Peripheral Arterial Hemodynamics Flashcards
Which is higher, systolic or diastolic velocity?
Systolic velocity.
Why is systolic velocity higher than disastolic velocity?
It is due to the heart pumping in systole and flow moving on its own momentum in diastole.
Do systolic velocities decrease or increase as the blood flows to the ankes?
It decreases.
Why is arterial flow pulsatile?
It is pulsatile primarily due to the pumping of the heart.
What do doppler velocity waveforms demonstrate?
Velocity changes throughout the cardiac cycle.
In normal LE and UE, flow reversal is primarily due to what?
The resistance of the distal vascular bed that the artery is feeding.
Are the distal vascular bed high or low resistance to flow at rest?
They are highly resistant to flow at rest.
What is the distal vascular beds resistance controlled by?
The resistance is controlled by arterioles.
What happens to the arterioles duiring excersise?
They open up and resistance lowers to increase flow needed by the muscles to work.
What does the resistance of distal vascular beds determine?
It determines the diastolic portion of velocity waveform.
What is resistance created by?
Arterioles.
What type of resistance is need to feed the brain, kidney, and liver?
Low resistance.
What is low resistance also known as?
Continuous flow.
What causes arterioles to open to reduce resistance and increase flow as necessary?
- Proximal obstruction.
- Inflammation
- Excerise
- Anything that may cause decreased peripheral resistance.
When does velocity change in peripheral arteries?
Velocity changes around a stenosis and occlusion.
How is the pressure and velocity at a stenosis?
Lower pressure, and higher velocity.
How is pressure and velocity post-stenosis?
Higher pressure, lower velocity than in stenosis.
What are the charactersistics of a pre-stenosis changes?
- not predicatable
- May be:
- Normal triphasic may indicate minor stenosis or good collaterals.
- No diastolic flow (high resistance)
- Biphasic or monophasic if proximal disease is present.
What are the characteristics of in-stenosis changes?
- velocity increases at least double pre-stenosis.
- Waveform is likely to have spectral broadening.
What are the characteristic of post-stenosis changes?
- velocities decrease along the artery distal to the stenosis.
- Intially post-stenoic turbulence is present.
- spectral broadening
- may have reversed flow under the peak.
- feathered peak velocities in waveform
- Father distal to stenosis, waveform will be different than pre-stenosis if it significant
- biphasic
- monophasic
How do pre-occlusive wave form look like?
- May have no diastolic flow.
- May have diastolic flow if good collaterals exist distal to the sample value.
- Velocity may be low.
What do in-occlusion waveforms look like?
- No doppler signal, no color.
- B-mode usually shows echoes.
how do post-occlusion waveforms looks like?
- Almost always has monophasic shape.
- low velocity.
What does aterial systole of a wave indicate?
indicates the inflow patency or obstruction.
What does the distalic portion of the wave indicate?
It indicates the resistance of the distal vascular bed.
How is high restsistance wave demonstrated?
Diastolic flow at baseline or below.
How is low resistance wave demonstrated?
It has a foward flow throughout the cycle. It indicates proximal obstruction or post-excersise or med.
How is NORMAL high resistance characterized?
High resistance waveforms has diastolic flow on or below the baseline.
Where are normally high resistance arteries located?
- LE ARTERIES
- UE ARTERIES
- ECA (goes to face)
- SMA pre-eating.
What is NORMAL low resistance characterized as?
Low resistance waveforms demonstrate continuous flow above the baseline.
Where is there normal low resistance waveform?
- ICA
- VERT (feeds the brain)
- CELIAC
- RENAL
How does excersise change the resistance of arterioles?
It changes the peripheral arteries from normally high resistance to low resistance so flow can increase and help muscles work.
How does eating change the resistance of the arterioles?
Changes the superior mesenteric artery from normally high resistance to low resistance to aid in digestion.
How does post-ischemia change the resistance of the arterioles?
Time can change a normally high resistance wave to low resistance. We see this when you come in from the cold and fingers,toes and cheeks may become low resistance to encourage flow.
How does resistance change due to hemodynamic obstruction?
