In vitro and in vivo evaluation of biohybrid tissue-engineered vascular grafts with transformative 1H/19F MRI traceable scaffolds

Biohybrid tissue-engineered vascular grafts (TEVGs) promise long-term durability due to their ability to adapt to hosts' needs. However, the latter calls for sensitive non-invasive imaging approaches to longitudinally monitor their functionality, integrity, and positioning. Here, we present an imaging approach comprising the labeling of non-degradable and degradable TEVGs' components for their in vitro and in vivo monitoring by hybrid 1H/19F MRI. TEVGs (inner diameter 1.5 mm) consisted of biodegradable poly(lactic-co-glycolic acid) (PLGA) fibers passively incorporating superparamagnetic iron oxide nanoparticles (SPIONs), non-degradable polyvinylidene fluoride scaffolds labeled with highly fluorinated thermoplastic polyurethane (19F-TPU) fibers, a smooth muscle cells containing fibrin blend, and endothelial cells. 1H/19F MRI of TEVGs in bioreactors, and after subcutaneous and infrarenal implantation in rats, revealed that PLGA degradation could be faithfully monitored by the decreasing SPIONs signal. The 19F signal of 19F-TPU remained constant over weeks. PLGA degradation was compensated by cells' collagen and α-smooth-muscle-actin deposition. Interestingly, only TEVGs implanted on the abdominal aorta contained elastin. XTT and histology proved that our imaging markers did not influence extracellular matrix deposition and host immune reaction. This concept of non-invasive longitudinal assessment of cardiovascular implants using 1H/19F MRI might be applicable to various biohybrid tissue-engineered implants, facilitating their clinical translation.

Assessing Time to Removal of Tunneled Dialysis Catheters after Arteriovenous Access Creation

BACKGROUND

Tunneled dialysis catheters (TDCs) are a temporary bridge until definitive arteriovenous (AV) access is established. Our objective was to evaluate the time to TDC removal in patients who underwent AV access creations with TDCs already in place.

METHODS

A single-center analysis of all AV access creations in patients with TDCs was performed (2014-2020). Primary outcome was time to TDC removal after access creation.

RESULTS

There were 364 AV access creations with TDCs in place. The average age was 58 years, 44% of patients were female, and 64% were Black. The median time to TDC removal was 113 days (range, 22-931 days) with 71.4% having a TDC >90 days after access creation. Patients with TDC >90 days were often older (60 vs. 54.7), had hypertension (98.1% vs. 93.3%), were diabetic (65.4% vs. 47.1%), and had longer average time to maturation (107.1 vs. 55.4 days, P < 0.001) and first access (114 vs. 59.4 days, P < 0.001). Multivariable analysis showed that older age was associated with prolonged TDC placement (odds ratio [OR] 1.03, 95% confidence interval [CI] 1.01-1.05, P = 0.005) and prosthetic graft use was associated with shorter TDC indwelling time (OR 0.09, 95% CI 0.04-0.23, P ≤ 0.001). Kaplan-Meier analysis showed that 87% of TDCs were removed at 1 year.

CONCLUSIONS

The majority of patients with TDCs who underwent AV access creation had prolonged TDC placement. Prosthetic graft use was associated with shorter catheter times. Close follow-up after access placement, improving maturation times, and access type selection should be considered to shortened TDC times.

Arteriovenous Access for Hemodialysis: A Review

Importance

Hemodialysis requires reliable vascular access to the patient's blood circulation, such as an arteriovenous access in the form of an autogenous arteriovenous fistula or nonautogenous arteriovenous graft. This Review addresses key issues associated with the construction and maintenance of hemodialysis arteriovenous access.

Observations

All patients with kidney failure should have an individualized strategy (known as Patient Life-Plan, Access Needs, or PLAN) for kidney replacement therapy and dialysis access, including contingency plans for access failure. Patients should be referred for hemodialysis access when their estimated glomerular filtration rate progressively decreases to 15 to 20 mL/min, or when their peritoneal dialysis, kidney transplant, or current vascular access is failing. Patients with chronic kidney disease should limit or avoid vascular procedures that may complicate future arteriovenous access, such as antecubital venipuncture or peripheral insertion of central catheters. Autogenous arteriovenous fistulas require 3 to 6 months to mature, whereas standard arteriovenous grafts can be used 2 to 4 weeks after being established, and "early-cannulation" grafts can be used within 24 to 72 hours of creation. The prime pathologic lesion of flow-related complications of arteriovenous access is intimal hyperplasia within the arteriovenous access that can lead to stenosis, maturation failure (33%-62% at 6 months), or poor patency (60%-63% at 2 years) and suboptimal dialysis. Nonflow complications such as access-related hand ischemia ("steal syndrome"; 1%-8% of patients) and arteriovenous access infection require timely identification and treatment. An arteriovenous access at high risk of hemorrhaging is a surgical emergency.

Conclusions and Relevance

The selection, creation, and maintenance of arteriovenous access for hemodialysis vascular access is critical for patients with kidney failure. Generalist clinicians play an important role in protecting current and future arteriovenous access; identifying arteriovenous access complications such as infection, steal syndrome, and high-output cardiac failure; and making timely referrals to facilitate arteriovenous access creation and treatment of arteriovenous access complications.

Salvage of infected autogenous arteriovenous fistulas, is it possible?

BACKGROUND

Infection in autogenous arteriovenous fistulas (AVFs) is a critical situation in patients with end stage renal disease (ESRD) that can lead to life threatening rupture or septicemia. To date, no standard guidelines regarding the surgical repair of the infected AVFs is available.

AIM

To evaluate the safety and efficacy of the surgical repair in the infected autogenous AVFs.

METHODS

This prospective study involved 64 ESRD patients who presented with infected autogenous AVFs. Repair of the infected autogenous AVFs was done in 50 cases, while ligation was needed in the other 14 cases. Aneurysmorrhaphy was done in the 26 cases of puncture site infection over venous aneurysms. In 20 cases of AVFs with anastomotic disruption, higher recreation in a proximal clean field (AVF loop anastomosis) was performed, while abscess drainage was done in the remaining four cases presented with non-communicating abscess over the vein. The 14 cases of ligated AVFs included 9 cases of infected ruptured AVFs with active bleeding and 4 cases with non-reconstructable puncture site infection.

RESULTS

After 1 year of follow up, 41 cases (82%) of the repaired AVFs (n = 50) remained patent and functioning as re-infection occurred in 9 cases. Six tunneled permanent catheters were implanted in the 14 cases with ligated AVFs, while the remaining 8 cases had new AVFs established (7 cases of them retained patent AVFs during the follow up period).

CONCLUSION

Surgical repair of the infected AVFs is an effective procedure that achieves many goals, such as saving patients' lives, maintaining the patency of the native fistula, and avoidance of creation of new AVFs in another site with exhaustion the available veins.

Guidelines on vascular access for hemodialysis from the Brazilian Society of Angiology and Vascular Surgery

Chronic kidney disease is a worldwide public health problem, and end-stage renal disease requires dialysis. Most patients requiring renal replacement therapy have to undergo hemodialysis. Therefore, vascular access is extremely important for the dialysis population, directly affecting the quality of life and the morbidity and mortality of this patient population. Since making, managing and salvaging of vascular accesses falls within the purview of the vascular surgeon, developing guideline to help specialists better manage vascular accesses for hemodialysis if of great importance. Thus, the objective of this guideline is to present a set of recommendations to guide decisions involved in the referral, evaluation, choice, surveillance and management of complications of vascular accesses for hemodialysis.

Unilateral Osler nodes, Janeway lesions and splinter haemorrhages associated with surgical arterio-venous fistula infection: a case report

BACKGROUND

Osler's nodes, Janeway lesions and splinter haemorrhages are cutaneous manifestations of infective endocarditis. They occur due to vascular occlusion by septic emboli and a resulting localized vasculitis. They are usually bilateral. We report a case of unilateral Osler's nodes, Janeway lesions and splinter haemorrhages due to an ipsilateral surgical arterio-venous fistula infection.

