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

Background, establishment and initial experiences of the Danish cardiovascular homograft biobank

Odense University Hospital is a major tertiary vascular hospital in Scandinavia, performing approx. 200 aortic repairs annually. This article presents the rationale behind this endeavor and the early outcomes of the initial implantation of locally processed homografts. All patients receiving a homograft were identified from the established homograft biobank database and their medical records were reviewed after obtaining consent. All surgeons in charge of homograft implantations were semi structured interviewed regarding the harvesting procedure, the tools for detecting available homografts, their quality and delivery. The National board of Health approved the biobank fulling the EU Directive of Tissues and Cells after 18 months of preparation. From May 6, 2021, to March 1, 2023, 26 patients had a homograft implantation, with 7 for mycotic aneurysms, 10 for aorto-iliac graft infection, 6 for infra-inguinal graft infection, and 3 for graft infection in thoracic aorta. Six (23%) were emergently performed. Two (7.7%) died within 30 days postoperatively, both following in situ replacement of an infected aortoiliac graft, corresponding to a 20% mortality in this subgroup. The incidence of reinfections was 19.2%; one each in the mycotic aneurysm group, the aortoiliac graft infection group, and the thoracic graft infection group. After 90 days, two patients were diagnosed with aorto-enteric fistula. All involved surgeons could easily identify available suitable homografts, and within 2 h have homografts of acceptable quality and requested dimensions. The establishment of the Danish Cardiovascular Homograft Biobank was straightforward and effectively serves cardiovascular procedures performed 24/7. Additionally, the initial experiences seem comparable to others experiences.

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.

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.

Bioengineering Human Tissues and the Future of Vascular Replacement

Cardiovascular defects, injuries, and degenerative diseases often require surgical intervention and the use of implantable replacement material and conduits. Traditional vascular grafts made of synthetic polymers, animal and cadaveric tissues, or autologous vasculature have been utilized for almost a century with well-characterized outcomes, leaving areas of unmet need for the patients in terms of durability and long-term patency, susceptibility to infection, immunogenicity associated with the risk of rejection, and inflammation and mechanical failure. Research to address these limitations is exploring avenues as diverse as gene therapy, cell therapy, cell reprogramming, and bioengineering of human tissue and replacement organs. Tissue-engineered vascular conduits, either with viable autologous cells or decellularized, are the forefront of technology in cardiovascular reconstruction and offer many benefits over traditional graft materials, particularly in the potential for the implanted material to be adopted and remodeled into host tissue and thus offer safer, more durable performance. This review discusses the key advances and future directions in the field of surgical vascular repair, replacement, and reconstruction, with a focus on the challenges and expected benefits of bioengineering human tissues and blood vessels.

Aneurysmal degeneration of the hood of a cryopreserved vein allograft two years after thrombosis

Cryopreserved vein allografts are used as alternative conduits for infrainguinal bypass but are prone to aneurysmal degeneration. A 60-year-old man presented with a pulsatile, tender right groin mass 2 years after thrombosis of a cryopreserved vein jump graft emanating from a prosthetic axillary to profunda bypass. Intraoperatively, the aneurysm was consistent with isolated dilatation of the hood of the thrombosed cryopreserved vein graft. This was excised and repaired with bovine pericardial patch angioplasty. The patient recovered with no recurrence for 2 years. Aneurysmal degeneration of the cryopreserved vein allograft can occur even after graft thrombosis.

Investigation of a method for long-term preservation of the vascular allograft

BACKGROUND/OBJECTIVE

During multiple organ procurement, blood vessels are routinely retrieved and stored in University of Wisconsin solution and then discarded after two weeks, if not used at organ transplantation owing to lack of a method for long-term preservation. Therefore, the aim of this study is to investigate a method for long-term preservation of vascular allografts in ethanol.

METHODS

Aorta and vena cava allografts were retrieved and stored in 75% ethanol solution for 12 months at 4°C. Four pigs were divided into two groups. A segment of aorta was excised and replaced by insertion of preserved aorta graft (Group A) or vena cava graft (Group V). The pigs were observed for six weeks. A laparotomy was performed and the vascular graft was harvested for histopathology followed by euthanasia at the end of study.

RESULTS

Three pigs recovered uneventfully, while one pig died from venous graft rupture in the third week after surgery. There was no aneurysmal formation or thrombosis in the grafts. Some calcification was seen over aorta allograft. On histopathology, the elastic pattern was almost normal, although the endothelial cells degenerated after preservation. After implantation, the formation of the endothelium cell-like layer was seen in both aorta and vena cava allografts.

CONCLUSION

Vascular allografts were functional after preservation for 12 months. The vena cava grafts had much less wall calcification than the aorta grafts. Further studies are necessary to investigate vascular graft remodelling with a longer observation period after implantation.

Medical therapy for cardiovascular and limb-related risk reduction in critical limb ischemia

Critical limb ischemia (CLI) constitutes the most advanced form of peripheral artery disease (PAD) and is characterized by ischemic rest pain, tissue loss and/or gangrene. Optimized medical care and risk factor modification in addition to revascularization could reduce the incidence of cardiovascular events and major adverse limb events, improving patients' quality of life and promising higher survival rates. Adequate adherence to cardioprotective medications, including antithrombotic therapy (e.g., antiplatelets, anticoagulants), cholesterol-lowering agents (e.g., statins, proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibitors), angiotensin-converting enzyme (ACE) inhibitors or angiotensin receptor blockers (ARBs), and smoking cessation should be strongly encouraged for patients with CLI. This review examines these guideline-recommended therapies in terms of cardiovascular and limb-related risk reduction in patients with CLI.

