Vein Allografts Research Articles

Decellularized cadaver vein allografts used for hemodialysis access do not cause allosensitization or preclude kidney transplantation

Background: Dimethyl sulfoxide-cryopreserved (CRY) cadaver vein allografts used for hemodialysis access in patients with renal failure recently have been shown to cause broad recipient allosensitization, measured by panel reactive antibody (PRA) assay. Synergraft (SYN) processing is a novel method of treating tissue that decellularizes the graft (including mismatched major histocompatibility antigens) and potentially should prevent allosensitization. Methods: Twenty hemodialysis patients underwent placement of an SYN-processed cadaver vein allograft. PRA assay was used prospectively to assess allosensitization in these patients at baseline and 1-month intervals after engraftment. These results were compared with our historic series of CRY allograft recipients. Results: There was no significant difference in baseline PRA values for SYN and CRY patients (2.8% versus 2.6%, respectively). None of the SYN patients became allosensitized at 3 months postengraftment (mean PRA, 3.2%), whereas all CRY recipients became highly sensitized at a mean of 3.1 months (mean PRA, 84.1%). This result was highly significant (P < 0.0001). Conclusion: SYN processing of cadaver vein allografts successfully removes antigenic material. The use of SYN allografts in patients with renal failure for hemodialysis access does not cause allosensitization and therefore should not preclude kidney transplantation. Am J Kidney Dis 40:1240-1243. © 2002 by the National Kidney Foundation, Inc.

Saphenous vein homograft containing a valve as a right ventricle-pulmonary artery conduit in the modified Norwood operation

J Thorac Cardiovasc Surg 2002;124:1041-2

Management of infected hemodialysis access grafts using cryopreserved human vein allografts

Background: One of the most feared complications of dialysis access is prosthetic arteriovenous (AV) graft infection, which is typically treated with AV graft removal followed by a staged dialysis graft placement elsewhere. Such a treatment approach often presents a challenge since many hemodialysis-dependent patients have limited venous access that may preclude a new AV graft or dialysis catheter placement. In this article, we review the management of AV graft infection using in situ cryopreserved human vein allografts. Data sources: Functional and antigenic characteristics as well as the clinical experience of cryopreserved human vein allograft in dialysis access are reviewed. Surgical technique of in situ cryopreserved human allograft placement for infected prosthetic AV graft is also described. Conclusions: Cryopreserved vein allograft is an acceptable graft conduit in difficult hemodialysis access situations. It offers surgeons the ability to deal with the infected graft in one operative procedure with low incidence reinfection and graft patency similar to conventional prosthetic graft replacement.

Improved technique of portal vein reconstruction in pediatric liver transplant recipients with portal vein hypoplasia.

Children with small or hypoplastic portal veins represent a challenge for liver transplantation. Graft loss of up to 70% has been reported in these patients in the past. A variety of techniques has been used in both cadaveric and living related transplants in an effort to overcome this problem. Variability arises as to whether to use a vascular graft and where on the portal system to attach the graft. We present our usage of a simple and straightforward interposition iliac vein allograft fashioned in a manner to achieve large anastomotic cross-sectional area on the confluence of the superior mesenteric/splenic veins. The procedure also overcomes problems of graft vein/portal vein size mismatch in the cases where liver and vein grafts are procured from much larger donors. A total of 14 children presented with hypoplastic portal vein (diameter<5 mm), of a total of 30 consecutive patients requiring cadaveric liver transplants, and benefited from this technique. Median recipient age was 10.5 months. Revascularization times ranged from 22 to 43 min with a mean of 33 min. All patients are alive and well at a mean follow-up of 329 days (10 months). All liver grafts are well and functioning. No portal vein problem was detected. Results from this technique are clearly encouraging. Because portal vein hypoplasia is a common problem in pediatric transplant candidates, we believe this alternative technique is of interest and should be added to the transplant surgeon's armamentarium.

