What are the Doppler ultrasound criteria suggested by Bandyk to prompt further work-up and potential repair of a failing graft?
Peak systolic velocity exceeding 300 cm/s and a peak systolic velocity ratio across the stenosis exceeding 3.5.
p.10
Strategies for Improving Prosthetic Graft Patency
What is the role of dual antiplatelet therapy in distal bypasses with prosthetic grafts?
It reduced the relative risk of graft occlusion by 35% without major hemorrhagic events.
What were the findings of the Albany group's comparison of bypasses with spliced vein segments to ePTFE and a Miller vein cuff?
The primary patency was better with the vein bypasses, although 25% of the spliced vein procedures required secondary revision. Spliced vein procedures involved increased operative time, longer hospital stays, greater intraoperative blood loss, and greater perioperative morbidity.
p.6
Prosthetic Grafts in Vascular Surgery
What is the purpose of extending the patch to reconfigure the distal anastomosis?
To provide adequate revision.
p.11
Clinical Applications of Prosthetic Grafts
What is the benefit of warfarin in patients with low velocity grafts?
It has been shown to be beneficial.
p.4
Strategies for Improving Prosthetic Graft Patency
What are the disadvantages of the Miller cuff technique?
Significant turbulence at the anastomotic reservoir, difficulty in achieving an adequate angle between the graft and recipient artery, and immediate and early graft failures.
p.2
Materials for Prosthetic Grafts
What are the most commonly used prosthetic materials for revascularization surgery?
Dacron and expanded polytetrafluoroethylene (ePTFE).
p.2
Materials for Prosthetic Grafts
What are the advantages of knitted Dacron grafts?
Better compliance but have larger pores.
p.5
Strategies for Improving Prosthetic Graft Patency
What is the Distal Vein Patch (DVP) technique designed to take advantage of?
Standard techniques known to all vascular surgeons with the potential benefit of a venous adjunct at the distal anastomosis of the prosthetic graft.
p.4
Strategies for Improving Prosthetic Graft Patency
What is the Miller cuff technique used for in prosthetic graft procedures?
A venous cuff is interposed between a prosthetic graft and the target artery to improve patency.
p.8
Clinical Applications of Prosthetic Grafts
What did a study of covalently bonded grafts find regarding systemic markers of hemostasis?
No increase in the systemic markers of hemostasis in vivo.
p.9
Clinical Applications of Prosthetic Grafts
What were the overall results of the Dutch multicenter randomized study regarding the therapy for prosthetic grafts and veins?
No advantage of one therapy over another for overall data, but the prosthetic group had better results with aspirin alone, whereas the vein group had better results with warfarin alone.
What are the potential causes of graft failure in prosthetic conduits?
Technical error, myointimal hyperplasia, and acceleration of atherosclerosis in the arterial bed.
p.7
Prosthetic Grafts in Vascular Surgery
What are the reported patency rates for heparin-bonded Dacron versus ePTFE for femoropopliteal bypass at 1 year?
80% for below-knee bypasses and primary and secondary rates of 82% and 97% for popliteal and tibial bypasses.
p.3
Materials for Prosthetic Grafts
Why is polypropylene only used as part of multi-component grafts?
Due to susceptibility to oxidation, which renders the polypropylene inert.
What are the reported primary patency rates for spiral laminar flow grafts for above-the-knee bypasses at 12, 24, and 30 months?
86%, 81%, and 81% respectively.
How can the failure of prosthetic conduits be classified?
As early, midterm, or late failures.
p.2
Materials for Prosthetic Grafts
Who developed the polyester fabric Dacron and in which year?
British chemists Whinfield and Dickinson in 1941.
Why is detection of a failing graft prior to thrombosis important?
It simplifies medical and operative management and improves long-term patency and limb salvage.
p.4
Strategies for Improving Prosthetic Graft Patency
What is the Taylor patch technique used for in prosthetic graft procedures?
The graft is partially sutured onto the target artery, and a vein patch is used to suture the rest of the graft onto the artery and increase the anastomotic surface area.
p.7
Limitations and Risks of Prosthetic Grafts
What is the potential concern associated with implantation of heparin-bonded grafts?
Heparin-induced thrombocytopenia.
p.3
Limitations and Risks of Prosthetic Grafts
What has impeded the use of human umbilical vein grafts?
An aneurysmal degeneration of the graft material.
p.8
Clinical Applications of Prosthetic Grafts
What is the purpose of adding an arteriovenous fistula at the distal anastomosis of a bypass?
To increase bypass success by decreasing graft thrombosis and reducing outflow resistance.
p.9
Materials for Prosthetic Grafts
What is the 'Patchula' Technique?
It involves opening the target tibial artery and corresponding tibial vein longitudinally and creating a common ostium with an onlay patch.
p.1
Strategies for Improving Prosthetic Graft Patency
What are some strategies for improving prosthetic graft patency?
Vein patches and cuffs, heparin-bonded grafts, spiral laminar flow grafts, distal arteriovenous fistula, deep venous arterialization, and adjunct medical therapies.
p.6
Prosthetic Grafts in Vascular Surgery
What is the DVP technique used for?
To improve prosthetic graft performance in critical limb ischemia.
p.4
Strategies for Improving Prosthetic Graft Patency
What are some strategies for improving prosthetic graft patency?
