
Tardus parvus
right & left (bilateral)
Which velocities are used to calculate the ICA/CCA ratio?
ICA = highest stenotic PSV
CCA = PSV of distal CCA (2cm proximal to bulb)
Is an ICA/CCA ratio helpful if no stenosis is visable?
No, only applicaple if stenosis is seen
Name the progession phases of stenosis (4)
< 50% - no hemodynamic changes
>50% - increase in velocity
Near occlusion - velocity decreases
Occlusion - no flow
What is the “string sign” on angio?
trickle flow
Ischemic changes due to decreased flow is a result of ___________
Stenosis
A stenosis can turn to total occlusion from (2)
Intraplaque hemorrhage
Thrombus
Trickle flow occurs __________ to ____________
distal
high-grade stenosis
Velocity in a high grade stenosis can appear 2 ways, name them
1) abnormally high
2) very low - doesn’t match what you would expect from the 2D appearance
To image trickle flow with doppler, doppler must be as sensitive as possible. What machine settings will help achieve this?
- Proper angle
- gain up
- scale down (<10cm/s)
- color scale down (<10cm/s)
- doppler filter as low as possible
- power doppler
Why is it important to locate trickle flow?
Trickle flow means the artery is not occluded. If there is trickle flow an endarterectomy can be done, but not if vessle is occluded. Makes a huge difference!!
ICA occlusion occurs secondary to ________ (2)
atherosclerosis
thrombus
What kind of plaque puts the ICA at a higher risk for occlusion?
ulcerative plaque
Define Ischemic
A decrease in the blood supply to a bodily organ, tissue, or part caused by constriction or obstruction of the blood vessels.
Define Arteriosclerosis
Hardening of the arteries, also called atherosclerosis, is a common disorder. It occurs when fat, cholesterol, and other substances build up in the walls of arteries and form hard structures called plaques.
What are the symptoms of ICA occlusion
Asymptomatic or stroke symptomes
What happens to the ECA when there is occlusion in the ICA?
Internalized ECA = low resistance
*looks like ICA - low resistance waveform. internalized and tapped so it’s the ECA
What happens to the CCA flow with ICA occlusion?
Externalized CCA
What are the treatment options for ICA occlusion?
1) Acute occlusion - direct endovascular thrombolysis (clot dissolving medications through a catheter)
2) Surgical revascularization via urgent carotid endarterectomy
3) Thrombectomy, or EC-IC (brain) bypass
4) Do nothing if found in a chronic pt
Define Thrombectomy
surgical removal of a clot from a blood vessel
Describe an externalized CCA
caused by ICA occlusion
high resistance (should not be)
dampened
Describe a CCA and ICA “thump”
When the regular flow hits the obstruction and causes the vessle to shift up and down <————>
(opposite direction of pusling)
Describe an Internalized ECA
Low resistance (should be high), looks like ICA
How do you confirm the identity of the ECA?
Cervical branches (ICA does not have them)
Temporal tap
Should doppler sensitivity be high, low, or in the middle, when determining occlusion?
The doppler should be set as sensitive as possible to be SURE there is NO flow!!!
DO NOT MISS FLOW and report as occluded when it is not!
How do you increase the sensitivity of the doppler?
- Steer the beam correctly
- Increase gain
- Decrease scale/PRF
- Decrease filter
- High frequency transducer
- Power doppler (color doppler energy)
If you do not see a waveform, what can you do to the spectral scale?
decrease
CCA occlusion occurs secondary to ___________
atherosclerosis & thrombis
What kind of plaque puts someone at risk for CCA occlusion ?
ulcertive plaque
What are symptoms of CCA occlusion?
- Asymptomatic
- stroke symptoms
- Reversed ECA
- Internalized ECA
- contralateral or vertebral velocities may increase to compensate
What occurs in the ECA with CCA occlusion?
Reversed flow
Internalized flow
What other vessels may experience increased velocites when there is CCA occlusion?
Why?
Contralateral CCA or Vertebrals
to compensate for the lack of flow in the occluded CCA
Summarizes the goals and steps to identify and characterize the stenosis
- Identify plaque
- characterize
- map the stenosis (proximal, jet, distal)
- PSV, EDV ( look at chart)
- compare ICA/CCA ratio
- compare to the other side
- velocities should be congruent with 2D appearance (if not, there may be low cardiac output, proximal stenosis, long segment, near occlusion/trickle flow)
What can cause CCA velocities to be higher than expected when no stenosis is present?
compensatory flow from contralateral vessel, or vertebral obstruction
Why does reversal of flow occur?
compensation for obstruction in another vessel
When will flow reversal of the Left CCA occur?
only if arch anomaly with Left CCA and Left Subclavian trunk
Which vessels can reverse bilaterally?
ECA
Vertebrals
Which CCA would be more likely to show flow reversal?
Right CCA (branches off brachiocephalic)
what is this an example of ?
why is this method used?
high ratio - long stenotic segment
Standardized charts assume normal cardiac output, no proximal stenosis, short stenotic segment:
ICA velocity lower than expected b/c long stenosis
CCA velocity is low due to low cardiac output (CHF or AS) or proximal stenosis
ICA velocity will not increase to target levels on chart
Use ratio to evaluate for amount of velocity increase:
Same theory as LE arterial with 2x increase=50% stenosed, etc. *compensates for low inaccurate flow
what can cause velocities to be lower than expected?
Low cardiac output
Proximal stenosis
Long segment
Near occlusion – trickle flow
Which of the following describes the finding of this exam?
left mid CCA stenosis > 70%
left CCA proximal stenosis
left ICA occlusion
right mid CCA stenosis > 70%
left mid CCA stenosis > 70%
What is the left ICA:CCA ratio?
0
- 76
- 0
- 3
1
What is the likely degree of stenosis of this left ICA?
<50%
50-69%
>70% but < near total occlusion
near occlusion
near occlusion
What is demonstrated on this exam?
occluded ICA
retrograde ECA
stenosis of proximal CCA with tardus parvus waveform
internalized ECA
occluded ICA
What is demonstrated on this exam?
stenosis of proximal CCA with tardus parvus waveform
retrograde ECA
internalized ECA
stenosis of mid CCA
internalized ECA