Peripheral arteries distal to s significant obstruction will become low resistance (tri to bi or mono) due to artieroles opening to encourage flow.
How does resistance change due to a pre-occlusion in the CCA?
CCA will chnage from low resistance to high resistance proximal to an ICA occlusion due to distal resistance.
How does resistance change due to a pre-occlusion in the ICA?
It will change from low to high resistance proximal to an intracranial ICA occlusion due to distal resistance.
Do velocities increase or decrease from the aorta to the ankles?
Velocity decreases.
Under what conditions can the normal triphasic signal become biphasic or monophasic?
- Excersise
- Inflammation
- Proximal significant obstruction
- close proximity to occlusion.
What is the hallmark flow pattern of a significant stenosis?
- in-stenosis: velocity is 2x the pre-stenosis velocity AND spectral broadening.
- post-stenotic: post-stenotic turbulence and further downstream a change in the waveform shape.
What flow pattern is this?
Triphasic
What flow pattern is this?
Biphasic
What flow pattern is this?
Monophasic
What flow pattern is this?
Stenotic with bruit
What flow pattern is this?
Staccato.
pre-occlusion.
What flow pattern is this?
Pendulum.
To and fro flow.
What flow pattern is this?
MONPHASIC; no diastole.
pre-occlusion
Where does the external iliac end?
Inguinal ligament
What are the 6 LE arterial diseases?
- Atherosclerosis
- Embolism
- Aneurysm
- Coarctation
- Entrapment
- Arteritis
What is the most common LE artery disease?
Atherosclerosis.
What layers of the artery does atherscelerosis affect?
Intima and media.
What is athersclerosis?
The thickening and hardening of the arteries which results in the loss of elasticity.
Where does athersclerosis commonly occur?
- CFA bifurcation
- SFA at adductor canal is most common.
- POP trifurcation.
What is the most common complications of an aorta aneurysm?
Rupture.
What is the most common complication of a popliteal aneurysm?
Embolism.
What is coarctation of aorta?
It is the congential narrowing causing decreased perfusion in all organs distally.
What does coarctation of aorta cause?
HTN due to decreased perfusion of kidneys.
Who is affected by coarctation of aorta?
Young people with hypertension.
What is popliteal entrapment?
Popliteal artery caught between the medial head of gastrocnemius muscle and fibrous man.
Who is primarily affected by popliteal entrapment?
men.
Where is cystic adventitial diseas usually seen?
Usually seen at popliteal artery.
What may cystic adventitial disease cause?
occlusion of the artery.
Who is primarily affected by cystic adventitial disease?
young people.
What is arteritits?
Inflammation of the artery.
How does arteritis appear?
Appears as a thickening of wall or “halo” around an artery.
What is takaysu?
It is chronic inflammation of aortic arch and large branches with fibrosis and narrowing or occlusion.
Who is primarily affected by takaysu?
females.
What is temporal arteritis?
Superficial temporal artery, “halo” effect.
What does polyarterisis mean?
multiple arteries inflammed.
What is the most common arteritis?
Thromboangitis Obliterans
aka “beurgers disease”
What are the risk factors & symptoms for beurgers disease?
- smokers
- men < 40 yrs
- occlusion of distal arteries
- rest pain
- ulcers early in disease.
What is the best way to identify arterial disease?
ABI’s with pedal waveforms.
for a LE arterial basic exam, what is the protocol?
- ABI’s→ ESSENTIAL
- CW doppler: DP & PT at a minimum.
- Segs, VPR, CW of proximal arteries will indicate general level.
- Excersise testing as needed.
- Toe pressures as needed.
- Duplex exam is extra-detailed, so best use is as needed, especially to obatin location of disease.
What should you do as yyou move distally from high velocity to low velocity from aorta to ankle?
Decrease scale.
What do you want to identify with color?
- artery and course.
- direction of flow
- color fill wall to wall.
What is color used for?
- indeitfy areas of turbulence
- Identify areas of no flow
- Identify collateral arteries.
How do you calcuate the PSV ratio?
Highets velocity at stenosis/pre-stenosis velocity.