Use of cryopreserved cadaver vein allograft for hemodialysis precludes renal transplantation due to allosensitization

Use of cryopreserved cadaver vein allograft for hemodialysis precludes renal transplantation due to allosensitization

Autologous Endothelialized Vein Allograft

Early graft failure after the use of less satisfactory autologous grafts (30% of all vein grafts) is caused primarily by the following problems: (1) suitable autologous transplants are limited; (2) biotechnology has not yet been able to produce reliable graft substitutes that are legally and ethically approved; and (3) current prosthetic materials are prothrombotic. To overcome these problems, we developed an easily accessible, quality-controlled graft. Human autologous venous endothelial cells (HAVECs) were isolated from short segments of peripheral veins unsuitable for bypass grafting. After mechanical deendothelialization of cryopreserved allograft veins (CAVs) and precoating with recipient autologous serum, these homologous cells were seeded by use of a rotating device. Growth of a confluent HAVEC layer within 1 week in a special incubator was observed. After histological and mechanical tests, 12 patients received 15 grafts in total. Bypass operation was followed by clinical and angiographic follow-up. Production period was 22+/-8 days. HAVEC-coated CAVs showed normal connective tissue wall structure and a tight endothelial monolayer (burst pressure >2000 mm Hg). To date, 12 CABG patients lacking suitable autologous graft material have been treated. One patient died of a cause unrelated to the grafts, which were found morphologically normal and patent during autopsy. Of 15 grafts, 2 were occluded at the first angiographic follow-up. The oldest graft has now been in place for approximately 3 years. Immune suppression was not administered. At present, autologous endothelialized CAVs present good alternative small-caliber grafts for patients lacking suitable autologous vessels.

Autologous Endothelialized Vein Allograft

Background Early graft failure after the use of less satisfactory autologous grafts (30% of all vein grafts) is caused primarily by the following problems: (1) suitable autologous transplants are limited; (2) biotechnology has not yet been able to produce reliable graft substitutes that are legally and ethically approved; and (3) current prosthetic materials are prothrombotic. To overcome these problems, we developed an easily accessible, quality-controlled graft. Methods and Results Human autologous venous endothelial cells (HAVECs) were isolated from short segments of peripheral veins unsuitable for bypass grafting. After mechanical deendothelialization of cryopreserved allograft veins (CAVs) and precoating with recipient autologous serum, these homologous cells were seeded by use of a rotating device. Growth of a confluent HAVEC layer within 1 week in a special incubator was observed. After histological and mechanical tests, 12 patients received 15 grafts in total. Bypass operation was followed by clinical and angiographic follow-up. Production period was 22±8 days. HAVEC-coated CAVs showed normal connective tissue wall structure and a tight endothelial monolayer (burst pressure &gt;2000 mm Hg). To date, 12 CABG patients lacking suitable autologous graft material have been treated. One patient died of a cause unrelated to the grafts, which were found morphologically normal and patent during autopsy. Of 15 grafts, 2 were occluded at the first angiographic follow-up. The oldest graft has now been in place for ≈3 years. Immune suppression was not administered. Conclusions At present, autologous endothelialized CAVs present good alternative small-caliber grafts for patients lacking suitable autologous vessels.

Use of cryopreserved cadaveric vein allograft for hemodialysis access precludes kidney transplantation because of allosensitization

Background: Dimethyl sulfoxide–cryopreserved cadaveric vein allografts have recently been proposed as an alternative to prosthetic grafts in the problem hemodialysis population. The transfer of mismatched major histocompatibility complex I and II molecules in association with these allografts can potentially lead to allosensitization in nonimmunosuppressed individuals. Methods: In a university-affiliated medical center, 20 consecutive patients receiving technically successful upper arm cadaveric vein allograft fistulas (CAVFs) for hemodialysis between April 1999 and April 2000 were studied. A control cohort of 20 patients on a kidney transplantation waiting list was selected by nurses blinded to the study. These patients were matched for age, sex, history of transfusion, pregnancy, cause of kidney failure, and prior transplantation. The panel reactive antibody (PRA) values were recorded in this group over the same time period as the CAVF group. Results: Patients receiving CAVFs had a mean PRA assay value of 84.1% (median, 96.5%) at an average of 3.1 months after engraftment (median, 1.5 months). The preengraftment PRA values were available for seven patients who were on the transplant waiting list. Six of these patients had nonreactive PRA assays before CAVF creation. All of these patients converted to positive PRA assays after CAVF creation with a mean value of 92.3% (median, 98%) at 2.85 months follow-up (median, 1.3 months). The mean PRA value for the control cohort was 5.5% (median, 2.5%), with no patients converting from a nonreactive to a reactive PRA assay during this same time interval. Conclusion: The use of dimethyl sulfoxide–cryopreserved cadaveric vein allografts for hemodialysis access leads to broad allosensitization as measured by PRA assay. Cryopreserved cadaveric vein allografts should not be used for hemodialysis access in potential kidney transplant recipients. (J Vasc Surg 2001;34:139-42.)

