Peripheral Bypass Graft Research Articles

Development of endothelium-denuded human umbilical veins as living scaffolds for tissue-engineered small-calibre vascular grafts

Tissue-engineered small-calibre vessel grafts may help to alleviate the lack of graft material for coronary and peripheral bypass grafting in an increasing number of patients. This study explored the use of endothelium-denuded human umbilical veins (HUVs) as scaffolds for vascular tissue engineering in a perfusion bioreactor. Vessel diameter (1.2 ± 0.4 mm), wall thickness (0.38 ± 0.09 mm), uniaxial ultimate failure stress (8029 ± 1714 kPa) and burst pressure (48.4 ± 20.2 kPa, range 28.4-83.9 kPa) were determined in native samples. The effects of endothelium removal from HUVs by enzymatic digestion, hypotonic lysis and dehydration were assessed. Dehydration did not significantly affect contractile function, tetrazolium dye reduction, mechanical strength and vessel structure, whereas the other methods failed in at least one of these parameters. Denudation by dehydration retained laminin, fibronectin, collagen and elastic fibres. Denuded HUVs were seeded in a perfusion bioreactor with either allogeneic HUVs endothelial cells or with saphenous vein endothelial cells harvested from patients with coronary artery disease. Seeding in a perfusion bioreactor resulted in a confluent monolayer of endothelial cells from both sources, as judged by histology and scanning electron microscopy. Seeded cells contained von Willebrand factor and CD31. In conclusion, denuded HUVs should be considered an alternative to decellularized blood vessels, as the process keeps the smooth muscle layer intact and functional, retains proteins relevant for biomechanic properties and for cell attachment and provides a suitable scaffold for seeding an autologous and flow-resistant endothelium.

Safety of catheter‐delivered plasmin in patients with acute lower extremity arterial or bypass graft occlusion: phase I results

Current treatment of acute peripheral artery or bypass graft occlusion utilizes catheter-directed thrombolysis of a plasminogen activator (PA). Plasmin is a direct-acting thrombolytic with a striking safety advantage over PA in preclinical models. To report the first use of purified plasmin for acute lower extremity arterial or bypass graft thrombosis in a phase I dose-escalation study of a catheter-delivered agent. Eighty-three patients with non-embolic occlusion of infrainguinal native arteries or bypass grafts were enrolled (safety population) into seven sequential dose cohorts to receive 25-175 mg of plasmin by intrathrombus infusion over 5 h. Arteriograms were performed at baseline, 2 h, and 5 h, and subjects were monitored for 30 days for clinical outcomes and laboratory parameters of systemic fibrinolysis. Major bleeding occurred in four patients (4.8%), and minor bleeding alone in 13 (15.7%), with no trend towards more bleeding at higher dosages of plasmin. There was a trend towards lower plasma concentrations of fibrinogen, α(2) -antiplasmin and α(2) -macroglobulin with increasing doses of plasmin, but the nadir fibrinogen concentration was > 350 mg dL(-1) at the highest plasmin dose. Individual nadir values were above 200 mg dL(-1) in 82 of 83 subjects, and were not different in patients with or without bleeding. Thrombolysis (≥ 50%) occurred in 79% of subjects receiving 125-175 mg of plasmin, as compared with 50% who received 25-100 mg. Catheter-delivered plasmin can be safely administered to patients with acute lower extremity arterial occlusion at dosages of 25-175 mg.

Peripheral bypass grafting in a patient with essential thrombocytosis: What should a vascular surgeon know?