Limb salvage after aneurysmal degeneration of a cryopreserved vein allograft: Searching the autologous veins of the arm is worth the effort

CLINICAL DATA

We hereby report a case of limb salvage involving a 64-year-old man who was hospitalized with ischemic foot ulcers for two months. Endarterectomy with patching and stenting of the left iliofemoral artery failed. A composite bypass of two segments of the endarterectomized superficial femoral artery and a cryopreserved saphenous vein graft was implanted one week later. On day 4 postoperatively, an infection (Staphylococcus epidermidis and Pseudomonas aeruginosa) was treated empirically with antibiotics. Four months later, the femoro-tibial bypass thrombosed and the patency was restored by thrombolysis. The aneurysmal cryopreserved vein was excised. Iterative complications followed and final success was attained after implantation of autologous cephalic and basilic veins. Four years later, this femoro-tibial is still patent.

PATHOLOGICAL ANALYSES

After a gross observation, the explant was dissected and the most significant sections were processed for histology, followed by analyses in scanning electron microscopy, light microscopy and transmission electron microscopy.

RESULTS

The explanted specimen showed a smooth flow surface proximally but a severe distortion distally, with an accumulation of poorly organized mural thrombi. The wall of the arterialized vein was accompanied with an important inflammatory reaction. The degradation of the collagen structure was evidenced in TEM. The fibrils of collagen were still individualized but were fragmented and did not display parallelly. The regular banding was preserved. The presence of Pseudomonas aeruginosa was shown inside the wall of the homologous vein.

COMMENTS

In case of sepsis, the most aggressive antibiotic treatments cannot fully eliminate the bacteremic colonizations within the wall of an alternative conduit. The cephalic and basilic autologous veins are proved to be preferable in absence of the autologous saphenous vein. The amputation was prevented and four years later the bypass is still patent. This is an outstanding result based upon the comorbidities of the patient. The most aggressive harvesting shall be recommended. This patient represented a considerable challenge and the clinical result is highly gratifying: the search for the autologous cephalic and basilic veins proved to be worth the effort.

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.

Statin therapy for reduction of cardiovascular and limb-related events in critical limb ischemia: A systematic review and meta-analysis

High-intensity statins are recommended for patients with peripheral artery disease (PAD). Critical limb ischemia (CLI) is the most advanced presentation of PAD. The benefit of statins in the CLI population is unclear based on the existent studies. Our objective was to perform a systematic review and meta-analysis regarding the efficacy of statin therapy in patients with CLI. PRISMA guidelines were followed. PubMed, EMBASE, and Cochrane CENTRAL databases were reviewed up to April 30, 2019. The primary outcomes included amputation rates and all-cause mortality. Secondary outcomes included primary patency rates, amputation-free survival and major adverse cardiac or cerebrovascular events (MACCE). Risk of bias was assessed with the Robins-I tool for observational studies. A random-effects model meta-analysis was performed. Heterogeneity was assessed with I2. Funnel plots and Egger’s test were used to assess publication bias. Nineteen studies including 26,985 patients with CLI were included in this systematic review. Among patients with known data on statin status, 12,292 (49.6%) were on statins versus 12,513 (50.4%) not on statins. Patients treated with statins were 25% less likely to undergo amputation (HR 0.75; 95% CI: 0.59–0.95; I2 = 79%) and 38% less likely to have a fatal event (HR 0.62; 95% CI: 0.52–0.75; I2 = 41.2%). Statin therapy was also associated with increased overall patency rates and lower incidence of MACCE. There was substantial heterogeneity in the analysis for amputation and amputation-free survival (I2 > 70%). In conclusion, statins are associated with decreased risk for amputation, mortality, and MACCE, as well as increased overall patency rates among patients with CLI. Future studies should assess whether other lipid-lowering medications in addition to high-intensity statins can further improve outcomes among patients with CLI. (PROSPERO registration number: CRD42019134160)

Potential of mesenchymal stem cells for bioengineered blood vessels in comparison with other eligible cell sources

Application of stem cells in tissue engineering has proved to be effective in many cases due to great proliferation and differentiation potentials as well as possible paracrine effects of these cells. Human mesenchymal stem cells (MSCs) are recognized as a valuable source for vascular tissue engineering, which requires endothelial and perivascular cells. The goal of this review is to survey the potential of MSCs for engineering functional blood vessels in comparison with other cell types including bone marrow mononuclear cells, endothelial precursor cells, differentiated adult autologous smooth muscle cells, autologous endothelial cells, embryonic stem cells, and induced pluripotent stem cells. In conclusion, MSCs represent a preference in making autologous tissue-engineered vascular grafts (TEVGs) as well as off-the-shelf TEVGs for emergency vascular surgery cases.

Cryopreserved Venous Allografts in Supra-inguinal Reconstructions: A Single Centre Experience

OBJECTIVE

This study introduces a novel technique for supra-inguinal arterial reconstructions with cryopreserved femoral vein and caval allografts with a low re-infection rate and an acceptable graft re-intervention rate on early mid term analysis.

METHODS

Patients treated from February 2012 to March 2018 with cryopreserved venous allograft reconstructions owing to infection in the supra-inguinal area were reviewed retrospectively. The primary end points were re-infection and the treatment related mortality rate. Secondary end points were 30 and 90 day and overall mortality and graft re-intervention rate.