CASE PRESENTATION

A fifty-two-year-old Sri Lankan female with end stage kidney disease presented with fever for five days with blurred vision, pain and redness of the right eye. She had a left brachio-cephalic arterio-venous fistula (AVF) created one month back. She complained of a foul-smelling discharge from the surgical site for past three days. Redness of the right eye with a hypopyon was noted. AVF site over the left cubital fossa was infected with a purulent discharge. Osler's nodes, Janeway lesions and splinter haemorrhages were noted in the distal fingers, thenar and hypothenar eminences of the left hand. Right hand and both feet were normal. No cardiac murmurs were heard. Blood cultures, vitreous sample cultures and pus cultures from the fistula site were all positive for methicillin sensitive Staphylococcus aureus. Infective endocarditis was excluded by a trans-oesophageal echocardiogram. She was treated with IV flucloxacillin and surgical excision of the AVF.

CONCLUSION

Infections of AVF can result in septic emboli formation which can have both anterograde arterial embolization and retrograde venous embolization. Arterial embolization can result in unilateral Osler's nodes, Janeway lesions and splinter haemorrhages. Venous embolization can cause metastatic infections in the systemic and pulmonary circulations.

Most complex brachiocephalic vein occlusion in hemodialysis patients can be treated with simple endovascular techniques in an office-based angiosuite

OBJECTIVE

Brachiocephalic vein (BCV) obstruction can cause dialysis access dysfunction and failure. Central vein stenosis involving the BCV may require advanced endovascular procedures. We report that most BCV occlusions can be treated using simple endovascular techniques on an outpatient basis.

METHODS

From January 2009 to January 2022, 115 hemodialysis patients underwent BCV endovascular revascularization. Seventy-three of the initial procedures were performed in an office-based angiosuite. Indications for the procedure were BCV occlusion endangering the performance of a previous arm access or making the creation of a new arm access unadvisable. We recorded and analyzed risk factors and procedural results, patency rates, complications, and mortality.

RESULTS

The median age was 62 years (range, 23-91 years); 56% were female. Most prevalent associated conditions were diabetes mellitus (61%) and hypertension (68%). Fifty-six patients (48.7%) presented with severe upper extremity edema ipsilateral to the side of pre-existing functioning access. Obstruction recanalization was effective using standard catheter and wire in 106 cases (92.1%) and transseptal needle in nine cases (7.8%), that included seven using inside-out procedure. Initial management of the BCV stenosis was percutaneous transluminal balloon angioplasty alone in 74 patients (64.3%), stenting in 33 (28.7%), and HeRO conduit in eight cases (7%). Treatment of other central venous lesions included 49 cases (42.6%). The procedure was successful in 99.1% of patients. No intraoperative complications occurred. All 92 patients with previous arm access maintained adequate performance (100%). In 22 of 23 patients (95.6%), new upper extremity access creation was effectively performed after the venous intervention. Overall clinical success rate was 92%. The mean postoperative monitoring was 23 months, the median was 12 months, and the range was 1 to 84 months. During this monitoring period, 266 endovascular procedures, 91% in the office and 9% in the hospital, were required to preserve access performance. Eventually, 49 patients (42.6%) were stented. Eleven patients (9.56%) had infections, and six required complete access removal. Other causes of access failure included two patients with central vein thrombosis and one with massive pulmonary embolus. At the end, nine patients (7.8%) had access failure. Thirty-two patients (27.8%) died of unrelated causes during the follow-up period. Seventy-six patients (66%) have maintained functional access. Kaplan-Meier curves determined median primary patency of 9.6 months, median primary assisted patency of 56.2 months, and secondary patency of 75% at 80 months.

CONCLUSIONS

Successful endovascular revascularization of BCV obstruction can be treated safely, with simple endovascular techniques in an office-based context with minor complication rates and durable results.

Six-year outcomes of a phase II study of human-tissue engineered blood vessels for peripheral arterial bypass

Objective

The human acellular vessel (HAV) was evaluated for surgical bypass in a phase II study. The primary results at 24 months after implantation have been reported, and the patients will be evaluated for ≤10 years.

Methods

In the present report, we have described the 6-year results of a prospective, open-label, single-treatment arm, multicenter study. Patients with advanced peripheral artery disease (PAD) requiring above-the-knee femoropopliteal bypass surgery without available autologous graft options had undergone implantation with the HAV, a bioengineered human tissue replacement blood vessel. The patients who completed the 24-month primary portion of the study will be evaluated for ≤10 years after implantation. The present mid-term analysis was performed at the 6-year milestone (72 months) for patients followed up for 24 to 72 months.

Results

HAVs were implanted in 20 patients at three sites in Poland. Seven patients had discontinued the study before completing the 2-year portion of the study: four after graft occlusion had occurred and three who had died of causes deemed unrelated to the conduit, with the HAV reported as functional at their last visit. The primary results at 24 months showed primary, primary assisted, and secondary patency rates of 58%, 58%, and 74%, respectively. One vessel had developed a pseudoaneurysm deemed possibly iatrogenic; no other signs of structural failure were reported. No rejections or infections of the HAV occurred, and no patient had required amputation of the implanted limb. Of the 20 patients, 13 had completed the primary portion of the study; however, 1 patient had died shortly after 24 months. Of the remaining 12 patients, 3 died of causes unrelated to the HAV. One patient had required thrombectomy twice, with secondary patency achieved. No other interventions were recorded between 24 and 72 months. At 72 months, five patients had a patent HAV, including four patients with primary patency. For the entire study population from day 1 to month 72, the overall primary, primary assisted, and secondary patency rate estimated using Kaplan-Meier analysis was 44%, 45%, and 60% respectively, with censoring for death. No patient had experienced rejection or infection of the HAV, and no patient had required amputation of the implanted limb.

Conclusions

The infection-resistant, off-the-shelf HAV could provide a durable alternative conduit in the arterial circuit setting to restore the lower extremity blood supply in patients with PAD, with remodeling into the recipient's own vessel over time. The HAV is currently being evaluated in seven clinical trials to treat PAD, vascular trauma, and as a hemodialysis access conduit.

Arteriovenous Fistula Nonmaturation: What's the Immune System Got to Do with It?

Background

Arteriovenous fistula (AVF) nonmaturation is a persistent problem, particularly among female and Black patients. Increasingly, the immune system has been recognized as an important contributor to vascular disease, but few studies have examined immune factors relative to AVF maturation outcomes. This study evaluated the association of serum panel reactive antibodies (PRA), a measure of immune system reactivity assessed in patients undergoing kidney transplant evaluation, with AVF nonmaturation.

Methods

We identified 132 patients at our institution who underwent surgical AVF placement between 2010-2019 and had PRA testing within 1 year of AVF creation. Multivariable logistic regression was used to determine the association of patient demographic and clinical factors, class I and class II PRA levels, and preoperative arterial and venous diameters with AVF maturation outcomes.

Results

AVF nonmaturation was more likely in females than males (44% versus 20%, P=0.003) and in Black than white patients (40% versus 13%, P=0.001). Class II PRA was higher in females than males (12%±23% versus 4%±13%, P=0.02). In the multivariable model, AVF nonmaturation was associated with class II PRA (adjusted odds ratio [aOR], 1.34 per 10% increase; 95% confidence interval [95% CI], 1.04 to 1.82, P=0.02) and Black race (aOR, 3.34; 95% CI, 1.02 to 10.89, P=0.03), but not with patient sex or preoperative arterial or venous diameters.

Conclusions

The association of elevated class II PRA with AVF nonmaturation suggests the immune system may play a role in AVF maturation outcomes, especially among female patients.