Hiperkoagulasyon durumlari nativ arter ve arteriyel greft trombozuna neden olabilir. Dogustan protein eksiklikleri disinda, miyeloproliferatif hastaliklar da trombotik vaskuler olaylara yol acabilir. Esansiyel trombositoz (ET), periferik arter trombozu ve buna bagli bacak iskemisinin nadir bir nedenidir. Bu yazida, istirahat agrisi ve sol ayak basparmaginda iyilesmeyen iskemik ulser ile basvuran ve ET’ye sekonder tromboz ve buna bagli siddetli yuzeyel femoral arter stenozu tanisi konan 57 yasinda bir erkek olgu sunuldu. Ayrica bu yazida, bacak iskemisine neden olan ET literatur bilgileri isiginda gozden gecirildi ve bu ender patolojinin klinik tedavisi cerrahi bakis acisiyla sunuldu. Anah tar soz cuk ler: Esansiyel trombositoz; bacak iskemisi; periferik arter hastaligi. Hypercoagulable states can be associated with native arterial and arterial graft thrombosis. Other than congenital protein deficiencies, myeloproliferative disorders may also lead to thrombotic vascular events. Essential thrombocytosis (ET) is a rare cause for peripheral arterial thrombosis and associated extremity ischemia. In this article, we present a 57-year-old male who was admitted with rest pain and non-healing ulcers on the left toe and diagnosed with an isolated severe stenosis of superficial femoral artery due to ET. This report also reviews the literature on ET which may cause extremity ischemia, and clinical management of this rare pathology from the surgical point of view.

Hemodynamic conditions in a failing peripheral artery bypass graft

The mechanisms of restenosis in autogenous vein bypass grafts placed for peripheral artery disease are not completely understood. We investigated the role of hemodynamic stress in a case study of a revised bypass graft that failed due to restenosis. The morphology of the lumen was reconstructed from a custom three-dimensional ultrasound system. Scans were taken at 1, 6, and 16 months after a patch angioplasty procedure. Computational hemodynamic simulations of the patient-specific model provided the blood flow features and the hemodynamic stresses on the vessel wall at the three times studied. The vessel was initially free of any detectable lesions, but a 60% diameter-reducing stenosis developed during the 16-month study interval. As determined from the simulations, chaotic and recirculating flow occurred downstream of the stenosis due to the sudden widening of the lumen at the patch location. Curvature and a sudden increase in the lumen cross-sectional area induced these flow features that are hypothesized to be conducive to intimal hyperplasia. Favorable agreement was found between simulation results and in vivo Doppler ultrasound velocity measurements. Transitional and chaotic flow occurs at the site of the revision, inducing a complex pattern of wall shear as computed with the hemodynamic simulations. This supports the hypothesis that the hemodynamic stresses in the revised segment, produced by the coupling of vessel geometry and chaotic flow, led to the intimal hyperplasia and restenosis of the graft.

Trends in the national outcomes and costs for claudication and limb threatening ischemia: Angioplasty vs bypass graft

Debate exists as to the benefit of angioplasty vs bypass graft in the treatment of lower extremity peripheral vascular disease. The associated costs are poorly defined in the literature. We sought to determine national estimates for the costs, utilization, and outcomes of angioplasty and bypass graft for the treatment of both claudication and limb threat. We searched the Nationwide Inpatient Sample (NIS) database (1999-2007), identifying patients who had an identifiable International Classification of Disease (ICD)-9 diagnosis code of atherosclerotic disease (claudication [440.21] or limb threat [440.22-440.24]). Of these, only patients who underwent intervention of angioplasty ± stent (percutaneous transluminal angioplasty [PTA; 39.50-39.90]), peripheral bypass graft (BPG; 39.29) or aortofemoral bypass (ABF; 39.25) were included. We compared demographics, costs, and comorbidities, as well as multivariable-adjusted outcomes of in-hospital mortality and major amputation. Additionally, we used the New Jersey State Inpatient and Ambulatory databases in order to better understand the influence of outpatient procedures on current volume and trends. There were 563,143 patients identified (PTA: 38%, BPG: 50%, ABF: 6%; 5.1%: multiple procedure codes). Patients who had PTA and BPG were similar in age (70.4 vs 69.5 years) but older than patients who had ABF (61.8 years, P < .01). Patients who underwent PTA were more often women (PTA: 46%, BPG: 42%, ABF: 45.2%; P < .01). Average costs for PTA increased over 60% for claudication between 2001 and 2007 ($8670 to $14,084) and limb threat ($13,903 to $23,196). For BPG, average costs increased 36% for both claudication ($9322 to $12,681) and limb threat ($16,795 to $22,910). In 2007, the average cost per procedure of PTA was higher than BPG for both claudication ($13,903 vs $12,681; P = .02) and limb threat ($23,196 vs $22,910; P = .04). The number of patients per year undergoing PTA increased threefold (15,903 to 46,138) for claudication and limb threat (6752 to 19,468). For BPG, procedures per year decreased approximately 40% for both claudication (13,625 to 9108) and limb threat (25,575 to 13,762). In-hospital mortality was similar for PTA and BPG groups for claudication (0.1% vs 0.2%; P = .04) and limb threat (2.1% vs 2.6%; P < .01). In-hospital amputation rates were significantly higher for patients who had PTA (7%) than BPG (3.9%, odds ratio [OR], 1.67 [1.49-1.85]; P < .01) or patients who underwent ABF (3.0%; OR, 2.32 [1.79, 3.03]; P < .01). PTA has altered the treatment paradigm for lower limb ischemia with an increase in costs and procedures. It is unclear if this represents an increase in patients or number of treatments per patient. Although mortality is slightly lower with PTA for all indications, amputation rates for limb-threat patients appear higher, as does the average cost. Longitudinal studies are necessary to determine the appropriateness of PTA in both claudication and limb-threat patients. The mortality benefit with PTA may be ultimately lost, and average costs elevated, if multiple interventions are performed on the same patients.

