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

Anticoagulation does not improve limb outcomes after lower extremity cryopreserved vein bypass

OBJECTIVE

Cryopreserved vein grafts serve as alternative conduits for infrainguinal bypass when autogenous vein is unavailable or inadequate. Anticoagulation has been advocated to improve outcomes, but published studies demonstrate conflicting results. We assessed the association of anticoagulation on outcomes after infrainguinal bypass with cryopreserved vein in patients with chronic limb-threatening ischemia.

METHODS

The Vascular Quality Initiative was queried (2003-2022) for infrainguinal bypass performed using cryopreserved vein graft for chronic limb-threatening ischemia. Baseline characteristics, procedural details, and outcomes between those discharged with or without anticoagulation were recorded. Univariable, Kaplan-Meier, and multivariable analyses were performed.

RESULTS

There were 2336 patients who underwent an infrainguinal bypass with cryopreserved vein conduit. The average age was 70.6 years and 63.5% were male. Bypass targets were femoral/popliteal (27.5%) and tibial (72.5%). Indication for intervention included rest pain (25.7%) and tissue loss (74.3%). Patients were discharged with aspirin (80.1%), a P2Y12 inhibitor (45.6%), and anticoagulation (47.3%). Patients discharged on postoperative anticoagulation more often were treated for rest pain (28.1% vs 23.5%), had a tibial bypass target (78.4% vs 67.2%), and less often underwent endarterectomy (27.8% vs 34.2%) (all P < .05). Kaplan-Meier analysis at 1 year demonstrated that postoperative anticoagulation had similar freedom from loss of primary patency/death (28.9% vs 34.3%), major amputation/death (62.3% vs 63.8%), and reintervention/major amputation/death (50.6% vs 53.8%) (all P > .05), but higher survival (85.1% vs 81.7%; P = .03). Multivariable analysis at 1 year demonstrated that postoperative anticoagulation had a similar likelihood for loss of primary patency/death (hazard ratio [HR], 0.95; 95% confidence interval [CI], 0.83.-1.09), major amputation/death (HR, 0.88; 95% CI, 0.74-1.05), and reintervention/major amputation/death (HR, 0.93; 95% CI, 0.79-1.08) (all P > .05), but a lower likelihood for death (HR, 0.59; 95% CI, 0.46-0.74; P < .001) compared with no anticoagulation. Postoperative aspirin was associated with a lower likelihood for amputation/death (HR, 0.74; 95% CI, 0.61-0.91; P = .003) and reintervention/major amputation/death (HR, 0.76; 95% CI, 0.64-0.9; P = .002). Postoperative P2Y12 inhibitor was associated with decreased likelihood for amputation/death (HR, 0.75; 95% CI, 0.63-0.9; P = .002) and reintervention/major amputation/death (HR, 0.78; 95% CI, 0.67-0.91; P = .001). Results were similar when analyzing patients who were not on anticoagulation preoperatively.

CONCLUSIONS

Postoperative anticoagulation after infrainguinal bypass using cryopreserved vein did not affect patency or limb salvage. Antiplatelet agents were associated with improved outcomes. Overall patency and limb salvage rates at 1 year were poor. When cryopreserved vein is used, surgeons should consider antiplatelet therapy for cryopreserved graft patency rather than anticoagulation.

Transplantation of cryopreserved cardiovascular homografts

Due to degeneration, homografts were since the 1950s only used strictly for replacement of complex arterial segments and lesions incl. the aortic valve, replacement of infected arterial prostheses, and vascular access for patients on haemodialysis. During the 1990s, rate-differentiated freezing methods and anti-crystallization agents proved to prevent crystallisation, and more widespread use with expanded indications incl. coronary and lower limb bypasses began justified by promising midterm results. In 2021, the first Scandinavian homograft biobank was founded in Odense in Denmark. This review summarises the history and the experiences from this biobank.

Evaluation of Arterial and Venous Allografts in Subinguinal Bypasses

BACKGROUND

Autologous saphenous vein is the preferred conduit for below-the-knee bypasses in patients with critical limb-threatening ischemia. Alternative graft must be considered for patients without (autologous saphenous vein). The aim of this article is to evaluate the mid-term performance of arterial allograft (AA) and venous allograft (VA) used as alternative conduits.

METHODS

This retrospective study included patients with critical limb-threatening ischemia, with or without a history of homolateral femoropopliteal bypass, and no autologous veins were available who underwent infrainguinal arterial reconstructions using VA or AA from 2008 to 2018. Patients undergoing revision operations for infected bypasses were excluded. Primary patency (PP), primary assisted patency, secondary patency, major amputation, and death from any cause were the endpoints. For each event, a set of analyses were performed.

