Hemodynamics and Wall Mechanics of Vascular Graft Failure

Blood vessels are subjected to complex biomechanical loads, primarily from pressure-driven blood flow. Abnormal loading associated with vascular grafts, arising from altered hemodynamics or wall mechanics, can cause acute and progressive vascular failure and end-organ dysfunction. Perturbations to mechanobiological stimuli experienced by vascular cells contribute to remodeling of the vascular wall via activation of mechanosensitive signaling pathways and subsequent changes in gene expression and associated turnover of cells and extracellular matrix. In this review, we outline experimental and computational tools used to quantify metrics of biomechanical loading in vascular grafts and highlight those that show potential in predicting graft failure for diverse disease contexts. We include metrics derived from both fluid and solid mechanics that drive feedback loops between mechanobiological processes and changes in the biomechanical state that govern the natural history of vascular grafts. As illustrative examples, we consider application-specific coronary artery bypass grafts, peripheral vascular grafts, and tissue-engineered vascular grafts for congenital heart surgery as each of these involves unique circulatory environments, loading magnitudes, and graft materials.

Open revascularization for chronic mesenteric ischemia in the endovascular era: a quaternary-center experience and management algorithm

Background

Chronic mesenteric ischemia (CMI) is a debilitating disease with a heavy burden on quality of life. Stenting of the superior mesenteric artery (SMA) is the first option for treatment, but there is a lack of consensus defining precise indications for open revascularization (OR).

Objectives

To describe a series of 4 patients with CMI treated with OR and to present an algorithm for the management of this condition.

Methods

Three patients presented with typical intestinal angina and weight loss. One patient was subjected to prophylactic revascularization during open abdominal aortic aneurysm repair. Surgical techniques included: 1) Bypass from the infrarenal aorta to the SMA; 2) Bypass from an aorto-bifemoral polyester graft to the SMA; 3) Bypass from the right iliac artery to the SMA; 4) Bypass from the right graft limb of an aorto-biiliac polyester graft to the median colic artery at Riolan's arcade. PTFE was used in all surgeries. All grafts were placed in a retrograde configuration, tunneled under the left renal vein, making a smooth C-loop. A treatment algorithm was constructed based on the institution's experience and a review of recent literature.

Results

All patients demonstrated resolution of symptoms and recovery of body weight. All grafts are patent after mean follow-up of two years.

Conclusions

Open revascularization using the C-loop configuration is a valuable technique for CMI and may be considered in selected cases. The algorithm constructed may help decision planning in other quaternary centers.

Aortobifemoral Bypass in Kidney Transplant Candidates: A Ten-Year Experience

In patients with severe aorto-iliac calcifications, vascular reconstructions can be performed in order to allow kidney transplantation. The aim of this study was to analyze the outcomes of kidney transplant candidates who underwent an aortobifemoral bypass (ABFB) for aorto-iliac calcifications. A retrospective study including all kidney transplant candidates who underwent an ABFB between 2012 and 2022 was performed. Primary outcome was 30-day morbidity-mortality after ABFB. Secondary outcome was accessibility to kidney transplant waiting list. Twenty-two ABFBs were performed: 10 ABFBs in asymptomatic patients presenting severe aorto-iliac circumferential calcifications without hemodynamic consequences, and 12 ABFBs in symptomatic patients in whom aorto-iliac calcifications were responsible for claudication or critical limb threatening ischemia. Overall 30-day mortality was 0%. Overall 30-day morbidity was 22.7%: 1 femoral hematoma and 1 retroperitoneal hematoma requiring surgical drainage in the asymptomatic group, and 2 digestive ischemia requiring bowel resection and 1 femoral hematoma requiring surgical drainage in the symptomatic group. Among the 22 patients, 20 patients could access to kidney waiting list and 8 patients underwent a kidney transplantation, including 3 living-donor transplantations. Aorto-iliac revascularization can be an option to overcome severe calcifications contraindicating kidney transplantation.

Long-Term Results of Femorodistal Sequential Composite-Bypass Combining Heparin-Bonded PTFE-Prosthesis and Autologous Vein Using the Deutsch Bridge Technique in Critical Limb-Threatening Ischemia

BACKGROUND

Autologous vein bypass provides excellent long-term results in critical limb-threatening ischemia (CLTI), but a substantial portion of patients have insufficient vein length. In limbs with two distal outflow vessels and limited vein length, a vascular prosthesis may be combined with autologous vein for a sequential composite bridge bypass (SCBB). Results regarding graft function, limb salvage and reinterventions are presented.

METHODS

Between January 2010 and December 2019, 47 consecutive SCBB operations with a heparin-bonded PTFE-prosthesis and autologous vein were performed. Grafts were followed with a duplex scan with prospective documentation in a computerized vascular database. Retrospective analysis of graft patency, limb salvage and patient survival was performed.

RESULTS

Mean follow-up was 34 months (range 1-127 months). 30-day mortality was 10.6% and 5-year patient survival 32%. Postoperative bypass occlusion occurred in 6.4% and late occlusions or graft stenoses in 30%. Two prostheses developed late infection and seven legs were amputated. Primary, primary assisted, secondary patency and limb salvage rate were 54%, 63%, 66% and 85% after 5 years, respectively.

CONCLUSIONS

SCBB patency and limb salvage were good despite a high early postoperative mortality. Combination of a heparin-bonded PTFE-prosthesis and autologous vein appears to be a valuable tool in CLTI in case of insufficient vein.

Long-Term Survival and Quality of Life After Fenestrated Endovascular Repair for Complex Abdominal Aortic Aneurysms

OBJECTIVES

Fenestrated endovascular repair (FEVAR) has become a widely used treatment option for complex abdominal aortic aneurysms (AAA) but long-term survival and quality of life (QoL) outcomes are scarce. This single center cohort study aims to evaluate both long-term survival and QoL after FEVAR.

METHODS

All juxtarenal and suprarenal AAA patients treated with FEVAR in a single-center between 2002 and 2016 were included. QoL scores, measured by the RAND 36-Item Short Form Survey (SF-36), were compared with baseline data of the SF-36 provided by RAND.

RESULTS

A total of 172 patients were included at a median follow-up of 5.9 years (IQR 3.0-8.8). Follow-up at 5 and 10 years post-FEVAR yielded survival rates of 59.9% and 18%, respectively. Younger patient age at surgery had a positive influence on 10-year survival and most patients died due to cardiovascular pathology. Emotional well-being was better in the research group as compared to baseline RAND SF-36 1.0 data (79.2 ± 12.4 vs 70.4 ± 22.0; P < 0.001). Physical functioning (50 (IQR 30-85) vs 70.6 ± 27.4; P = 0.007) and health change (51.6 ± 17.0 vs 59.1 ± 23.1; P = 0.020) were worse in the research group as compared to reference values.

CONCLUSIONS

Long-term survival was 60% at 5-years follow-up, which is lower than reported in recent literature. An adjusted positive influence of younger age at surgery was found on long-term survival. This could have consequences for future treatment indication in complex AAA surgery but further large-scale validation is necessary.