A novel strategy for organ allografts using sublethal (7 Gy) irradiation followed by injection of donor bone marrow cells via portal vein.

A new strategy for organ allografts that does not require recourse to immunosuppressants is established in mice. The strategy includes sublethal (7 Gy) irradiation followed by the injection of donor bone marrow cells (BMCs) via the portal vein (P.V.) and organ allografts 1 day after irradiation. Irradiation doses (< or =7 Gy) are found to allow the recipients to survive without the need to reconstitute the BMCs, as the recipient hematolymphoid cells can gradually recover. One hundred percent of recipients irradiated with 7 Gy followed by either P.V. or i.v. injection of donor BMCs accept organ allografts (the skin, pancreas, and adrenal glands) for more than 1 year. However, organ allograft survival rates decrease when irradiation doses are reduced; the skin graft survival rate of mice treated with 6.5 Gy and P.V. injection of BMCs is 79%, whereas that of mice treated with 6.5 Gy and i.v. injection is 50%, indicating that the P.V. injection of BMCs induces persistent tolerance more effectively than the i.v. injection. H-2 typing reveals that almost all the hematolymphoid cells (>98%) in the peripheral blood and hematolymphoid organs are donor-derived even 1 year after the treatment (7 Gy and P.V.). The T cells are tolerant to both donor-type and host-type MHC determinants. The major mechanism underlying the persistent tolerance induced by this strategy seems to be because of clonal deletion. This simple and safe strategy would be of great advantage for human organ transplantation.

New alternatives in management of the infected vascular prosthesis.

Infection of vascular prosthetics implanted for arterial occlusive disease occurs in approximately 1-5% of patients, including early and late clinical presentation. The incidence of infection depends on the anatomical site, with the highest rate occurring in vascular access grafts placed for hemodialysis and in inguinal and lower extremity incisions in patients undergoing bypass procedures for femoropopliteal tibial occlusion. Treatment of prosthetic graft infection has traditionally included antimicrobials, excision of the infected prosthesis, and extraanatomical bypass. With the recognition that prosthetic infection secondary to Staphylococcus epidermidis can be managed with less extensive procedures, clinical data have been reported on in situ replacement with antibiotic-bonded prostheses. Patients who have S. aureus isolated, including methicillin-resistant S. aureus, or gram-negative pathogens, still require conventional graft excision and extraanatomical bypass. Selective review of the English-language literature. Recent clinical series show that management by graft excision of infected infrarenal aortic prosthetics and axillofemoral bypass results in 2- and 5-year survival rates of 67% and 47%, and limb salvage rates in survivors of 93% and 82% at 2 and 5 years. In situ replacement with a rifampicin-bonded prosthesis has been accomplished successfully in smaller numbers of patients and shows promising early results. Other methods under study include cryopreserved arterial and femoral vein allografts and autogenous femoral vein grafts, but data are limited when used as replacement for infected prosthetics. Advances in the management of infected vascular prostheses over the last decade have led to improved mortality and decreased amputation rates with conventional excision and extraanatomical bypass. Newer methods including in situ graft replacement with antibiotic-impregnated prosthetics appear suitable for low-virulence S. epidermidis infection. Early results are promising for cryopreserved allografts and autogenous femoral vein in situ grafts; however, more clinical experience and longer follow-up will be needed to confirm their durability in a contaminated field.

Saphenous vein homograft: a superior conduit for the systemic arterial shunt in the Norwood operation

Background. Excessive pulmonary blood flow increases ventricular volume work in the face of inadequate systemic cardiac output, low diastolic blood pressure, and inadequate coronary perfusion. Using the smallest available 3-mm polytetrafluoroethylene shunts have been successful, although catastrophic shunt thrombosis has occasionally been observed. To avoid thrombosis with a smaller conduit, saphenous vein homografts (SVG) were used to construct the modified Blalock–Taussig (BT) shunts.Methods. From January 1998 to April 1999, 25 patients weighing 3.1 kg (3.0 kg or less, n = 9), at a mean age of 8.9 days, underwent stage I Norwood using an SVG BT shunt. Common heart defects were aortic atresia (n = 8), mitral atresia and double-outlet right ventricle (n = 5), and unbalanced AVC (n = 5). Mean BT shunt size was 3.2 mm, with 12 patients having shunts that were 3 mm or smaller.Results. Thirty-day hospital mortality was 8% (2 of 25). No shunt thrombosis was seen, despite banding the BT shunt in 3 patients. One patient had BT revision because of an anatomic issue not directly related to the shunt material.Conclusions. Excellent results may be achieved using SVG BT shunts in the Norwood operation. This conduit seems less likely to thrombose, both acutely and chronically, allowing the use of appropriately smaller-sized shunts in small neonates.