RESULTS

Overall, 111 patients (63 VAs and 48 AAs) were included, with 108 having below-the-knee bypass. The median follow-up time was 27.8 months (15.6-37.4). The difference in PP between the 2 allograft types was significant (P = 0.049), with 65.9% (43.7-81.0), 44.1% (24.2-62.3), and 44.1% (24.2-62.3) in the AA group, respectively, at 6, 12, and 18 months, whereas 55.6% (40.0-68.6), 46.0% (30.6-60.2), and 33.2% (18.2-49.0) in the VA group. The choice of an AA over a VA was an independent factor associated with patency (for PP: hazard ratio [HR] = 0.43 [0.24-0.75], P = 0.003); primary assisted patency: HR = 0.52 (0.30-0.89], P = 0.018; and secondary patency: HR = 0.49 (0.27-0.88), P = 0.016. The allograft type did not affect either the incidence of major amputation or death from any cause (respectively, HR = 1.20 [0.49-2.93], and 0.88 [0.37-2.14]).

CONCLUSIONS

The nature of the allograft appears to influence the patency of infrainguinal reconstruction, but not the course of the disease. Performant alternative grafts answering infectious issues are needed.

Comparison of arterial and venous allograft bypass in chronic limb-threatening ischemia

INTRODUCTION

Femoro-popliteal bypass with autologous vascular graft is a key revascularization method in chronic limb-threatening ischemia (CLTI). However, the lack of suitable autologous conduit may occur in 15-45% of the patients, necessitating the implantation of prosthetic or allogen grafts. Only little data is available on the outcome of allograft use in CLTI.

AIMS

Our objective were to evaluate the long term results of infrainguinal allograft bypass surgery in patients with chronic limb-threatening ischemia (CLTI) and compare the results of arterial and venous allografts.

METHODS

Single center, retrospective study analysing the outcomes of infrainguinal allograft bypass surgery in patients with CLTI between January 2007 and December 2017.

RESULTS

During a 11-year period, 134 infrainguinal allograft bypasses were performed for CLTI [91 males (67.9%)]. Great saphenous vein (GSV) was implanted in 100 cases, superficial femoral artery (SFA) was implanted in 34 cases. Early postoperative complications appeared in 16.4% of cases and perioperative mortality (<30 days) was 1.4%. Primary patency at one, three and five years was 59%, 44% and 41%, respectively, while secondary patency was 60%, 45% and 41%, respectively. Primary patency of the SFA allografts was significantly higher than GSV allografts (1 year: SFA: 84% vs. GSV: 51% p = 0,001; 3 years: SFA: 76% vs. GSV: 32% p = 0,001; 5 years: SFA: 71% vs. GSV: 30% p = 0.001). Both primary and secondary patency of SFA allograft implanted in below-knee position were significantly higher than GSV bypasses (p = 0.0006; p = 0.0005, respectively). Limb salvage at one, three and five years following surgery was 74%, 64% and 62%, respectively. Long-term survival was 53% at 5 years.

CONCLUSION

Allograft implantation is a suitable method for limb salvage in CLTI. The patency of arterial allograft is better than venous allograft patency, especially in below-knee position during infrainguinal allograft bypass surgery.

Comparative efficacy of autologous versus cadaveric saphenous vein grafts in cerebral revascularization surgery

OBJECTIVE

Cerebral bypasses are performed for the purpose of either flow augmentation for ischemic cerebrovascular disease or flow replacement for vessel sacrifice during complex aneurysm or tumor surgery. Saphenous vein grafts (SVGs) are commonly used interposition grafts. The authors of this study sought to compare the efficacy of autologous versus cadaveric SVGs in a large series of cerebral bypasses using interposition vein grafts with long-term angiographic follow-up.

METHODS

All intracranial bypass procedures performed between 2001 and 2018 were reviewed. Demographic, clinical, angiographic, and operative data were recorded and then analyzed according to SVG type.

RESULTS

A total of 308 consecutive intracranial bypasses were performed during the study period, 53 (17.2%) of which were bypasses with an interposition SVG (38 autologous, 15 cadaveric). At a median follow-up of 2.2 months (IQR 0.2-29.1), 39 (73.6%) bypasses were patent (26 [68.4%] autologous, 13 [86.7%] cadaveric, p = 0.30). Comparing autologous and cadaveric SVG recipients, there were no statistically significant differences in age (p = 0.50), sex (p > 0.99), history of smoking (p = 0.75), hypertension (p > 0.99), diabetes mellitus (p = 0.13), indication for bypass (p = 0.27), or SVG diameter (p = 0.65). While there were higher intraoperative (autologous, 100.0 ml/min, IQR 84.3-147.5; cadaveric, 80.0 ml/min, IQR 47.3-107.8; p = 0.11) and postoperative (autologous, 142.2 ml/min, IQR 76.8-160.8; cadaveric, 92.0 ml/min, IQR 69.2-132.2; p = 0.42) volumetric flow rates in the autologous SVGs compared to those in the cadaveric SVGs, the difference between the two groups did not reach statistical significance. In addition, the blood flow index, or ratio of postoperative to intraoperative blood flow, for each bypass was similar between the groups (autologous, 1.3, IQR 0.9-1.6; cadaveric, 1.5, IQR 1.0-2.3; p = 0.37). Kaplan-Meier estimates showed no difference in bypass patency rates over time between autologous and cadaveric SVGs (p = 0.58).

