Peripheral Arterial System 3 Flashcards
3What is the role of duplex doppler in the study of bypass graphs? 3
- Establish baseline hemodynamics
- Identify correctable lesions before graft thrombosis
- Provide information to aid in decision regarding treatment alternatives
What are indications for arterial bypass and stent surveillance duplex testing? 7
- Post- op follow up and routine surveillance
- Acute onset of pain
- Persistent, non-healing ulcers
- Decreased ABI >0.15 compared to previous exam
- Dismissed or absent peripheral pulses
- Recent history of loss of limb swelling and suggestive of graft failure and ischemia
- Pulsatile mass near an anastomotic site or intervention site
What is a Aoroto- Iliac stent or bypass?
Abdominal aorta to unilateral or bilateral iliac
What is a Aorto-fem graft?
Abdominal aorta to unilateral or bilateral femoral
What is a Ax-fem graft?
Axillary to CFA, Axillary to FA or axillary to DFA
What is a fem fem graft?
Right CFA to left CFA or vice versa
Label the image
What are different types of synthetic grafts? 2
- PTFE
- Dacron
Label the image
What are autogenous bypasses or stents?
Vein bypasses
What are different types of Vein bypasses? 4
- In- Situ vein
- Reversed vein
- Autogenous veins commonly used
- Modified biological grafts
What is an in-Situ vein?
Vein left in original location with valves cut and branches lighted
What is a reveresed vein?
Vein is lighted, reversed and attached to arteries
What are some autogenous veins commonly used? 4
- Great saphenous vein
- Small saphenous vein
- Basilic vein
- Cephalic vein
What are some modified biological grafts? 3
- Human umbilical vein
- Cryopreserved saphenous vein
- Bovine
What is composite graft?
Synthetic graft connected to vein
What are different types of bypass anastomoses? 3
- End to end
- End to side
- Side to side
What is a mechanism of graft failure?
Early graft failure (<30days)
What is early graft failure (<30 days) due to? 4
- Technical errors such as poor choice of inflow or outflow vessels, retained valves, intimal flaps, clamp injury, suture placement at the anastomotic site, etc.
- Undiagnosed hypercoagulable disorder can cause early thrombosis
- Graft infection is rare but possible
- Can occur without a mechanical defect or cause
Why would a graft fail within months 1-24?
Myointimal hyperplasia can develop and cause a stensois. Can occur anywhere in the bypass but occurs most often at a valve site or at either anastomosis site
Why would be a mechanism of graft failure greater than 2 years?
- Atherosclerotic progression: can cause a stenosis within the inflow and outflow vessels
- Aneurysmal degeneration in mature vein grafts
What is the mechanism of trauma in terms of trauma?
Trauma to the graft can lead to thrombosis or Thromboembolism
What is a mechanism of stent failure? 2
- Technical failures
- Disease location
Stunting is often used to treat what?
Complicated lesions
Technical failures (<30 days post op) or >30 days post op is usually caused by what?
Re-current stenosis
What are common locations of graft obstruction? 5
- Valve site
- Anastomoses
- Inflow tract
- Outflow tract
- Graft kink
Without any specific symptoms, ultrasound is performed on bypass grafts at what intervals?
Routine intervals as part of a standard postoperative care
What is the arterial bypass graft/stent surveillance protocol? 7
- Supine, head slightly elevated. Externally rotate the hip and bend the knee
- Transducer
- Obtain Bilateral ABI’s
- Evaluate for abnormalities in the graft or stent
- Locate anastomotic site s
- Information about graft/ stent length
- Locate any previously occluded grafts
In terms of the arterial bypass graft/ stent surveillance protocol, what do we do in terms of transducer selection? 4
- 5-7 linear for deep bypass grafts
- 10-12 linear for superficial, in Situ vein grafts
- 3-5 curvilinear for aorta or iliacs
- 10 CW probe for ankle/ arm pressures
Once the graft stent location is determined, obtain images with and without colour, and spectral of what? 7
- Inflow/ proximal native artery
- Proximal anastomosis
- Proximal graft/stent
- Mid graft/ stent
- Distal Graft/ stent
- Distal anastomosis
- Outflow/ distal native artery
When a stenotic area is identified what must we do?
Walk the sample through and obtain PSVs and waveforms
Where are three areas we “walk” the sample volume?
- Within 2cm proximal to the stenosis
- At the highest point within the stenosis
- Distal to stenosis
After we walk the sample volume with stenosis what do we do? 3
- Document post stenotic turbulence and bruits
- Measure lumen narrowing in SAG and TRANS
- Repeat for other grafts/ stents if present
Early post op patterns (first two months), may not be multiphasic and be low resistance due to what?
Reactive hyperaemia
After the early post op period, waveform will be what?
Low resistance and monophasic in initial scans and should change to high resistance and multiphasic in follow up scans
Graft material will determine the severity of what?