Fresh arterial allograft as a replacement for an infected common femoral prosthetic graft and recurrent false aneurysm

Replacing an infected vascular prosthetic conduit with an allograft is a possible solution of this complication given the low recurrence of infection. It is most commonly utilized for cases where the use of autologous tissue is not an option. We present the case of a 70-year-old patient who had undergone repeated vascular reconstructions in the right lower limb. He was admitted to our department due to a progressively growing mass in the right groin and subsequently placed on the waiting list for a fresh allograft. The patient had the infected false aneurysm and prosthetic material of the femoral bifurcation replaced with an arterial allograft. The previous femoral popliteal autovenous bypass graft was reimplanted into the allograft. There were signs of sepsis during the operation; however, the blood culture was negative. Cultures from neither the wound nor the drain revealed the presence of any bacteria. The patient was discharged on the seventh post-operative day with prophylactic antibiotics. An early followup confirmed that there were no signs of recurrent infection and that the reconstruction remained patent. Seven and half months after the surgery, the femoral popliteal bypass graft became occluded and a conservative approach was chosen. A small thrombosed false aneurysm of the graft was revealed two years after the surgery due to transient non-compliance of the patient to immunosuppression therapy. It was treated conservatively. Two and a half years after the surgery, the allograft still remains open and the limb is preserved.

Vascular Remodeling of Clinically Used Patches and Decellularized Pericardial Matrices Recellularized with Autologous or Allogeneic Cells in a Porcine Carotid Artery Model

Background: Cardiovascular surgery is confronted by a lack of suitable materials for patch repair. Acellular animal tissues serve as an abundant source of promising biomaterials. The aim of our study was to explore the bio-integration of decellularized or recellularized pericardial matrices in vivo. Methods: Porcine (allograft) and ovine (heterograft, xenograft) pericardia were decellularized using 1% sodium dodecyl sulfate ((1) Allo-decel and (2) Xeno-decel). We used two cell types for pressure-stimulated recellularization in a bioreactor: autologous adipose tissue-derived stromal cells (ASCs) isolated from subcutaneous fat of pigs ((3) Allo-ASC and (4) Xeno-ASC) and allogeneic Wharton’s jelly mesenchymal stem cells (WJCs) ((5) Allo-WJC and (6) Xeno-WJC). These six experimental patches were implanted in porcine carotid arteries for one month. For comparison, we also implanted six types of control patches, namely, arterial or venous autografts, expanded polytetrafluoroethylene (ePTFE Propaten® Gore®), polyethylene terephthalate (PET Vascutek®), chemically stabilized bovine pericardium (XenoSure®), and detoxified porcine pericardium (BioIntegral® NoReact®). The grafts were evaluated through the use of flowmetry, angiography, and histological examination. Results: All grafts were well-integrated and patent with no signs of thrombosis, stenosis, or aneurysm. A histological analysis revealed that the arterial autograft resembled a native artery. All other control and experimental patches developed neo-adventitial inflammation (NAI) and neo-intimal hyperplasia (NIH), and the endothelial lining was present. NAI and NIH were most prominent on XenoSure® and Xeno-decel and least prominent on NoReact®. In xenografts, the degree of NIH developed in the following order: Xeno-decel > Xeno-ASC > Xeno-WJC. NAI and patch resorption increased in Allo-ASC and Xeno-ASC and decreased in Allo-WJC and Xeno-WJC. Conclusions: In our setting, pre-implant seeding with ASC or WJC had a modest impact on vascular patch remodeling. However, ASC increased the neo-adventitial inflammatory reaction and patch resorption, suggesting accelerated remodeling. WJC mitigated this response, as well as neo-intimal hyperplasia on xenografts, suggesting immunomodulatory properties.

[Visceral debranching in hybrid surgery of thoracoabdominal aortic aneurysms]

Presented herein is a review of the literature dedicated to the method of visceral debranching, i. e., switching of the visceral and renal branches of the abdominal aorta to its intact portion, using synthetic vascular prostheses as the first stage of hybrid surgical treatment of thoracoabdominal aortic aneurysms prior to endovascular aortic aneurysm repair. This is accompanied and followed by describing the history of the problem, operative technique, results of studies, as well as the data from registries and meta-analyses. Also discussed are the main complications of the method and measures of their prevention. We conclude that hybrid surgery of the thoracoabdominal portion of the aorta is a promising method in a particular cohort of patients, especially those at high surgical risk of 'open' aortic surgery.

Does washing medical devices before and after use decrease bacterial contamination?: An in vitro study

ABSTRACT

Surface treatment of medical devices may be a way of avoiding the need for replacement of these devices and the comorbidities associated with infection. The aim of this study was to evaluate whether pre- and postcontamination washing of 2 prostheses with different textures can decrease bacterial contamination.The following microorganisms were evaluated: Staphylococcus aureus, Staphylococcus epidermidis, Proteus mirabilis and Enterococcus faecalis. Silicone and expanded polytetrafluoroethylene vascular prostheses were used and divided into 3 groups: prostheses contaminated; prostheses contaminated and treated before contamination; and prostheses contaminated and treated after contamination. Treatments were performed with antibiotic solution, chlorhexidine and lidocaine. After one week of incubation, the prostheses were sown in culture medium, which was incubated for 48 hours. The area of colony formation was evaluated by fractal dimension, an image analysis tool.The antibiotic solution inhibited the growth of S epidermidis and chlorhexidine decrease in 53% the colonization density for S aureus in for both prostheses in the pre-washing. In postcontamination washing, the antibiotic solution inhibited the growth of all bacteria evaluated; there was a 60% decrease in the colonization density of S aureus and absence of colonization for E faecalis with chlorhexidine; and lidocaine inhibited the growth of S aureus in both prostheses.Antibiotic solution showed the highest efficiency in inhibiting bacterial growth, especially for S epidermidis, in both washings. Lidocaine was able to reduce colonization by S aureus in post-contamination washing, showing that it can be used as an alternative adjuvant treatment in these cases.

Experimental comparative study of arterial implants made of silicone reinforced with polyester fabric and expanded polytetrafluoroethylene (PTFE) in rabbits aorta

OBJECTIVES

the aim of this study was to compare the outcomes of a new silicone vascular prostheses with PTFE vascular prostheses, on a rabbit experimental model.

METHODS

forty rabbits underwent infra-renal aorta replacement with 4 mm diameter prostheses, twenty animals with PDMS and twenty animals with PTFE (control group). Retrograde aortic angiography was performed to assess patency. Histological graft samples were examined by electron microscopy to evaluate prostheses endothelialization.

RESULTS

patency rates were 100% for both grafts after 30 days; after 60 days, patency rate for PDMS was 92.3% (±7.4), and 73,8% (±13.1) at 90 days. PTFE grafts had patency rates of 87.5% (±11.7) at 60 and 90 days. No statistically significant difference was found in between groups for patency rates (p=0.62). Postoperative complications (death, paraplegia) rates (p=0.526) and aortic clamping times (p=0.299) were comparable in both groups. No statistically significant difference for stenosis was found on angiographical analysis between groups (p=0.650). Electron microscopy revealed limited anastomotic endothelial ingrowth in both prostheses.