CONCLUSIONS

Cadaveric SVGs are a reasonable interposition graft option in cerebral revascularization surgery when autologous grafts are not available.

Single Tertiary Care Center Outcomes After Lower Extremity Cadaveric Vein Bypass for Limb Salvage

OBJECTIVE

Cadaveric saphenous vein (CV) conduits are used in rare instances for limb salvage in patients without autogenous veins although long-term outcome data are scarce. This study was designed to evaluate the outcomes of CV bypass in patients with threatened limbs.

METHODS

We retrospectively reviewed the charts from 2010 to 2017 of 25 patients who underwent 30 CV allografts for critical limb ischemia and acute limb ischemia. Patient charts were reviewed for demographics, comorbidities, smoking status, indications for bypass, and outcomes. Primary outcomes included graft patency, major amputation rates, and mortality. Secondary outcomes measured included infection rates, 30-day major adverse cardiac events (MACE) and major adverse limb events (MALE). Statistical analysis was performed using time series and Kaplan-Meier survival curves.

RESULTS

A total of 30 limbs received CV lower extremity bypasses (20 males, 10 female), and the average age was 68 ± 4 years. Primary patency rates were 71%, 42%, and 28% at 3, 6, and 12 months, respectively. Assisted primary patency rates were 78%, 56%, and 37% at 3, 6, and 12 months, respectively. Secondary patency rates were 77%, 59%, and 28% at 3, 6, and 12 months, respectively. Minor amputations, defined as amputations below the transmetatarsal level occurred in 5 (20%) patients. Wound infection occurred in 8 (32%) patients which was managed with local wound care and no patients required an extraanatomic bypass for limb salvage. Thirty-day MALE occurred in 7 (23.3%) patients. We had no 30-day mortality or MACE. The average graft length was 64.2 ± 8 cm with an average graft diameter of 3.9 ± 2 mm. Amputation-free survival and overall survival at 12 months were 20 (68%) and 21 (84%), respectively.

CONCLUSIONS

Cadaveric saphenous vein allograft may be used as a bypass conduit as a viable surgical option before limb amputation. Despite the poor patency rates, the limb salvage rates of cadaveric vein grafts demonstrate that this alternate conduit may be considered when no autogenous vein is available.

Increased warm ischemia time during vessel harvest decreases the primary patency of cryopreserved conduits in patients undergoing lower extremity bypass

OBJECTIVE

Autologous vein is the preferred conduit for lower extremity bypass. However, it is often unavailable because of prior harvest or inadequate for bypass owing to insufficient caliber. Cryopreserved cadaveric vessels can be used as conduits for lower extremity revascularization when autogenous vein is not available and the use of prosthetic grafts is not appropriate. Many studies have shown that donor characteristics influence clinical outcomes in solid organ transplantation, but little is known regarding their impact in vascular surgery. The purpose of this study was to examine the effects donor variables have on patients undergoing lower extremity bypass with cryopreserved vessels.

METHODS

The tissue processing organization was queried for donor blood type, warm ischemia times (WITs), and serial numbers of cryopreserved vessels implanted at a single center from 2010 to 2016. The serial numbers were then matched with their respective patients using the institutional Clinical Data Repository and patient data were obtained from the Clinical Data Repository and chart review. Primary outcomes were primary patency of the bypass conduits and limb salvage. Time to loss of patency was evaluated using Kaplan-Meier methods and a Cox proportional hazards model determined risk-adjusted predictors of patency and limb salvage.

RESULTS

Sixty patients underwent lower extremity bypass with 65 cryopreserved vessels (23 superficial femoral arteries, 41 saphenous veins, 1 femoral vein). Thirty-eight procedures were reoperations. There were 21 inflow, 44 outflow, and 44 infrainguinal procedures. Preexisting comorbidities did not differ significantly between those who lost patency and those who did not. The mean WIT among the entire cohort was 892.3 ± 389.1 minutes (range, 158.0-1434.0 minutes). The median follow-up was 394 days. Kaplan-Meier analysis demonstrated an overall 1-year primary patency rate of 51%. Primary patency at 1 year was 67% and 41% for inflow and outflow procedures, respectively, and did not differ significantly between the two groups (P = .15). Donor-to-recipient ABO incompatibility was not associated with loss of primary patency. The 1-year amputation-free survival was 74%. Primary patency significantly decreased with each hourly increase in WIT on risk-adjusted analysis (hazard ratio, 1.1; P = .02).

CONCLUSIONS

Higher cryopreserved vessel WIT was associated with increased risk-adjusted loss of primary patency in this cohort. At 1 year, the overall primary patency was 51% and amputation-free survival was 74%. Vascular surgeons should be aware that WIT may affect outcomes for lower extremity bypass.