RESULTS

Of the 23 patients treated with cryopreserved venous allografts for infection in aorto-iliac area, 21 (91%) patients underwent reconstruction with cryopreserved femoral veins and two (9%) with vena cava. Indications for treatment were aortic graft infections (n = 12 [52%]), mycotic aneurysms (n = 5 [22%]), femorofemoral prosthetic infections (n = 3 [13%]), anastomotic pseudo-aneurysms (n = 2 [9%]), and aortic thrombosis with intestinal spillage (n = 1 [4%]). In hospital and 90 day mortality were 9% (n = 2); overall treatment related mortality during the median follow up of 15 months was 13% (n = 3). During the follow up, two allografts were re-operated on owing to anastomotic dilatation and one because of re-infection, resulting in a re-intervention rate of 13% (n = 3). None of the grafts was lost and there were no amputations. At the end of follow up 17 patients (74%) were alive. Kaplan-Meier estimation for survival was 76% (95% confidence interval [CI] 57%-95%) at one year and 70% (95% CI 49%-91%) at two years.

CONCLUSION

Cryopreserved venous allografts appear to be an infection resistant and reasonably safe reconstruction material in the aorto-iliac axis based upon the early mid term analysis from a single centre experience. Further research is needed to compare their performance with other biological reconstruction material.

Delivery of targeted gene therapies using a hybrid cryogel-coated prosthetic vascular graft

OBJECTIVES

The success of prosthetic vascular grafts in the management of peripheral arterial disease is frequently limited by the development of anastomotic neointimal hyperplasia (ANIH), with the host response to prosthetic grafts beginning soon after implantation. To address this, we combine a platform of polyethylene terephthalate (PET) fabric with an applied cryogel layer containing biologic agents to create a bioactive prosthetic graft system, with the ability to deliver therapeutics targeting modulators of the ANIH-associated transcriptome response, along with antithrombotic agents.

METHODS

Hybrid graft materials were synthesized by cryopolymerization of methacrylated alginate and heparin onto electrospun (ePET), knitted PET (kPET), or woven PET (wPET). Arg-Gly-Asp (RGD) peptides were added to increase cell adhesion. Scanning electron microscopy (SEM) was used to study the microstructure at 1 day, and 2, 4, and 8 weeks. Physical properties such as swelling ratio, pore connectivity, shape recovery, and stiffness were evaluated. Human aortic endothelial cell (HAoEC) adherence was visualized using confocal microscopy after 24 hours and proliferation was evaluated with a resazurin-based assay for 7 days. Confocal microscopy was used to assess delivery of adeno-associated virus (AAV-GFP) after incubation of hybrid grafts with HAoECs. Heparin activity of the materials was measured using an anti-Xa assay.

RESULTS

SEM demonstrated large interconnected pores throughout the entire structure for all graft types, with minimal degradation of the cryogel after 8 weeks. Hybrid materials showed a trend towards increased shape recovery, increased stiffness, decreased swelling ratio, and no difference in pore connectivity. HAoECs incorporated, adhered, and proliferated over 7 days on all materials. HAoECs were successfully transduced with AAV-GFP from the hybrid graft materials. Anti-Xa assay confirmed continued activity of heparin from all materials for over 7 days.

CONCLUSIONS

We have developed a bioactive prosthetic graft system with a cryogel coating capable of delivering biologic agents with antithrombotic activity. By applying the cryogel and selected agents onto PET prior to graft implantation, this study sets the stage for the system to be individualized and tailored to the patient, with bioengineering and targeted gene therapy strategies dovetailing to create an improved prosthetic graft adaptable to emerging knowledge and technologies.

Cryopreserved Allografts for Treatment of Chronic Limb-Threatening Ischemia in Patients Without Autologous Saphenous Veins

BACKGROUND

Revascularization is the best alternative to reduce symptoms and to improve the limb salvage rate in patients with chronic limb-threatening ischemia (CLI). Alternative grafts as synthetic prostheses and allografts must be considered for patients without a suitable autologous graft. Our aim was to evaluate outcomes of cryopreserved allografts used as a vascular conduit for bypass surgery in the infrainguinal territory.

METHODS

A retrospective analysis (January 1995 to January 2014) of the Registry of vascular and valvular allografts transplant in the autonomous community of Catalonia, Spain was performed for identifying patients with CLI who required infrainguinal bypass with cryopreserved arterial allografts. Statistical analysis was performed using SPSS, ver. 20, for Mac (Chicago).

RESULTS

A total of 149 patients with CLI (mean age of 70.1 years) were analyzed. One hundred two patients (68.5%) had a grade IV lesion (Fontaine classification). In the overall follow-up, 24.8% of patients required a reintervention. Overall graft occlusion, infection, and dilation rate were 52.3%, 6%, and 5.4% respectively. Overall 30-day mortality was 0.7%. Five-year primary patency rate and limb salvage rate were 38.6% and 50.2%, respectively. Survival rate at 5 years was 54.2%. Major adverse limb event (MALE)-free rate was 21.5% at 5 years. Revascularization to a distal target vessel was an independent positive predictive risk factor for a lower limb salvage rate and lower primary patency rate. Dyslipidemia was related to a lower limb salvage rate and represents a risk factor involved in MALEs.

CONCLUSIONS

Although arterial allografts seem to represent a suboptimal alternative, some selected patients could beneficiate from them. Five-year results are disappointing, and more studies are required to know other predictive factors for better selection of patients.