CONCLUSION

in this experimental model, PDMS and PTFE vascular prostheses had comparable outcomes and PDMS prosthesis could be used as a vascular graft.

Resorbable vascular grafts show rapid cellularization and degradation in the ovine carotid

Small-diameter vascular grafts perform poorly as arterial bypasses. We developed a cell-free, resorbable graft intended to remodel in situ into a living vessel. The graft consisted of a soft electrospun poly(glycerol sebacate) (PGS) core, a PGS prepolymer (pPGS) coating, and a reinforcing electrospun poly(ε-caprolactone) (PCL) sheath. The core contained 4.37 ± 1.95 μm fibers and had a porosity of 66.4 ± 3.2%, giving it large pores to encourage cellular infiltration and pro-healing macrophages. The sheath contained 6.63 ± 0.89 μm fibers and had a porosity of 80.5 ± 2.1%. in vitro testing suggested that the stress achieved at arterial pressure would be 13-fold lower than the yield stress of the graft. Grafts were implanted as 7 cm carotid interpositions in two sheep. Sheep were maintained on dual antiplatelet therapy and followed with duplex ultrasound. One graft ruptured at 13 days. The second animal was euthanized with a dilated graft at 15 days. Histology showed near-total degradation of the core and a robust inflammatory response within the sheath. Little neotissue had formed within the graft wall or lumen, but the graft had become surrounded by fibroblast-rich and vascularized connective tissue. Because PCL is commonly used in resorbable grafts, this mechanical destabilization was unexpected. We speculate that the inflammatory response instigated by the rapidly degrading PGS intensified degradation of the PCL and that the large pores enabled a prolonged acute host-graft reaction which attacked the entire bulk of the material, speeding weakening. Future work will focus on how to moderate inflammation and improve remodeling of grafts in large animals.

Vascular access cannulation in hemodialysis patients: technical approach

INTRODUCTION

The vascular access cannulation technique varies among clinics, and guidelines on vascular access give little importance to cannulation techniques. The objective of this study was to evaluate the cannulation technique and to determine which factors are associated with each detail of the technique.

MATERIAL AND METHODS

The vascular access cannulation was evaluated in 260 patients undergoing hemodialysis. The type and anatomical location of the vascular access, the cannulation technique, direction, gauge, and distance between needles, besides bevel direction and needle rotation were registered.

RESULTS

The arteriovenous fistula was the most frequent vascular access (88%), the most used cannulation technique was area (100%), the needle direction was anterograde in most cases (79.5%), and the mean distance between the tips of needles was 7.57±4.43 cm. For arteriovenous grafts, the proximal anatomical location (brachial artery) and cannulation with 16G needles in anterograde position were more predominant. For arteriovenous fistulas, the distal anatomical location (radial artery) and cannulation through 15G needles were more common. Cannulation of vascular access in retrograde direction was associated with a greater distance between needles (13.2 ± 4.4 vs 6.1 ± 3 cm, p < 0.001). Kt/V was higher when the distance between needles was higher than 5 cm (1.61 ± 0.3 vs. 1.47 ± 0.28, p < 0.01).

CONCLUSIONS

The vascular access cannulation technique depends on the vascular access characteristics and expertise of cannulators. Clinical trials are required for the formulation of guidelines for vascular access cannulation.

Two-stage repair of DeBakey type IIIb aneurysm, using total arch replacement

Background

Open repair for chronic DeBakey type IIIb dissecting aortic aneurysm is an invasive procedure involving open proximal anastomosis under hypothermic cardiac arrest, with significant morbidity in high-risk patients. We adopted a two-stage repair strategy using total arch replacement with the elephant trunk technique, which enables aortic crossclamping and avoids open proximal anastomosis at the second-stage graft replacement through a left thoracotomy.

Methods

From January 2008 to October 2018, we performed DeBakey type IIIb dissecting aortic aneurysm repair in 76 cases, and compared the results of two-stage repair (group 1, 25 cases) and single-stage repair using graft replacement with open proximal anastomosis through a left thoracotomy (group 2, 31 cases).

Results

In group 1, the elephant trunk technique was successful in all cases. The second intervention included endovascular repair (13 cases) and graft replacement through a left thoracotomy (7 cases). Five cases were followed up conservatively because the false lumen was thrombosed after the elephant trunk technique. Aorta-related adverse events were seen in 5 cases in group 1 (1 re-dissection, 1 rupture, 2 stent-graft-induced new entries, 1 stent-graft migration) and 6 in group 2 (1 additional thoracic endovascular aortic repair, 1 rupture, 4 acute type A aortic dissections). There were no statistical differences between the two groups regarding aorta-related adverse events and death. The postoperative course was acceptable in both groups.

Conclusions

Single-stage repair with open proximal anastomosis is an option in patients not at high risk for invasive surgery, while two-stage repair is recommended for high-risk patients.

Hybrid surgical and endovascular repair for anastomotic pseudoaneurysms after total arch replacement

An 83-year-old woman who had undergone total arch replacement for a thoracic aortic aneurysm seven years prior experienced concurrent rupture of second and third branch anastomotic pseudoaneurysms. A stent graft was initially deployed across the pseudoaneurysm from the third branch to the left subclavian artery. Following the left axillary and left carotid arterial bypass, the origin of the second branch was embolized with metallic coils. As a result, both anastomotic pseudoaneurysms were undetectable by both completion angiogram and postoperative CT. By combining surgical and endovascular procedures, ruptured anastomotic pseudoaneurysms after total arch replacement can be repaired without a risky resternotomy.

Improved endothelialization of small-diameter ePTFE vascular grafts through growth factor therapy

Background

Prosthetic vascular grafts in humans characteristically lack confluent endothelialization regardless of the duration of implantation. Use of high-porosity grafts has been proposed as a way to induce endothelialization through transgraft capillarization, although early experiments failed to show increased healing in man.

Objectives

We hypothesized that transduction of tissues around the prosthetic conduit with vectors encoding VEGF receptor-2 (VEGFR2) ligands would augment transinterstitial capillarization and induce luminal endothelialization of high-porosity ePTFE grafts.

Methods

Fifty-two NZW rabbits received 87 ePTFE uni- or bilateral end-to-end interposition grafts in carotid arteries. Rabbits were randomized to local therapy with adenoviruses encoding AdVEGF-A165, AdVEGF-A109 or control AdLacZ and analyzed at 6 and 28 days after surgery by contrast-enhanced ultrasound and histology.

Results

AdVEGF-A165 and AdVEGF-A109 dramatically increased perfusion in perigraft tissues at 6 days (14.2 ± 3.6 or 16.7 ± 2.6-fold increases, P < 0.05 and P < 0.01). At 28 days, the effect was no longer significantly higher than baseline. At 6 days, no luminal endothelialization was observed in any of the groups. At 28 days, AdVEGF-A109- and AdVEGF-A165-treated animals showed enhanced ingrowth of transinterstitial capillaries (66.0 ± 13.7% and 77.4 ± 15.7% of graft thickness vs 44.7 ± 24.4% in controls, P < 0.05) and improved luminal endothelialization (11.2 ± 26.3% and 11.4 ± 22.2%, AdVEGF-A109 and AdVEGF-A165 vs 0% in controls, P < 0.05). No increased stenosis was observed in the treatment groups as compared to LacZ controls.

