Do additional surgical techniques at the lower end of bypasses in the leg improve the chance of the bypass working and saving the leg from amputation?

If the artery to the lower leg is blocked, replacement of the blocked segment with a bypass graft can save the leg from amputation and reduce the pain resulting from inadequate blood supply to the leg. The best material to use for a bypass graft is the patient's own vein (autologous vein). If a suitable vein is not available, then an artificial tube (synthetic graft) is used. The outcome from these synthetic grafts is less favourable than with autologous veins if the graft extends to below the knee. This review looked at six trials, with a combined total of 885 patients, which compared different methods of making these grafts. Results from two trials which looked at the effect of inserting a cuff of vein at the lower end of the synthetic graft before attaching it to the artery below the knee are conflicting. With one study showing that the bypass graft remains functional for a longer period of time and in the other study no benefit was seen. If a synthetic graft is made in a fashion imitating the shape of a vein cuff, then the same benefit can be achieved. The results also show that when short lengths of vein are joined together to form a sufficiently long graft, the bypass works for longer, although this does not result in fewer amputations. Finally, there is no added benefit for graft patency or amputation rate if a connection is made between the artery and the vein (fistula) when constructing a vein cuff with the synthetic graft but the operation takes longer.

Authors' conclusions: 

There is some evidence that a vein cuff at the distal anastomosis site improves primary graft patency rates for below knee PTFE graft, but this does not reduce the risk of limb loss. Evidence for this beneficial effect of vein cuffed PTFE grafts is weak and based on an underpowered trial. Pre-cuffed PTFE grafts have comparable patency and limb salvage rates to vein cuff PTFE grafts. The use of spliced veins improved secondary patency but this did not translate into improved limb salvage. The use of an AVF alone showed no added benefits. A large study with a specific focus on below knee vein cuff prosthetic grafts, including PTFE, is required.

Read the full abstract...
Background: 

The use of prosthetic grafts such as polytetrafluorethylene (PTFE) or Dacron to bypass occluded arteries in the lower leg is an accepted practice in the absence of suitable autologous vein. The aim is limb salvage or functional improvement in critical limb ischaemia, but patency rates for below knee prosthetic bypasses are low. Creating a vein cuff at the distal anastomosis is thought to improve outcomes. Other techniques including the use of pre-cuffed synthetic grafts, spliced segments of vein and the creation of an arterio-venous fistula (AVF) are also used to improve patency.

Objectives: 

To compare the beneficial effects of using vein cuffed prosthetic grafts for below knee bypass in critical limb ischaemia with other types of reconstruction.

Search strategy: 

The Cochrane Peripheral Vascular Diseases Group Trials Search Co-ordinator searched the Specialised Register (last searched May 2012) and CENTRAL (2012, Issue 5) for publications comparing prosthetic infragenicular bypass using vein cuffs with other bypass techniques.

Selection criteria: 

Randomised controlled trials comparing interposition vein cuff prosthetic graft with autologous vein graft and non-cuffed prosthetic graft for infragenicular bypass in patients with critical limb ischaemia were included. Trials comparing vein cuff prosthetic grafts with or without AVF and vein cuff prosthetic grafts with pre-cuffed prosthetic grafts were also included.

Data collection and analysis: 

The trials were selected and assessed independently by two review authors.

Main results: 

Six trials with a combined total of 885 patients were included in this review. Only studies using prosthetic PTFE grafts were identified.

Two trials compared PTFE graft with or without a vein cuff. In one underpowered trial for below knee bypass the cumulative primary patency rate was statistically significantly higher in the vein cuff group (80.3% versus 65.3% at 12 months and 51.8% versus 29.1% at 24 months, P = 0.03). There was no statistically significant difference in secondary patency (82.9% versus 72.5% and 58.6% versus 34.9%, P = 0.14) and limb salvage rates (86.3% versus 71.8% and 82.6% versus 62.2%, P = 0.08) at 12 and 24 months respectively. The other trial showed no statistically significant difference between the groups at three years in the below knee femoro-popliteal bypasses (primary patency rate 26% (95% confidence interval (CI) 18 to 38) and 43% (95% CI 33 to 58), secondary patency rate 32% (95% CI 23 to 44) and 42% (95% CI 31 to 56) and limb salvage rate 64% (95% CI 54 to 75) and 61% (95% CI 50 to 74) in the collar and no collar groups respectively). In the femoro-distal bypass group, the differences in primary patency, secondary patency and limb salvage rates were also not statistically significant at three years (primary patency rate 20% (95% CI 11 to 38) and 17% (95% CI 9 to 33), secondary patency rate 22% (95% CI 12 to 39) and 20% (95% CI 11 to 35) and limb salvage rate 59% (95% CI 46 to 76) and 44% (95% CI 32 to 61) in the collar and no collar groups respectively).

One trial compared pre-cuffed PTFE grafts with vein cuffed grafts. There was no statistically significant difference in primary patency rate (62% pre-cuffed PTFE versus 52% vein cuff PTFE and 49% versus 44%, P = 0.53), secondary patency rate (66% pre-cuffed PTFE versus 53% vein cuff PTFE and 55% versus 50%, P = 0.30) or limb salvage rate (75% pre-cuffed PTFE versus 72% vein cuff PTFE and 62% versus 65%, P = 0.88) at 12 and 24 months respectively.

One trial compared spliced vein grafts with vein cuffed PTFE grafts. At 24 months, the secondary patency rate was statistically significantly higher in the spliced vein group (86% in the spliced vein and 52% in the vein cuff group, P < 0.05). There was no statistical significant difference in primary patency rate (44% versus 50%, P > 0.05) and limb salvage rate (94% versus 85%, P > 0.05).

Two trials compared vein cuff PTFE grafts with and without AVF. There was no statistical significant difference at 24 months in primary patency rate (29% versus 36%, P = 0.77; 32% versus 28%, P = 0.2), secondary patency rate (40% versus 40%, P = 0.89; 28% versus 24%, P = 0.2) and limb salvage rate (65% versus 70%, P = 0.97; 62% versus 71%, P = 0.3).

Share/Save