Solid, shape recovered “Bulk” nitinol: Part II—Mechanical properties

The use of Nitinol for medical purposes was first reported in the late 1960s. Today Nitinol is commonly used for the manufacture of stents, which are primarily used in peripheral and coronary bypass graft interventions. The application of NiTi in orthopedics is an exciting prospect but one that has yet to be realized. Nitinol's unique mechanical behavior is derived from the coordinated atomic movements manifesting in phase transformations from cubic austenite to monoclinic martensite. These phase transformations are solid-to-solid phase transformations that occur without diffusion or plasticity, potentially making them reversible. They involve changes in the crystalline structure that can be induced by changes in either temperature or stress. In addition to phase transformations, Nitinol's mechanical strength is strongly dependent on the alloy composition and the method in which the material is processed, i.e. rolled, drawn, extruded, or forged. The mechanical work, combined with the intermediate heat treatment steps, contribute to modify microstructure, transformation temperatures and mechanical properties. These manufacturing processing steps lead to texturing (crystallographic alignment) of the material. Alignment of the atomic planes from texture in the polycrystalline material have a marked influence on the mechanical properties by either limiting or promoting phase transformations and shape recovery strains. This paper focuses on the fatigue and fracture properties of Nitinol.

A longitudinal study of remodeling in a revised peripheral artery bypass graft using 3D ultrasound imaging and computational hemodynamics.

We report a study of the role of hemodynamic shear stress in the remodeling and failure of a peripheral artery bypass graft. Three separate scans of a femoral to popliteal above-knee bypass graft were taken over the course of a 16 month period following a revision of the graft. The morphology of the lumen is reconstructed from data obtained by a custom 3D ultrasound system. Numerical simulations are performed with the patient-specific geometries and physiologically realistic flow rates. The ultrasound reconstructions reveal two significant areas of remodeling: a stenosis with over 85% reduction in area, which ultimately caused graft failure, and a poststenotic dilatation or widening of the lumen. Likewise, the simulations reveal a complicated hemodynamic environment within the graft. Preliminary comparisons with in vivo velocimetry also showed qualitative agreement with the flow dynamics observed in the simulations. Two distinct flow features are discerned and are hypothesized to directly initiate the observed in vivo remodeling. First, a flow separation occurs at the stenosis. A low shear recirculation region subsequently develops distal to the stenosis. The low shear region is thought to be conducive to smooth muscle cell proliferation and intimal growth. A poststenotic jet issues from the stenosis and subsequently impinges onto the lumen wall. The lumen dilation is thought to be a direct result of the high shear stress and high frequency pressure fluctuations associated with the jet impingement.