Stenosis
What do we analyze with arterial bypass and stent surveillance duplex testing? 6
- ABI or TBI
- PSV and flow direction
- Velocity ratio
- Waveform patterns and changes including flow direction and post stenotic turbulence
- Image data
- Consider reasons that the image and velocity data may not agree
What does a normal greyscale and colour look like for grafts/bypass? 5
- No intraluminal echoes
- Colour fills the lumen form wall to wall in SAG and TRV
- Vein graft walls are smooth and uniform
- Synthetic grafts have “double line” wall appearance
- Stent walls are typically seen within the lumen
What does the normal inflow artery bypass look like? 2
- Multiphasic
- VR <2.0
How does the normal proximal anastomosis graft present?3
- VR <2.0
- Bifurcations and branches- waveforms may display disturbed patterns which become normal distally
- Due to size changes, a large inflow artery feeding a small diameter graft may produce a higher VR
What does a normal Body of graft/ stent look like with bypass/ stents? 2 (psv values)
- PSV <150cm/s and VR <2.0 throughout
- Vein grafts <4mm, PSV at least >40-45 cm/s
In terms of a normal Body of graft/stent, larger grafts may demonstrate what?
Lower velocities, 35 cm/s
In terms of a normal Body of graft/stent, waveform patterns should remain the same as what?
Inflow artery unless it displays hyperemic flow due to recent placement
What does a normal distal anastomosis look like?
- usually there is a size change from a wider graft to a narrower artery which results in an increased velocity
- Normal VR is <3.0
In a normal distal anastomosis, due to the vessel angle and size change, what happens to the waveform?
May display a disturbed pattern
What does a normal outflow artery look like? 3
- Velocities remained unchanged
- VR <2.0
- Waveforms similar to graft/ stent body
What are some abnormal stenotic disease features? 7
- Post stenotic turbulence
- Waveform changes
- Colour bruit
- Aliasing within the stenosis
- Increased PSV
- Spectral broadening
- Echogenic material
In an abnormal graft/ stent what would greyscale and colour look like? 5
- Lumen reduction
- Residual valve cusps
- Aneurysmal dilation and thrombus in aging grafts
- Colour does not fill the lumen
- Aliasing within a stenosis
What does an abnormal inflow artery look like with a graft/stent? 2
- VR >2.0 (indicates hemodynamically significant lesions >50%)
- Significant inflow artery obstruction is indicated by monophasic waveform pattern (at least 2cm proximal to the anastomosis)
What does a abnormal proximal anastomosis look like with grafts/ stents? 2
- Hemodynamically significant stenosis (>50%)
- VR > 2.0 (or >3.0 if graft diameter is much smaller than the inflow vessel)
What does an abnormal body of graft/stent (variable by lab or source) look like on any graft body?
- > 50% stenosis: PSV >180 and Vr >2.0
- > 70% stenosis: PSV >300 cm/s and Vr >3.5
What does an abnormal graft/stent look like?3
- Impending vein graft failure
- Obstruction in the inflow tract
- Distal anastamosis or outflow tract obstruction
In terms of the impending vein graft failure with an abnormal body of graft/stent, what does it entail? Think psv and size.
PSV <40-45 cm/s throughout a normally sized graft (<4mm in diameter)
What does the obstruction in the inflow tract of a abnormal body of graft/stent look like?
Monophasic waveform in the graft
What does the distal anastomosis or outflow tract obstruction look like with an abnormal body of graft/ stent?
High resistance or “staccato” pattern
What does an abnormal distal anastomosis look like?2
- Vr >3.0
- Consider a size mismatch between the bypass and outflow artery if there is an increased velocity without intraluminal echoes
What an abnormal graft/stent occlusion look like?2
- No flow detected by spectral doppler or colour in TRV and SAV
- Intraluminal echoes may be seen
What does this image demonstrate?
Vein graft stenosis
Label the image
Label the classification of graft stenosis
What does this image demonstrate?
In situ graft stenosis
What does this image demonstrate?
The colour bruit that appears distal to a stenosis of a graft
What does this image demonstrate?
A waveform of a graft stenosis IN the stenosis
What is other pathology that can be seen with Abnormal arterial bypass?2
- Pseudoaneurysm
- Aneurysmal dilatation
Where might pseudoaneurysms appear?
May occur at anastomotic sites
What is aneurysmal dilatation?3
- Focal or diffuse enlargement 1.5x the proximal arterial segment
- Intraluminal thrombus may be seen within the aneurysm
- Occurs most commonly in native artery near the anastomosis
What does this image demonstrate?
Vein graft aneurysm
Arteriovenous fistulas are unique to what type of grafts?
In-situ bypass grafts
Arteriovenous fistulas are a tributary of what?
The GSV which connects via a perforator with the deep system and is left un-ligated after creation of the bypass
In the arteriovenous fistula the perforator vein as what?
A fistula from the graft into the deep system
What does the proximal arteriovenous fistula look like?
Constant antegrade flow (monophasic)
What does a distal arteriovenous fistula look like?
Bypass graft shows little to no diastolic flow
Where can entrapment of graft occur?
Knee
In terms of entrapment of a graft, if a knee slightly bent, what is seen?
Normal flow
In terms of entrapment of a graft, if the knee is straight what is seen?
no flow is detected in the graft by doppler or colour flow