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• W3159622667 abstract "In the United States, hemodialysis remains the most common treatment modality for kidney failure, chosen by almost 90% of incident patients. A functioning vascular access is key to providing adequate hemodialysis therapy. Recently, major innovations in devices and technology for hemodialysis vascular access care have rapidly changed the landscape. Novel endovascular devices for creation of arteriovenous fistulas may offer a solution to the barriers encountered in initiating maintenance hemodialysis with a permanent vascular access rather than a central venous catheter (CVC). Furthermore, in the prevalent hemodialysis population, the minimally invasive endovascular arteriovenous fistula procedure should help improve long wait times for vascular access creation, which remains a major barrier to reducing CVC dependence. Bioengineered grafts are being developed and may offer another option to polytetrafluoroethylene grafts. Early studies with these biocompatible grafts are promising, as additional studies continue to evaluate their clinical outcomes in comparison to cryopreserved or synthetic options. Prolonging the vascular access patency with appropriate use of devices such as drug-coated balloons and stent grafts may complement the novel techniques of creating arteriovenous access. Finally, innovative solutions to treat stenosed and occluded thoracic central veins can provide an approach to creating a vascular access and allow patients with exhausted vasculature to remain on hemodialysis. The robust developments in hemodialysis vascular access are likely to change practice patterns in the near future. In the United States, hemodialysis remains the most common treatment modality for kidney failure, chosen by almost 90% of incident patients. A functioning vascular access is key to providing adequate hemodialysis therapy. Recently, major innovations in devices and technology for hemodialysis vascular access care have rapidly changed the landscape. Novel endovascular devices for creation of arteriovenous fistulas may offer a solution to the barriers encountered in initiating maintenance hemodialysis with a permanent vascular access rather than a central venous catheter (CVC). Furthermore, in the prevalent hemodialysis population, the minimally invasive endovascular arteriovenous fistula procedure should help improve long wait times for vascular access creation, which remains a major barrier to reducing CVC dependence. Bioengineered grafts are being developed and may offer another option to polytetrafluoroethylene grafts. Early studies with these biocompatible grafts are promising, as additional studies continue to evaluate their clinical outcomes in comparison to cryopreserved or synthetic options. Prolonging the vascular access patency with appropriate use of devices such as drug-coated balloons and stent grafts may complement the novel techniques of creating arteriovenous access. Finally, innovative solutions to treat stenosed and occluded thoracic central veins can provide an approach to creating a vascular access and allow patients with exhausted vasculature to remain on hemodialysis. The robust developments in hemodialysis vascular access are likely to change practice patterns in the near future. The US Data Renal System (USRDS) reports that, for 86.9% of all incident patients with kidney failure, hemodialysis remains the chosen treatment modality and that 80% initiate hemodialysis with a dialysis catheter.1Saran R. Robinson B. Abbott K.C. et al.US Renal Data System 2019 annual data report: epidemiology of kidney disease in the United States.Am J Kidney Dis. 2020; 75: S1-S64PubMed Google Scholar Although a well-functioning hemodialysis vascular access is a “lifeline,” complications related to vascular access also continue to be a significant reason for increased morbidity and mortality in hemodialysis patients. A multidisciplinary team approach along with improved processes of care are key to creating and maintaining vascular access. This review provides an overview of the advances in technology relevant to hemodialysis vascular access. The primary focus is on newer devices used to create a minimally invasive arteriovenous fistula (AVF), a promising alternative to synthetic arteriovenous graft (AVG), and devices to bypass a central vein stenosis/occlusion. Advances made to improve the vascular access patency are also discussed (Fig 1). The global prevalence of chronic kidney disease (CKD), especially in the elderly population, is expected to grow sharply in the future.2Jha V. Garcia-Garcia G. Iseki K. et al.Chronic kidney disease: global dimension and perspectives.Lancet. 2013; 382: 260-272Abstract Full Text Full Text PDF PubMed Scopus (2175) Google Scholar,3Agarwal A.K. Haddad N.J. Vachharajani T.J. Asif A. Innovations in vascular access for hemodialysis.Kidney Int. 2019; 95: 1053-1063Abstract Full Text Full Text PDF PubMed Scopus (13) Google Scholar Over the past 60 years, hemodialysis vascular access options have largely remained restricted to AVF, AVG, and central venous catheter (CVC). AVF remains the access preferred over AVG because of its lower infection rate, fewer thrombosis events, and higher long-term patency.4Woo K. Lok C.E. New insights into dialysis vascular access: what is the optimal vascular access type and timing of access creation in CKD and dialysis patients?.Clin J Am Soc Nephrol. 