Cyclic Strain Improves Strength and Function of a Collagen-Based Tissue-Engineered Vascular Media

Tissue-engineered blood vessels may provide a solution to the lack of suitable blood vessels for coronary and peripheral vessel bypass grafting. Cyclic strain can be used to provide a more physiological environment that may result in tissue that more closely resembles native artery. In this study, cyclic strain is applied to a collagen-based, tissue-engineered vascular medium. An increased culture time was used to allow the tissue to adhere to the silastic sleeve and to eliminate longitudinal compaction. Cyclic strain improved tissue strength through increased collagen content as well as some radial tissue compaction. Mechanical stimulation promoted a more contractile phenotype and led to a greater contractile response to the vasoconstrictor endothelin-1.

A randomized controlled trial comparing an intraoperative goal-directed strategy with routine clinical practice in patients undergoing peripheral arterial surgery

We hypothesized that, in vascular surgery patients, the application of a goal-directed strategy based on a pulse contour-derived cardiac index would be associated with a better haemodynamic status than the application of routine perioperative care and that the amount of fluid and/or inotropes required in such a goal-directed therapy depended on the general anaesthetic technique used. Patients undergoing peripheral arterial bypass grafting were randomly assigned to three groups. In group 1, haemodynamic management was performed according to routine clinical practice. In the two other groups (groups 2 and 3) a goal-directed therapy was applied aiming to maintain the pulse contour-derived cardiac index above 2.5 l m min. Patients in groups 1 and 2 received sevoflurane-based anaesthesia and patients in group 3 propofol-based anaesthesia. Haemodynamic variables, amount of fluid and administration of inotropes were assessed at different time intervals. The amount of fluid administered was not significantly different between the groups. Two patients in group 1, 13 patients in group 2 and 12 patients in group 3 were treated with dobutamine (P < 0.001). None of the patients anaesthetized with sevoflurane (groups 1 and 2) experienced postoperative cardiovascular complications, whereas four patients in the total intravenous group (group 3) experienced major postoperative cardiovascular complications (P = 0.005). In the conditions of the present study, the application of a goal-directed therapy aiming to maintain the cardiac index above 2.5 l min m did not result in a higher tissue oxygen delivery than when applying the standard haemodynamic strategy nor did it depend on the anaesthetic technique used.

Tissue-Engineered Vascular Adventitia with Vasa Vasorum Improves Graft Integration and Vascularization Through Inosculation

Tissue-engineered blood vessel is one of the most promising living substitutes for coronary and peripheral artery bypass graft surgery. However, one of the main limitations in tissue engineering is vascularization of the construct before implantation. Such a vascularization could play an important role in graft perfusion and host integration of tissue-engineered vascular adventitia. Using our self-assembly approach, we developed a method to vascularize tissue-engineered blood vessel constructs by coculturing endothelial cells in a fibroblast-laden tissue sheet. After subcutaneous implantation, enhancement of graft integration within the surrounding environment was noted after 48 h and an important improvement in blood circulation of the grafted tissue at 1 week postimplantation. The distinctive branching structure of end arteries characterizing the in vivo adventitial vasa vasorum has also been observed in long-term postimplantation follow-up. After a 90-day implantation period, hybrid vessels containing human and mouse endothelial cells were still perfused. Characterization of the mechanical properties of both control and vascularized adventitia demonstrated that the ultimate tensile strength, modulus, and failure strain were in the same order of magnitude of a pig coronary artery. The addition of a vasa vasorum to the tissue-engineered adventitia did not influence the burst pressure of these constructs. Hence, the present results indicate a promising answer to the many challenges associated with the in vitro vascularization and in vivo integration of many different tissue-engineered substitutes.