Morbidity of femoropopliteal bypass surgery

A systemic review of published reports on the incidence of early (<30 days) adverse events occurring after above- or below-knee femoropopliteal bypass surgery was conducted to provide contemporary outcomes data for comparative reporting. A total of 38 articles were included describing 6,374 femoropopliteal bypasses in 6,007 patients. Fifty-two percent were male and the mean age was 64.6 years (range, 40 to 93 years). The various studied types of complications were reported in 10 to 34 of 38 articles and definitions were often missing. The overall 30-day morbidity rate was 36.8%. The wound infection rate was 7.8% (range, 0.0 to 17.4%) accompanied with dermal necrosis in 0.4%. Graft infection was described in 2.4% (range, 0.0 to 5.3%) of cases. Postoperative bleeding was seen in 7.4% (range, 0.0 to 26%), of which 2.5% required return to surgery. Occlusions were reported in 12.0% (range, 0.0 to 59%). Lymphedema occurred in 2.9% (range, 0.0 to 9.6%) of cases and surgical site seroma formation occurred in 2.0% (range, 1.0% to 3.0%). Overall 30-day mortality rate was 2.3% (range 0.0 to 4.3%). Pooled data comparing vein grafts and prosthetic grafts revealed no significant difference (P = .10; risk ratio = 0.82; 95% confidence interval, 0.66-1.03; I(2) = 0%) in the incidence of complications. This review confirmed the morbidity of femoropopliteal bypass surgery is inconsistently reported and definitions are lacking. Because one-third of patients can be expected to experience an adverse event after femoropopliteal bypass grafting, standards on defining and reporting complications are necessary if comparative outcome standards are developed.

Cryopreserved saphenous vein graft in infrainguinal bypass

OBJECTIVE

Autogenous saphenous vein is the ideal conduit for lower extremity revascularization. Unfortunately, autogenous vein is unavailable in up to 20% of patients. Synthetic grafts provide an alternative; however, their use in distal revascularization has shown varying results. In addition, infected surgical sites preclude their use. Currently, there are limited outcome data for cryopreserved saphenous vein use in regard to long-term patency and limb salvage rates.

METHODS

Cryopreserved saphenous vein allograft use in infrainguinal bypass was studied retrospectively in a community setting. End points included primary patency, limb salvage, and early complications. Records of patients receiving cryopreserved allografts by nine vascular surgeons within one hospital system from 2006 to 2012 were reviewed.

RESULTS

Fifty-three patients, mean age 69 years (standard deviation, 12.3; range, 28-90 years), underwent 60 operations. Indications for surgery included limb-threatening ischemia (48%), tissue loss (30%), previous graft or site infection (10%), claudication (7%), or other (5%). The mean follow-up period was 23.9 months (standard deviation, 21.0; range, 0-64 months). Primary patency was maintained in 53% of patients at 1 year and in 22% at 3 years. Limb salvage was achieved in 74% of patients at 1 year and in 70% at 2 years. Thirteen early complications included 8 thromboses, 2 deaths, 2 amputations, and 1 anastomotic disruption. Fifteen patients (28%) underwent additional ipsilateral operations with use of synthetic conduits after initial cryopreserved allografts failed.

CONCLUSIONS

Cryopreserved vein allografts displayed poor short-term and long-term patency, whereas limb salvage rates at 1 and 2 years remained acceptable. However, >25% of patients required additional ipsilateral operations with use of synthetic conduits after previous failed cryopreserved allograft use. Our data indicate that cryopreserved vein graft is a suboptimal choice of conduit in a noninfected field.

Vascular grafts

Autogenous vein is the conduit of choice in the surgical creation of bypasses of small-to-medium-caliber vessels in patients with peripheral occlusive arterial disease and will remain so for the near future. The success rate of bypasses using conduits of diameters greater than 6 mm has been excellent, whereas the majority of bypasses using smaller conduits fail within 5 years. In addition, due to a steep increase in rates of diabetes and decreasing cardiovascular mortality rates, increasing challenges are presented by this population. These facts have motivated much of the research in the cardiovascular arena over the past four decades, with improved techniques and new materials. Strategies to improve outcomes include the use of alternative materials including autologous, nonautologous and prosthetic grafts, utilizing different methods for their harvesting and preservation; tissue engineering, using either polymer- or biological-based scaffolds for cell seeding; endovascular methodologies; and gene therapy. This report presents an overview of the several options currently available in the management of patients with peripheral arterial occlusive disease, as well as the ongoing research directed towards the creation of an artificial engineered vessel, discussing experimental work in which endothelial cells have been seeded on different scaffolds and finally the potential application of gene therapy in the field of vascular reconstruction.