Targeted Delivery of Bioactive Molecules for Vascular Intervention and Tissue Engineering

Cardiovascular diseases are the leading cause of death in the United States. Treatment often requires surgical interventions to re-open occluded vessels, bypass severe occlusions, or stabilize aneurysms. Despite the short-term success of such interventions, many ultimately fail due to thrombosis or restenosis (following stent placement), or incomplete healing (such as after aneurysm coil placement). Bioactive molecules capable of modulating host tissue responses and preventing these complications have been identified, but systemic delivery is often harmful or ineffective. This review discusses the use of localized bioactive molecule delivery methods to enhance the long-term success of vascular interventions, such as drug-eluting stents and aneurysm coils, as well as nanoparticles for targeted molecule delivery. Vascular grafts in particular have poor patency in small diameter, high flow applications, such as coronary artery bypass grafting (CABG). Grafts fabricated from a variety of approaches may benefit from bioactive molecule incorporation to improve patency. Tissue engineering is an especially promising approach for vascular graft fabrication that may be conducive to incorporation of drugs or growth factors. Overall, localized and targeted delivery of bioactive molecules has shown promise for improving the outcomes of vascular interventions, with technologies such as drug-eluting stents showing excellent clinical success. However, many targeted vascular drug delivery systems have yet to reach the clinic. There is still a need to better optimize bioactive molecule release kinetics and identify synergistic biomolecule combinations before the clinical impact of these technologies can be realized.

Utilization of Vasculoprotective Therapy for Peripheral Artery Disease: A Systematic Review and Meta-analysis

INTRODUCTION

Practice guidelines recommend that patients with peripheral artery disease receive antiplatelets, statins, and angiotensin-converting enzyme (ACE) inhibitors or angiotensin receptor blockers (ARBs). We sought to quantify the rates of prescribing these therapies in patients with peripheral artery disease in the literature.

METHODS

We performed a systematic review and meta-analysis of treatment prescribing rates in observational studies containing peripheral artery disease patients published on or after the year 2000. We also assessed whether prescribing rates are increasing over time.

RESULTS

A total of 86 studies were available for analysis. The aggregate sample size across all studies was 332,555. The pooled estimates for utilization of antiplatelets, statins, and ACE inhibitors or ARBs were 75% (95% confidence interval [CI], 71%-79%), 56% (95% CI, 52%-60%), and 53% (95% CI, 49%-58%), respectively. Statin use was directly related to publication year (+2.0% per year, P < .001), but this was not the case for antiplatelets (P = .68) or ACE inhibitors or ARBs (P = .066).

CONCLUSIONS

Although some improvement in statin prescribing has occurred in recent years, major practice gaps exist in the treatment of peripheral artery disease. Effective measures to close these gaps should be implemented.

Statin therapy improved long-term prognosis in patients with major non-cardiac vascular surgeries: a systematic review and meta-analysis

OBJECTIVE

To investigate whether statin intervention will improve the long-term prognosis of patients undergoing major non-cardiac vascular surgeries.

METHODS

Major database searches for clinical trials enrolling patients undergoing major non-cardiac vascular surgeries, including lower limb revascularization, carotid artery surgeries, arteriovenous fistula, and aortic surgeries, were performed. Subgroup analyses, stratified by surgical types or study types, were employed to obtain statistical results regarding survival, patency rates, amputation, and cardiovascular and stroke events. Odds ratio (ORs) and 95% confidence intervals (CIs) were calculated by Review Manager 5.3. Sensitivity analysis, publication bias and meta-regression were conducted by Stata 14.0.

RESULTS

In total, 34 observational studies, 8 prospective cohort studies and 4 randomized controlled clinical trials (RCTs) were enrolled in the present analysis. It was demonstrated that statin usage improved all-cause mortality in lower limb, carotid, aortic and mixed types of vascular surgery subgroups compared with those in which statins were not used. Additionally, the employment of statins efficiently enhanced the primary and secondary patency rates and significantly decreased the amputation rates in the lower limb revascularization subgroup. Furthermore, for other complications, statin intervention decreased cardiovascular events in mixed types of vascular surgeries and stroke incidence in the carotid surgery subgroup. No significant publication bias was observed. The meta-regression results showed that the morbidity of cardiovascular disease or the use of aspirin might affect the overall estimates in several subgroups.

CONCLUSIONS

This meta-analysis demonstrated that statin therapy was associated with improved survival rates and patency rates and with reduced cardiovascular or stroke morbidities in patients who underwent non-cardiac vascular surgeries.

A Strange "Collection" after Surgery for an Aneurysm of the Popliteal Artery

The popliteal fossa is the site of several diseases that may be similar in the clinical setting but very different in etiology, treatment, and prognosis. The contemporary presentation of more than one of these conditions is a rare though potentially fatal combination that may lead to a delay in the diagnosis and therapeutic approach. In this report, we describe the case of a patient who presented at our Vascular Department for persistent pain and severe swelling of the right popliteal fossa 8 months after the surgical treatment of a symptomatic popliteal aneurysm by mean of a Dacron prosthetic graft. With the suspect of the graft infection, as defined by angio-computer tomography and fluorodeoxyglucose positron emission tomography, the patient underwent graft removal and revascularization with a biologic conduit. Subsequent surgical revisions for unjustified recurrent hematic collections were necessary without any significative clinical improvement. The histologic analysis of the removed tissue was consistent with a high-grade sarcoma, and the patient underwent above-the-knee amputation of the right limb.

Cryopreserved Human Allografts for the Reconstruction of Aortic and Peripheral Prosthetic Graft Infection

Background: This study aimed to present cases with cryopreserved human allografts (CHAs) for vascular reconstruction in both aortic and peripheral infected prosthetic grafts.