Suggested treatment protocol for improving patency of femoral-infrapopliteal cryopreserved saphenous vein allografts

Purpose: Cryopreserved saphenous vein allografts are used for femoral-infrapopliteal bypass graft purposes when adequate autogenous vein is unavailable. Anticoagulation, immunosuppression therapy, or both have been suggested means for improving allograft patency. Immunosuppression has significant cost and morbidity and has produced variable results. Our successful treatment of luminal surface hypercoagulability associated with certain endovascular procedures prompted the use of an anticoagulation protocol prospectively to improve graft patency and limb salvage for patients receiving femoral-infrapopliteal cryopreserved saphenous vein allografts. Methods: Between September 1995 and October 1999, 24 patients (15 men and nine women) were enrolled in a prospective clinical trial for salvage of 26 severely ischemic lower limbs with femoral-infrapopliteal cryopreserved saphenous vein allograft bypass grafts. All patients were treated with a protocol (aspirin, low-dose heparin, low molecular weight dextran 40, dipyridamole, and warfarin), and no immunosuppressive agents were used. The cryopreserved saphenous vein allografts were matched to patients by ABO and Rh compatibility. Indications for revascularization were ischemic rest pain (n = 8), nonhealing ulcer (n = 13), or focal gangrene (n = 5), and no usable autogenous vein was available. Follow-up ranged from 2 to 35 months (mean, 19 months). We studied the location and type of outflow anastomosis, specific outflow vessel, morbidity, death, secondary procedures (digital/transmetatarsal amputation), and complications related to the treatment protocol. Life table analyses of primary graft patency and limb salvage were compared with other current reported data. Results: Primary graft patency with Kaplan-Meier life table analysis was 96% at 6 months, 87% at 12 months, and 82% at 18 and 24 months. There were no reoperations for acute graft occlusion. One graft underwent late segmental aneurysmal degeneration and rupture. There were no procedure-related deaths or bleeding complications. During late follow-up, anticoagulation was discontinued in three patients (12%) because of gastrointestinal bleeding. Limb salvage was 88% at 6 months and 80% at 12, 18, and 24 months. Patients returned to ambulatory status that was limited only by their other comorbidities. Conclusion: Femoral-infrapopliteal bypass graft for limb salvage with a cryopreserved saphenous vein allograft can be an acceptable alternative when autogenous vein is not available. Our treatment protocol substantially improved allograft patency and limb salvage when compared with current published data. (J Vasc Surg 2000;32:731-8.)

Blalock-Taussig Shunt Using Fresh Saphenous Vein Homograft

The occurrence of life-threatening early and late complications following the use of expanded polytetrafluoroethylene grafts for modified Blalock-Taussig shunts prompted the application of saphenous vein homografts instead. In 21 patients with cyanotic congenital heart disease, fresh saphenous vein homografts were used for Blalock-Taussig shunts from February 1998. The veins were obtained from blood-group matched patients undergoing coronary bypass grafting in the next operating room. There was no early or late mortality. Clinical and echocardiographic studies showed that all shunts were patent and functioning well at an average follow-up of 11 months. This simple homograft technique has no ischemic time and requires no chemical or antibiotic contact.

Successful surgical thrombectomy of renal allograft vein thrombosis in the early postoperative period

We report the successful surgical treatment of two cases of renal vein thrombosis, each occurring early after kidney transplantation. Prompt intervention was a result of accurate diagnosis by color Doppler ultrasonography. Invasive radiological procedures were not useful. Although recent advances in thrombolytic therapy have created several alternatives to open surgery, the rationale for surgical exploration in these cases was to remove the thrombus quickly, to avoid the postoperative bleeding complications of thrombolytic therapy, and to correct any technical or anatomic problems.

