Analysis of risk factors for occlusions of a synthetic femoropopliteal bypass graft

© 2015, Institut za Vojnomedicinske Naucne Informacije/Documentaciju. All rights reserved. Background/Aim. Femoropopliteal bypass is a revasculariza-tion technique of lower extremities with excellent outcome. The great saphenous vein is the best graft material, but if it is not adequate or has been removed, synthetic grafts are an useful al-ternative. Graft occlusion is the most significant complication with the most serious consequences. The aim of this study was to analyse predictive factors for the synthetic femoropopliteal bypass occlusions. Methods. This retrospective case-control study included all patients who underwent synthetic femoropop-liteal bypass due to peripheral arterial occlusive disease at the Vascular Surgery Center, Clinical Center of Kragujevac, Serbia, from 2007 to 2013. The cases group were the patients with femoropopliteal graft occlusion (n = 44), with the control group consisted of the patients without such an outcome (n = 88). Re-sults. Significant effects to occlusion were: concomitant cardio-vascular disease (adjustedOR 27.05; 95% CI 4.74; 154.35), a type of femoropopliteal bypass (adjustedOR 16.50; 95% CI 4.05; 67.24), previous vascular intervention (adjustedOR 4.67; 95% CI 1.20; 18.14), clinical stage of the disease (adjustedOR 3.73; 95% CI 1.94; 7.18), administration of postoperative oral anticoagulant therapy (adjustedOR 0.05; 95% CI 0.01; 0.23) and the use of angiotensin converting enzyme inhibitors (adjustedOR 0.14; 95% CI 0.03; 0.70). A significant synergism was shown for the following combina-tions of the observed risk factors: type of femoropopliteal bypass and cardiovascular disease, type of femoropopliteal bypass and previous vascular intervention, previous vascular intervention and cardiovascular disease, previous vascular intervention and beta blockers, cardiovascular disease and diabetes, type of femoropopliteal bypass and antiaggregant therapy, clinical stage of disease and cardiovascular disease, previous vascular interven-tion and antiaggregant therapy. Conclusion. Concomitant car-diovascular disease, below-knee femoropopliteal bypass, ad-vanced stage of vascular disease and non-use of anticoagulant therapy and angiotensin-converting enzyme inhibitors are the significant predictors of graft occlusion after synthetic femoro-popliteal bypass. Their synergistic effect determines the impor-tance of diabetes, use of beta blockers and platelet antiaggregant therapy

