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Short Vein Grafts from the Distal Superficial Femoral, Popliteal, or Infrapopliteal Arteries to More Distal Arteries for Limb Salvage
The superficial femoral artery (SFA) is the infrainguinal vessel most commonly involved with severe atherosclerotic occlusive disease. Thus, it is not surprising that vascular surgeons have been reluctant to accept the concept of preferentially using an inflow site distal to the common femoral artery (CFA). the CFA might not be safe or feasible and a more distal donor site must be considered if limb salvage is to be achieved. These situations include patients who come to the hospital with dense groin scarring caused by previous interventions or have a groin infection. Also, increasingly, patients are found to have insufficient lengths of autogenous vein as a result of previous cardiac or infrainguinal bypass procedures.
Because of a surprisingly low incidence of short vein graft failure caused by progression of proximal arteriosclerosis (6%), and because these bypasses have had a better outcome in restricted outflow situations, we currently use the distal, most continuously patent portion of the arterial tree for inflow in bypass procedures to the infrapopliteal arteries. This approach has also evolved from previously published experiences demonstrating the efficacy and durability of shorter arterial bypasses originating from the distal SFA, the popliteal artery, and the tibial arteries. The superiority of the short vein approach, in terms of graft patency and limb salvage, has not conclusively been demonstrated, yet it offers several real and potential advantages.
General Considerations
Critical limb ischemia (CLI) continues to be the only clear indication for arterial bypasses below the popliteal artery in patients with advanced arteriosclerosis. Approximately 70% of these patients come to the hospital with tissue loss, and the remaining patients complain of severe rest pain.
Despite recent improvement in computed tomography and magnetic resonance imaging of the peripheral vascular system, we rely primarily on contrast arteriogram and duplex arteriography. The hemodynamic significance of arterial stenosis should be documented by intraarterial blood pressure measurements with liberal use of vasodilators. If a significant blood pressure gradient in measured proximal to the elected bypass inflow site, we favor preoperative or operative balloon angioplasty to diminish the magnitude of the operation or to shorten the length of the vein graft required for the arterial reconstruction. In fact, we have not hesitated to perform a proximal angioplasty of the SFA or the popliteal artery in tandem with a short distal vein bypass.
This combined approach has been limited to patients who lack a sufficiently long saphenous vein or who have groin infection or a disadvantaged outflow tract. In a review of 300 infrapopliteal bypasses, only 72 (24%) originated form the CFA. However, our use of distal inflow sites may be in part because almost half of these patients were diabetics and up to a 40% stenosis of the inflow arteries was considered acceptable.
Improved Graft Patency Rates
In 1981, Veith and associates compared the patency results for 290 popliteal bypasses originating from the CFA to 60 popliteal bypasses originating from the SFA or the above-knee popliteal artery. At 4 years, the cumulative patency rates were 66% and 81%, respectively. Although the difference was not statistically significant, it attested to the durability of these nonstandard inflow sites. Similarly, the 4-year patency for 79 infrapopliteal bypasses originating from the CFA was 50%, and for the 129 bypasses originating from the SFA or the popliteal artery it was 58% at comparable intervals. Finally, a series of 153 popliteal to infrapopliteal bypasses published by the Montefiore group generated an acceptable primary bypass patency rate of 55% at 5 years.
In our data, we measured the length of the vein graft in the infrapopliteal bypasses rather than the site of inflow, and only then was it possible to document the superiority of the shorter grafts in terms of patency. This was in a retrospective review of 237 infrapopliteal vein bypasses performed in 215 patients in which these bypasses were arbitrarily divided into two groups according to the length of the vein. In the long-vein-graft group (117 bypasses) the vein varied from 42 to 92 cm, with a mean of 60.9 ±9 cm, and in the short-vein group (120 bypasses) the vein length varied from 6 to 40 cm, with a mean of 24.7 ±8 cm. Both groups were comparable for diabetic status, indication for operation, and the site for the distal anastomosis.
Poor runoff was more prevalent in the short-vein group. Despite this important variable, the short-vein group had a significantly better patency rate at 3 years (45% long veins vs. 63% short veins, p < .05). When the 3-year graft patency rates for bypasses performed in the presence of good runoff were compared for the short and long veins, these differences were found to be statistically insignificant. Conversely, in poor or disadvantaged outflow situations, superior patency results were achieved by the short-vein bypasses. In addition, the 2-year graft patency for the 44 longest vein bypasses from the CFA to the distal third of the infrapopliteal arteries were compared to the 24 shortest tibiotibial vein bypasses. The results obtained were even more pronounced in favor of the short-vein group (45% vs. 86%).
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