Materials and Methods: This is a single center, observational descriptive study with retrospective analysis. In all cases, the infected prosthetic graft material was completely removed. At discharge, patients were administered anticoagulants. Follow-up examinations included clinical visits, echo-color-Doppler ultrasounds, or computed tomography angiography within 30 days and at 3, 6, and 12 months after the treatment, and then twice per year.

Results: We treated 21 patients (90% men, n=19) with the mean age of 71±12 years and mean interval between the initial operation and replacement with CHA of 30 months [range, 1–216; interquartile range (IQR), 2–36]. In-hospital mortality was 14% (n=3); no CHA-related complication led to death. Limb salvage was 100%. No patient was lost at the median follow-up of 14 months (range, 2–61; IQR, 6–39). No rupture, aneurysmal degeneration, or re-infection occurred. Estimated freedom from CHA-related adverse events (95% confidence interval, 43–63) was 95% at 3 years.

Conclusion: In our experience, CHAs are a viable option for prosthetic graft infections and provide satisfactory clinical results and favorable stability because of a very low rate of CHA-related adverse events during follow-up.

Late Fate of Cryopreserved Arterial Allografts

OBJECTIVE

Initial enthusiasm for use of cryopreserved arterial allografts was subsequently tempered by suboptimal long-term outcome. Thrombosis, anastomotic pseudo-aneurysm, allograft disruption, aneurysmal degeneration, recurrent intestinal fistulization, and persistent infection are commonly reported in series with long-term follow-up. The authors reviewed their experience over the past 15 years with the use of cryopreserved arterial allografts as a vascular substitute for vascular prosthetic infection or for primary arterial infection, to investigate allograft-related complications.

MATERIAL AND METHODS

A retrospective analysis of prospectively collected data was conducted for 103 cryopreserved arterial allografts inserted in 96 patients between July 2000 and July 2015. There were 78 patients with infected vascular prosthesis (IVP), nine patients with an aorto-enteric fistula (AEF), and nine patients with primary arterial infection (PAI).

RESULTS

The in-hospital mortality was eight out of 78 (9%) IVP patients, three out of nine AEF patients, and zero out of nine PAI patients. Median follow-up was 49 months. Allograft-related re-interventions were necessary in 29% of the patients with IVP and four of the patients with AEF, but none of the patients with PAI. Five-year survival for the IVP, AEF, and PAI patients was 53%, 44%, and 90%, respectively.

CONCLUSION

This series highlights some shortcomings of cryopreserved arterial allografts in the long term, including suboptimal outcome-results and shortage of material. The authors discuss the allograft-related complications and suggest some tricks to minimize their risk.

Surgical Skills Training with Cryopreserved Rat Stomachs

The objective of this study is to present a high-fidelity bench model of cryopreserved stomachs that can be used while learning surgical skills. Thirty stomachs were harvested from Wistar rats at the end of non-abdominal research studies. The stomachs were washed with cold saline solution and filled with hyaluronic acid solution. The organs were then placed into cryovials and cryopreserved at -30 °C for 60 days. The stomachs were thawed to room temperature on the day of the surgical skills practice and two full-thickness incisions were made. Reporting on their experiences, 22 participants (73.33%) felt that the cryopreserved stomach was identical to in vivo rat stomachs, 24 (80.00%) reported that the stomach was easy to handle, and 27 (90%) reported the tissue was non-friable. Moreover, 29 participants (96.6%) finished the suturing without tears and 100% recommended it as a biomaterial for surgical training. The cryopreserved stomach is a practical, reproducible, low-cost, and high-fidelity bench model that allows surgical fellows to learn how to handle a stomach and improve their surgical abilities before performing surgery on patients or laboratory animals.

Treatment of popliteal artery aneurysms by means of cryopreserved homograft

BACKGROUND

Autologous saphenous vein is considered the gold standard conduit in the femoral-popliteal revascularization for popliteal artery aneurysms (PAAs). In several cases, it may be absent or unsuitable for length or diameter and so it may be considered unfit for a conduit. In such patients, a synthetic graft or the endovascular correction can be useful, but results are controversial. In this retrospective case series, we have analyzed the safety and efficacy of the cryopreserved homograft (CHg) as a conduit in the PAA revascularization.

METHODS

In the period between January 2005 and December 2013, 54 PAAs have been treated with an arterial CHg. Indications to surgery were asymptomatic aneurysm with >25-mm diameter in 30 cases (55.6%), ischemic symptoms in 20 (37%), and compressive symptoms in 4 (7.4%). An urgent treatment was performed in 8 cases (14.8%) for severe ischemic symptoms. All cases have been operated by the same vascular team: a posterior surgical approach was preferred whenever possible (33 cases, 61.1%). All patients received a clinical and radiologic follow-up, and all data were collected in a specific database. A >10-mm diameter increase of the conduit was considered significant for an aneurysmatic degeneration.

RESULTS

The primary outcomes were complications and reoperation rate, limb salvage, and primary and secondary patency. Secondary outcome was the incidence of aneurysmatic degeneration of the CHg. Mean diameter of the homografts was 6.3 mm (range, 4-8 mm). In the 30-day postoperative period, 7 PAAs (13%) developed a complication: 3 wound infections, 3 graft thrombosis, and 1 anastomotic bleeding. Six cases needed a reoperation: 2 surgical revascularizations, 2 wound debridement, and 1 anastomotic hemostasis; 1 major amputation was necessary for graft failure after the revascularization. Mean follow-up was 34.8 months (range, 1-96). Five cases (9.3%) developed a graft complication with 4 reoperations necessary (7.4%): 2 grafts required a percutaneous transluminal angioplasty for a perigraft stenosis and 2 underwent a femorodistal bypass in CHg for severe ischemic symptoms after CHg occlusion. Another one CHg occlusion was treated conservatively because it was clinically asymptomatic. Primary patency was 96.3%, 93.9%, and 88.3% at 12, 36, and 60 months, respectively; secondary patency was 98.1% at 12, 36, and 60 months. Freedom from amputation resulted in 98.1%. No aneurysmatic degeneration was observed. Univariate and multivariate analysis showed urgent surgery to be independent risk factors for complications, reoperations, and CHg occlusion (P < 0.05).