Basic data related to surgical infrainguinal revascularization procedures: a twenty year update

In 1990, Dalman and Taylor published a compilation of reported data that were identified by them as related to infrainguinal revascularization procedures in peripheral vascular surgery during the decade of the 1980s. The intervening 20 years has seen revolutionary advances in the field of peripheral vascular surgery, especially in the adoption of endovascular techniques, and an explosion of data related to emerging technologies in the field of infrainguinal revascularization. The tables in this manuscript reflect the evolution of our surgical knowledge during the turn of the 21st century. The superior patency of autologous saphenous vein in all positions is reaffirmed.

Limb salvage with CryoVein cadaver saphenous vein allografts used for peripheral arterial bypass: role of blood compatibility

Patients suffering from limb-threatening ischemia often have scarce or inadequate autogenous veins for complex lower limb revascularization. One option for such patients is to use conduit consisting of cadaver saphenous vein allograft (CSVA) as a final surgical option before limb amputation. This study reviewed retrospectively the patency of CryoVein CSVA allografts, processed by CryoLife, Inc., in 54 implant cases of lower extremity arterial bypass over a span of 6 years. Patient demographics, graft patency, limb salvage, and blood type matching of donor to recipient were analyzed. Kaplan-Meier analysis showed postoperative primary patency rates of 89, 63%, 30%, 17%, and 9% at 1, 3, 6, 12, and 18 months, respectively. Secondary patency rates were 89%, 74%, 63%, 63%, and 54% at 1, 3, 6, 12, and 18 months, respectively. Limb salvage rates were 67% at 12 months and 54% at 18 months. Median follow-up was 467 days. Of the 34 cases where the patient received a blood-group compatible CSVA, 30 had limb salvage and only six of 20 noncompatible grafts offered limb salvage (p = 0.05). Although primary patency rate was poor at 1 year, high secondary patency and limb salvage rates support the use of CSVA as a peripheral bypass conduit alternative. Cases with donor-recipient ABO blood type compatibility had significantly better limb salvage.

A reappraisal of saphenous vein grafting

Autologous saphenous vein grafting has been broadly used as a bypass conduit, interposition graft, and patch graft in a variety of operations in cardiac, thoracic, neurovascular, general vascular, vascular access, and urology surgeries, since they are superior to prosthetic veins. Modified saphenous vein grafts (SVG), including spiral and cylindrical grafts, and vein cuffs or patches, are employed in vascular revascularization to satisfy the large size of the receipt vessels or to obtain a better patency. A loop SVG helps flap survival in a muscle flap transfer in plastic and reconstructive surgery. For dialysis or transfusion purposes, a straight or loop arteriovenous fistula created in the forearm or the thigh with an SVG has acceptable patency. The saphenous vein has even been used as a stent cover to minimize the potential complications of standard angioplasty technique. However, the use of saphenous vein grafting is now largely diminished in treating cerebrovascular disorders, superior vena cava syndrome, and visceral revascularization due to the introduction of angioplasty and stenting techniques. The SVG remains the preferable biomaterial in coronary artery bypass, coronary osteoplasty, free flap transfer, and surgical treatment of Peyronie disease. Implications associated with saphenous vein grafting in vascular access surgery for the purpose of dialysis and chemotherapy are considerable. Vascular cuffs and patches have been developed as an important and effective means of enhancing the patency rates of the grafts by linking the synthetic material to the receipt vessel. In addition, saphenous veins can be a cell source for tissue engineering. We review the versatile roles that saphenous vein grafting has played as well as its current status in therapy.

Fifteen years of infrapopliteal arterial reconstructions with cryopreserved venous allografts for limb salvage

OBJECTIVE

The availability of autologous vein grafts remains the limiting factor in infragenual bypass surgery in many patients with critical limb ischemia (CLI). Alternatives such as prosthetic conduits are known to have a poor outcome and most are not resistant to infection. Based on previous experimental work, we started to use cryopreserved saphenous vein allografts for this indication 15 years ago. To evaluate their outcome, we performed a retrospective study of those bypasses with distal anastomosis on a crural or pedal vessel.

METHODS

Between November 1991 and December 2005, 108 cryopreserved great saphenous vein allografts were implanted for in 92 patients (42 women, 50 men) with a mean age of 71 years (range, 39-88 years). All patients received low-dose immunosuppressive therapy for up to 1 year after intervention. Follow-up was conducted until amputation, death, or the end of the study in March 2007.

RESULTS

Nondiabetic atherosclerosis the cause of CLI in 57%, 41% had diabetes, and 2% had Buerger disease. Forty-one conduits were performed for primary reconstructions and 67 for redo reconstructions. During a mean follow-up of 26.4 months, 69 occlusions occurred. Primary and secondary patency rates were 56% and 73% at 1 year, 32% and 60% at 3 years, and 17% and 38.5% at 5 years. Survival rates were 87.4% at 1 year and 64.5% at 5 years. At multivariate analysis, the intake of statins was predictive for improved patency (hazard ratio [HR], 0.09; P = .024) and for prolonged survival (HR, 0.335; P = .045). The presence of diabetes showed a trend for inferior patency (HR, 2.325; P = .116) and for decreased amputation risk (HR, 0.592; P = .078).