Conclusions

This study suggests that transient local overexpression of VEGFR2 ligands in the peri-implant tissues at the time of graft implantation is a novel strategy to increase endothelialization of high-porosity ePTFE vascular grafts and improve the patency of small-diameter vascular prostheses.

Vascularization in Craniofacial Bone Tissue Engineering

Craniofacial bones, separate from the appendicular skeleton, bear a significant amount of strain and stress generated from mastication-related muscles. Current research on the regeneration of craniofacial bone focuses on the reestablishment of an elaborate vascular network. In this review, current challenges and efforts particularly in advances of scaffold properties and techniques for vascularization remodeling in craniofacial bone tissue engineering will be discussed. A microenvironment of ischemia and hypoxia in the biomaterial core drives propagation and reorganization of endothelial progenitor cells (EPCs) to assemble into a primitive microvascular framework. Co-culture strategies and delivery of vasculogenic molecules enhance EPCs' differentiation and stimulate the host regenerative response to promote vessel sprouting and strength. To optimize structural and vascular integration, well-designed microstructures of scaffolds are biologically considered. Proper porous structures, matrix stiffness, and surface morphology of scaffolds have a profound influence on cell behaviors and thus affect revascularization. In addition, advanced techniques facilitating angiogenesis and vaculogenesis have also been discussed. Oxygen delivery biomaterials, scaffold-free cell sheet techniques, and arteriovenous loop-induced axial vascularization strategies bring us new understanding and powerful strategies to manage revascularization of large craniofacial bone defects. Although promising histological results have been achieved, the efficient perfusion and functionalization of newly formed vessels are still challenging.

Bioresorbable Scaffolds in Spontaneous Coronary Artery Dissection: Long-Term Follow-Up in 4 Patients

Spontaneous coronary artery dissection is a rare condition, and diagnosis and treatment are challenging among patients who present with acute coronary syndrome. Typically, the condition affects young females who have no underlying atherosclerotic disease. To date, few cases of bioresorbable scaffold implantation for the treatment of spontaneous coronary artery dissection have been reported. Therefore, we describe the cases of 4 patients whom we treated with scaffolds. We evaluated the long-term results by using intravascular ultrasound and optical coherence tomographic scanning.

Experimental implantation of an arterial substitute made of silicone reinforced with polyester fabric in rabbits

OBJECTIVES

The aim of this study was to analyze silicone tubes with an internal diameter of 4 mm as a possible material for vascular prostheses.

METHODS

Grafts were implanted into the infrarenal aortas of 33 rabbits. Fluoroscopic examinations were performed within 150 days after surgical implantation. Sample grafts were analyzed via electron microscopy to evaluate the eventual endothelialization of the prostheses.

RESULTS

The patency rates of the prostheses were 87% (±6.7%) after 30 days, 73% (±9.3%) after 60 days and 48% (±12%) after 120 days. The material presented characteristics that support surgical implantation: good tolerance promoted by polyester tear reinforcement, ease of postoperative removal and a lack of pseudoaneurysms. However, intimal hyperplasia was a limiting factor for the patency rate.

CONCLUSIONS

We concluded that polydimethylsiloxane has limited potential as an alternative material for small vascular prostheses.

Computational modelling of clot development in patient-specific cerebral aneurysm cases

ESSENTIALS: Clotting in cerebral aneurysms is a process that can either stabilize the aneurysm or lead to rupture. A patient-specific computational model capable of predicting cerebral aneurysm thrombosis is presented. The different clotting outcomes highlight the importance of personalization of treatment. Once validated, the model can be used to tailor treatment and to clarify clotting processes in aneurysms.

BACKGROUND

In cerebral aneurysms, clotting can either stabilize the aneurysm sac via aneurysm occlusion, or it can have a detrimental effect by giving rise to embolic occlusion.

OBJECTIVE

The work presented in this study details the development of an in silico model that combines all the salient, clinically relevant features of cerebral aneurysm clotting. A comprehensive computational model of clotting that accounts for biochemical complexity coupled with three-dimensional hemodynamics in image-derived patient aneurysms and in the presence of virtually implanted interventional devices is presented.

METHODS

The model is developed and presented in two stages. First, a two-dimensional computational model of clotting is presented for an idealized geometry. This enables verification of the methods with existing, physiological data before the pathological state is considered. This model is used to compare the results predicted by two different underlying biochemical cascades. The two-dimensional model is then extended to image-derived, three-dimensional aneurysmal topologies by incorporating level set methods, demonstrating the potential use of this model.

RESULTS AND CONCLUSION

As a proof of concept, comparisons are then made between treated and untreated aneurysms. The prediction of different clotting outcomes for different patients demonstrates that with further development, refinement and validation, this methodology could be used for patient-specific interventional planning.

Modified T-Graft for Extracorporeal Membrane Oxygenation in a Patient with Small-Caliber Femoral Arteries

Extracorporeal membrane oxygenation (ECMO) is generally used as a last resort to provide cardiopulmonary support in patients whose advanced cardiac or respiratory failure does not respond to less invasive treatments. Lower-limb ischemia secondary to the large diameter of the arterial cannula is one of ECMO's major limitations: in patients who have small-caliber arteries, the cannulas can reduce native blood flow. The creation of a T-graft-a well-described technique to avoid limb ischemia-enables flow into the ECMO cannula without jeopardizing blood flow to the limb. However, leaving the graft exposed through an open groin wound can result in dislodgment, and it increases the risk of infection. We describe our modification of a conventional T-graft in an 18-year-old woman who had systolic heart failure, acute respiratory distress syndrome, and small-caliber femoral vessels. We tunneled a polytetrafluoroethylene graft inside a Dacron graft, then ran the combined graft through a subcutaneous tunnel similar to that created for a peripheral bypass. Thus, the graft was protected from environmental exposure and the risk of infection. Our technique seems safer and more secure than the original T-graft technique, and we recommend its consideration during ECMO cannulation.

A Case of Disseminated Intravascular Coagulation after Thoracic Endovascular Aortic Repair

I report a hemorrhagic complication due to disseminated intravascular coagulation after thoracic endovascular aortic repair for a dissecting aortic aneurysm. A 74-year-old man underwent thoracic endovascular aortic repair and carotid-carotid artery bypass to close the primary entry site of the dissecting aortic aneurysm. Postoperatively, he developed a gradually expanding cervical hematoma. Laboratory data showed disseminated intravascular coagulation. He could not extubated until postoperative day 6 because of the risk of airway obstruction. He was treated with transfusion to replenish the coagulation factor. Disseminated intravascular coagulation may occur secondary to thrombus formation in the false lumen after thoracic endovascular aortic repair.

Crosslinked acellular saphenous vein for small-diameter vascular graft

OBJECTIVE

Patients with congenital and acquired heart diseases or arteriopathy require small-diameter vascular grafts for arterial reconstruction. Autologous veins are the most suitable graft, but when absent, an alternative is necessary. This work addresses the issue.