Outcome analysis and surveillance of infra inguinal arterial bypass graft

BACK GROUND : In Crtical Limb Ischemia, Infrainguinal bypass surgery is the mainstay of therapeutic interventions aimed at limb salvage. The outcome of surgery is the chief determinant of limb salvage and is affected by multiple factors. The graft patency rates have been related to clinical severity of ischemia, distal run-off,patients risk factors, and Diabetes. This study is planned to review the factors that will influence the outcome of infrainguinal bypass and to identify those factors that are modifiable, and will help in improving the outcome of the procedures ,improve the patency of the graft and limb salvage rate. AIM : To assess early postoperative outcomes in patients undergoing Infrainguinal bypass surgery ,to study the factors affecting the outcomes and to identify failing graft. METHODS AND MATERIALS : It is Prospective study in 56 patients from January 2010 to January 2012.Case records and angiograms of patients who underwent femoropopliteal bypass procedures. CLI and incapicitating claudication is the main indication for surgery. Data pertaining to patient risk factors and co-morbidities were evaluated. CT angio performed in all patients to assess the occlusive pattern, status of popliteal artery and run off status and the lesions were classified as per TASC 2007 classification. Infrainguinal bypass surgery were considered for all patients. Standard operative procedures were followed. Postoperatively all patients were given Plain Heparin or LMWH for 5 days & Tab. Aspirin 150mg OD & Tab. Clopidogrel 75mg and other drugs as per their co-morbidities. Graft surveillance was done by symptomatic analysis of rest pain status, palpable popliteal pulse and distal pulses, examination with handheld Doppler for signals and with Pre and post operative ABI. All patients were followed from the day of surgery to the end of 12th month. Statistical analysis of the graft patency rates were calculated with respect to the CT Angio run off status,risk factors, etiolgical factors,and limb salvage rate. RESULTS : In this study, most of the patients had presented at the age around 40 to 60 yrs. Smoking obviously forms a significant risk factor in the development of PAD as the incidence of smoking in this case series was 83.3%. Toe gangrene is commonest clinical presentation is58.9%. ASO is commonest etiology of 67.8%. Incidence of CAD, CKD and diabetes mellitus was very high in patients with outflow via collaterals. The incidence of CLI patients with single vessel runoff group are 53.5%, double vessel runoff group are 41.07% and three vessels run off group is 5.3%. Among total of 56 patients, femoro popliteal bypass forms the common form of bypass with 43 patients compared to femoro distal bypass in other patients. Among various post operative complications minor amputations being 33.9% is the commonest complication. Patients with wound infection in our series was 12.5%. During the post operative follow up period one patient expired in the early postoperative period due to myocardial infarction. In our study group infra inguinal arterial bypass surgery, out of total 56 grafts, for 43patients RGSV and 13 (1 = Composite graft) PTFE grafts used. Graft occlusion rate is 16.07% and Graft failing rate is 10.7%.Primary patency rate of graft at the end of one year is 80 % (n=44) .Graft thrombosis rate in this study is 16.36% (n=9). Six grafts were identified during their failing stage in the study, out of which 3 patients underwent Redo bypass surgery (PAP 82.1%). Among redo group for 2, grafts patency restored and their limbs salvaged and 1 graft occluded subsequently and resulted in limb amputation. The p values for primary patency, cumulative patency rates with respect to the run off status at 12th month were 0.324, 0.509 respectively and were statistically insignificant.Primary assisted patency rate in this study is 82.1%. Limb salvage rate was 94.54%. Failing graft in this study is 10.9% ( n=6 ). Major Amputation rate in this study is (5.3 %). The graft patency was compared in relation to etiological factors in 56 patients. In atherosclerosis group of 38 grafts used, out them n=29 had patent grafts, n=4 occluded and n=6 were failing. In thromboangitis obliterans n=11 were patent and n=4 were occuled. In Arteritis group n=1 patent and n=1 occuled. TAO and arteritis had increased risk of graft occlusion during the follow up. The occurrence of graft stenosis or occlusion is more common in patients who underwent infragenicular bypasses than above knee bypass. In this study one case of Atrial myxoma presented with CLI , had undergone femoro-proximal popliteal bypass surgery and graft was patent compared with literature (18) Vascular. 2005 Jul-Aug;13(4):222-9. The rate of limb salvage in patients with failed grafts was 83.3% fo 1 year, when compared to literature (only 50% at 2 yrs after failure. - Midwestern vascular surgical society Chicago September 2003). CONCLUSION : • Infrainguinal revasularisation surgery has acceptable graft patency and survival rates. • Graft patency rates were not adversely affected by poor runoff vessels, and when there was a reformation of the popliteal artery even when the out flow vessels were not adequately visualized angiographically. • High limb salvage rates when compared to the relatively low graft patency rates explains the collateral formation after bypass procedures. • Femoro popliteal bypass grafting is still treatment of choice where endovascular facilities available for patients with disabling claudicants and in CLI especially with TASC C and D lesions. • Patients with poor conduit quality, active tobacco use and LV dysfunction have poorer clinical outcome • Graft surveillance is essential throughout the life to identify the failing graft and to intervene at appropriate time,to prolong the graft patency. KEY WORDS Infrainguinal revasularisation, Graft surveillance, Graft patency,Conduit, CT angio, Primary Assited Patency