CONCLUSION

Cryopreserved saphenous vein allografts are a valuable alternative to prosthetic materials when autologous veins are not available. Our limb salvage and patency rates are higher then those described for prosthetic grafts at the infrapopliteal level in most studies. Moreover, these grafts are resistant to infection when performed for revascularization in patients with an infected ulcer. Better graft and patient selection, better graft surveillance and immunologic matching, and standard use of statins could possibly improve the results even further. Shortage in availability might be a limiting factor for their widespread use.

24-carat gold, 14-carat gold, or platinum standards in the treatment of critical limb ischemia: bypass surgery or endovascular intervention?

Critical limb ischemia (CLI) remains a poorly understood, rarely reported, and inconsistently treated major global healthcare epidemic. The incidence in the US is estimated at 1% of the population aged 50 years and older and at approximately double that rate in the over-70 age group. These frequencies are expected to increase significantly with the aging population and the expected increase in diabetes. Within 1 year of being diagnosed with CLI, 40% to 50% of the now 20 million US diabetics will experience an amputation, and 20% to 25% will die. The estimate for treating CLI in the US alone is $10 to $20 billion per year, but just a 25% reduction in amputations could save $2.9 to $3.0 billion annually. Infrainguinal bypass surgery (IBS) utilizing autogenous saphenous vein has been considered the "24-carat gold standard" treatment for CLI, but over the last decade, endovascular therapy has emerged to seriously challenge IBS, which has created considerable controversy. Despite an overall lack of "hard" level I data, many interventionists are questioning the role of IBS as a first-line CLI therapy or are at least now considering IBS a "tainted" gold standard ("14-carat"). This review will examine the available evidence, but there should be no doubt regarding the huge global clinical and economic impact of CLI and amputations.

Impact of freezing/thawing procedures on the post-thaw viability of cryopreserved human saphenous vein conduits

BACKGROUND

Cryopreserved human blood vessels are important tools in reconstructive surgery. However, patency of frozen/thawed conduits depends largely on the freezing/thawing procedures employed.

METHODS

Changes in tone were recorded on rings from human saphenous vein (SV) and used to quantify the degree of cryoinjury after different periods of exposure at room temperature to the cryomedium (Krebs-Henseleit solution containing 1.8M dimethyl sulfoxide and 0.1M sucrose) and after different cooling speeds and thawing rates following storage at -196 degrees C.

RESULTS

Without freezing, exposure of SV to the cryomedium for up to 240 min did not modify contractile responses to noradrenaline (NA). Pre-freezing exposure to the cryomedium for 10-120 min attenuated significantly post-thaw maximal contractile responses to NA, endothelin-1 (ET-1) and potassium chloride (KCl) by 30-44%. Exposure for 240 min attenuated post-thaw contractile responses to all tested agents markedly by 62-67%. Optimal post-thaw contractile activity was obtained with SV frozen at about -1.2 degrees C/min and thawed slowly at about 15 degrees C/min. In these SV maximal contractile responses to NA, ET-1 and KCl amounted to 66%, 70% and 60% of that produced by unfrozen controls. Following cryostorage of veins for up to 10 years the responsiveness of vascular smooth muscle to NA was well maintained.

CONCLUSION

Cryopreservation allows long-term banking of viable human SV with only minor loss in contractility.

Survival rates of patients with malignant melanoma of the skin

This paper reports on cases of malignant melanoma of the skin diagnosed in Finland between 1963 and 1968. Sufficient data for estimating the survival was obtained in 691 cases. The ten-year relative survival rate for the entire series was 41% for males and 53% for females. This sex difference remained constant throughout the various divisions of the material. The ten-year relative survival rate of males with tumour in stage I was 52% and that of females 59%. The highest survival rate of stage I tumour in males was for the tumours of the lower extremities (77%) and in females for those in the head and neck (79%). The relative survival of patients with tumour of the trunk in stage I was lowest in both sexes (males 49%, females 45%). The ten-year relative survival rate of patients with a local recurrence was 33% in males and 27% in females. The relative ten-year survival rates of patients with superficial melanoma were 130% in males and 92% in females.

In vivo and mechanical properties of peritoneum/fascia as a novel arterial substitute

OBJECTIVE

This study evaluates the efficacy of bovine peritoneum/fascia as an arterial substitute.

METHODS AND OUTCOME MEASURES

Twelve dogs underwent bilateral femoral artery patch angioplasty with a glutaraldehyde-fixed bovine peritoneal/fascial patch (PFA patch) on one side and polyester patch on the contralateral side. Arteriograms were performed just before vessel harvest at 1 and 6 months, and vessels were evaluated for aneurysms and inflammation. Histologic analysis included intima area, media thickness, and lumen area. Immunofluorescence for CD 34 and Factor VIII was done to evaluate endothelialization and alpha-actin for smooth muscle cell growth. Mechanical strength testing was evaluated in separate PFA patches and compared independently to a commercially available bovine pericardial patch and polyester patch.