CONCLUSIONS

In this retrospective study, the use of CHg showed to be safe and effective in the surgery of PAAs, either in the short or in the long-term follow-up. Urgent surgery can be considered predictive of graft failure. In our experience, CHg can be considered a good alternative conduit to the autologous saphenous vein.

Surgical Intervention for Peripheral Arterial Disease

The prevalence of peripheral arterial disease (PAD) is increasing worldwide, with recent global estimates exceeding 200 million people. Advanced PAD leads to a decline in ambulatory function and diminished quality of life. In its most severe form, critical limb ischemia, rest pain, and tissue necrosis are associated with high rates of limb loss, morbidity, and mortality. Revascularization of the limb plays a central role in the management of symptomatic PAD. Concomitant with advances in the pathogenesis, genetics, and medical management of PAD during the last 20 years, there has been an ongoing evolution of revascularization options. The increasing application of endovascular techniques has resulted in dramatic changes in practice patterns and has refocused the question of which patients should be offered surgical revascularization. Nonetheless, surgical therapy remains a cornerstone of management for advanced PAD, providing versatile and durable solutions to challenging patterns of disease. Although there is little high-quality comparative effectiveness data to guide patient selection, existing evidence suggests that outcomes are dependent on definable patient factors such as distribution of disease, status of the limb, comorbid conditions, and conduit availability. As it stands, surgical revascularization remains the standard against which emerging percutaneous techniques are compared. This review summarizes the principles of surgical revascularization, patient selection, and expected outcomes, while highlighting areas in need of further research and technological advancement.

Optimal management of infrainguinal arterial occlusive disease

Peripheral arterial occlusive disease is becoming a major health problem in Western societies as the population continues to age. In addition to risk of limb loss, the complexity of the disease is magnified by its intimate association with medical comorbidity, especially cardiovascular and cerebrovascular disease. Risk factor modification and antiplatelet therapy are essential to improve long-term survival. Surgical intervention is indicated for intermittent claudication when a patient’s quality of life remains unacceptable after a trial of conservative therapy. Open reconstruction and endovascular revascularization are cornerstone for limb salvage in patients with critical limb ischemia. Recent advances in catheter-based technology have made endovascular intervention the preferred treatment approach for infrainguinal disease in many cases. Nevertheless, lower extremity bypass remains an important treatment strategy, especially for reasonable risk patients with a suitable bypass conduit. In this review, we present a summary of current knowledge about peripheral arterial disease followed by a review of current, evidence-based medical and surgical therapy for infrainguinal arterial occlusive disease.

Defining utility and predicting outcome of cadaveric lower extremity bypass grafts in patients with critical limb ischemia

OBJECTIVE

Despite poor long-term patency, acceptable limb salvage has been reported with cryopreserved saphenous vein bypass (CVB) for various indications. However, utility of CVB in patients with critical limb ischemia (CLI) remains undefined. The purpose of this analysis was to determine the role of CVB in CLI patients and to identify predictors of successful outcomes.

METHODS

A retrospective review of all lower extremity bypass (LEB) procedures at a single institution was completed, and CVB in CLI patients were further analyzed. The primary end point was amputation-free survival. Secondary end points included primary patency and limb salvage. Life tables were used to estimate occurrence of end points. Cox regression analysis was used to determine predictors of limb salvage.

RESULTS

From 2000 to 2012, 1059 patients underwent LEB for various indications, of whom 81 received CVB for either ischemic rest pain or tissue loss. Mean age (± standard deviation) was 66 ± 10 years (male, 51%; diabetes, 51%; hemodialysis dependence, 12%), and 73% (n = 59) had history of failed ipsilateral LEB or endovascular intervention. None had sufficient autogenous conduit for even composite vein bypass. Infrainguinal CVB (infrapopliteal target, 96%; n = 78) was completed for multiple indications including Rutherford class 4 (42%; n = 34), class 5 (40%; n = 32), and class 6 (18%; n = 15). Eleven (14%) had CLI and concomitant graft infection (n = 8) or acute on chronic ischemia (n = 3). Intraoperative adjuncts (eg, profundaplasty, suprainguinal stent or bypass) were completed in 49% (n = 40) of cases. Complications occurred in 36% (n = 29), with 30-day mortality of 4% (n = 3). Median follow-up for CLI patients was 11.8 (interquartile range, 0.4-28.4) months with corresponding 1- and 3-year actuarial estimated survival (± standard error mean) of 84% ± 4% and 62% ± 6%. Primary patency of CVB for CLI was 27% ± 6% and 17% ± 6% at 1 and 3 years, respectively. Amputation-free survival was 43% ± 6% and 23% ± 6% at 1 and 3 years, respectively, and significantly higher for rest pain (59% ± 9%, 36% ± 10%) compared with tissue loss (31% ± 7%, 14% ± 7%; log-rank, P = .04). Freedom from major amputation after CVB for CLI was 57% ± 6% and 43% ± 7% at 1 and 3 years. Multivariable predictors of limb salvage for the CVB CLI cohort included postoperative warfarin (hazard ratio [HR], 0.4; 95% confidence interval [CI], 0.2-0.8), dyslipidemia (HR, 0.4; 95% CI, 0.2-0.9), and rest pain (HR, 0.4; 95% CI, 0.2-0.9). Predictors of major amputation included graft infection (HR, 3.1; 95% CI, 1.1-9.0).