Topological flow structures and stir mixing for steady flow in a peripheral bypass graft with uncertainty

AbstractWith growing focus on patient‐specific studies, little attempt has yet been made to quantify the modelling uncertainty. Here uncertainty in both geometry definition obtained from in vivo magnetic resonance imaging scans and mathematical models for blood are considered for a peripheral bypass graft. The approximate error bounds in computed measures are quantified from the flow field in steady state simulations with rigid walls assumption.A brief outline of the medical image filtering and segmentation procedures is given, as well as virtual model reconstruction and surface smoothing. Diversities in these methods lead to variants of the virtual model definition, where the mean differences are within a pixel size. The blood is described here by either a Newtonian or a non‐Newtonian Carreau constitutive model.The impact of the uncertainty is considered with respect to clinically relevant data such as wall shear stress. This parameter is locally very sensitive to the surface definition; however, variability in the topology has an effect on the core flow field and measures to study the flow structures are detailed and comparison performed. Integrated effect of the Lagrangian dynamics of the flow is presented in the form of stir mixing, which also has a strong clinical relevance. Copyright © 2010 John Wiley &amp; Sons, Ltd.

Spontaneous pseudoaneurysm of a femoro-popliteal Omniflow® II graft treated with a stentgraft

We report the case of a symptomatic spontaneous leak of a biosynthetic graft (Omniflow (II) treated endovascularly with a stentgraft. Potential degeneration of biosynthetic grafts with aneurysm formation is a well known problem with a reported incidence of up to 7 %. Implantation of a stentgraft for treatment of a pseudoaneurysm is a valuable treatment option in native arteries; however its use in Omniflow II bypass grafts has not been reported so far. Surveillance of peripheral bypass grafts with duplex ultrasound may be helpful to detect morphological alterations of the graft.

Multi-contrast high spatial resolution black blood inner volume three-dimensional fast spin echo MR imaging in peripheral vein bypass grafts

The purpose of this study is to primarily evaluate the lumen area and secondarily evaluate wall area measurements of in vivo lower extremity peripheral vein bypass grafts patients using high spatial resolution, limited field of view, cardiac gated, black blood inner volume three-dimensional fast spin echo MRI. Fifteen LE-PVBG patients prospectively underwent ultrasound followed by T1-weighted and T2-weighted magnetic resonance (MR) imaging. Lumen and vessel wall areas were measured by direct planimetry. For graft lumen areas, T1- and T2-weighted measurements were compared with ultrasound. For vessel wall areas, differences between T1- and T2-weighted measurements were evaluated. There was no significant difference between ultrasound and MR lumen measurements, reflecting minimal MR blood suppression artifact. Graft wall area measured from T1-weighted images was significantly larger than that measured from T2-weighted images (P < 0.001). The mean of the ratio of T1- versus T2-weighted vessel wall areas was 1.59 (95% CI: 1.48-1.69). The larger wall area measured on T1-weighted images was due to a significantly larger outer vessel wall boundary. Very high spatial resolution LE-PVBG vessel wall MR imaging can be performed in vivo, enabling accurate measurements of lumen and vessel wall areas and discerning differences in those measures between different tissue contrast weightings. Vessel wall area differences suggest that LE-PVBG vessel wall tissues produce distinct signal characteristics under T1 and T2 MR contrast weightings.

Periadventitial Rapamycin-Eluting Microbeads Promote Vein Graft Disease in Long-Term Pig Vein-Into-Artery Interposition Grafts

Neointima formation and atherosclerosis compromise long-term graft patency in aortocoronary and peripheral vein bypass grafts. We investigated the short- and long-term effects of periadventitial application of a sustained-release formulation of rapamycin on experimental pig vein grafts with similar dimensions and kinetics to human saphenous vein bypass grafts. Periadventitial application of rapamycin-eluting polyvinyl alcohol microspheres (60 microg . cm(-2)) to porcine saphenous vein-to-carotid artery interposition grafts inhibited vein graft positive and vascular smooth muscle cell proliferation in 1-week grafts. It also decreased neointima formation and wall thickening in 4-week vein grafts compared with controls. The inhibition of vein graft thickening was not sustained; however, a catch-up phenomenon was observed, and there was no therapeutic benefit evident in 12-week grafts. Increasing the dose of rapamycin to 120 microg . cm(-2) was associated with significant local toxicity manifest by high rates of graft rupture (25%), inhibition of adventitial neoangiogenesis, and a paradoxical acceleration of vein graft disease as evidenced by increased vascular smooth muscle cell proliferation. Local toxicity and poor long-term efficacy limits the clinical applicability of locally applied, sustained rapamycin release in vein graft disease.