RESULTS

All vessels examined at both 1 and 6 months were patent with no arteriographic evidence of stenosis. There was no evidence of aneurysm formation in any vessel and no difference between groups in inflammatory reaction. One polyester patch at 1 month developed an infection. Microscopic evaluation of experimental vessels revealed no difference between groups in intima area at 1 month (2.1 +/- 1.2 vs 2.2 +/- 1.2 mm 2 ; P = .5) and at 6 months (1.81 +/- 1.2 vs 1.9 +/- 1.2 mm 2 ; P = .5). There was no difference in media thickness, but the PFA patch group had a greater lumen area at 1 month (8.8 +/- 2.9 vs 9.8 +/- 3.0 mm 2 ; P = .02) and 6 months (10.5 +/- 4.2 vs 11.7 +/- 5.6 mm 2 ; P = .02). Immunofluorescence for CD34 and Factor VIII demonstrated complete re-endothelialization of all patches. The polyester patch had a chronic inflammatory response, but not the PFA patch. Mechanical strength testing demonstrated that compared to pericardium, the PFA patch had superior ( P < .05) failure tension, stiffness, and suture pull-out strength, whereas extensibility, fatigue tension, relax slope, and creep tests were not different. Polyester demonstrated superior suture pull-out, stiffness, relax slope, and failure strain ( P < .05), but it was not different in failure tension and extensibility than the PFA patch. However, the PFA patch had significantly less creep (0.25 +/- 0.25 vs 4.92 +/- 0.84; P < .01).

CONCLUSIONS

The PFA patch has similar clot-resistant properties to polyester and is superior to the pericardial patch in mechanical strength. It is a promising endothelial alternative for not only arterial patches but other vascular products.

CLINICAL RELEVANCE

The search for an artificial, thromboresistant, and intimal hyperplasia resistant interface between blood and native blood vessels still continues. This study demonstrates the feasibility and proof of concept of the peritoneum's clot-resistant properties. When adding the underlying fascia, it serves as an ideal arterial patch. Other studies are underway evaluating its feasibility as a bypass graft and a "drug coated"-like stent lining.

Meta-analysis of allograft bypass grafting to infrapopliteal arteries

OBJECTIVE

To determine graft patency and limb preservation after allograft bypass grafting to infrapopliteal arteries for different allograft materials.

DESIGN

Meta-analysis of case series that used survival analysis to describe outcomes.

METHODS

Studies published from 1982 through 2003 were identified from electronic databases and pertinent original articles. Four series of cryopreserved arterial allografts, 10 series of cryopreserved vein allografts, three series of cold-storaged vein allografts, and 16 series of umbilical-cord vein allografts were included in separate random-effects meta-analyses.

RESULTS

A graphical display of pooled survival curves of graft patency showed cold-storaged veins to have the best outcome in the first 4 years, followed by cryopreserved arteries, umbilical-cord veins, and cryopreserved veins. The respective 5-year pooled patency were 24, 21, 30, and 19%. For foot preservation, the best outcome was achieved with cryopreserved arteries followed by cryopreserved veins, umbilical-cord veins, and cold-storaged veins. A reference meta-analysis of polytetrafluoroethlylene grafts occupied the top position for graft patency and the second position for foot preservation.

CONCLUSION

In leg revascularisation for critical ischaemia, graft patency is poor for allografts generally, but using peripheral allografts in repeat attempts at revascularisation is a valid strategy to prevent major amputation. A role for umbilical-cord vein allografts remains uncertain.

Infragenual cuff-compression reduces venous contamination in contrast-enhanced MR angiography of the calf

PURPOSE

To reduce venous contamination at the calf level in three-dimensional contrast-enhanced MR angiography (CE-MRA) by applying continuous infragenual cuff-compression.

MATERIALS AND METHODS

Ten patients with clinically relevant peripheral arterial occlusive disease (PAOD) underwent dynamic three-dimensional CE-MRA of the calf. Six consecutive measurements were acquired with the first measurement serving as mask. Cuff-compression of 50 mmHg was attached below the knee. To allow intra-individual comparison, compression was applied unilaterally. The cuff was inflated three minutes before scanning and was continued throughout the MRA session. Venous contamination and arterial visualization scores were ranked using a five-point rating scale. Contrast-to-noise ratios (CNRs) of superficial enhancing calf-veins on the uncompressed and compressed calf sides were evaluated. An asymmetry index (AI) defined by CNR(mean) (uncompressed)/CNR(mean) (compressed) was introduced to describe the ratio in venous contrast agent supply between both sides quantitatively.

RESULTS

Three-dimensional CE-MRA of the calves demonstrated significantly lower superficial venous contamination scores (P < 0.004) and clearly improved arterial visualization (P < 0.009) on the compressed side. Additionally, AI values were larger than 1 (P < 0.02), indicating a higher contrast agent supply in the superficial veins on the uncompressed side.

