Grafts and Stents Flashcards
What manoeuvres can improve SVG latency during harvest?
limited touch
limit distention pressure <150mmHg
blood solution less damaging to endothelium
Heparin/papverin
What are advantages/disadvantages for reversed vein graft?
valve lysis not required
options for anatomic/non-anatomic placement
potential size mismatch at anastomoses
hemodnamic effect of intact valves
valves can complicate thrombectomy
What are advantages/disadvantages for non-reversed vein graft?
improved vein to artery size match
options for anatomic/non-anatomic placement
valve lysis required
What are advantages/disadvantages in-situ vein graft?
limited skin incision
reduced manipulation of the vein
improved size match
subcutaneous position assists in graft revision
valve lysis required
subcutaneous position risk for exposure with wounds infection
length limitation for proximal anastomosis
What are risk factors for future contralateral leg intervention at time of ipso bypass?
age <0.7
if 3RF need for contralteral vein 25-50%
What is ideal SVG size for bypass?
3.5 best
<3 highest risk of failure
What are different types of valvulotomes?
Mills
expandable
fixed
Do intact valves in reversed vein adversely effect long-term latency?
No
What configuration should most arm vein be implanted?
reversed as most have wall to thin for valve lysis
Which is the most commonly used arm vein?
cephalic
What is the top three choice for bypass conduit?
GSV
arm vein
LSV (third due to difficult harvest and limited length
What can you do to elongate the LSV?
harvest the Giacomini in continuity
What is the latency for popliteal vein? SFA artery?
similar to SVG
1 year patency 60%
What is the most common cause of early graft failure?
technical at anastomosis
what is the failure rate of graft caused by atherosclerosis?
4% annual loss
What are intraoperative ways to assess graft patency?
doppler
palpation
angio
flowmeter
duplex
angioscopy
What are intra-operative duplex criteria for bypass grafts?
normal<125
Moderate 125-180 ratio 2-3
Severe >189 w spectral broadening, ratio 2.5-5 repair
high-grade >300, ratio >5
low flow <40, low PVR–consider anticoag
lowfloe, high PVR–consider AVF, alternate target
What to do if moderate stenosis identified?
papaverine and rescan
consider angio
What are postoperative duplex criteria?
normal 150, ratio <1.5
Mild >150, ratio 1.5-2
mod (50-75% >180, ratio >2.5, rescan leave alone if stable
severe (>75%), >300ratio >3.5 repair
low -flow <40, repair
How to manage post-op mod stenosis?
rescan in 4-6 weeks if not progression continue observation 3 month interval
How to manage post op severe stenosis
repair
What other index is concerning for graft stenosis?
ABI drop of >0.15
Name different types of prosthetic grafts?
Dacron
ePTFE
hybrid stent
polyurethane
How much does dacron increase in size after implantation?
10-20%
What are failure modes of prosthetic grafts?
blood interface (no antithrombotic mechanisms)
infection
compliance
What cells adhere to graft wall
Complement, coagulation cascade, plt, neutrophils and macs adhesion
Why is graft infection bad with prosthetic?
biofilm reduces abx effectiveness
50% amp rate
50% mortality
How does compliance influence failure?
stiff graft can lead to area of excessive mechanical stress which can lead to IH
What is anti-pot/anti-coag after prothetic graft?
ASA (lowers graft occlusion by 40%)
warfarin doubles bleeding events so only if at high risk of occlusion
Name options for cryopreserved grafts for bypass.
cryo SVG
HUV
CFA
bovine carotid artery
bovine mesenteric vein
How can cryopreservation effect allografts?
vessel can become less compliant
can have micro changes to histology of intima
diminished vasodilatory function
What is overall latency of cryo grafts?
its poor but limb salvage rate better then expected
likely du to repeated revasc attempts or situational perfusion enhancement
What aortic stent design features help prevent graft failure?
positive fixation
column support
friction
What are examples of positive fixation?
hook
barbs
anchors
supplemental staples
What is column support?
long iliac sealing zone to help prevent infrarenal migration
What are some anatomical features that can lead to graft limb occlusion?
iliac injury
calcification
tortuosity
stenosis
limb oversizing
How much overlap between components?
2-3 cm infrarenal
5-7cm thoracic
What are mechanism of failure of aortic stent grafts?
migration
neck dilation
fracture
limb occlusion
sac expansion
What is the definition of stent migration?
movement of more then 10mm or any movement with new type I/need of secondary procedure
What are some graft complication specific to thoracic?
retrograde type A
compression (with excessive oversizing)
Name some AAA devices.
aneurx medtronic
excluder gore
zenith cool
powerlink engologix
talent medtronic
ovation trivascular
Name thoracic devices.
cTag gore
talent medtronic
Tx2 cook
alpha cook
What are some stent interaction with vessel wall?
vessel injury fluid dynamics (oversizing leads to areas of low wall shear stress which leads to IH) strut characteristics (flow over struts can cause areas of low wall shear stress)
What are advantages/disadvantages of BE stents?
high radial force
high radio-opacityno oversizing needed
high precision
requires delivery sheath
can’t treat lesion with variable diameter
low flexibility
not resistant to external compression
risk of dislodgment off balloon
What are advantages/disadvantages of SE stents?
high flexibility
no delivery sheath needed
treats lesions with variable diameter
resistant to compression
low radio-opacity
oversizing needed
low radial force
What is the definition of radial force?
force required to produce a 50% reduction in the luminal diameter of the stent
What differences in radial force between stainless steel and nitinol stents?
SS relies on design for radial force
nitinol relies on inherent nature of the metal
What are the differences in open and closed cell stents?
closed cell every stent wire interconnected. less flexible
may prevent distal embolization
Which stent to use:
concern about embolization
fresh thrombus
high external forces
ostial lesions
venous
heavily calcified
infrainguinal
dialysis
branch points
long iliac lesio
covered
covered
SE
BE
SE oversized
BE
SE
SE
BE
SE (calibre change