Stabilised decellularised vascular grafts in an ovine carotid model

Background: There is an urgent clinical need for an alternative vascular graft, especially for smaller artery applications such as in below-knee and coronary artery bypass. Currently available synthetic grafts have unacceptably low patency rates, while autologous saphenous vein grafts are not feasible in one third of patients. Decellularised vascular grafts have been investigated as alternative conduits, but this chemical treatment results in degradation of the extracellular matrix. Chemical stabilization of elastin with penta-galloyl glucose (PGG) combined with collagen stabilisation during covalent heparinisation was previously investigated by our group in a small animal model and shown to be effective and safe. The current study describes their evaluation in a large animal (ovine) model. Methods: Porcine mammary arteries were harvested, decellularised according to an established protocol involving rinsing with sodium hydroxide, alcohol (ETOH), treatment with DNAse/RNAse enzymes, immersion in PGG and subsequently surface modified with covalently bound heparin. Samples of the grafts were also tested for radial and suture retention strength. The prepared grafts were implanted as interposition grafts into the carotid arteries of 6 sheep, using industry standard 6mm expanded polytetrafluoroethylene (ePTFE) on the contralateral side of each animal as control. In-situ patency was determined by ultrasound and angiography at two months, following which the grafts were explanted for macro- and microscopic analysis. Results: In-vitro evaluation: Grafts showed significant levels of bound heparin (14.56 mg/g vs 0.69mg/g in untreated tissue) and demonstrated similar mechanical properties to those of human carotid arteries. Survival: Five out of six sheep survived the full 2-month implant period, while the remaining animal developed sepsis shortly after implantation and was euthanized on day 4. Patency: None of the decellularised grafts were patent at explant, as assessed by ultrasound, angiography and macroscopic examination. Two of the five control (ePTFE) grafts were patent. Microscopic analysis: An inflammatory cell infiltrate with vascularised granulation tissue was found encasing the decellularised xenografts with little or no sign of endothelial cell infiltration. Signs of early occlusion, likely due to technical factors, was noted at the sites of anastomosis. Conclusion: Although demonstrating similar mechanical properties to human carotid arteries, and promising results in the small animal model, the stabilised decellularised vascular grafts failed to achieve endothelialisation or patency in this sheep carotid model. Significant calibre mismatch between the test graft and the native artery is thought to be the primary factor in the failure of these grafts, highlighting the potential difficulty in acquiring grafts of an appropriate size from animal sources

Global Vascular Guidelines on the Management of Chronic Limb-Threatening Ischemia

Chronic limb-threatening ischemia (CLTI)is associated with mortality, amputation, and impaired quality of life. These Global Vascular Guidelines (GVG)are focused on definition, evaluation, and management of CLTI with the goals of improving evidence-based care and highlighting critical research needs. The term CLTI is preferred over critical limb ischemia, as the latter implies threshold values of impaired perfusion rather than a continuum. CLTI is a clinical syndrome defined by the presence of peripheral artery disease (PAD)in combination with rest pain, gangrene, or a lower limb ulceration >2 weeks duration. Venous, traumatic, embolic, and nonatherosclerotic etiologies are excluded. All patients with suspected CLTI should be referred urgently to a vascular specialist. Accurately staging the severity of limb threat is fundamental, and the Society for Vascular Surgery Threatened Limb Classification system, based on grading of Wounds, Ischemia, and foot Infection (WIfI)is endorsed. Objective hemodynamic testing, including toe pressures as the preferred measure, is required to assess CLTI. Evidence-based revascularization (EBR)hinges on three independent axes: Patient risk, Limb severity, and ANatomic complexity (PLAN). Average-risk and high-risk patients are defined by estimated procedural and 2-year all-cause mortality. The GVG proposes a new Global Anatomic Staging System (GLASS), which involves defining a preferred target artery path (TAP)and then estimating limb-based patency (LBP), resulting in three stages of complexity for intervention. The optimal revascularization strategy is also influenced by the availability of autogenous vein for open bypass surgery. Recommendations for EBR are based on best available data, pending level 1 evidence from ongoing trials. Vein bypass may be preferred for average-risk patients with advanced limb threat and high complexity disease, while those with less complex anatomy, intermediate severity limb threat, or high patient risk may be favored for endovascular intervention. All patients with CLTI should be afforded best medical therapy including the use of antithrombotic, lipid-lowering, antihypertensive, and glycemic control agents, as well as counseling on smoking cessation, diet, exercise, and preventive foot care. Following EBR, long-term limb surveillance is advised. The effectiveness of nonrevascularization therapies (eg, spinal stimulation, pneumatic compression, prostanoids, and hyperbaric oxygen)has not been established. Regenerative medicine approaches (eg, cell, gene therapies)for CLTI should be restricted to rigorously conducted randomizsed clinical trials. The GVG promotes standardization of study designs and end points for clinical trials in CLTI. The importance of multidisciplinary teams and centers of excellence for amputation prevention is stressed as a key health system initiative. © 2019 Society for Vascular Surgery and European Society for Vascular Surger