CONCLUSION

Infragenual cuff-compression minimizes venous overlay in three-dimensional CE-MRA at calf level by reduction of contrast agent supply in the superficial veins.

Effects of green tea polyphenol on preservation of human saphenous vein

The potential role of green tea polyphenol (GtPP) in preserving the human saphenous vein was investigated under physiological conditions. The vein segments were incubated for 1, 3, 5, 7 and 14 days, either after 4h of treatment with 1.0mg/ml GtPP or in the presence of GtPP at the same concentration. After incubation, the endothelial cell viability, endothelial nitric oxide synthase (eNOS) expression and the vein histology were evaluated. When the veins were not treated with GtPP, the viability of the endothelial cells was significantly reduced with the progress in the culture time, and none of the cells expressed eNOS after 5 days. Furthermore, severe histological changes and structural damage were observed in the non-treated veins. In contrast, incubating the veins after 4h of GtPP treatment significantly prevented these phenomena. The cellular viability of the GtPP-treated vein was approximately 64% after 7 days, and eNOS expression was maintained up to 40%, compared to that of the fresh vein. The histological observations showed that the vasculature was quite similar to that of the fresh vein. When incubated with GtPP, the vein could also be preserved for 1 week under physiological conditions retaining both its cellular viability (61%) and eNOS expression level (45%) and maintaining its venous structure without any morphological changes. These results demonstrate that GtPP treatment may be a useful method for preserving the HSV.

Cryopreserved saphenous vein allografts in infrainguinal revascularization: analysis of 240 grafts

INTRODUCTION

Cryopreserved saphenous vein allografts (Cryograft; CryoLife, Kennesaw, Ga) have been used as conduit in infrainguinal revascularization when autogenous vein is inadequate or unavailable. Although some studies of Cryografts report poor long-term patency, an anticoagulation protocol may improve outcome. We evaluated our experience with Cryografts to further define their role in lower extremity revascularization. Patients and methods Between March 1992 and March 2002, 240 infrainguinal revascularization procedures with Cryografts were performed in 199 limbs of 177 patients. Eighty-nine percent of procedures were performed because of ischemic rest pain or tissue loss, and 75% of vein grafts were implanted into infrapopliteal targets. Most patients received anticoagulation therapy with warfarin sodium or aspirin, or both, postoperatively. Mean age of the cohort was 78 years; 61% were women; 75% had hypertension, 58% had diabetes, and 38% had renal dysfunction; and 47% were current or past smokers.

RESULTS

Mean follow-up was 7 months (range, 0-48 months). Primary patency rate was 83% at 1 month, 50% at 6 months, 30% at 12 months, and 18% at 24 months. Diabetes adversely affected graft patency. Warfarin sodium or antiplatelet therapy did not significantly improve graft patency. Limb salvage was 80% at 1 year and 71% at 2 years.

CONCLUSIONS

Cryografts have low primary patency rates that are not affected by anticoagulation with warfarin sodium. Short-term patency of these grafts may be sufficient to heal ischemic wounds and thereby prevent limb loss. However, other less expensive alternatives, eg, prosthetic grafts with vein cuffs, are available and appear to have better patency. Accordingly, use of Cryografts should be limited to revascularization through infected fields in patients without autogenous conduit.

Meta-analysis of polytetrafluoroethylene bypass grafts to infrapopliteal arteries

CONTEXT

Reports of polytetrafluoroethylene (PTFE) bypass grafting to the infrapopliteal arteries have often used survival analysis of acceptable quality to describe a wide range of long-term results. In theory, these results may be combined if variability between series and time intervals is considered.

OBJECTIVE

Meta-analysis was performed to gain insight into long-term graft patency and foot preservation after PTFE bypass grafting to infrapopliteal arteries.

DATA SOURCE

Studies published from 1982 through 2001 were identified from the PubMed database and pertinent original articles.

STUDY SELECTION

Three investigators selected 43 studies that used survival analysis, reported 2-year patency rates, and included at least 15 bypass procedures. Data extraction and transformation: Based on standard life-tables or survivor curves, an interval success rate was calculated for each month in each series. The monthly success rates were combined across series, enabling construction of pooled survivor curves.

DATA SYNTHESIS

Random-effects meta-analysis yielded 5-year pooled estimates (SE) of 30.5% (7.6%) for primary graft patency, 39.7% (5.5%) for secondary graft patency, and 55.7% (5.0%) for foot preservation. During the entire follow-up, pooled estimates were slightly higher for series of PTFE grafts with adjunctive procedures compared with series of PTFE grafts only. Sensitivity analysis: A simulation using only unfavorable assumptions showed a decrease of less than 5% at 5 years for all outcomes, and smaller differences at subgroup meta-analysis. Funnel plots suggested that publication bias was unlikely.

CONCLUSION

This meta-analysis indicated moderate success for PTFE bypass grafts to infrapopliteal arteries, but the role of adjunctive procedures at the distal anastomosis remains uncertain.