Module 8 : Peripheral Arterial System Part 3 Flashcards
what are the 3 roles of ultrasound in arterial bypass and stent surveillance duplex exam
- establish baseline hemodynamics post revascularization
- identify correctable lesions before graft thrombosis
- provide information to aid in decision regarding treatment alternatives
what are 7 indications for graft/stent exam
- post op follow up
- new symptom of claudication or something
- decreased ABI >0.15 compared to previous exam
- absent peripheral pulses
- pulsatile mass near an anastomotic site or intervention site
- digital cyanosis
- dependant rubor
what are 4 different types of bypasses/stents
- aorta-iliac
- aorto-fem
- ax-fem
- fem-fem
what are the 2 types fo lower extremity venous grafts
- PTFE
- Dacron
what is an autogenous bypass
- vein bypass
what are the 2 types of vein bypasses
- in-situ vein
- reversed vein
what is an in-situ bypass
- vein left in original location with valves cut and branches ligated
what is a reversed vein bypass
- vein is ligated reversed and attaches to arteries
what are the 4 common autogenous veins commonly used
- GSV
- SSV
- basilic vein
- cephalic vein
what are the 3 modified biologic grafts
- human umbilical vein
- cryopreserved saphenous vein
- bovine
what is a composite graft
- synthetic graft connected to a vein
what are the 3 types of bypass anastomoses
- end to end
- end to side
- side to side
what are 9 mechanisms of graft failure
- early graft failure <30 due to errors in bypass construction
- intimal hyperplasia can cause stenosis 1-2years
- atherosclerotic progression can cause stenosis > 2years
- undiagnosed hyper coagulable disorder
- infection
- aneurysmal detection
- trauma to thrombosis
- thromboembolism
- early graft failure
what are 2 mechanisms of stent failure
- stenting used to create complicated lesions and technical failures can occur <30days
- recurrent stenosis >30days
where can disease be located in LE grafts
- focal or diffuse
- one or multiple levels
what are 5 common location of graft obstruction
- valve site
- anastomoses
- inflow tract
- outflow tract
- graft kink
what are the locations of images for graft/stent evaluation
- inflow prox native artery
- prox anastomiss
- prox graft/stent
- mid graft/stent
- distal graft/stent
- distal anastomoses
- outflow dist native artery
why might the wave flow pattern early post op be low resistance
- reactive hyperaemia
what should we analyze when there is a graft stenosis
- ABI or TBI
- PSV and flow direction
- velocity ratios
- waveform patterns and changes
- image data
what determines the severity of a graft stenosis
- graft material
what would a normal grayscale & color look like in a graft/stent
- no intraluminal echoes
- color fills the lumen from wall to wall in SAG and TRV
- synthetic grafts have double line wall
- stent walls seen within lumen but difficult in deeper grafts
what is the waveform and VR of the inflow artery normally
- triphasic
- Vr < 2.0
normal characteristics of proximal anastomoses site
- Vr < 2
- bifurcations and branches have disturbed patterns
- large inflow artery feeding a small diameter graft to produce higher Vr
- asses for intraluminal echoes
normal PSV and Vr in the body of a graft
< 180 cm/s
Vr < 2.0
normal sized PSV of vein graft body
- = 4mm
- PSV > 40-45 cm/s
normal PSV and Vr in body of stent
< 190cm/s
Vr < 1.5
normal waveform pattern in body of stent/graft
- same as inflow artery through non obstructed graft
what is the normal characteristics of the distal anastomosis site
- size change from larger vessel to smaller vessel increases velocity
- Vr < 3.0
- asses for intraluminal echoes
- may see disturbed pattern
normal outflow artery characteristics
- velocities unchanged
- Vr < 2.0
- waveforms similar to graft/stent body
what would indicate an abnormal graft/stent
- decrease ABI < 0.15 indicates disease progression
what would be an abnormal grayscale & color with grafts/stents
- lumen reduction
- color doesnt fill lumen from wall to wall
- aliasing within stenosis
- residual valve cusps in vein grafts
- aneurysmal dilatations and thrombus
what would indicate and abnormal inflow artery in a graft/stent
- Vr > 2.0
- post stenotic turbulence
- waveform changes with hemodynamically significant lesion
- significant inflow artery obstruction is indicated by monophasic waveform
what would be the characteristics of a hemodynamically significant stenosis in the prox anastomosis
- Vr > 2.0
- increased PSV
- spectral broadening
- post stenotic turbulence
- echogenic material
PSV and Vr in > 50% stenotic graft body
PSV 180cm/s
Vr > 2.0
PSV and Vr in > 70% stenotic graft body
PSV > 300 cm/s
Vr > 3.5
PSV and Vr in > 50% stenotic stent body
PSV > 190cm/s
Vr > 1.5
PSV and Vr in > 70% stenotic stent body
PSV > 275 cm/s
Vr >/= 3.5
what is impending vein graft failure indicated by
PSV < 40-45 cm/s
what is an obstruction in the inflow tract indicated by
- monophasic waveform in the graft
what is a distal anastomoses or outflow tract obstruction indicated by
- high resistance waveform pattern
- no end diastolic velocity and staccato pattern
what would the Vr be in a > 50% stenosis in distal anasotmese site
Vr > 3.0
- post stenotic turbulence and distal waveform changes
what determines the the severity of the stenosis
- graft material
what would indicate a graft/stent occlusion
- no flow by spectral or color
- intraluminal echoes seen
what are 3 other pathologies
- pseudoaneuryms
- aneurysmal dilation
- entrapment of a graft
what is a pseudoaneurysm
- pulsatile mass identified by color and doppler sen to communicate with bypass or native artery through a patent neck
what is aneurysmal dilatation
- focal enlargement twice the proximal arterial segment
- intraluminal thrombus within the aneurysm
what is an entrapment pf a graft
- can occur at the knee
- with the leg slightly bent normal flow seen
- with the leg straight no flow is detected