Use of an autologous artery for tibial artery bypass in a trauma patient

Peripheral artery bypass grafting is a commonly performed procedure. The present report describes the use of an autologous artery for tibial artery bypass graft following a gunshot wound to the calf. Approximately 4 cm of proximal peroneal artery was harvested for use as a bypass graft. At one year postoperatively, an arterial duplex scan showed patency of the tibioperoneal trunk to the posterior artery bypass.

Rolling autogenetic dermis up to form a tube may be used as scaffold in tissue-engineered blood vessels

Coronary and peripheral artery bypass grafting are widely being used to deal with vascular deficiencies currently, and a man-made synthetic tube or autogenous arteries or veins are needed a lot. But one's autogenous arteries or veins are limited, and artificial graft substitute isn't yet available in clinical applications because of many disadvantages. Various polymeric materials have been used as scaffolds, but without satisfying results due to intimal hyperplasia and the rate of degradation. Autogenetic dermis, which has the advantages of resistance to immunogenicity, good biocompatibility, and appropriate mechanical and physiological properties, has gained our attention to use it as a scaffold for tissue-engineered blood vessels. What is more, autogenetic dermis can be harvested easily. So we postulate that autogenetic dermis rolled up to form a tube may be an ideal scaffold for tissue-engineered blood vessels.

Successful Human Vascular Reconstructions with Long-Term Refrigerated Venous Homografts

Fresh autologous vein grafts are commonly used for infrainguinal vascular reconstructions with good results. Previously we have confirmed the high viability index of homografts even after long-term storage at 4°C in tissue culture medium. In this clinical study, we have evaluated the in vivo efficiency of this storage method in humans with major peripheral graft infections. Between April 2006 and November 2008, data from patients who underwent graft excision and venous allograft reconstruction were collected prospectively (5 men, 2 women, mean age 68 years). Six patients had acute ischemia at the time of allograft reconstruction, while 3 had experienced anastomosis rupture. Allograft reconstruction was performed as an emergency procedure in 3 cases. The observed parameters included patient survival, limb salvage, persistence or recurrence of infection and allograft patency. In the follow-up period reoperation, excision or thrombectomy was necessary in 3 cases. There were no perioperative deaths, early amputations, persistent or recurrent infections. In conclusion, this study demonstrates the efficacy of long-term 4°C storage of venous allografts for revascularization in cases with peripheral bypass graft infection. We suggest that this technique is a useful option for graft preservation and propose a wide-scale introduction.

Is Balloon Angioplasty of Peri-Anastomotic Stenoses of Failing Peripheral Arterial Bypasses Worthwhile?

Surgical revision of failing peripheral arterial bypass grafts has generally been shown to provide superior patency rates compared to balloon angioplasty. We analyzed whether balloon angioplasty, specifically of peri-anastomotic stenoses (PAS), provided acceptable patency rates, because surgery for these lesions is more difficult and is likely associated with higher complication rates compared to surgical revision of stenoses in the body of a graft. This is a retrospective review of PAS balloon angioplasties performed at a single institution between January 1, 1999, and September 1, 2005. We report ''primary site patency'' as a stenosis treated by balloon angioplasty, ''revised primary site patency'' as a stenosis treated by repeat balloon angioplasty, and ''secondary site patency'' as an angioplastied stenosis treated surgically or when the graft thrombosed and was revised surgically. All procedures were performed in an endovascular operating room based on duplex scan findings suggesting a significant stenosis. 48 PAS in 33 autologous vein and 15 prosthetic grafts were treated by balloon angioplasty in 42 patients. Mean follow-up was 12 months (range, 1-49 months). Interventions were performed on 22 femoropopliteal grafts (11 proximal, 11 distal), 20 femorotibial grafts (5 proximal, 15 distal), 2 axillofemoral grafts (2 proximal anastomoses), 2 popliteal-pedal grafts (1 proximal, 1 distal), and 1 common iliac-femoral graft (proximal). Life-table analysis revealed 2-year primary, assisted primary, and secondary patency rates of 38%, 58%, and 84%, respectively. No major complications occurred with any endovascular intervention. Balloon angioplasty of PAS resulted in acceptable 2-year assisted primary patency rate of almost 60%. Endovascular intervention avoided repeat incisions in scarred groins, higher rates of nerve injury and infection, significant blood loss, and longer length of hospital stays. We recommend that balloon angioplasty of PAS be attempted before resorting to surgical intervention, especially in cases of hostile anastomotic wounds.

