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Human Umbilical Vein and Other Biografts for Atherosclerotic Lower Extremity Occlusive Disease
The choice of intervention and conduit for lower extremity arterial reconstructions when the ipsilateral greater saphenous vein (GSV) is not present remains controversial. Many reconsider less optimal endovascular interventions, and others opt for use of the contralateral GSV, followed by other autogenous veins, sometimes used as composite grafts. When no autogenous conduit is available, options for revascularization include prosthetic grafts, modified biologic grafts, endovascular recanalization, or limb amputation.
This has led to exploration of other biologic tissues, such as human umbilical vein (HUV) grafts, fresh and cryopreserved venous and arterial homografts, and bovine heterografts. The potential benefit of biografts is the availability of an off-the-shelf graft that handles similarly to autogenous tissue and that has presumed improved patency and decreased risk of infection.
There has been variable level of enthusiasm regarding modified biologic grafts over the past several decades. The development of new endovascular techniques and the inherent problems with biologic grafts have diminished their role in treatment of vascular diseases. The choice to use a biologic graft currently is usually influenced by tissue loss, active infection, and small vessel caliber. Unfortunately, few studies directly compare the efficacy of modified biografts against prosthetic grafts.
Human Umbilical Vein Grafts
The use of glutaraldehyde-tanned umbilical grafts was first reported by Dardik in 1976. The original umbilical grafts were prepared by manually stripping the human umbilical cord tissue and stabilizing the vessel wall with glutaraldehyde. More recently, grafts were prepared with computer-controlled mechanical lathes, giving a uniform wall thickness, and a Dacron mesh was added on the outer surface to decrease risk of aneurysmal degeneration. The process of glutaraldehyde tanning resulted in a conduit devoid of endothelium. The graft was not at increased risk for thrombosis caused by rejection, but it lacked the antithrombotic benefits of an endothelial lining. Previously, the HUV graft was available from Synovis Life Technologies (St. Paul, MN), but it is currently off the market and there are no imminent plans to return it, mainly because of U.S. Food and Drug Administration (FDA) requests for tracing the umbilical cord to the infant to decrease risk of transmittable diseases.
Technical Features
HUV grafts do not tolerate traction in the tunneling process and require passage through a tube during their placement to prevent damage to the graft. Similarly, standard vascular clamps were not applied to these grafts; tourniquet control was used to avoid damage to the conduit. Thrombosed grafts were difficult to declot with balloon catheters. To decrease the risk of anastomotic aneurysm formation, the manufacturer suggested that the entire wall, including supporting Dacron mesh, be incorporated in the suture line. Finally, postoperative anticoagulation was also strongly recommended.
Patency Data
Dardik, in his initial experience with 907 bypasses performed for critical limb ischemia in 95% of patients, found a 5-year assisted primary patency rate of 57% for femoropopliteal and 33% for femorocrural bypasses. After the graft was modified, the same group reported on 71 additional infrageniculate bypasses, with a 58% primary patency for below-knee popliteal reconstructions and 36% for crural reconstructions. Secondary patency was 64% and 41%, respectively. Results of patency and limb salvage from other studies of HUV were similar for bypasses above the knee but were variable for more distal bypasses ( Table 1 ).
TABLE 1
Patency for Human Umbilical Vein Grafts
| Author | Year | No. of Grafts Implanted | Patency of Popliteal Bypass (%) | Patency of Crural Bypass at 5 Years (%) |
|---|---|---|---|---|
| Dardik | 1988 | 907 | 57 | 33 |
| Batt | 1990 | 105 | — | 29 (3 years) |
| Sommeling | 1990 | 227 | 55% below knee, 57% above knee | 19 |
| Dardik | 1995 | 71 | 58 | 36 |
| Sato | 1995 | 111 | — | 60.9 |
| Johnson (VA) | 2000 | 261 | 49 | — |
| Dardik | 2002 | 283 | 56 | 43 |
Comparative Studies
In 1982, Cranley and colleagues reported a 3-year patency of 59% for saphenous vein, 35% for polytetrafluoroethylene (PTFE), and 31% for HUV for tibial reconstructions for critical limb ischemia. The New England Society of Vascular Surgery Registry in 1991 compared HUV and extended PTFE (ePTFE) and found improved 5-year patency with HUV over ePTFE for femoropopliteal above-knee bypass (69% vs. 45%) and for below-knee bypass (45% vs. 22%). A Veterans’ Affairs (VA) randomized prospective study of HUV found a 5-year assisted primary patency of 53% for above-knee bypasses with HUV versus 73% for GSV and 39% for ePTFE. However, patients with HUV had the highest early thrombosis and amputation rate. Other randomized studies comparing HUV to ePTFE have found higher patency rates for HUV at 3 to 6 years, ranging from 42% to 75% versus 22% to 34% for PTFE.
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