Operative adjuncts for distal revascularization

Vein patching reduces neointimal thickening associated with prosthetic graft implantation

PURPOSE

Modified anastomotic techniques utilizing autogenous vein-cuffs or patches have been devised with the hope of improving prosthetic graft patency. The mechanisms of the presumed improvement in patched anastomoses have never been elucidated and remain speculative. We characterized the healing response of the Taylor vein patch in prosthetic arteriovenous fistulae in a canine model of intimal hyperplasia.

METHODS

Six adult dogs underwent placement of bilateral (6 patched, 6 control) 4-mm diameter expanded polytetrafluoroethylene loop femoral artery-vein fistulae. Serial duplex ultrasound examinations confirmed graft patency until explant at 6 weeks. Differential light microscopy with computerized image analysis was performed on serial 5-microm sections. Intimal thickness through the venous anastomosis and outflow veins of Taylor patch and control (nonpatched) grafts were compared. Cell type-specific immunocytochemical antibody stains for smooth muscle cells (alpha SMC actin) and endothelial cells (von Willebrand factor) were performed.

RESULTS

Eleven of 12 grafts remained patent for 6 weeks, 1 control graft thrombosed. Mean duplex-derived peak systolic velocities of patched (96 cm/sec) and control (108 cm/sec) grafts were similar. Microscopy revealed more intimal pannus anastomotic suture line ingrowth in controls (mean thickness = 178 microm) than Taylor patched grafts (mean 147 microm, p = 0.0002). Significantly less intimal thickening was present in the outflow vein of patched (mean thickness = 90 microm) versus control grafts (mean 195 microm, P <0.0001). The intima maintained a single cell layer of vWF + endothelial cells, while the majority of the cells comprising the lesion expressed alpha SMC actin.

CONCLUSION

Perianastomotic pannus is primarily composed of intimal smooth muscle cells. Neointimal thickening is significantly reduced in prosthetic arteriovenous fistulae created with the Taylor vein patch in a canine model. Reduction in perianastomotic intimal thickening may explain the reported clinical improvement in prosthetic bypass graft patency when modified with vein patch techniques.

Polytetrafluoroethylene femorodistal grafts: can the use of a vein collar offer patients a reasonable chance of success?

The growing number of patients with critical ischemia who lack a suitable autogenous vein for grafting pose a particular problem for the vascular team. In such patients the use of a polytetrafluoroethylene graft with a distal anastomotic vein cuff or patch has been advocated as an alternative to primary amputation. The use of such adjunctive techniques is reviewed through a 3-year retrospective study of 50 patients under the care of one surgeon. Data analyzed include patient demographics, risk factors, and presenting symptoms. All patients were included in a Duplex graft surveillance program. The cumulative patency rates at 1 and 2 years were 56% and 55%, respectively, with limb salvage rates of 85% and 80%. The data support a reconstructive approach to maintain the quality of the patient's life.

Venous allografts for infrainguinal vascular bypass

Between 1978 and 1993, 107 patients received venous allografts for infrainguinal revascularization because autogenous material was unavailable. These operations comprised 7.4% of 1442 reversed vein bypass procedures performed during the same period. Alloveins were harvested during varicose vein stripping and stored up to 10 days in saline solution containing heparin and antibiotics. Veins with or without minimal degenerative changes were used and when necessary segments were sutured end-to-end to obtain a convenient length. The patients comprised 95 men and 12 women of age range 44-87 years. All operations were performed for limb salvage (rest pain and gangrene); 40 femoropopliteal and 67 femorocrural bypasses were performed; 66 were primary reconstructions and 41 secondary reconstructions. The operative mortality rate was 3.7%. Early thrombosis occurred in 18 patients (16.8%), nine of whom were successfully reoperated upon. The cumulative patency rates for all bypass operations was 82.9%, 38.7% and 21.3% at 30 days, 3 and 5 years, respectively, the limb salvage rates being 84.8%, 48.0% and 29.2%, respectively. Allografts may have a place in lower-limb bypass surgery in the absence of veins, polytetrafluoroethylene or human umbilical vein.