An adventitial painting modality of local drug delivery to abate intimal hyperplasia

A major medical problem is the persistent lack of approved therapeutic methods to prevent postoperative intimal hyperplasia (IH) which leads to high-rate failure of open vascular reconstructions such as bypass grafting. Hydrogel has been widely used in preclinical trials for perivascular drug administration to mitigate postoperative IH. However, bulky hydrogel is potentially pro-inflammatory, posing a significant hurdle to clinical translation. Here we developed a new modality of directly "painting" drug-loaded unimolecular micelles (UM) to the adventitia thus obviating the need for a hydrogel. To render tissue adhesion, we generated amine-reactive unimolecular micelles with N-hydroxysuccinimide ester (UM-NHS) terminal groups to form stable amide bonds with the adventitia. To test periadventitial application, we either soaked balloon-injured rat carotid arteries in crosslinked UM-NHS (Mode-1) or non-crosslinked UM-NHS (Mode-2), or painted the vessel surface with non-crosslinked UM-NHS (Mode-3). The UM-NHS were loaded with or without a model drug (rapamycin) known to be IH inhibitory. We found that Mode-1 produced a marked IH-mitigating drug effect but also caused severe tissue damage. Mode-2 resulted in lower tissue toxicity yet less drug effect on IH. However, the painting method, Mode-3, demonstrated a pronounced therapeutic effect (75% inhibition of IH) without obvious toxicity. In summary, we present a simple painting modality of periadventitial local drug delivery using tissue-adhesive UM. Given the robust IH-abating efficacy and low tissue toxicity, this prototype merits further development towards an effective anti-stenosis therapy suitable for open vascular reconstructions.

Tailoring of arteriovenous graft-to-vein anastomosis angle to attenuate pathological flow fields

Arteriovenous grafts are routinely placed to facilitate hemodialysis in patients with end stage renal disease. These grafts are conduits between higher pressure arteries and lower pressure veins. The connection on the vein end of the graft, known as the graft-to-vein anastomosis, fails frequently and chronically due to high rates of stenosis and thrombosis. These failures are widely believed to be associated with pathologically high and low flow shear strain rates at the graft-to-vein anastomosis. We hypothesized that consistent with pipe flow dynamics and prior work exploring vein-to-artery anastomosis angles in arteriovenous fistulas, altering the graft-to-vein anastomosis angle can reduce the incidence of pathological shear rate fields. We tested this via computational fluid dynamic simulations of idealized arteriovenous grafts, using the Bird-Carreau constitutive law for blood. We observed that low graft-to-vein anastomosis angles ([Formula: see text]) led to increased incidence of pathologically low shear rates, and that high graft-to-vein anastomosis angles ([Formula: see text]) led to increased incidence of pathologically high shear rates. Optimizations predicted that an intermediate  ([Formula: see text]) graft-to-anastomosis angle was optimal. Our study demonstrates that graft-to-vein anastomosis angles can significantly impact pathological flow fields, and can be optimized to substantially improve arteriovenous graft patency rates.

Clinical characteristics and outcomes of infective endocarditis: impact of haemodialysis status, especially vascular access infection on short-term mortality

BACKGROUND

Patients on haemodialysis (HD) are at high risk of infective endocarditis (IE). Research comparing the microbiological features as well as clinical characteristics and outcomes of HD and non-HD patients with IE is limited. Specifically, no data focussed on vascular access infections (VAIs) have been reported.

METHODS

The medical records of patients with IE were retrospectively reviewed from January 2010 to February 2020 in a referral hospital in Korea. Those with definite or possible IE by modified Duke criteria were included in the study. The clinical characteristics, microbiological features, echocardiographic findings and outcomes of the patients were analysed.

RESULTS

Of the 80 patients with IE, 34 had undergone HD and 46 had not. HD patients with IE had a higher in-hospital mortality rate (50% vs. 17.4%, p = .004) than non-HD patients. In multivariable stepwise Cox proportional hazards regression analysis, HD (hazard ratio = 2.633; 95% confidential interval: 1.053-6.582; p = .038) was predictors of 60-day mortality in IE patients. In HD patients, the presence of VAI was associated with a high in-hospital mortality rate (70.59% vs. 29.41%, p = .039) and all of the patients with VAIs (100%) had methicillin-resistant S. aureus (MRSA) as a causative pathogen.

CONCLUSIONS

HD patients with IE showed high in-hospital mortality. HD, high C-reactive protein levels and lower left ventricular ejection fraction were predictors of 60-day mortality in IE patients. In particular, HD patients with VAIs had higher mortality rates and MRSA should be considered as the causative microorganism.

Outcome of tibio-saphanous arteriovenous fistula in patients with failed upper extremity dialysis access: A report of two cases

Arteriovenous fistulas (AVF) are the preferred access for hemodialysis in patient with end stage renal disease. Usually, distal vessels of upper limb are preferred. There are situations in which the upper limb cannot be a site for AVFs or graft as in cases of bilateral central venous stenosis or with exhausted sites in upper limb. In these cases, lower limb AVF can be considered. Tibial-saphanous (ankle) fistula should be the preferred site over femoral AVF/graft following the principle of distal to proximal. Also, femoral AVFs are associated with more ischemic and infective complications. The present report describes successful hemodialysis in two patients with tibial-saphanous fistula a site rarely used as an option for HD access. Hemodialysis for over 1 year in one patient and 6 months in the other portrays the success of this approach.

Challenges and Possibilities of Cell-Based Tissue-Engineered Vascular Grafts

There is urgent demand for biologically compatible vascular grafts for both adult and pediatric patients. The utility of conventional nonbiodegradable materials is limited because of their thrombogenicity and inability to grow, while autologous vascular grafts involve considerable disadvantages, including the invasive procedures required to obtain these healthy vessels from patients and insufficient availability in patients with systemic atherosclerosis. All of these issues could be overcome by tissue-engineered vascular grafts (TEVGs). A large body of evidence has recently emerged in support of TEVG technologies, introducing diverse cell sources (e.g., somatic cells and stem cells) and novel fabrication methods (e.g., scaffold-guided and self-assembled approaches). Before TEVG can be applied in a clinical setting, however, several aspects of the technology must be improved, such as the feasibility of obtaining cells, their biocompatibility and mechanical properties, and the time needed for fabrication, while the safety of supplemented materials, the patency and nonthrombogenicity of TEVGs, their growth potential, and the long-term influence of implanted TEVGs in the body must be assessed. Although recent advances in TEVG fabrication have yielded promising results, more research is needed to achieve the most feasible methods for generating optimal TEVGs. This article reviews multiple aspects of TEVG fabrication, including mechanical requirements, extracellular matrix components, cell sources, and tissue engineering approaches. The potential of periodic hydrostatic pressurization in the production of scaffold-free TEVGs with optimal elasticity and stiffness is also discussed. In the future, the integration of multiple technologies is expected to enable improved TEVG performance.

Xenogeneic-free generation of vascular smooth muscle cells from human induced pluripotent stem cells for vascular tissue engineering

Development of mechanically advanced tissue-engineered vascular grafts (TEVGs) from human induced pluripotent stem cell (hiPSC)-derived vascular smooth muscle cells (hiPSC-VSMCs) offers an innovative approach to replace or bypass diseased blood vessels. To move current hiPSC-TEVGs toward clinical application, it is essential to obtain hiPSC-VSMC-derived tissues under xenogeneic-free conditions, meaning without the use of any animal-derived reagents. Many approaches in VSMC differentiation of hiPSCs have been reported, although a xenogeneic-free method for generating hiPSC-VSMCs suitable for vascular tissue engineering has yet to be established. Based on our previously established standard method of xenogeneic VSMC differentiation, we have replaced all animal-derived reagents with functional counterparts of human origin and successfully derived functional xenogeneic-free hiPSC-VSMCs (XF-hiPSC-VSMCs). Next, our group developed tissue rings via cellular self-assembly from XF-hiPSC-VSMCs, which exhibited comparable mechanical strength to those developed from xenogeneic hiPSC-VSMCs. Moreover, by seeding XF-hiPSC-VSMCs onto biodegradable polyglycolic acid (PGA) scaffolds, we generated engineered vascular tissues presenting effective collagen deposition which were suitable for implantation into an immunodeficient mice model. In conclusion, our xenogeneic-free conditions for generating hiPSC-VSMCs produce cells with the comparable capacity for vascular tissue engineering as standard xenogeneic protocols, thereby moving the hiPSC-TEVG technology one step closer to safe and efficacious clinical translation.