BACKGROUND

Tissue-engineering efforts to create such grafts by modifications of acellular natural scaffolds are considered a promising area.

METHODS

Homologous saphenous veins harvested from cadavers and organ donors were processed by decellularization with detergent and enzymatic digestion, followed by crosslinking by dye-mediated photooxidation. They were validated for acellularity, mechanical strength, and crosslink stability. In-vitro and in-vivo cytotoxicity and hemocompatibility studies were conducted. Collagen conformity was studied by Fourier transform infrared spectroscopy, and heat stability by differential scanning calorimetry. A limited large animal study was performed.

RESULTS

The processing method delivered biocompatible, hemocompatible, effectively crosslinked grafts, with high heat stability of 126 , an enthalpy value of 183.5 J·g(-1), and collagen conformity close to that of the native vein. The mechanical strength was 250% better than the native vein. The presence of extracellular matrix proteins allowed the acellular vein to become a triple-layered vascular structure in the sheep venous system.

CONCLUSION

Crosslinking after decellularization by the dye-mediated photooxidation method could be reproduced in any human vein to obtain a small-diameter vascular grafts.

Incidence and timing of hypotension after transcervical carotid artery stenting: correlation with postoperative complications

OBJECTIVES

To assess the incidence and timing of hypotension after carotid artery stenting (CAS) and its correlation with postoperative complications.

BACKGROUND

CAS-associated postoperative hypotension has been linked to surgical morbidity and mortality, especially to stroke and cardiac complications.

METHODS

Ninety-seven consecutive patients undergoing transcervical CAS were monitored for at least 12 hr after operation. Hypotension was defined as systolic blood pressure < 90 mm Hg. Patients were divided into three groups: normal blood pressure and early (≤6 hr) and late (>6 hr) hypotension. Complications were recorded.

RESULTS

Hypotension occurred in 34% of the patients (early hypotension in 63% of them). Hypotension was recorded in 21.6% of patients during surgery and in 21.6%, 15.5%, and 1.0% at 6, 12, and 24 hr postoperatively. Bradycardia occurred in 26.8% during operation and in 25.8%, 13.4%, and 10.3% at 6, 12, and 24 hr after surgery. Intraoperative bradycardia (P = 0.01) and hypotension (P = 0.02) were predictors of postoperative hypotension. The overall rate of complications was 5% without differences between the study groups. The mean length of stay was 3, 3.6, and 2.8 days in the normotensive, early hypotension, and late hypotension groups, respectively.

CONCLUSIONS

Most postoperative hypotension episodes occurred within the first 6 hr, and more than one-third between the 6 and 12 hr post-procedure. All patients with late hypotension were asymptomatic. There was no difference in complications between the study groups. In patients undergoing ambulatory CAS, hemodynamic monitoring in the postoperative period is particularly important during the first 12 hr.

Biomechanics and biocompatibility of the perfect conduit-can we build one?

No currently available conduit meets the criteria for an ideal coronary artery bypass graft. The perfect conduit would combine the availability and complication-free harvest of a synthetic vessel with the long-term patency performance of the internal mammary artery. However, current polymer conduits suffer from inelastic mechanical properties and especially poor surface biocompatibility, resulting in early loss of patency as a coronary graft. Approaches to manufacture an improved conduit using new polymers or polymer surfaces, acellular matrices, or cellular constructs have to date failed to achieve a commercially successful alternative. Elastin, by mimicking the native extracellular environment as well as providing elasticity, provides the 'missing link' in vascular conduit design and brings new hope for realization of the perfect conduit.

eNOS transfection of adipose-derived stem cells yields bioactive nitric oxide production and improved results in vascular tissue engineering

This study evaluates the durability of a novel tissue engineered blood vessel (TEBV) created by seeding a natural vascular tissue scaffold (decellularized human saphenous vein allograft) with autologous adipose-derived stem cells (ASC) differentiated into endothelial-like cells. Previous work with this model revealed the graft to be thrombogenic, likely due to inadequate endothelial differentiation as evidenced by minimal production of nitric oxide (NO). To evaluate the importance of NO expression by the seeded cells, we created TEBV using autologous ASC transfected with the endothelial nitric oxide synthase (eNOS) gene to produce NO. We found that transfected ASC produced NO at levels similar to endothelial cell (EC) controls in vitro which was capable of causing vasorelaxation of aortic specimens ex vivo. TEBV (n = 5) created with NO-producing ASC and implanted as interposition grafts within the aorta of rabbits remained patent for two months and demonstrated a non-thrombogenic surface compared to unseeded controls (n = 5). Despite the xenograft nature of the scaffold, the TEBV structure remained well preserved in seeded grafts. In sum, this study demonstrates that upregulation of NO expression within adult stem cells differentiated towards an endothelial-like lineage imparts a non-thrombogenic phenotype and highlights the importance of NO production by cells to be used as endothelial cell substitutes in vascular tissue engineering applications.

Low-permeability Gore Excluder device versus the original in abdominal aortic aneurysm size regression

We sought to compare the efficacy of a low-permeability version of the Gore Excluder™ device with that of the original device. We used volumetric analysis and maximum transverse diameter measurements to examine abdominal aortic aneurysm size regression after endovascular aneurysm repair.From November 2002 through April 2007, 101 patients (82% men; mean age, 71.5 ± 8.9 yr) underwent endovascular aneurysm repair with the Excluder stent-graft: 34 with the original device, and 67 with the low-permeability device. Only patients without endoleak and with preprocedural and 1- and 2-year follow-up computed tomographic scans were included. Eight patients with type II endoleak and 2 with type I endoleak were excluded. Maximum abdominal aortic aneurysm diameter and volume were measured before endovascular aneurysm repair and annually thereafter. Postprocessing, multiplanar computed tomography, and 3-dimensional reconstructions were compared with baseline measurements. Diameter and volume changes that were greater than 5 mm or that exceeded 10% were considered significant.At 12 months, the mean maximum transverse diameter had decreased by -0.16 ± 12.1 mm in recipients of the original device and by -4.8 ± 5.9 mm in recipients of the low-permeability device (P = NS). In addition, mean reduction in volume had changed by -17 ± 16 mL in original-device recipients and by -36.1 ± 37.9 mL in low-permeability device recipients (P < 0.01).One-year follow-up revealed that the low-permeability stent-graft resulted in a greater decrease in abdominal aortic aneurysm volume than did the original stent-graft.