Controlling Transplant Vasculopathy in Cryopreserved Vein Grafts with Polyethylene Glycol and Glutathione During Transport

Background: the biological characteristics of cryopreserved allografts are poorly understood, although many factors are known to influence their outcome. This study examines the development of transplant vasculopathy in both fresh and cryopreserved vein allografts and specifically assesses the efficacy of a transport solution containing 10% polyethylene glycol and 10 μM glutathione (PEG/GSH). Methods: jugular veins were harvested from control donor rabbits and transplanted as interposition carotid bypass grafts in 30 New Zealand White (NZW) rabbits. Ten received the fresh jugular veins (fresh). Ten animals received jugular veins which had been harvested, transported in a physiological solution, cryopreserved and stored in a standard fashion (cryopreserved). Ten animals received jugular veins which had been harvested, transported in the same solution with the addition of PEG/GSH, cryopreserved and stored in a standard fashion (PEG/GSH). Cryopreserved jugular veins were stored for 6 weeks before transplantation. All animals were sacrificed 28 days postoperatively. Vein grafts were perfusion-fixed and wall dimensions were determined by planimetry. Results: all transplanted grafts were patent at harvest. The control cryopreserved vein grafts showed a 54% increase in mean intimal thickness (63±10 μm vs. 41±3 μm p<0.05) but no change in mean medial thickness (125±9 μm vs. 119±13 μmp =n.s. ) compared to the fresh allograft. Transport of the grafts in PEG/GSH solution resulted in the abolition of the increase in intimal thickness (41±4 μmp <0.01) associated with cryopreservation without a change in medial thickness (140±15 μmp =n.s.) compared to the cryopreserved allograft. Conclusion: cryopreserved vein grafts develop significant intimal hyperplasia compared to freshly transplanted grafts. The use of PEG/GSH in the transport solution significantly reduces this transplant graft intimal hyperplasia to that which develops in fresh grafts and may lead to improvements in the clinical use of cryopreserved veins.

IMMUNE RESPONSE TO CANINE LYOPHILIZED VEIN ALLOGRAFTS

423 We investigated the immune response to lyophilized allograft vein transplants implanted in the canine venous system without immunosuppression. Lyophilized veins (n=20) were prepared by vacuum freeze drying canine jugular veins within 24 hours of harvest. The grafts were stored at room temperature for two weeks before they were transplanted as interposition grafts into the femoral veins of 10 mongrel dogs. Each animal received an end to end interposition autograft (n=10) vein in one limb, and a randomly assigned allograft (n=10) in the opposite limb. Typing for three blood group factors (DEA-1.1/1.2/7) was obtained. Pre and posttransplant lymphocyte crossmatches were performed on each animal. Transplants were performed independent of blood type or crossmatch result. Aspirin was given perioperatively. Vein grafts were harvested after six weeks, and histologic evaluation was performed. Both allografts and autografts had a patency rate of 70%. Positive crossmatch was not associated with graft occlusion. None of the six negative preoperative crossmatches became positive postransplant. Lymphocytic CD3 + T cell infiltrate as measured by cell count per high power field, was not significantly different between allografts and autografts (1.44±0.82 vs. 1.08±0.42, p=N.S.). Cellular infiltrate was similar in allografts regardless of positive (n=4) or negative (n=6) crossmatch results (1.46±0.95 vs. 1.43±0.821). There was a trend for more cellular infiltrate in allografts implanted in blood type mismatched (n=3) recipients (1.97±1.17 vs. 1.22±0.61 p=N.S.). Lyophilized vein allografts implanted in the venous system without immunosuppression have the same patency rate as autografts. CD3 + T lymphocytic infiltrate and patency rates are similar regardless of positive pretransplant crossmatch or blood type mismatch. Lyophilized vein allografts represent an alternative for venous reconstruction. Supported in part by a grant from the Physicians Medical Education and Research Fund, Knoxville, TN.

Current Status Of Cryopreserved Saphenous Vein Homografts

The lack of suitable autogenous tissue and the easy availability of cryopreserved allograft veins have recently led to increased utilization of allograft bypasses. Improved methods of cryopreservation have been shown to maintain integrity of the endothelial and smooth muscle cell layers prior to implantation, increasing enthusiasm for the vein bank. However, after implantation, immune reactions result in eventual cell death and fibrosis of the conduit, with poor long-term patency. Attempts at modification of the immune response are preliminary and suggest a potential for improved patency. However, long-term patency remains poor, with only 19 to 42% of grafts patent at 2 years. Current use of the cryopreserved allograft vein should be limited to distal bypass for limb salvage in the absence of suitable autogenous tissue or revascularization for limb-threatening ischemia in an infected field in the absence of suitable autogenous tissue.