Human iPS Cell-derived Tissue Engineered Vascular Graft: Recent Advances and Future Directions

Tissue engineered vascular grafts (TEVGs) generated from human primary cells represent a promising vascular interventional therapy. However, generation and application of these TEVGs may be significantly hindered by the limited accessibility, finite expandability, donor-donor functional variation and immune-incompatibility of primary seed cells from donors. Alternatively, human induced pluripotent stem cells (hiPSCs) offer an infinite source to obtain functional vascular cells in large quantity and comparable quality for TEVG construction. To date, TEVGs (hiPSC-TEVGs) with significant mechanical strength and implantability have been generated using hiPSC-derived seed cells. Despite being in its incipient stage, this emerging field of hiPSC-TEVG research has achieved significant progress and presented promising future potential. Meanwhile, a series of challenges pertaining hiPSC differentiation, vascular tissue engineering technologies and future production and application await to be addressed. Herein, we have composed this review to introduce progress in TEVG generation using hiPSCs, summarize the current major challenges, and encapsulate the future directions of research on hiPSC-based TEVGs. Graphical abstract.

Transit Time Flowmetry and Vein Size Are Predictive of Arteriovenous Fistula Maturation

Background

This study aimed to assess the effect of vessel size and flow characteristics on the maturation of autogenous radiocephalic arteriovenous fistulae (RCAVFs).

Methods

We retrospectively reviewed records of patients undergoing RCAVF creation at a single medical center from January 2013 to December 2019. Operative variables were compared between patients whose fistulae matured and those whose fistulae failed to mature.

Results

Overall, 152 patients (33 of whom were women) with a mean age of 62.6±13.6 years underwent RCAVF creation; functional maturation was achieved in 123. No statistically significant differences were observed between patients in whom maturation was or was not achieved in terms of the following variables: female sex (20.3% vs. 25.0%), radial artery size (2.5 vs. 2.4 mm), and pulsatility index (0.69 vs. 0.62). Low intraoperative transit time flowmetry (TTF; 150.4 vs. 98.1 mL/min) and small vein size (2.4 vs. 2.0 mm) were associated with failure of maturation. The best cutoff diameter for RCAVF TTF and cephalic vein size were 105 mL/min and 2.45 mm, respectively.

Conclusion

In patients who undergo RCAVF creation, vein diameter on preoperative ultrasonography and intraoperative TTF are predictors of functional maturation. We identified an intraoperative TTF cutoff value that can be used for intraoperative decision-making.

Total Resection of Infected Peripheral Hemodialysis Grafts Has a Favorable Impact on Outcomes

BACKGROUND

Surgical resection could be an eradication treatment for patients with infected hemodialysis arteriovenous grafts (AVGs). This study aimed to investigate the outcomes of 3 surgical methods, including total resection, subtotal resection, and revision.

METHODS

The patients who underwent surgical excision of infected AVGs performed at a single center from August 2012 to March 2019 were retrospectively analyzed. The following 3 surgical methods were used in our study: revision, subtotal resection, and total resection. Patients' demographics, medical history, perioperative details, reconstruction time, and follow-up data were collected. The outcomes including perioperative complications (within 30 days), mortality, reinfection rate of AVGs, with new access reconstruction or not, and the outcomes between reconstruction and nonreconstruction in the follow-up period were evaluated.

RESULTS

Forty-one patients had infected AVGs in our study. Patients' mean age was 62 years, and 65.9% of the patients were female. The mean duration from the time of diagnosis to the operation was 14.4 days. Signs and symptoms at presentation included fever (51.2 %), swelling (43.9%), pain (58.5%), erythematous change (92.7%), and more severe features, such as altered consciousness (14.6%) and hypotension (12.2%). The pathological changes in the infected grafts included bleeding (29.3%), pus formation (73.2%), pseudoaneurysm (26.8%), and graft exposure (17.1%). Wound and graft cultures revealed an infectious etiology with fungi (7.3%), Pseudomonas aeruginosa (12.2%), Enterococcus spp. (2.4%), and Staphylococcus spp. (58.5%), with methicillin-resistant Staphylococcus aureus accounting for only 7.3%. Total resection, subtotal resection, and revision surgery were performed in 17.1%, 63.4%, and 19.5% of patients, respectively. Seven patients with complications required reoperation (17.1%), and adhesion ileus and hospital-acquired pneumonia occurred in only 2.4% and 7.3% of patients, respectively. During follow-up, most patients (82.9%) had reconstruction of the peripheral hemodialysis access with mean time of 64.3 (range: 21-92) days; mean time of use of new access was 90.5 days; and mean time of removal of catheter was about 106.3 days. Mortality rates in patients without and with reconstructed AV access during follow-up were 50% and 18%, respectively (P < 0.004). Eight cases (19.5%) had recurrence of AV access infections during follow-up; of these, 2 had revision surgery and 6 had subtotal resection. However, no patient with total resection had recurrent infections.

CONCLUSIONS

The total resection group had no recurrent infection compared to the subtotal and revision groups. In addition, patients with reconstruction of peripheral hemodialysis access had a low mortality rate during the follow-up period.

Management of Vascular Infections in Low- and Middle-Income Countries

Background: Vascular infections are rare and challenging conditions with significant deaths and morbidity. Their management necessitates a multi-disciplinary approach and substantial human and financial resources. The management selected may be influenced by the available resources in low- and middle-income countries (LMICs), where such resources may be variable. Methods: We reviewed the published literature and reviewed the management options for various vascular infections with a focus on carotid, aortic, infrainguinal, and dialysis access infections. Results: Recommendations related to prevention and treatment will be offered from the perspective of LMICs. The general principles for prevention are in compliance with established surgical site infection guidelines and minimize the use of prosthetic material. Early detection and intervention by removing all infected prosthetic material, debridement, drainage, and coverage of the infected field with vascularized tissue are essential steps in the management of the infection. Revascularization using an extra-anatomic or in situ approach is individualized based on the resources and expertise available. Conclusions: The prevention and management of vascular infections in LMICs are effective by adhering to time-proven principles even with limited resources.

Arteriovenous Grafts' Types of Indications and Their Infection Rate

BACKGROUND

Arteriovenous graft infection is a well-known and frequent complication. The objective of this study was to compare infection rates of primary and secondary indicated arteriovenous grafts (AVGs).

SUBJECTS AND METHODS

Retrospectively, we evaluated the indications for AVGs created at our institution which became infected. One hundred forty AVGs were evaluated. Of these AVGs, 33 (23.6%) were primary and 107 (76.4%) secondary indicated.

RESULTS

Infection of a primary AVG was detected in 5 patients (15.2 %). Infection of a secondary AVG was detected in 30 patients (28.0%). Primary and secondary patency were significantly lower in patients with infected AVG (P = 0.006; P = 0.0001). The effect of diabetes mellitus and age on development of infection was not confirmed.

CONCLUSIONS

Indications for AVG creation clearly influence the future risk of infection. If the indication to use the AVG is to correct a complicated arteriovenous fistula, the risk of infection is 2 times higher.

Real-World Usage of the WavelinQ EndoAVF System

BACKGROUND

Dependent on existing deep to superficial perforating venous branches, the WavelinQ EndoAVF System is a novel technique used to create an arteriovenous fistula (AVF) between ulnar or radial veins and concomitant arteries for dialysis access. We sought to examine a single center's success rates and short-term follow-up using this device.

METHODS

All consecutive patients undergoing placement of a WavelinQ AVF from October 2018 to July 2019 were included. Preoperative/intraoperative variables including demographics, preoperative/postoperative duplex ultrasonography, success rate of procedure, and subsequent endovascular/surgical procedures were obtained. Descriptive statistics and comparison of groups requiring subsequent intervention were performed.

RESULTS

Thirty-five patients underwent placement of the WavelinQ AVF, with 32 (91%) patients having at least one documented follow-up. These patients were predominantly male (23/32, 72%) with an average age of 60.2 and 23 of 32 (72%) patients were on dialysis. Initial fistula creation success rate was 100%. Average procedural length was 120 min, fluoroscopy time 9.6 min, and contrast usage 52.2 mL. Eight of 32 (25%) patients had perioperative complications (3 hematomas, 3 contrast extravasations, 1 resolved vessel spasm all resolving spontaneously, and 1 pseudoaneurysm requiring surgical repair). Thirteen of 32 (41%) patients underwent subsequent endovascular interventions to assist with maturation [9/32 (28%) branch coiling, 5/32 (16%) angioplasty/stenting, and 3/32 (9%) access thrombectomy] and 4 of 32 (13%) patients required subsequent surgical interventions (1 pseudoaneurysm repair, 1 revision of fistula, and 2 definitive AVF creation in thrombosed grafts). The majority of accesses (30/32, 94%) were ulnar-ulnar fistulas and overall patency at average follow-up of 73 days was 88% (28/32) with average brachial artery inflow volume of 1,078 cc/min and average cephalic vein (18/32) outflow volume of 447 cc/min. Eleven of 23 (48%) patients on dialysis were successfully using the EndoAVF at follow-up.