New technique for single-staged repair of aortic coarctation and coexisting cardiac disorder

The management of adults with aortic coarctation and a coexisting cardiac disorder is still a surgical challenge. Single-staged procedures have lower postoperative morbidity and mortality rates than do 2-staged procedures. We present our experience with arch-to-descending aorta bypass grafting in combination with intracardiac or ascending aortic aneurysm repair.From October 2004 through April 2010, 5 patients (4 men, 1 woman; mean age, 45.8 ± 9.4 yr) underwent anatomic bypass grafting of the arch to the descending aorta through a median sternotomy and concomitant repair of an intracardiac disorder or an ascending aortic aneurysm. Operative indications included coarctation of the aorta in all cases, together with severe mitral insufficiency arising from damaged chordae tendineae in 2 patients, ascending aortic aneurysm with aortic regurgitation in 2 patients, and coronary artery disease in 1 patient. Data from early and midterm follow-up were reviewed.There was no early or late death. Follow-up was complete for all patients, and the mean follow-up period was 34.8 ± 18 months (range, 18 mo-5 yr). All grafts were patent. No late graft-related sequelae or reoperations were observed.For single-staged repair of aortic coarctation with a coexistent cardiac disorder, we propose arch-to-descending aorta bypass through a median sternotomy as an alternative for selected patients.

Urological complication following aortoiliac graft: case report and review of the literature

CONTEXT

Ureteral stenosis and ureterohydronephrosis may be serious complications of aortoiliac or aortofemoral reconstructive surgery.

CASE REPORT

A 62-year-old female patient presented with a six-month history of left lumbar pain. She was a smoker, and had mild chronic arterial hypertension and Takayasu arteritis. She had previously undergone three vascular interventions. In two procedures, Dacron prostheses were necessary. Excretory urography showed moderate left ureterohydronephrosis and revealed a filling defect in the ureter close to where the iliac vessels cross. This finding was compatible with ureteral stenosis, and the aortoiliac graft may have been the reason for this inflammatory process. The patient underwent laparotomy, which showed that there was a relationship between the ureteral stenosis and the vascular prosthesis. Segmental ureterectomy and end-to-end ureteroplasty with the ureter crossing over the prosthesis anteriorly were performed. There were no complications. The early and late postoperative periods were uneventful. The patient evolved well and the results from a new excretory urogram were normal. We concluded that symptomatic ureterohydronephrosis following aortoiliac graft is a real complication and needs to be quickly diagnosed and treated by urologists.

Use of the IntuiTrak stent-graft delivery system for percutaneous abdominal aortic aneurysm exclusion: initial single-center experience

The exclusion of abdominal aortic aneurysms by endovascular techniques has enabled the treatment of patients who have high-risk comorbidities that preclude safe surgical repair. Since the development of the unibody bifurcated endovascular stent-graft for abdominal aortic aneurysm exclusion, remarkable technological improvements have facilitated stent-graft delivery and reduced the required size of the access site. Our initial institutional experience with the use of the Endologix IntuiTrak Express Delivery System for the Powerlink stent-graft (in 7 patients) shows that the device is suited for percutaneous use without sequelae. Herein, we describe the IntuiTrak system and the successful results of its use: we achieved percutaneous access and closure in all 7 patients, with no conversions to open repair or vascular exposure.

Endovascular repair of injury to a persistent sciatic artery

Herein, we present the case of a 22-year-old man who sustained a gunshot wound to a persistent sciatic artery. Endovascular stent management of the arterial injury obviated the need for surgical repair and revascularization in the presence of acute trauma. We believe this to be the 1st report of a completely endovascular repair of a penetrating traumatic injury to a persistent sciatic artery.In addition, we review the origin and significance of persistent sciatic artery, and we discuss the treatment of sequelae that are associated with this vascular anomaly.

Quality of life after replacement of the ascending aorta in patients with true aneurysms

True aneurysms of the ascending aorta often remain undetected, yet their sequelae carry a high rate of mortality and morbidity. The operative risk of nonemergent replacement of the ascending aorta is low. It is important to consider quality of life in determining the most appropriate treatment for patients who have aneurysms but have not yet experienced major complications.From January 1999 to December 2003, 134 consecutive patients underwent replacement of a dilated ascending aorta at our center. Another 124 patients with acute or chronic aortic dissections, aortic rupture, or intramural hematoma were excluded. Standard SF-36 and general health questionnaires were sent to all 124 survivors who could be traced. Follow-up was 98.4% complete. The mean age of the survivors was 61.7 +/- 11 years, and 63.4% were men. Operative procedures consisted of supracoronary replacement of the ascending aorta in 35.9%, the Wheat procedure in 44%, the David procedure in 11.2%, the Bentall-DeBono procedure in 9%, and the Cabrol procedure in 2.2%. Patients were monitored until May 2005.Thirty-day and midterm mortality rates were 3.7% and 3.9%, respectively. Morbidity due to stroke was 6%, to bleeding 6%, and to myocardial infarction 4.4%. Postoperative quality-of-life evaluation revealed many subscales of SF-36 that were below the norm when compared with a standard population in physically dominated categories.Replacement of the dilated ascending aorta carries acceptable risk in regard to operative death and postoperative quality of life, although this last showed some decline in comparison with quality of life in a normal, healthy population.

Endovascular repair of a ruptured descending thoracic aortic aneurysm

Endovascular aneurysm repair has considerable potential advantages over the surgical approach as a treatment for thoracic aortic rupture, in part because open surgical repair of ruptured thoracic aortic aneurysms is associated with high mortality and morbidity rates. We describe the successful endovascular deployment of stent-grafts to repair a contained rupture of a descending thoracic aortic aneurysm in an 86-year-old man whose comorbidities prohibited surgery. Two months after the procedure, magnetic resonance angiography showed a patent stent-graft, a patent left subclavian artery, and complete exclusion of the aneurysm.

Mathematical Model analysis of Wallstent and Aneurx: dynamic responses of bare-metal endoprosthesis compared with those of stent-graft

We performed this study in order to analyze the mechanical properties of bare-metal Wallstent endoprostheses and of AneuRx stent-grafts and to compare their responses to hemodynamic forces. Mathematical modeling, numerical simulations, and experimental measurements were used to study the 2 structurally different types of endoprostheses. Our findings revealed that a single bare-metal Wallstent endoprosthesis is 10 times more flexible (elastic) than is the wall of the aneurysmal abdominal aorta. Graphs showing the changes in the diameter and length of the stent when exposed to a range of internal and external pressures were obtained. If the aorta is axially stiff and resists length change, a force as large as 1 kg can act in the axial direction on the aortic wall. If the stent is not firmly anchored, it will migrate. In contrast, a fabric-covered, fully supported, stent-graft such as the AneuRx is significantly less compliant than the aorta or the bare-metal stent. During each cardiac cycle, the stent frame tends to move due to its higher elasticity, while the fabric resists movement, which might break the sutures that join the fabric to the frame. Elevated local transmural pressure, detected along the prosthesis graft, can contribute to material fatigue.

Abdominal Aortic dissections: anatomic and clinical features and therapeutic options

Isolated abdominal aortic dissections are rare events. Their anatomic and clinical features are different from those of atherosclerotic aneurysms. We report 4 cases of isolated abdominal aortic dissection that were successfully treated with surgical or endovascular intervention. The anatomic and clinical features and a review of the literature are also presented.

Superior vena caval bypass using the superficial femoral vein for treatment of superior vena cava syndrome

We present the case of a 71-year-old woman who had benign, symptomatic, superior vena cava syndrome that was treated with open surgical bypass using the superficial femoral vein. The patient had an uneventful hospital course and experienced relief of her symptoms. We conclude that the superficial femoral vein is an acceptable bypass conduit for open surgical management of superior vena cava syndrome.

