Composite Sequential Bypass for Lower Extremity Occlusive Disease

Indications

Graft patency after a distal bypass is limited by several factors. Typically, extensive multilevel disease exists, and the runoff may be compromised, increasing outflow resistance. This causes low flow rates through bypass grafts and can particularly limit the patency of prosthetic grafts. In addition, bypass to the distal tibial or pedal vessels is often required to ensure adequate outflow, and the long graft length inherently increases the resistance to blood flow. Kinking or compression of prosthetic grafts at the knee joint also decreases blood flow rates and fosters thrombosis. Size and compliance mismatch between prosthetic graft and native artery inevitably occurs at the distal anastomotic interface and is thought to increase the incidence of intimal hyperplasia. These factors combine to increase resistance, decrease flow rates, and thereby compromise graft patency. Composite sequential grafting overcomes many of these inadequacies.

A composite sequential graft allows the construction of a femorotibial bypass of sufficient length in the absence of adequate autologous vein. In addition, by placing the popliteal anastomosis above the knee, there is little chance of prosthetic graft kinking. Finally, the use of autologous vein in the distal segment allows a vein graft interface with the native artery, thereby reducing size and compliance mismatch and also anastomotic intimal hyperplasia.

Dale, Pridgen, and Shoulders first attempted to overcome these factors by using a combination of polytetrafluoroethylene (PTFE) and saphenous vein sewn end-to-end to construct a composite bypass. Their initial experience with 17 patients was disappointing and resulted in 16 graft occlusions within the first year. Subsequent reports have shown some improvement in early patency rates for pure composite grafts, but they are still unsatisfactory compared with saphenous vein bypass.

In 1972, DeLaurentis and Friedmann modified the direct composite technique in an attempt to overcome these limitations. They originally reported composite sequential grafts in three patients, using Dacron graft to the popliteal level in an end-to-side fashion. Saphenous vein was then anastomosed to the artery just below this anastomosis in an end-to-side fashion and used to bypass to a distal patent vessel. A 10-year follow-up study of 33 femoropopliteal and 22 femorotibial composite sequential grafts documented cumulative patency rates of 48% and 42%, respectively, at 5 years. The overall limb salvage rate was 86%.

Flinn and associates described an initial experience with composite sequential grafts in 1984. Sequential saphenous vein grafts and sequential all-prosthetic grafts with a side-to-side anastomosis with the popliteal artery were compared with 30 composite sequential grafts. Cumulative life-table patency at 1 year and 2 years were 93% and 80%, respectively. These results were not statistically significantly different from the all-vein group but were significantly improved over the all-prosthetic group. Furthermore, they confirmed that the longer operative time required for composite sequential grafting did not result in a significant increase in morbidity and mortality, as compared with standard greater saphenous vein femorotibial bypass.

Verta described his experience with the inverted- Y or piggyback technique with a limb of PTFE to the popliteal artery and a second limb of saphenous vein off of the PTFE to the distal vessel. He reported on 31 femorotibial grafts and 23 femoropedal grafts. By life-table analysis, 2-year and 4-year patency rates were 81% and 72%, respectively. Limb-salvage rates were 88% and 79% at these times.

Alexander and associates compared composite sequential grafts with in-situ saphenous vein, all-prosthetic femorotibial grafts, and prosthetic femoropopliteal grafts to an isolated popliteal segment. As anticipated, the in-situ saphenous vein group was significantly superior to the others. Patency rates at 2 years and limb-salvage rates were statistically greater in the composite sequential group compared with the all-prosthetic and blind segment groups.

Gargiulo, Veith, and associates described their experience with composite sequential grafts in a 14-year period. Twenty-five composite sequential bypass were performed in 24 patients, using a modified configuration of the prosthetic–vein anastomosis. Cumulative primary patency rates were 80% at 3 years and 65% at 5 years. The limb-salvage rate was 85% at 4 years.