CONCLUSIONS

The WavelinQ AVF system has a high initial procedural success rate, although a significant portion of patients require subsequent endovascular procedures to aid in maturation. Further work on determining factors predictive of need for reintervention is necessary.

Recent Advances in Arteriovenous Access Creation for Hemodialysis: New Horizons in Dialysis Vascular Access

Recent advances in technology show promise in providing greater vascular access options for hemodialysis patients. This review discusses novel methods for creating an anastomosis for arteriovenous (AV) fistulas and new materials for prosthetic AV grafts. Two technologies for endovascular arteriovenous fistula creation, the Ellipsys and WavelinQ endovascular systems, are discussed. When an AV fistula is not possible, an AV graft or devices to augment the AV fistula may be appropriate. New materials that have been developed that show promise as an alternative to the expanded polytetrafluoroethylene graft are discussed. Such potential conduits include bioengineered vessels and both allogenic or xenogenic biologic grafts. Devices designed to optimize blood flow to reduce maturation failure and improve AV fistula outcomes are explored.

Peripheral vascular access for therapeutic plasma exchange: A practical approach to increased utilization and selecting the most appropriate vascular access

BACKGROUND

Therapeutic plasma exchange (TPE) is used in the treatment of many diseases. At present, peripheral vascular access (PVA) is an underutilized method of vascular access in TPE. It should be considered more frequently due its relatively low risk for adverse events, particularly infections.

METHODS

The Advancing Vascular Access in Apheresis Working Group met in December 2017 for an extensive review and discussion of vascular access for TPE and developed a "road map" providing detailed information regarding clinical situations in which PVA-based TPE would and would not be appropriate.

RESULTS

The road map is consistent with current recommendations that PVA should be used in combination with TPE whenever possible. PVA should be considered for patients who do not have existing central lines and who are stable. The patient should have peripheral veins that will allow for adequate treatment and must be able to comply with the process of achieving and maintaining peripheral access. There should be expert clinical assessment of veins, and this evaluation may include ultrasound and/or near infrared evaluation. Conditions that would prompt a switch from PVA to an alternate method of venous access include loss of venous access, patient preference, or development of a requirement for very frequent treatment over a long period of time.

CONCLUSIONS

While PVA is not suitable for all patients requiring TPE, it has significant safety advantages over other approaches and should be employed whenever possible.

Application of Human Induced Pluripotent Stem Cells in Generating Tissue-Engineered Blood Vessels as Vascular Grafts

In pace with the advancement of tissue engineering during recent decades, tissue-engineered blood vessels (TEBVs) have been generated using primary seed cells, and their impressive success in clinical trials have demonstrated the great potential of these TEBVs as implantable vascular grafts in human regenerative medicine. However, the production, therapeutic efficacy, and readiness in emergencies of current TEBVs could be hindered by the accessibility, expandability, and donor-donor variation of patient-specific primary seed cells. Alternatively, using human induced pluripotent stem cells (hiPSCs) to derive seed vascular cells for vascular tissue engineering could fundamentally address this current dilemma in TEBV production. As an emerging research field with a promising future, the generation of hiPSC-based TEBVs has been reported recently with significant progress. Simultaneously, to further promote hiPSC-based TEBVs into vascular grafts for clinical use, several challenges related to the safety, readiness, and structural integrity of vascular tissue need to be addressed. Herein, this review will focus on the evolution and role of hiPSCs in vascular tissue engineering technology and summarize the current progress, challenges, and future directions of research on hiPSC-based TEBVs.

18F-FDG PET/CT and 99mTc-HMPAO-WBC SPECT/CT effectively contribute to early diagnosis of infection of arteriovenous graft for hemodialysis

OBJECTIVE

An arteriovenous graft (AVG) is indicated in hemodialysis patients with failed arteriovenous access. Early treatment of AVG infection is important because an advanced prosthetic infection leads to the removal of the prosthesis. The aim of this study was to evaluate the benefits of ¹⁸F-FDG PET/CT and ^99mTc-HMPAO-WBC SPECT/CT in early detection of AVG infections.

SUBJECTS AND METHODS

Fifty-one AVGs were evaluated. ¹⁸F-FDG PET/CT and ^99mTc-HMPAO-WBC SPECT/CT studies were performed at intervals of 10, 20-30, and 40-50 weeks after AVG insertion. Agreement between the imaging methods and reference parameters (i.e. clinical presentation, C-reactive protein and microbiological findings on the hemodialysis cannula extracted after hemodialysis from AVG) was evaluated.

RESULTS

The study results showed that focal accumulation of the radiopharmaceuticals can be considered a sign of AVG infection. At 10 weeks after AVG implantation, the focal ¹⁸F-FDG findings showed the best agreement with the reference parameters (agreement coefficients AC1 - clinical status: 0.693, CRP: 0.605, cannula microbiology: 0.518, respectively). At 20 to 30 weeks after AVG implantation, the diagnostic value of focal ^99mTc-HMPAO-WBC accumulation increased (AC1 coefficients: 0.658, 0.658, 0.408) and was similar to that of focal ¹⁸F-FDG uptake (AC1s: 0.656, 0.570, 0.409). Between 40 and 50 weeks since AVG implantation, the diagnostic significance of focal ^99mTc-HMPAO-WBC accumulation (AC1 coefficients: 0.771, 0.811, 0.611) slightly exceeded the diagnostic value of focal ¹⁸F-FDG accumulation (AC1 coefficients: 0.524, 0.456, 0.569).

CONCLUSION

¹⁸F-FDG PET/CT and ^99mTc-HMPAO-WBC SPECT/CT can both serve as important tools contributing to early diagnosis of AVG infection.

Septic embolization from stented arteriovenous fistula

Anastomotic stenosis of an arteriovenous fistula is often amenable to percutaneous intervention (angioplasty and stenting) and unlikely to be complicated by infection. A 69-year-old man underwent pre-emptive arteriovenous fistula construction that required interval placement of a covered stent for juxta-anastomotic stenosis. The patient presented 1 year after the intervention with systemic sepsis that required stent graft explantation and revision. This is a unique case report showing an infected stent graft, placed to restore secondary patency, that was later found to be the source of bacteremia and septic pulmonary emboli.

Relevance of a skilled vascular surgeon and optimized facility practices in the long-term patency of arteriovenous fistulas: a prospective study

Introduction:

Arteriovenous fistulas (AVF) are the best hemodialysis vascular accesses, but their failure rate remains high. Few studies have addressed the role of the vascular surgeon's skills and the facility's practices. We aimed to study these factors, with the hypothesis that the surgeon's skills and facility practices would have an important role in primary failure and patency rates at 12 months, respectively.

Methods:

This was a single-center, prospective cohort study carried out from March 2005 to March 2017. Only incident patients were included. A single surgeon made all AVFs, either in the forearm (lower) or the elbow (upper). Vascular access definitions were in accordance with the North American Vascular Access Consortium.

Results:

We studied 113 AVFs (65% lower) from 106 patients (39% diabetics, 58% started with catheter). Time to first connection was 21.5 days (IR: 14 - 31). Only 14 AVFs (12.4%) underwent primary failure and 18 failed during the first year. Functional primary patency rate was 80.9% (SE 4.1) whereas primary unassisted patency rate, which included PF, was 70.6% (4.4). Logistic regression showed that diabetes (OR = 3.3, 95%CI 1.38 - 7.88, p = .007) and forearm location (OR = 3.03, 95CI% 1.05 - 8.76, p = 0.04) were predictors of AVF failure. Patency of lower and upper AVFs was similar in non-diabetics, while patency in diabetics with lower AVFs was under 50%. (p = 0.003).