Bentall procedure using cryopreserved valved aortic homografts: mid- to long-term results

The Bentall procedure is the standard operation for patients who have lesions of the ascending aorta associated with aortic valve disease. In many cases, however, mechanical prosthetic conduits are not suitable. There are few reports in the English-language medical literature concerning the mid- to long-term outcome of Bentall operations with cryopreserved homografts. Therefore, we reviewed our experience with this procedure and valved homografts. From January 1997 through December 2002, 21 patients underwent a Bentall operation with cryopreserved homografts at our institution. There were 14 males and 7 females; the mean age was 36 +/- 21 years (range, 15-74 years). Eleven patients had undergone previous aortic valve surgery. All patients had aortic dilatation or aneurysms involving the ascending aorta. Indications for surgery included aortic valve stenosis or insufficiency, and aortic valve endocarditis (native valve or prosthetic). One patient had Takayasu's arteritis and 3 had Marfan syndrome. There was 1 hospital death (due to sepsis), but no other major postoperative complications. The mean hospital stay was 14 +/- 7 days. Follow-up echocardiographic and computed tomographic scans were performed yearly. The mean follow-up was 34 months (6-72 months). Follow-up imaging revealed no calcifications or degenerative processes related to the homograft. Four patients had minimal valve regurgitation. Two patients died during follow-up. The 3-year actuarial survival rate was 85.7%. Our data suggest that the Bentall procedure with a valved homograft conduit is a safe procedure with excellent mid- to long-term results, comparable to results reported with aortic valve replacement with a homograft.

Extensive retroperitoneal fibrosis with duodenal and ureteral obstruction associated with giant inflammatory aneurysm of the abdominal aorta

We report a case of abdominal aortic aneurysm complicated by retroperitoneal fibrosis with both duodenal and bilateral ureteral obstruction. The patient underwent successful bilateral transurethral ureteral stenting, and then he was referred for surgical treatment of the aneurysm. Massive retroperitoneal fibrosis was found at surgery, and the mass was removed along with the diseased aorta, which was replaced by a bifurcated Dacron prosthesis; duodenolysis and ureterolysis were concomitantly performed. Ureteral stents were removed on the 8th postoperative day. Follow-up assessment at 1 year showed normalization of the urinary tract structure at echography and good hemodynamic performance of the vascular prosthesis at Doppler examination. To our knowledge, no other case of duodenal and bilateral ureteral stenosis secondary to massive retroperitoneal reactive fibrosis in association with abdominal aortic aneurysm has been reported.

Reoperation in a Jehovah's Witness 22 years after aortic allograft reconstruction of the right ventricular outflow tract

We report the case of a 29-year-old male Jehovah's Witness who presented with hemolysis and right heart failure as a consequence of extreme calcification of an aortic valve-containing allograft and Dacron prosthesis that had been placed 22 years earlier to repair tetralogy of Fallot. Reoperation had been denied by several other centers, because of the patient's refusal to undergo blood transfusion. For 2 weeks preoperatively, we raised the patient's hemoglobin level by treating him with recombinant erythropoietin, oral iron, and folic acid. At surgery, under normothermic cardiopulmonary bypass, we replaced the aortic allograft in the right ventricular outflow tract with a cryopreserved pulmonary allograft, also containing a valve. The postoperative course was uneventful, and the patient was released from the hospital on the 13th postoperative day in excellent condition.

Management of intramural hematoma of the ascending aorta and aortic arch: the risks of limited surgery

We present the case of a 57-year-old woman who had an intramural hematoma of the ascending aorta and aortic arch. After initial blood pressure control and imaging studies, the patient underwent limited surgical repair that consisted of ascending aortic replacement. One week postoperatively, the aortic arch hematoma progressed to a full dissection that extended into the proximal descending aorta. Emergent aortic arch replacement was required. Current world medical literature regarding thoracic aortic intramural hematoma is presented. This case supports the treatment of intramural hematomas of the ascending aorta and arch by surgical replacement of both segments with a Dacron graft, with the patient under deep hypothermic circulatory arrest.

Perigraft-to-right atrial shunt for aortic root hemostasis

We have modified the technique of perigraft-to-right atrial shunt to control hemorrhage after aortic root replacement. We have performed this operation in 2 patients, including one who had acute aortic dissection and another who underwent aortic root replacement and single-vessel coronary artery bypass. Neither patient required re-exploration for bleeding, and both shunts closed spontaneously during the follow-up period without any related complications. With this modification, even in the presence of concomitant coronary artery bypass grafting, hemostasis was achieved with preservation of the proximal vein graft.

Hypercoagulable state leading to paraplegia in a middle-aged man

A 37-year-old man presented with an unusual thrombotic disorder characterized by acute paraplegia and the absence of palpable pulses due to extensive arterial thrombosis of the aorta and its distal branches. The patient had an extremely complicated course that necessitated multiple revascularization procedures over a 1.5-year period. This case is unusual not only because of its complexity but also because of the patient's relatively young age, his lack of risk factors for vascular disease, and the presence of a neurologic deficit that improved when circulation was restored. More unusual, however, is the fact that all diagnoses were excluded except for a high lipoprotein(a) level. To our knowledge, this is the 1st reported case in which aortic thrombosis has been related to hypercoagulability.

Implantation of cryopreserved allograft pulmonary monocusp patch to treat nonthrombotic femoral vein incompetence

We implanted cryopreserved allograft monocusp patches made from cadaveric pulmonary arteries to correct nonthrombotic valvular insufficiency of the common femoral vein in patients with chronic venous ulcers. Thirty-eight patients with 40 ulcers of longer than 3 years' duration underwent valvular repair of the common femoral vein from September 1995 through November 2001. We studied ulcer healing and competence of the monocusp patches using duplex ultrasonography Three patients with a total of 4 ulcers were lost to follow-up; therefore, 35 patients with 36 ulcers were available for examination. Twenty-four ulcers healed, and 12 did not. Of the 24 healed ulcers, 5 recurred. Four of the 5 ulcers were treated, 3 by monocusp patch replacement and 1 by iliac vein dilation and stenting. All such recurrent ulcers healed. The 5th recurrent ulcer was not treated, because the patient refused therapy Therefore, of the 24 ulcers that healed initially, 23 were healed at the end of the study Of the 12 unhealed ulcers, 4 were treated: 2 by ligation of incompetent perforating veins, 1 by saphenous vein ligation and partial stripping, and 1 by monocusp replacement. All 4 ulcers healed. The other 8 patients, all of whom had severe monocusp insufficiency, refused therapy. Therefore, of the 12 ulcers that did not heal initially, 4 were healed after additional treatment. No implanted monocusp patch developed clots. The ulcers remained healed when the prostheses remained competent. We conclude that monocusp patches can restore valvular competence to the femoral vein in patients who have primary valve insufficiency. In such patients, venous ulcers heal rapidly after prosthesis implantation if the monocusp remains competent and if there is no severe incompetence of the superficial venous system or of perforating veins.

