Scandinavian Miller Collar Study Group. PTFE bypass to below knee arteries: distal vein collar or not? A Prospective randomised Multicentre study. EJVES 2010; 39: 747-54.
In a nutshell
Vein infrainguinal bypass grafting is known to be associated with significantly higher patency rates and limb salvage compared with prosthetic grafts. However, when prosthetic graft is used the interposition of a vein cuff or collar is believed to result in improved patency rates. This trial was designed to assess whether use of a vein cuff or collar in patients undergoing prosthetic femoro to below knee popliteal bypass grafting or femorodistal bypass grafting is associated with improved patency rates and limb salvage in patients with critical limb ischaemia.
Three-hundred and fifty-two patients with critical limb ischaemia (rest pain, tissue loss or gangrene) were randomised into two groups: bypass grafting with vein cuff interposition or bypass grafting with direct anastamosis without vein interposition. There was no difference between the two groups at baseline. The primary outcome was primary occlusion. The secondary outcomes were secondary occlusion and amputation (below knee, above knee or foot). Two-hundred and two patients underwent femoro to below knee popliteal bypass and 150 underwent femorodistal bypass grafting. For femoropopliteal bypass grafting, at three years the primary patency was 26% (95% CI 18-38) with a vein cuff compared with 43% (95% CI 33-58) without (p=0.0853). For femorodistal bypass, the three year primary patency rate was 20% (95% CI 11-38) with a vein cuff and 17% (95% CI 9-33) without (p=0.228). There was no significant difference in limb salvage with or without vein cuff in femoropopliteal bypass (64% vs 61%; p=0.757) or femorodistal bypass (59% vs. 44%; p=0.187). Similarly, there was no difference in survival at three years between the two groups (60% vs 67% for femoropopliteal bypass; 66% vs. 53% for femorodistal bypass grafting).
Second opinion
This randomised trial casts doubt on the generally held opinion that use of a vein collar or cuff with prosthetic bypass grafting in the infrainguinal region results in improved patency rates. However, it was only powered to detect a 50% improvement in primary patency with use of a vein cuff. Furthermore, the trial was stopped without having recruited the 190 patients estimated to be required in the femorodistal bypass graft group in the sample size calculation. On the other hand, while it was estimated that 130 patients would be required in the femoro to below knee popliteal bypass group, 220 were recruited.
It is not clear who carried out the assessment of patency of the grafts and whether those carrying out the assessment were blinded to the type of procedure performed. The method by which a graft occlusion was identified was not stated by the authors.
The patency rates reported in this study both for femoro to below knee popliteal bypass and femorodistal bypass at three years are low. This is probably due to the fact that all patients in this trial were suffering from critical ischaemia. The high mortality rates at three years highlight the extensive burden of disease in patients with critical ischaemia.
The verdict
- Use of a vein cuff in prosthetic femoro to below knee popliteal bypass and femorodistal bypass grafting does not appear to improve patency rates or limb salvage.
- Further research in this area is required.
Kevin Cassar
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