Conclusions:

Results suggest that a long-lasting, suitable AVF is feasible in almost all patients. The surgeon's skills and facility practices can have an important role in the long term outcome of AVF.

Evaluation of an elastic decellularized tendon-derived scaffold for the vascular tissue engineering application

Due to the limited success rate of currently available vascular replacements, tissue engineering has received tremendous attention in recent years. A main challenge in the field of regenerative medicine is creating a mechanically functional tissue with a well-organized extracellular matrix, particularly of collagen and elastin. In this study, the native collagen scaffold derived from decellularized tendon sections, as a scaffold having the potential to be used for vascular tissue engineering applications, was studied. We showed that the elasticity of the scaffolds was improved when crosslinked with the bovine elastin. The effect of different concentrations of elastin on mechanical properties of the collagen scaffolds was evaluated of which 15% elastin concentration was selected for further analysis based on the results. Addition of 15% elastin to collagen scaffolds significantly decreased Young's modulus and the tensile stress at the maximum load and increased the tensile strain at the maximum load of the constructs as compared to those of the collagen scaffolds or control samples. Moreover, tubular elastin modified collagen scaffolds showed significantly higher burst pressure compared to the control samples. Smooth muscle cells and endothelial cells cultured on the elastin modified collagen scaffolds showed high viability (>80%) after 1, 3, and 7 days. Furthermore, the cells showed a high tendency to align with the collagen fibers within the scaffold and produced their own extracellular matrix over time. In conclusion, the results show that the decellularized tendon sections have a great potential to be used as scaffolds for vascular tissue engineering applications. © 2019 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 107A: 1225-1234, 2019.

Good long-term patency: 10-year follow-up using the mid-thigh adductor loop arteriovenous graft

Introduction:

Definitive access in patients requiring renal replacement therapy is an ever-increasing challenge. For those where autogenous venous access is no longer a viable option, arteriovenous grafts can be considered. This article describes long-term follow-up, complications and patency rates of the mid-thigh ‘adductor loop’ arteriovenous graft.

Methods:

50 mid-thigh loop arteriovenous grafts have been inserted into 48 patients in our unit over the past 11 years. A prospective database was collected on patients receiving an arteriovenous graft at our unit by the senior author. All remained under the care of our unit ensuring accurate follow-up data collection and database was updated at regular intervals.

Results:

Death-only censored primary patency at 1, 3 and 5 years was 76%, 44% and 23%, respectively. Patients receiving transplants were not censored as follow-up of the arteriovenous grafts was possible. Secondary patency at 1, 3 and 5 years was 95%, 63% and 45%. These rates are higher than previous studies looking at lower limb arteriovenous grafts. Graft thrombosis occurred in 14 patients (28%). Six patients were treated for an infection (12%) but only four grafts were excised; much lower than documented in previous studies.

Conclusion:

Autogenous venous access remains the perceived gold standard for patients requiring dialysis for end stage renal failure, despite some published data reporting poor outcomes. We have shown that adductor loop arteriovenous grafts can be a reliable, safe and long-term alternative in those whom fistula formation is not possible and may have a role earlier in the patient journey than previously thought, as a result of good patency and lower complications.

Arteriovenous Fistula Maturation in Prevalent Hemodialysis Patients in the United States: A National Study

BACKGROUND

Arteriovenous fistulas (AVFs) are the preferred form of hemodialysis vascular access, but maturation failures occur frequently, often resulting in prolonged catheter use. We sought to characterize AVF maturation in a national sample of prevalent hemodialysis patients in the United States.

STUDY DESIGN

Nonconcurrent observational cohort study.

SETTING & PARTICIPANTS

Prevalent hemodialysis patients having had at least 1 new AVF placed during 2013, as identified using Medicare claims data in the US Renal Data System.

PREDICTORS

Demographics, geographic location, dialysis vintage, comorbid conditions.

OUTCOMES

Successful maturation following placement defined by subsequent use identified using monthly CROWNWeb data.

MEASUREMENTS

AVF maturation rates were compared across strata of predictors. Patients were followed up until the earliest evidence of death, AVF maturation, or the end of 2014.

RESULTS

In the study period, 45,087 new AVFs were placed in 39,820 prevalent hemodialysis patients. No evidence of use was identified for 36.2% of AVFs. Only 54.7% of AVFs were used within 4 months of placement, with maturation rates varying considerably across end-stage renal disease (ESRD) networks. Older age was associated with lower AVF maturation rates. Female sex, black race, some comorbid conditions (cardiovascular disease, peripheral artery disease, diabetes, needing assistance, or institutionalized status), dialysis vintage longer than 1 year, and catheter or arteriovenous graft use at ESRD incidence were also associated with lower rates of successful AVF maturation. In contrast, hypertension and prior AVF placement at ESRD incidence were associated with higher rates of successful AVF maturation.

LIMITATIONS

This study relies on administrative data, with monthly recording of access use.

CONCLUSIONS

We identified numerous associations between AVF maturation and patient-level factors in a recent national sample of US hemodialysis patients. After accounting for these patient factors, we observed substantial differences in AVF maturation across some ESRD networks, indicating a need for additional study of the provider, practice, and regional factors that explain AVF maturation.

Comparison between open and pharmacomechanical repair of acutely thrombosed arteriovenous hemodialysis fistulae within a decade

INTRODUCTION

Different declotting techniques are available for acutely thrombosed arteriovenous hemodialysis fistulae (AVF). The aim of this single-center study was to compare immediate and follow-up results between surgical repair and a modified interventional lyse-and-wait technique characterized by prolonged local reaction times of recombinant tissue-plasminogen activator (rtPA).

MATERIALS AND METHODS

We retrospectively analyzed medical records of 110 consecutively treated patients between the years 2003 and 2013. All patients were on hemodialysis (HD) and suffered from an acutely thrombosed AVF. The treatment standards changed in the course of time, wherefore we compared 2 groups: the open repair (OR) (N = 50) and the endovascular repair (ER) group (N = 60).

FINDINGS

We found no significant differences in success rates (OR 92%/ER 96.7%; P = 0.28), immediate failures (IFs) (OR 8%/ER 10%; P = 0.71), and temporary catheter placements (TCPs) (OR 10%/ER 6.7%; P = 0.52). Furthermore, there were no differences in cumulative primary patency rates (P = 0.42) and secondary patency rates (P = 0.97).The infection rate was significantly increased after OR (8%) compared to ER (0%); P = 0.026. The hospital stay in days was shorter after ER (5.2 ±2.8) vs. OR (9.0 ± 3.5); P < 0.001.

CONCLUSION

The modified lyse-and-wait technique with prolonged local reaction times is a successful alternative to surgical repair for acutely thrombosed AVF. Clear benefits are less infections and significant shorter hospital stays after ER. However, OR remains the preferred treatment for aneurysms and anastomotic stenoses.

Thigh arteriovenous grafts. Quantitative comparison with alternative options: A meta-analysis

Thigh arteriovenous grafts are required in a number of patients with exhausted upper extremity veins and comprise 1%-5% of the total access procedures performed. Alternative autogenous lower extremity options are the rarely used sapheno-tibial arteriovenous fistulae, the saphenous vein transpositions, and the femoral vein transpositions. The latter have proven to be the most durable lower limb access procedures, with low infection rates and their primary patency rates ranged from 74% up to 87% at 2 years. Synthetic thigh grafts are suitable for patients who are not good candidates for any upper limb or any autogenous lower limb access and their secondary patency rates ranged from 54% up to 83% at 2 years. Thigh grafts often get infected and their average weighed infection rate in 920 such grafts included in eight large series was 22.9%. A literature search was performed to evaluate thigh grafts compared with alternative options using meta-analysis. Lower limb accesses were found superior compared to HeRO^® device regarding 1-year primary failure rate (odds ratio = 0.28, confidence interval = 0.09-0.88, p = 0.03) and additionally autogenous lower limb accesses were found superior compared to thigh grafts regarding the 1-year primary failure rate (odds ratio = 6.54, confidence interval = 2.29-18.72, p = 0.0005).