Denatured venous homograft as an arterial substitute in civilian vascular injuries. Thirty months' experience

Autologous saphenous vein (ASV) for arterial reconstruction, in vascular limb injuries is the graft material of choice. Denatured saphenous vein homograft (DSVH), thanks to its characteristics of readily available autologous biological prosthesis, has been proposed as alternative. We report our prospective experience with DSVH employed for arterial reconstruction in civilian limb vascular injuries. From January 1994 to June 1996, DSVH was implanted in 16 male patients (pts.) treated for arterial civilian injuries of eight upper limbs and eight lower limbs. In 14 cases it was performed as an interposition graft and in two cases a bypass. We performed a 30-month follow-up and a 20-month mean follow-up. Four patients had graft thrombosis at the first postoperative week and were submitted to the replacement of the graft with reappearance of distal arterial pulse; one of them had graft failure at the fifth postoperative week and because the necrosis due to extensive soft tissue damage, he was submitted to limb amputation. After 30-months' follow-up we obtained 75% primary patency rate and 93% secondary patency rate. In the absence of suitable ASV, DSVH appears to be an interesting alternative for arterial repair in limbs in civilian vascular injuries.

Human saphenous vein allograft bypass grafts: Immune response

Although it has been claimed that allografts of blood vessels might be successful because of minimal immunogenicity, they are subject to frequent and early failure, the cause of which has not been thoroughly investigated. We sought to define the immune response to allograft bypass. In a prospective trial, 40 patients underwent cryopreserved venous allograft bypass. Allograft biopsies were performed at implantation and at allograft explantation in instances of graft failure. Tissues were evaluated in a blinded manner by means of standard histologic examination and paraffin immunohistochemical analysis with monoclonal antibodies against a variety of immune markers. During the 31-month follow-up period, 22 allografts were removed, and 19 were suitable for immunohistochemical study. Of these 19, 6 (32%) had moderate or severe infiltrates, which were evenly distributed throughout the intima, media, and adventitia. Immunohistochemical study of the explants demonstrated all of these infiltrates to be leukocytes (+LCA), which were predominantly activated T lymphocytes (+CD3, CD8, CR3) containing cytotoxic granules (+TIA-1). Macrophages were uncommon (+CD68); B cells (+L26, CD79) and natural killer cells (+CD56) were rare. Immunosuppression was associated with decreased presence of cytotoxic granules (TIA-1). Human venous allografts are immunogenic and prompt a T cell–mediated response. Allografts also fail without strong evidence of rejection, presumably because of local injury, hypercoagulability, or stasis. It may be possible to modify the contribution of rejection to venous allograft failure by means of immunosuppression and to modify the contribution of local hypercoagulability by means of anticoagulation. (J Vasc Surg 1998;27:492-9.)

Femorodistal Bypass Using Cryopreserved Venous Allografts for Limb Salvage

Critical ischemia due to extensive femoropopliteal occlusive disease often leads to amputation in patients in whom an autologous vein is unavailable for reconstruction. The purpose of this nonrandomized prospective study is to evaluate the usefulness of cryopreserved venous allografts (CPVA) as an arterial substitute in these cases. Between October 1990 and March 1993, long bypass to a tibial or a foot artery using a CPVA was performed in 25 consecutive patients with ulcerations or gangrene. There were 19 women and six men with a mean age of 72 years (range: 51-90). The indication for allograft reconstruction was absence (17 cases) or unsuitability (eight cases) of an autologous vein graft. Greater saphenous vein allografts were harvested from multiple organ donors and frozen at -80 degrees C with 12% dimethylsulfoxide (DMSO). Sixteen patients had undergone one or more previous unsuccessful limb salvage attempts. The plantar arch was absent or incomplete in 16 patients (64%). Patients were followed up prospectively for a mean of 21 months (range: 3-32). One patient died early (32 days) and three patients died late with patent bypasses. Cumulative survival rate was 77% at 1 year and 72% at 2 years. Cumulative secondary patency rate (Kaplan-Meier) was 88% at 1 months, 72% at 6 months, and 52% at 1 year. The cumulative limb salvage rate was 78% at 2 years. When an autologous vein is unavailable, long bypass using a CPVA is a simple, quick, minimally traumatic, economical, and effective method to achieve limb salvage in patients with severe distal arterial occlusive disease. However, CPVA causes immunoreaction and there is a risk of proximal postanastomotic stenosis. Doppler ultrasound surveillance of a subcutaneous graft allows accurate assessment and repair of the abnormalities with no increase in mortality or morbidity.