In vivo differentiation of two vessel wall layers in lower extremity peripheral vein bypass grafts: Application of high‐resolution inner‐volume black blood 3D FSE

Lower extremity peripheral vein bypass grafts (LE-PVBG) imaged with high-resolution black blood three-dimensional (3D) inner-volume (IV) fast spin echo (FSE) MRI at 1.5 Tesla possess a two-layer appearance in T1W images while only the inner layer appears visible in the corresponding T2W images. This study quantifies this difference in six patients imaged 6 months after implantation, and attributes the difference to the T(2) relaxation rates of vessel wall tissues measured ex vivo in two specimens with histologic correlation. The visual observation of two LE-PVBG vessel wall components imaged in vivo is confirmed to be significant (P < 0.0001), with a mean vessel wall area difference of 6.8 +/- 2.7 mm(2) between contrasts, and a ratio of T1W to T2W vessel wall area of 1.67 +/- 0.28. The difference is attributed to a significantly (P < 0.0001) shorter T(2) relaxation in the adventitia (T(2) = 52.6 +/- 3.5 ms) compared with the neointima/media (T(2) = 174.7 +/- 12.1 ms). Notably, adventitial tissue exhibits biexponential T(2) signal decay (P < 0.0001 vs monoexponential). Our results suggest that high-resolution black blood 3D IV-FSE can be useful for studying the biology of bypass graft wall maturation and pathophysiology in vivo, by enabling independent visualization of the relative remodeling of the neointima/media and adventitia.

Mortality after major amputation in diabetic patients with critical limb ischemia who did and did not undergo previous peripheral revascularization: Data of a cohort study of 564 consecutive diabetic patients

Background To evaluate the survival after major lower limb amputation, at a level either below (BKA) or above (AKA) the knee, in diabetic patients admitted to hospital because of critical limb ischemia (CLI). Methods From January 1999 to December 2003, 564 diabetic patients were consecutively admitted to our Foot Center because of CLI and followed up until December 2005. A revascularization procedure was performed in 537 patients (95.2%): in 420 with peripheral angioplasty, in 117 with peripheral bypass graft. Neither endoluminal nor surgical revascularization was practicable in 27 (4.8%) patients. Results Major amputation was performed in a total of 55 (9.8%) patients. Among the clinical and demographic variables evaluated, age was significantly lower (67.3±10.1 vs. 76.7±10.4, P<.001), duration of diabetes was higher (17.1±11.1 vs. 13.4±10.0, P=.013), and current smoking was more frequent (38.5% vs. 25.0%, P<.001) in revascularized amputees. The amputation free median time for revascularized patients was 5.11 months, and for nonrevascularized patients, 0.33 months. The log-rank test for equality of survivor function without amputation between amputees with or without revascularization was 31.76 ( P<.001). Among the 55 amputees, 11 (28.2%) out of the 39 revascularized patients and 13 (81.2%) out of the 16 nonrevascularized patients died. The log-rank test for equality of survivor function was 6.83 ( P=.009). The Cox model performed to evaluate the association between the recorded variables and the mortality showed a significant hazard ratio only with age (hazard ratio for 1 year 1.11, P=.003, confidence interval 1.04–1.19). Conclusions Our data suggest that the revascularization allows to postpone the major amputation, and that the survival of revascularized amputees is better than that of nonrevascularized amputated patients. All these data offer further encouragement to revascularize all diabetic patients with CLI.