Vascular Surgery

This book aims to provide a brief overview of conventional open vascular surgery, endovascular surgery and pre- and post-operative management of vascular patients. The collections of contributions from outstanding vascular surgeons and scientists from around the world present detailed and precious information about the important topics of the current vascular surgery practice and research. I hope this book will be used worldwide by young vascular surgeons and medical students enhancing their knowledge and stimulating the advancement of this field

Fabrication of Human Serum Albumin Film for Enhanced Hemocompatibility and Mitigation of Intimal Hyperplasia Under Physiologically Relevant Flow Shear Conditions

Current endovascular stents and synthetic vascular grafts have poor clinical outcomes in small diameter applications due to high incidence of thrombogenicity and intimal hyperplasia. To address this, we have developed an albumin film for mitigation of the complications of platelet adhesion and smooth muscle cell hyperplasia and hypertrophy. A human serum albumin (HSA) film is fabricated on an anchoring layer of poly (glycidyl methacrylate) on surfaces of metallic and polymeric substrates. The PGMA and HSA layers are characterized by FT-IR spectroscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy and contact angle analysis. We have confirmed the thromboresistance of albumin film by in vitro measurement of adsorption of human fibrinogen and platelets. We found that albumin film controlled the adsorption of fibrinogen evidenced by measurement of fluorescently labeled protein and adhesion force measurement. Human platelet adhesion was significantly lower on albumin coated compared to uncoated substrates. Smooth muscle cells play a key role in progression of intimal hyperplasia and hence we assessed the proliferation, hypertrophy and contractile state of cells in static and flow conditions. A vascular simulator was employed to provide forces of cyclic strain and flow shear to smooth muscle cells on albumin coated and uncoated ePTFE grafts. It was found that albumin film controlled proliferation and maintained the contractile state of smooth muscle cells on nitinol and ePTFE substrates. We developed a flow circulation loop model to assess the response of fibrinogen and platelets on albumin coated and uncoated e PTFE grafts. A significantly lower adsorption of fibrinogen and platelet adhesion was measured on albumin coated e PTFE grafts compared to uncoated grafts. Exhibiting strong adhesion strength to polymeric and metallic substrates, human albumin film fabricated using PGMA as an anchoring layer has been shown to shield the surface from adhesive protein fibrinogen and prevents adhesion of platelets thereby providing an anti-thrombogenic layer. Human albumin has been shown to maintain a controlled proliferation profile and spindle shaped morphology of vascular smooth muscle cells with increased expression of contractile protein smooth muscle alpha actin mitigating the complication of intimal hyperplasia post a percutaneous interventional procedure and bypass surgery

New insights in diagnostic and treatment modalities of native aortic and prosthetic graft infections

In this thesis several aspects of the diagnosis and treatment of infectious native aortic aneurysm (INAA) and vascular graft and endograft infection (VGEI) are investigated. Part I is mainly about diagnostics. Part II describes various biological materials used in vascular surgery. Part I contains a study focusing on INAA and another study focusing on the reporting of [18F]FDG PET/CT scans for the diagnosis of VGEI. In addition, a case is described, in which the importance of a systematic approach in the diagnosis of VGEI is emphasized. The second part of this thesis contains a study on the use of Omniflow II in different anatomical locations in both an infectious and non-infectious setting. Furthermore, it contains two studies on the use of different patches (including the bovine pericardial patch) used for carotid endarterectomy