Venous adjuncts at the anastomosis, heparin bonding to the prosthetic luminal surface, and the addition of a distal arteriovenous fistula.
p.9
Strategies for Improving Prosthetic Graft Patency
What is the role of adjunct medical therapy in improving prosthetic graft patency?
It has been debated, and there is no clear, consistent data to suggest an ideal adjunct medical therapy.
What does graft surveillance involve?
Clinical evaluation for recurrent or new symptoms of limb ischemia, examination of pulses, and ankle–brachial index.
p.4
Strategies for Improving Prosthetic Graft Patency
What are the disadvantages of the Taylor patch technique?
Direct exposure of the tibial artery to the ePTFE graft for the proximal half of the anastomosis, anastomotic constriction, and difficulty in placement at the inframalleolar position due to anatomic space constraints.
p.8
Clinical Applications of Prosthetic Grafts
What is the technique of deep venous arterialization (DVA) directed at providing options for?
Patients with a 'desert foot' who would otherwise undergo amputation due to disadvantaged arterial runoff.
p.1
Materials for Prosthetic Grafts
What are the properties of an ideal prosthetic conduit?
Impermeable, compliant, biocompatible, durable, easy to sterilize, available in different sizes, resistant to thrombosis and infection, and cost-effective.
p.2
Materials for Prosthetic Grafts
What is the theoretic enhancement of the property of a prosthetic graft achieved by carbon coating?
Enhancement of the luminal surface of the graft.
What did the Cochrane Review report about the role of aspirin in preventing postoperative thrombosis after lower extremity bypass?
It reported an improved graft patency with aspirin for up to 12 months in patients with prosthetic grafts.
p.7
Materials for Prosthetic Grafts
What is the purpose of heparin bonding on the inner surface of a prosthetic conduit?
To reduce graft thrombosis and hyperplasia.
p.8
Materials for Prosthetic Grafts
What is the difference between covalently bonded grafts and older grafts?
Covalently bonded grafts do not lead to subsequent release of heparin into the bloodstream, unlike older grafts that used ionic interaction with the graft surface.
p.9
Clinical Applications of Prosthetic Grafts
What did a Dutch multicenter randomized study compare in patients who underwent infrainguinal bypass?
Aspirin versus warfarin therapy.
What imaging technique has been added to graft surveillance protocols?
Vascular laboratory imaging.
p.1
Clinical Applications of Prosthetic Grafts
What are the different indications for which vascular surgeons use prosthetic grafts?
Aortic aneurysm repair, arterial bypass in the upper and lower extremities, and dialysis access creation.
p.3
Clinical Applications of Prosthetic Grafts
What are the advantages of prosthetic AV grafts?
Ease of placement, shorter time from operation to utilization, and a potentially large surface area for cannulation.
p.5
Prosthetic Grafts in Vascular Surgery
What is the primary patency at 2 years for grafts using ePTFE with a vein cuff compared to composite saphenous vein grafts?
49% for the vein cuff patients versus 44% for the composite vein patients.
p.6
Materials for Prosthetic Grafts
What are the advantages of a venous adjunct at the distal anastomosis?
Biologic and mechanical factors, including fibrinolytic and antiplatelet activity, and minimizing expansibility mismatch.
p.7
The Blood-Material Interface
How does heparin bonding affect platelet adherence and thrombus formation?
It reduces platelet adherence and thrombus formation on the graft surface.
p.3
Prosthetic Grafts in Vascular Surgery
What is the reported 16-month patency of 4mm lower extremity polypropylene grafts in dogs?
81% compared with 69% and 20% for Dacron and ePTFE, respectively.
p.8
Strategies for Improving Prosthetic Graft Patency
What is the purpose of inducing a spiral laminar flow pattern in prosthetic grafts?
To inhibit the formation of neointimal hyperplasia and stabilize flow patterns through stenotic areas.
p.9
Clinical Applications of Prosthetic Grafts
What did The Boston Veterans Affairs Hospital Prospective Study compare?
Dual therapy, aspirin and warfarin.
p.9
Materials for Prosthetic Grafts
What is the 'Spiral Laminar Flow'?
A concept of flow in a vessel, with a corresponding prosthetic graft constructed to reproduce this flow pattern.
p.1
Limitations and Risks of Prosthetic Grafts
What are the reasons for a growing proportion of patients needing bypass surgery to lack suitable autogenous venous conduit?
Previous harvesting of the veins for coronary artery bypass, prior lower extremity revascularization procedures, small vein caliber, active infection at the vein harvest site, and vein varicosities or thrombosis.
What is the 30-day failure rate of human umbilical vein composite grafts compared to ePTFE grafts and GSV conduits?
15.4% compared to 10.5% in ePTFE grafts and 7.5% in GSV conduits.
p.11
Cellular Interaction and the Coagulation Cascade
What happens when blood encounters an artificial surface in the coagulation cascade?
Adsorption of proteins activates the complement and coagulation cascades.
p.11
The Blood-Material Interface
What is the role of prosthetic grafts with blood-compatible materials at the blood-material interface?
To minimize activation of the body’s prothrombotic and hyperplastic responses.
What are the complications associated with the use of bovine carotid artery grafts during fistula revision procedures?
Graft thrombosis and infection occur at higher rates compared with native conduit AV fistulae.