CONCLUSIONS

In CLI patients with no autologous conduit and prior failed infrainguinal bypass, CVB outcomes are disappointing. CVB performs best in patients with rest pain, particularly those who can be anticoagulated with warfarin. However, it may be an acceptable option in patients with minor tissue loss or concurrent graft infection, but consideration should be weighed against the known natural history of nonrevascularized CLI and nonbiologic conduit alternatives, given potential cost implications.

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.

Antibody-mediated rejection of arterialised venous allografts is inhibited by immunosuppression in rats

Objectives and Design

We determined in a rat model (1) the presence and dynamics of alloantibodies recognizing MHC complexes on quiescent Brown-Norway (BN) splenic cells in the sera of Lewis (LEW) recipients of Brown-Norway iliolumbar vein grafts under tacrolimus immunosuppression; and (2) the presence of immunoglobulins in the wall of acute rejected vein allografts.

Materials and Methods

Flow cytometry was used for the analysis of day 0, 14 and 30 sera obtained from Lewis recipients of isogeneic iliolumbar vein grafts (group A) or Brown-Norway grafts (group B, C) for the presence of donor specific anti-MHC class I and II antibodies. Tacrolimus 0.2 mg/kg daily was administered from day 1 to day 30 (group C). Histology was performed on day 30.

Results

Sera obtained preoperatively and on day 30 were compared in all groups. The statistically significant decrease of anti MHC class I and II antibody binding was observed only in allogenic non-immunosuppressed group B (splenocytes: MHC class I - day 0 (93%±7% ) vs day 30 (66%±7%), p = 0.02, MHC class II - day 0 (105%±3% ) vs day 30 (83%±5%), p = 0.003; B-cells: MHC class I - day 0 (83%±5%) vs day 30 (55%±6%), p = 0.003, MHC class II - day 0 (101%±1%) vs day 30 (79%±6%), p = 0.006; T-cells: MHC class I - day 0 (71%±7%) vs day 30 (49%±5%), p = 0.04). No free clusters of immunoglobulin G deposition were detected in any experimental group.

Conclusion

Arterialized venous allografts induce strong donor-specific anti-MHC class I and anti-MHC class II antibody production with subsequent immune-mediated destruction of these allografts with no evidence of immunoglobulin G deposition. Low-dose tacrolimus suppress the donor-specific antibody production.

Cryopreserved autologous saphenous vein for staged treatment of bilateral popliteal aneurysms: report of three cases

Popliteal artery aneurysms are the most common aneurysmal disease of the lower extremity. Although endovascular solutions are gaining consensus, open surgery with interposition grafting remains the standard of care. The great saphenous vein (GSV) is the most commonly used conduit and shows the best long-term results. However, optimal vein segments can sometimes be unavailable, thus leading to the use of unsuitable segments or prosthetic grafts. We report the cases of 3 patients who had bilateral popliteal aneurysms and only 1 GSV that was considered suitable for grafting, without alternative venous segments. All patients underwent staged treatment with the use of the GSV. After the first operation, the remaining GSV was cryopreserved and then reused for the contralateral limb. All patients had an uneventful outcome. No graft occlusions and no aneurysmal dilatations were detected at follow-up. Cryopreservation of autologous vein for staged treatment of bilateral popliteal aneurysms is feasible and seems to avoid the risk of residual GSV loss during the time inbetween the interventions.

Inhibiting connexin channels protects against cryopreservation-induced cell death in human blood vessels

OBJECTIVES

Cryopreserved blood vessels are being increasingly employed in vascular reconstruction procedures but freezing/thawing is associated with significant cell death that may lead to graft failure. Vascular cells express connexin proteins that form gap junction channels and hemichannels. Gap junction channels directly connect the cytoplasm of adjacent cells and may facilitate the passage of cell death messengers leading to bystander cell death. Two hemichannels form a gap junction channel but these channels are also present as free non-connected hemichannels. Hemichannels are normally closed but may open under stressful conditions and thereby promote cell death. We here investigated whether blocking gap junctions and hemichannels could prevent cell death after cryopreservation.

MATERIALS AND METHODS

Inclusion of Gap27, a connexin channel inhibitory peptide, during cryopreservation and thawing of human saphenous veins and femoral arteries was evaluated by terminal deoxynucleotidyl transferase dUTP nick end labelling (TUNEL) assays and histological examination.

RESULTS

We report that Gap27 significantly reduces cell death in human femoral arteries and saphenous veins when present during cryopreservation/thawing. In particular, smooth muscle cell death was reduced by 73% in arteries and 71% in veins, while endothelial cell death was reduced by 32% in arteries and 51% in veins.

CONCLUSIONS

We conclude that inhibiting connexin channels during cryopreservation strongly promotes vascular cell viability.

Cryopreserved saphenous vein allograft for infragenicular bypass in the presence of foot infection

We report our distal bypass experience with cryopreserved saphenous vein allograft (CSVA) in 12 patients presenting with infection and no autologous saphenous vein available. Twelve patients underwent 13 arterial reconstructions. The mean age of the cohort was 68.4 years. Ninety-two percent (92%) of the patients presented with Rutherford Class 5 or 6 disease which required wide debridement and copious irrigation of all infected tissue beds. All distal anastomoses were to infragenicular vessels. Two patients died with patent grafts during follow-up for an 83% survival rate. Three grafts failed during follow-up between one and 36.3 months, of which two underwent amputation for an 82% limb salvage rate. The primary and primary assisted patency rate was 40% and 60% at 18 months follow-up, respectively, and no recurrent infections. In patients who have complex risk factors and the presence of infection, CSVA appears to be a reasonable option for limb salvage.