Interrupted aortic arch in an adult single-stage extra-anatomic repair

Interrupted aortic arch is a rare congenital malformation of the aortic arch that occurs in 3 per million live births. Defined as a loss of luminal continuity between the ascending and descending portions of the aorta, this anomaly entails a very poor prognosis without surgical treatment. To our knowledge, the world medical literature contains only 12 reports of isolated interrupted aortic arch diagnosed in adults. Nine of these patients underwent successful surgical repair, but 1 died during the early postoperative period. We describe a 10th successful surgical repair, which involved a 42-year-old woman who had an asymptomatic type B interrupted aortic arch (characterized by interruption between the left subclavian and left carotid arteries). We performed a single-stage extra-anatomic repair by placing a 16-mm extra-anatomic Dacron graft between the ascending and descending portions of the thoracic aorta and by interposing a 7-mm extra-anatomic Dacron graft between the 16-mm graft and the left subclavian artery. The patient recovered uneventfully and continued to do well 6 months later.

Presentation of infantile aortic coarctation in an adult

Rarely, the initial presentation of aortic coarctation, a congenital anomaly, occurs in adults. Surgical repair is indicated for symptomatic patients. We report the case of a 68-year-old woman who underwent successful surgical repair of the infantile (preductal) type of aortic coarctation with use of an interposition graft.

Recent modifications of the fontan procedure for complex congenital heart disease

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Management of infected vascular prostheses. The vascular homograft revisited

Treatment of infected aortic femoral grafts is difficult and controversial. We describe the case of a patient who presented for recurrent infections of an aorto-bifemoral prosthesis. An arterial homograft was used to replace the Dacron prosthesis. One year later, the patient is free of symptoms and is doing well. Although early experiences with long-term use of homografts showed late degeneration of the grafts, 2 points should now be raised in favor of homograft use: new techniques of fresh antibiotic storage of homografts appear to have improved durability; and if replacement of a homograft ever becomes necessary, implantation of a Dacron prosthesis could likely be performed in an aseptic environment. While the use of homografts may constitute a reasonable alternative for treating patients with infected vascular grafts, firm conclusions cannot be drawn until we have seen larger series of patients and longer follow-up periods than those few reported to date.

Aortic replacement with sutureless intraluminal grafts

To avoid the anastomotic complications and long cross-clamp times associated with standard suture repair of aortic lesions, we have implanted sutureless intraluminal grafts in 122 patients since 1976. Forty-nine patients had disorders of the ascending aorta, aortic arch, or both: their operative mortality was 14% (7 patients), and the group's 5-year actuarial survival rate has been 64%. There have been no instances of graft dislodgment, graft infection, aortic bleeding, or pseudoaneurysm formation. Forty-two patients had disorders of the descending aorta and thoracoabdominal aorta: their early mortality was 10% (4 patients), and the group's 5-year actuarial survival rate has been 56%. There was 1 early instance of graft dislodgment, but no pseudoaneurysm formation, graft erosion, aortic bleeding, intravascular hemolysis, or permanent deficits in neurologic, renal, or vascular function. Thirty-one patients had the sutureless intraluminal graft implanted in the abdominal aortic position: their early mortality was 6% (2 patients), and the 5-year actuarial survival rate for this group has been 79%. There were no instances of renal failure, ischemic complication, postoperative paraplegia, pseudoaneurysm, or anastomotic true aneurysm. Our recent efforts have been directed toward developing an adjustable spool that can adapt to the widest aorta or the narrowest aortic arch vessel; but in the meanwhile, the present sutureless graft yields shorter cross-clamp times, fewer intraoperative complications, and both early and late results as satisfactory as those afforded by traditional methods of aortic repair.

Use of a removable vena caval filter for prevention of recurrent embolism after emergency pulmonary embolectomy: a flexible approach

Intraluminal vena caval filters, inserted via the transvenous approach, are used often in the prevention of recurrent pulmonary embolism. Until lately, such filters have been unremovable. In a recent case, however, we treated a patient who experienced acute massive pulmonary embolism after having undergone an emergency right hemicolectomy. He underwent a successful emergency pulmonary embolectomy with the help of cardio-pulmonary bypass; to prevent recurrent embolism, we inserted a removable intracaval filter through the right atriotomy with an introducer set. On the 7th postoperative day, the absence of significant residual thrombi was confirmed by means of phlebography, and the caval filter was removed percutaneously via the femoral approach. Although the value of routine use of the filter in this application has yet to be established, we feel that it warrants further investigation because it relieves the surgeon, during an emergency procedure, of the need to decide quickly whether or not to place a filter. The question becomes one of whether or not to remove the filter, and that decision can await the results of proper postoperative diagnostic studies.

Initial clinical experience with an endoluminal spiral prosthesis for treating complicated venous thrombosis and preventing pulmonary embolism

Fourteen patients with complicated venous thrombosis or recurrent pulmonary embolism were treated by implantation of an endoluminal spiral prosthesis subsequent to balloon angioplasty, surgical thrombectomy or embolectomy, a combination of these, or, in 2 cases, no other treatment. The patients were divided into 2 groups, based on their primary diagnosis and the purpose of the prosthesis. Group I included 8 patients with extensive iliofemoral or caval thrombosis, caused by congenital caval stenosis (1 case) or extravascular compression or retraction (7 cases); 7 of these patients had had previous operations, and the remaining patient had undergone thrombolysis, which failed. The current treatment consisted of balloon angioplasty and surgical thrombectomy or embolectomy, and implantation of an endoluminal spiral stent to prevent elastic recoil of the vessel. In 4 cases, an arteriovenous fistula was constructed and was taken down 3 months later; in 1 additional patient, a bilateral arteriovenous fistula was created. Group II comprised 6 patients with recurrent pulmonary embolism (4 cases), massive pulmonary embolism (1 case), or paradoxical bilateral carotid artery embolism (1 case). Four of these patients underwent surgical thrombectomy or embolectomy, while 2 had no treatment other than filter implantation. All 6 underwent transluminal implantation of a helix caval filter (a modification of the endoluminal spiral stent). All but 1 implantation was accomplished by means of either a transfemoral or a transjugular cutdown; the remaining implantation was performed transatrially after a pulmonary embolectomy. The only device-related complication was a retroperitoneal hematoma in Group I, resulting from perforation of the inferior vena cava by the guidewire during device implantation. This complication necessitated an emergency laparotomy and takedown of the arteriovenous fistula, which resulted in rethrombosis of the left iliofemoral vein. The other 7 stented veins were patent at early phlebographic follow-up, as were all 5 of those studied later. One Group-I patient died 4 months after surgery, due to tumor progression and without signs of caval restenosis. Twelve months postoperatively, 1 Group-II patient died of urosepsis without a recurrence of pulmonary embolism. Four of the 6 Group-II patients were studied late postoperatively, and all of their stented vessels were patent. There was no operative mortality or postoperative embolism. On the basis of these results, we conclude that endoluminal stenting with an expandable spiral prosthesis is a promising method for remote venous reconstruction. Moreover, it appears that the modified stent, or helix caval filter, compares favorably with commercially available filters.