Grafts Flashcards
What is a miller cuff?
What is a taylor patch?
What are disadvantages of miller cuff?
Turbulence
What are disadvantages of Taylor patch?
Lose venous endothelium on half anastomosis and need a lot of vein
What is a distal vein patch?
Venous patch, prosthetic anast to it
If you can’t use vein for tibial bypass, what is the best alternative?
Heparin bonded ePTFE - some recent studies shows noninferiority
Which graft theoretically promotes lateral flow to decrease shear and decrease adhesion molecules/intimal hyperplasia?
Spiral flow graft
What graft technique is available for poor arterial runoff
“Patchula” AV fistula to decrease outflow resistance
Is there any benefit to dual antiplatelet therapy for peripheral bypass?
CASPAR trial - maybe benefit in prosthetic grafts. ASA of benefit in prosthetic grafts based on Cochrane review
How often should you survey peripheral bypass grafts?
3, 6 months then annually
What is the Bandyk criteria for graft stenosis?
PSV > 300. Ratio > 3.5
How low of a velocity predicts mid graft failure?
< 45 cm/s
What causes early (< 6 months) graft failures?
Technical - poor inflow/outflow, thrombophilia
When do grafts fail due to myointimal hyperplasia?
Mid term - 6-24 months
When do grafts fail due to progression of disease?
Late, > 24 months
What is more effective for graft occlusions - thrombolysis or thrombectomy?
< 2 weeks of symptoms - thrombolysis, > 2 weeks - thrombectomy. STILE and TOPAS trials
What are 4 contraindications to thrombolysis?
- Recent surgery
- Non viable limb
- Bleeding disorders
- Hemorhagic stroke
What are 4 CT findings consistent with graft infection?
- Peri graft air
- Peri graft fluid
- Pseudoaneurysm
- Soft tissue attenuation
Which types of graft infection organisms mandate removal?
Pseudomonas, MRSA
Which procedure has the highest incidence of graft infection?
Ax-fem (5-8%)
What is the incidence of graft infection for fem pop or fem tib?
Fem pop 1-5%, Fem tib 2 - 4%
What is the risk of graft infection with a peripheral stent?
Very low < 0.1%
What is the risk of aortofemoral graft infection?
< 3%
What is an early versus late graft infection?
early < 4 mo, late > 4 mo
What is a Szilagyi Grade 1 graft infection?
cellulitis involving the wound
What is a Szilagyi grade 2 graft infection?
infection involving subcutaneous tissue
What is a Szalgyi type 3 graft infection?
Infection of the vascular prosthesis
What is a P0 graft infection?
infection of a cavitargy graft (abdo/thoracic)
What is a P1 graft infection?
Infection of graft which entire course is non cavitary (ax fem, carotid subclavian etc)
What is a P2 graft infection?
Infection of the extracavitary portion of a graft whos origin is cavitary (e.g. femoral portion of ABF)
What is a P3 graft infection?
infection involving prosthetic patch angioplasty (femoral patch, carotid patch)
What are the 3 most severe Bunt’s classification of graft infections?
Graft enteric erosion
Graft enteric fistula
Aortic stump sepsis after excision of infected graft
When do most cavitary graft infections (e.g. aortic) occur?
Late - mean time more than 40 months
What are the differences between arterial and venous endothelium
Arterial endothelium = tightly packed cells aligned in direction of flow
What are 3 major differences between the structure of vein and arterial walls
- Endothelium: Arterial endothelium are tightly packed and highly aligned in direction of flow, veins are cuboid and poorly developed tight junctions
- Veins have poorly developed IEL
- Arteries have higher elastin content to accomodate pulsatile flow
Name 3 types of valvulotomes. Which is the best?
- Modified Mills
- Adjustable (LeMaitre)
- Fixed (Uresil)
No difference in prospective RCT comparing clinical outcomes of fixed and adjustable valvulotome
What are 9 causes of early vein graft failure?
Inflow:
- Underestimated proximal lesion
- Low flow states
Outflow:
- Severe tibial disease - 10x increased risk of graft failure
Extrinsic causes:
- Hematoma
- Tunnelling error
- Hypercoagulable state
Vein defects:
- Focal - e.g. retained valve/intimal flap/anastomotic issue
- Undersized conduit < 3 mm
- Sclerosis/calcification
What is the incidence of thrombosis or re-exporation within 30 days of infrainguinal vein bypass?
5% (PREVENT III trial)
What drug was used in the PREVENT III and IV trials to prevent vein graft failure?
Edifoligide
What was the main outcome of PREVENT III and IV trials?
Treatment with edifoligide has no influence on vein bypass durability
When performing intra-op duplex to evaluate surgical bypass, what does PSV <40 mean and high PVR? How should you manage this?
Low flow
Consider adjunctive procedure - distal AV fistula/jump graft to alternate target
When performing intra-op duplex to evaluate surgical bypass, what does PSV <40 mean and low PVR? How should you manage this?
Low-flow graft - consider anticoagulation
Caveat: large caliber vein, reversed vein to pedal outflow artery
When performing intra-op duplex to evaluate surgical bypass, what does PSV >300 mean? How should you manage this?
Critical stenosis
Repair defect +/- angio
When performing intra-op duplex to evaluate surgical bypass, what does PSV >180 mean? How should you manage this?
Severe stenosis
Repair defect or if no defect seen perform angio
When performing intra-op duplex to evaluate surgical bypass, what does PSV 125-180 mean? How should you manage this?
Moderate stenosis
Administer papaverine and rescan in 5 min, consider angio
When performing intra-op duplex to evaluate surgical bypass, what does PSV < 125 mean? How should you manage this?
Normal flow.
No further intervention.
During cryopreservation, why do plasma membranes rupture? How to prevent this?
Rupture results from the vapor pressure gradient between the intracellular and extracellular components. Cooling slowly results in cell dehydration but rapid cooling can lead to plasma membrane rupture
Name 2 cryoprotectants
- dimethylsulfoxide
- glycerol
What is the primary patency of cryopreserved saphenous vein grafts for peripheral bypasses at 1 year?
30%
What is the limb salvage rate of bypasses using cryopreserved saphenous vein at 2 years?
70% (higher than primary patency which is only 30% at 1 year)