Phage treatment of an aortic graft infected with Pseudomonas aeruginosa

Management of prosthetic vascular graft infections caused by Pseudomonas aeruginosa can be a significant challenge to clinicians. These infections often do not resolve with antibiotic therapy alone due to antibiotic resistance/tolerance by bacteria, poor ability of antibiotics to permeate/reduce biofilms and/or other factors. Bacteriophage OMKO1 binding to efflux pump proteins in P. aeruginosa was consistent with an evolutionary trade-off: wildtype bacteria were killed by phage whereas evolution of phage-resistance led to increased antibiotic sensitivity. However, phage clinical-use has not been demonstrated. Here, we present a case report detailing therapeutic application of phage OMKO1 to treat a chronic P. aeruginosa infection of an aortic Dacron graft with associated aorto-cutaneous fistula. Following a single application of phage OMKO1 and ceftazidime, the infection appeared to resolve with no signs of recurrence.

Susceptibility of ePTFE vascular grafts and bioengineered human acellular vessels to infection

BACKGROUND

Synthetic expanded polytetrafluorethylene (ePTFE) grafts are routinely used for vascular repair and reconstruction but prone to sustained bacterial infections. Investigational bioengineered human acellular vessels (HAVs) have shown clinical success and may confer lower susceptibility to infection. Here we directly compared the susceptibility of ePTFE grafts and HAV to bacterial contamination in a preclinical model of infection.

MATERIALS AND METHODS

Sections (1 cm²) of ePTFE (n = 42) or HAV (n = 42) were inserted within bilateral subcutaneous pockets on the dorsum of rats and inoculated with Staphylococcus aureus (10⁷ CFU/0.25 mL) or Escherichia coli (10⁸ CFU/0.25 mL) before wound closure. Two weeks later, the implant sites were scored for abscess formation and explanted materials were halved for quantification of microbial recovery and histological analyses.

RESULTS

The ePTFE implants had significantly higher abscess formation scores for both S. aureus and E. coli inoculations compared to that of HAV. In addition, significantly more bacteria were recovered from explanted ePTFE compared to HAV. Gram staining of explanted tissue sections revealed interstitial bacterial contamination within ePTFE, whereas no bacteria were identified in HAV tissue sections. Numerous CD45⁺ leukocytes, predominantly neutrophils, were found surrounding the ePTFE implants but minimal intact neutrophils were observed within the ePTFE matrix. The host cells surrounding and infiltrating the HAV explants were primarily nonleukocytes (CD45^-).

CONCLUSIONS

In an established animal model of infection, HAV was significantly less susceptible to bacterial colonization and abscess formation than ePTFE. The preclinical findings presented in this manuscript, combined with previously published clinical observations, suggest that bioengineered HAV may exhibit low rates of infection.

Percutaneous Coronary Intervention Versus Optimal Medical Therapy for Stable Angina in Advanced CKD: A Decision Analysis

BACKGROUND

Percutaneous coronary intervention (PCI) use is low in the setting of stable symptomatic angina in individuals with advanced chronic kidney disease (CKD) despite high cardiovascular risk in this population, and PCI is frequently deferred out of concern for precipitating dialysis therapy. Whether this is appropriate is uncertain, and patient-centered data comparing the relative risks and benefits of continued medical therapy versus PCI in patients with advanced CKD and stable angina are scarce.

STUDY DESIGN

Decision analysis.

SETTING & POPULATION

Hypothetical cohort of individuals with advanced CKD (stages 4-5 with estimated glomerular filtration rates ≤ 20mL/min/1.73m2) and stable angina.

MODEL, PERSPECTIVE, & TIMELINE

A Markov model with a Monte Carlo simulation through 12 cycles, that is, 3 years of 3-month intervals, with 10,000 microsimulations predicted mean quality-adjusted life-years.

INTERVENTION

PCI first, medical management, or dialysis (hemodialysis [HD]) followed by PCI.

OUTCOMES

Outcomes modeled were progression to HD therapy (for those not assigned to the preemptive HD strategy), catheter infection, and death.

RESULTS

Our analysis showed mean quality-adjusted life-years of 1.103 ± 0.69 for PCI first, 1.088±0.70 for medical management, and 0.670±0.58 for HD followed by PCI. Probabilistic sensitivity analysis found PCI as the preferred strategy > 60% of the time.

LIMITATIONS

Values for probabilities and utilities were estimated and/or derived from multiple sources that were not uniform in their populations in terms of age, comorbid condition burden, and degree of kidney failure, and several simplifying assumptions were made.

CONCLUSIONS

Our analysis demonstrates that quality-adjusted life expectancy is similar for the PCI first and medical management strategies in patients with advanced CKD with stable angina and that the decision depends on patient preferences other than those incorporated in our model. Both strategies are superior to preemptive dialysis.

Arteriovenous Grafts: Much Maligned But in Need of Reconsideration?

There are substantial variations in arteriovenous fistula (AVF) use among hemodialysis patients in different countries, in different regions of the U.S., and even in different hemodialysis units within a single metropolitan area. These variations persist after adjustment for patient demographics and comorbidities, suggesting that practice patterns play a major role in determining the frequency of AVF use. These observations led to vascular access guidelines urging nephrologists and surgeons to increase AVF creation in patients with chronic kidney disease. Over the past 20 years, as clinicians have adopted these guidelines, the prevalence of AVF use in hemodialysis patients has increased substantially. At the same time, clinicians have recognized important limitations of an unwavering "Fistula First" approach. First, a substantial proportion of AVFs fail to mature even when routine preoperative vascular mapping is used, leading to prolonged catheter dependence. Second, certain patient subgroups are at high risk for AVF nonmaturation. Third, nonmaturing AVFs frequently require interventions to promote their maturation. Fourth, AVFs that require such interventions have shortened cumulative patency. Fifth, arteriovenous grafts (AVG) have several advantages over AVFs, including lower primary failure rates, fewer interventions prior to successful cannulation, and shorter duration of catheter dependence with its associated risk of bacteremia. All these observations have led nephrologists to propose an individualized approach to vascular access, with AVG being preferred in patients who initiate hemodialysis with a catheter, particularly if they are at high risk for AVF nonmaturation and have a relatively short life expectancy.

Arteriovenous Access Failure, Stenosis, and Thrombosis

Vascular access–related complications can lead to patient morbidity and reduced patient quality of life. Some of the common arteriovenous access complications include failure to mature, stenosis formation, and thrombosis.

Arteriovenous Access: Infection, Neuropathy, and Other Complications

Complications of vascular access lead to morbidity and may reduce quality of life. In this module, we review both infectious and noninfectious arteriovenous access complications including neuropathy, aneurysm, and high-output access. For the challenging patients who have developed many complications and are now nearing their last vascular access, we highlight some potentially novel approaches.

Lower Extremity Permanent Dialysis Vascular Access

Hemodialysis remains the most commonly used RRT option around the world. Technological advances, superior access to care, and better quality of care have led to overall improvement in survival of patients on long-term hemodialysis. Maintaining a functioning upper extremity vascular access for a prolonged duration continues to remain a challenge for dialysis providers. Frequently encountered difficulties in clinical practice include (1) a high incidence of central venous catheter-related central vein stenosis and (2) limited options for creating a functioning upper extremity permanent arteriovenous access. Lack of surgical skills, fear of complications, and limited involvement of the treating nephrologists in the decision-making process are some of the reasons why lower extremity permanent dialysis access remains an infrequently used option. Similar to upper extremity vascular access options, lower extremity arteriovenous fistula remains a preferred access over arteriovenous synthetic graft. The use of femoral tunneled catheter as a long-term access should be avoided as far as possible, especially with the availability of newer graft-catheter hybrid devices. Our review provides a summary of clinical evidence published in surgical, radiology, and nephrology literature highlighting the pros and cons of different types of lower extremity permanent dialysis access.