A cost-effectiveness analysis of infrainguinal bypass in the absence of great saphenous vein conduit

BACKGROUND

Good-quality great saphenous vein (GSV) is the preferred conduit for infrainguinal surgical revascularizations, but it is not available in all patients. We sought to identify the alternative conduit that would maximize cost-effectiveness in the context of infrapopliteal bypass for critical limb ischemia and nonhealing foot wounds.

METHODS

A Markov model was used to create a detailed simulation of 10-year outcomes in a hypothetical Edifoligide for the Prevention of Infrainguinal Vein Graft Failure (PREVENT) III-type patient cohort undergoing infrainguinal bypass for nonhealing foot wounds. The following management options were evaluated: (1) conservative therapy (local wound care, amputation as needed); (2) primary amputation; (3) bypass with autologous alternative vein (AAV), including arm or lesser saphenous vein; (4) bypass with GSV <3 mm in diameter; (5) bypass with polytetrafluoroethylene (PTFE); (6) cryopreserved venous allograft; and (7) cryopreserved arterial allograft. Estimates of 10-year total costs were incorporated into the model. Cost-effectiveness was measured in terms of incremental United States dollars per additional year of ambulation.

RESULTS

Bypass with AAV had the highest effectiveness as measured in median years of ambulation. After primary amputation, bypass with PTFE had the lowest total costs. With incremental cost-effectiveness ratios of $5325 and $21,228, bypass with PTFE or AAV appeared to be cost-effective alternatives to conservative therapy for nonhealing ischemic wounds. Primary amputation, GSV <3 mm, and allograft options were dominated (ie, more costly and less effective). Primary amputation was weakly dominated.

CONCLUSIONS

Bypass with PTFE or AAV appears to be a cost-effective option for the management of critical limb ischemia and nonhealing foot wounds when good-quality GSV is not available.

Preimplantation processing of ex vivo-derived vascular biomaterials: effects on peripheral cell adhesion

The use of ex vivo-derived scaffolds as vascular conduits has shown to be a clinically valid approach to repair or bypass occluded vessels. Implantation of allogeneic tissue grafts requires careful processing to lower immunogenicity and prevent bacterial infection. However, the mechanical/chemical treatments used to prepare biological scaffolds can result in significant alterations to the native structure and surface chemistry, which can affect in vivo performance. Of particular importance for vascular grafts are binding interactions between the implanted biomaterial and host cells from the circulation and adjacent vasculature. Here we present a comparison of four strategies used to decellularize allogeneic human umbilical vein (HUV) scaffolds: ethanol/acetone, sodium chloride, sodium dodecyl sulfate (SDS), or Triton X-100. Scanning electron microscopy revealed that all four techniques achieved removal of native cells from both the lumenal and ablumenal surfaces of HUV grafts. Platelets and promyelocytic HL-60 cells showed preferential binding on the more loosely structured ablumenal surface, although low surface coverage was observed overall by peripheral blood cells. Vascular endothelial cell adhesion was highest on HUV decellularized using ethanol/acetone, and significantly higher than on SDS-processed grafts (p = 0.016). Primary cells showed high viability on the lumenal surface regardless of decellularization technique (over 95% in all cases). These results demonstrate the critical effects of various chemical processing strategies on the adhesive properties of ex vivo-derived vascular grafts. Careful application-specific consideration is warranted when selecting a processing strategy that minimizes innate responses (e.g. thrombosis, inflammation) that are often deleterious to graft survival.

Functional, morphologic, and molecular characterization of cold storage injury

OBJECTIVE

Cold storage is used to preserve tissue for later transplantation. There is particular interest in prolonging cold storage time for transplantation purposes. To date, the mechanisms that contribute to vascular dysfunction in response to cold storage are poorly understood. The present study aims to characterize cold storage injury of blood vessels on functional and molecular levels.

METHODS

To assess vessel function of mouse aorta, isometric force measurements were performed in a Mulvany myograph after cold storage at 4°C for various intervals. Morphologic changes were judged by histologic analysis of aortic cross-sections. To characterize cold storage-induced alterations on RNA levels, microarray analysis with subsequent polymerase chain reaction analysis was performed.

RESULTS

Cold storage for 2 days revealed significant impairment of vessel function with respect to potassium-induced vessel tone development and acetylcholine-induced vessel relaxation. Detailed analysis of acetylcholine-mediated vascular response using specific pharmacologic blockers revealed that calcium-activated potassium channels seem to be impaired after 2 days of cold storage. At this point, no severe histologic changes (eg, elastic fiber disruption) were visible. RNA expression of 24 genes was significantly changed due to cold storage even after 2 hours. These include genes associated with vessel tone development (prostaglandin E(3) receptor), cardiovascular function (adiponectin), electron transport chain (uncoupling protein 1), or calcium signaling (protein kinase A regulatory subunit 2b).

CONCLUSIONS

Long-term cold storage impairs vascular function, especially with respect to potassium signaling by calcium-dependent potassium channels. Microarray analysis confirmed impairment of pathways that are involved in calcium signaling and vascular function. Furthermore, various genes were significantly altered even after 2 hours, significantly before functional impairment was observed.