Endovascular Stent Graft Repair is an Effective and Safe Alternative Therapy for Arteriovenous Graft Pseudoaneurysms

OBJECTIVE/BACKGROUND

Pseudoaneurysm formation occurs in 2-10% of hemodialysis arteriovenous grafts (AVGs). Surgical repair often requires pseudoaneurysm resection, interposition graft placement, and insertion of a catheter as a bridge. Endovascular stent graft repair is a controversial alternative therapy. This study was performed to examine the effectiveness and mid-term outcomes of stent graft repair for AVG pseudoaneurysms.

METHODS

All patients who had undergone stent graft repair for AVG pseudoaneurysms between December 2012 and July 2015 were identified from hospital medical records for retrospective analysis. Outcome measures were technical success, early and late complications, and primary and secondary patency rates.

RESULTS

A total of 37 stent graft repairs of AVG pseudoaneurysms were performed in 35 patients (42.9% men; mean age 66.9 years). The mean time from AVG creation to pseudoaneurysm repair was 69 months. The indications of treatment (as per the institutional policy) were large pseudoaneurysm (56.7%), impending rupture (27.1%), and bleeding (16.2%). Mean pseudoaneurysm diameter was 23.0 mm. The most common diameter and length of stent graft used were 7 mm (67.6%) and 50 mm (48.6%), respectively. Technical success was 100%. Only one early complication occurred after stent graft repair, which was due to recurrence of the pseudoaneurysm as a result of a short landing zone. Late complications included infection (17.1%) and thrombosis (37.1%). The 1, 6, and 12 month primary patency rates were 89.2%, 55.5%, and 22.0%, respectively. The 1, 6, and 12 month secondary patency rates were 100%, 88.6%, and 78.6%, respectively. The median follow up was 12.3 months.

CONCLUSIONS

The study demonstrates that endovascular stent graft repair is an effective and safe alternative therapy for AVG pseudoaneurysms. However, the rate of thrombosis and infection was high and needs to be balanced against open surgery in future studies.

Comparison of standard forearm prosthetic loop grafts to composite semiloop forearm grafts ("semi-grafts") in hemodialysis patients: A prospective study

INTRODUCTION

To prospectively assess the performance of composite semiloop antebrachial grafts ("semi-grafts," SGs) in hemodialysis patients.

METHODS

Eighty-five patients who received 67 loop antebrachial grafts (LG-group) and 25 antebrachial semigrafts (SG-group) were enrolled. SGs were defined as those originating from the brachial artery and anastomosed with the proximal mature mid-antebrachial cephalic vein. Cephalic vein length should be at least 10 cm in length and of ≥5 mm in diameter for inclusion in the SG-group. LG-group included all possible outflow vein options of minimum diameter 3 mm. Kaplan-Meier statistics was used for comparison of groups.

FINDINGS

Main indication for a SG was a failing radiocephalic fistula with extensive distal cephalic vein stenosis not amenable to correction or failed after endovascular repair or requiring long interposition grafting. The mean follow-up period was 20.16 ± 22.6 and 29.6 ± 36.7 months for the LG- and SG-group, respectively (P = 0.14). Forty-two patients died during the follow-up. Primary patency (up to first intervention or failure) at 6 and 12 months for LG- vs. SG-group was 93.9% vs. 83.7% and 47% vs. 55.8% (P = 0.08). Secondary patency (up to abandonment) was 58.2% vs. 61.1% and 36% vs. 45.8% at 12 and 24 months (P = 0.18). Mortality at 48 months was 22.4% (LG-group) and 24% (SG-group) (P = 0.9).

DISCUSSION

There was a trend toward better primary and secondary patency rates for the SGs especially in the long-term. This is a valuable option in selected patients that access surgeons and nephrologists should be aware of.

Impact of Staphylococcus aureus protein A (spa) genetic typing in cases of prosthetic shunt graft infections

INTRODUCTION

In January 2014 an internal audit was performed at the department of surgery, division of vascular surgery of the Medical University Graz, Austria, to assess the short and long-term outcomes of prosthetic shunt graft implantations performed between December 1998 and December 2013. A 10.8 % explantation rate due to graft infection was detected. The majority of the cases were associated with Staphylococcus aureus. The aim of this study was to clarify whether this constitutes a nosocomial problem.

PATIENTS AND METHODS

Between December 1998 and December 2014 a total of 490 prosthetic shunt grafts were implanted. After exclusion of 54 cases, 436 shunts remained for statistical analysis. Genetic analysis (spa typing) was acquired from three new cases with involvement of S. aureus in 2014. The impact of several factors (e.g. sex, institute for dialysis, age, type of prosthesis, implantation surgeon and position of shunt) on the shunt graft infection rate was statistically analyzed.

RESULTS

Of the prostheses 14.0 % (61 out of 436) had to be explanted of which 12.4 % (54/436) were due to infection. In 77.8 % (42/54) bacteria were found in blood and/or wound cultures. Staphylococcus aureus was present in 76.2 % (32/42) of the cases with detected bacteria and in all cases was sensitive to methicillin. The infection rate was not significantly dependent on any of the investigated factors; however, the factor "institute for dialysis" had a remarkable p‑value of 0.060 with the infection rate ranging from 8.5 % to 18.2 % depending on the institution. Three different S. aureus protein A (spa) types were found: t015, t359, t6265. The detection of three different spa types means that these patients had different sources of S. aureus so that a nosocomial problem is very unlikely.

CONCLUSION

Genetic typing of spa is a suitable technique for distinguishing between nosocomial and community acquired sources of prosthetic shunt graft infections.

The importance of success prediction in angioaccess surgery

Access to the circulation is an "Achilles' heel" of chronic hemodialysis. According to the current guidelines, autologous arteriovenous fistula is the best choice available. However, the impossibility of immediate use and the high rate of non-matured fistulas place fistula far from an ideal hemodialysis vascular access. The first attempt at constructing an angioaccess should result in functional access as much as possible. After failed attempts, patients and nephrologists lose their patience and confidence, which results in high percentage of central venous catheter use. Predictive models could help, but clinical judgment still remains crucial. Early referral to the nephrologist and vascular access surgeon, careful preoperative examinations, preparation of patients and duplex sonography mapping of the vessels are very important in the preoperative stage. In the operative stage, it is crucial to understand that angioaccess procedures should not be considered as minor procedures and these operations must be performed by surgeons with demonstrable interest and experience. In the postoperative stage, appropriate surveillance of the maturation process is also important, as well as good cannulation skills of the dialysis staff. The purpose of this review article is to stress the importance of success prediction in order to avoid unsuccessful attempts in angioaccess surgery.

Bioengineered human acellular vessels for dialysis access in patients with end-stage renal disease: two phase 2 single-arm trials

BACKGROUND

For patients with end-stage renal disease who are not candidates for fistula, dialysis access grafts are the best option for chronic haemodialysis. However, polytetrafluoroethylene arteriovenous grafts are prone to thrombosis, infection, and intimal hyperplasia at the venous anastomosis. We developed and tested a bioengineered human acellular vessel as a potential solution to these limitations in dialysis access.

METHODS

We did two single-arm phase 2 trials at six centres in the USA and Poland. We enrolled adults with end-stage renal disease. A novel bioengineered human acellular vessel was implanted into the arms of patients for haemodialysis access. Primary endpoints were safety (freedom from immune response or infection, aneurysm, or mechanical failure, and incidence of adverse events), and efficacy as assessed by primary, primary assisted, and secondary patencies at 6 months. All patients were followed up for at least 1 year, or had a censoring event. These trials are registered with ClinicalTrials.gov, NCT01744418 and NCT01840956.

FINDINGS

Human acellular vessels were implanted into 60 patients. Mean follow-up was 16 months (SD 7·6). One vessel became infected during 82 patient-years of follow-up. The vessels had no dilatation and rarely had post-cannulation bleeding. At 6 months, 63% (95% CI 47-72) of patients had primary patency, 73% (57-81) had primary assisted patency, and 97% (85-98) had secondary patency, with most loss of primary patency because of thrombosis. At 12 months, 28% (17-40) had primary patency, 38% (26-51) had primary assisted patency, and 89% (74-93) had secondary patency.

INTERPRETATION

Bioengineered human acellular vessels seem to provide safe and functional haemodialysis access, and warrant further study in randomised controlled trials.

FUNDING

Humacyte and US National Institutes of Health.