2016; 11: 1487-1494Crossref PubMed Scopus (53) Google Scholar In 2017, 80% of patients were using a CVC at hemodialysis (HD) initiation, whereas use of AVF at HD initiation rose from 12% to 17% from 2005 to 2017. AVG is used as an alternative access, but it has lower primary 1-year patency (51% for AVG vs 86% for AVF; P < 0.001).5Portoles J. Lopez-Gomez J.M. Gruss E. Aljama P on behalf of the MAR Study GroupCourse of vascular access and relationship with treatment of anemia.Clin J Am Soc Nephrol. 2007; 2: 1163-1169Crossref PubMed Scopus (12) Google Scholar The CVC is the least desirable form of vascular access because of its 2- to 3-fold higher risk of morbidity and mortality burden.6Ravani P. Quinn R. Oliver M. et al.Examining the association between hemodialysis access type and mortality: the role of access complications.Clin J Am Soc Nephrol. 2017; 12: 955-964Crossref PubMed Scopus (60) Google Scholar, 7Lok C.E. Mokrzycki M.H. Prevention and management of catheter-related infection in hemodialysis patients.Kidney Int. 2011; 79: 587-598Abstract Full Text Full Text PDF PubMed Scopus (136) Google Scholar, 8Poinen K. Quinn R.R. Clarke A. et al.Complications from tunneled hemodialysis catheters: a Canadian observational cohort study.Am J Kidney Dis. 2019; 73: 467-475Abstract Full Text Full Text PDF PubMed Scopus (26) Google Scholar However, dependence on CVC results from factors that include lack of timely patient education and counseling, surgical delays, financial barriers to creation of permanent predialysis vascular access, high rate of primary AVF failure, poor sustained outcomes with endovascular interventions, and inadequate surgical training. Dysfunctional vascular access reduces quality of life and worsens patient-centered outcomes. The risk factors for vascular access failure include female sex, advanced age, and multiple comorbidities such as diabetes mellitus, cardiovascular disease, obesity, and frailty.9Vachharajani T.J. Atray N.K. Aging veterans and the end-stage renal disease management dilemma in the millennium.Hemodial Int. 2007; 11: 456-460Crossref PubMed Scopus (6) Google Scholar, 10Vachharajani T.J. Moossavi S. Jordan J.R. Vachharajani V. Freedman B.I. Burkart J.M. Re-evaluating the fistula first initiative in octogenarians on hemodialysis.Clin J Am Soc Nephrol. 2011; 6: 1663-1667Crossref PubMed Scopus (63) Google Scholar, 11Allon M. Robbin M.L. Increasing arteriovenous fistulas in hemodialysis patients: problems and solutions.Kidney Int. 2002; 62: 1109-1124Abstract Full Text Full Text PDF PubMed Google Scholar, 12Hod T. Desilva R.N. Patibandla B.K. Vin Y. Brown R.S. Goldfarb-Rumyantzev A.S. Factors predicting failure of AV “fistula first” policy in the elderly.Hemodial Int. 2014; 18: 507-515Crossref PubMed Scopus (38) Google Scholar The National Kidney Foundation’s Kidney Disease Outcomes Quality Initiative (KDOQI) 2019 vascular access guideline suggested a patient-centered approach to access selection.13Lok C.E. Huber T.S. Lee T. et al.on behalf of the National Kidney Foundation. KDOQI clinical practice guideline for vascular access: 2019 update.Am J Kidney Dis. 2020; l75: S1-S164Abstract Full Text Full Text PDF Scopus (273) Google Scholar Procedures to maintain vascular access may result in missed treatments and repeated hospital admissions, and remain a major burden on the health care system. The total cost to manage maintenance HD patients in the United States was approximately $35 billion in 2015, highlighting the need for innovations in HD vascular access.14Saran R. Robinson B. Abbott K.C. et al.US Renal Data System 2016 annual data report: epidemiology of kidney disease in the United States.Am J Kidney Dis. 2017; 69: S1-S434PubMed Google Scholar The 20%-60% primary maturation failure rate observed with AVFs created using the open surgical technique has prompted innovations in creation of an anastomosis with a minimally invasive endovascular technique.15Dember L.M. Beck G.J. Allon M. et al.Effect of clopidogrel on early failure of arteriovenous fistulas for hemodialysis: a randomized controlled trial.JAMA. 2008; 299: 2164-2171Crossref PubMed Scopus (571) Google Scholar The approval of 2 devices by the US Food and Drug Administration (FDA) has paved the way for creating an AVF at a site in the mid-forearm using an endovascular technique (endoAVF). The dictum of preferentially selecting a distal versus proximal site for AVF creation in the upper extremity is considered standard of care, but often the mid-forearm AVF site (called Gracz fistula) is overlooked due to lack of surgical skills or for the relative ease of creating a more proximal anastomosis at the elbow.16Gracz K.C. Ing T.S. Soung L.S. Armbruster K.F. Seim S.K. Merkel F.K. Proximal forearm fistula for maintenance hemodialysis.Kidney Int. 1977; 11: 71-75Abstract Full Text PDF PubMed Scopus (117) Google Scholar The endoAVF offers an opportunity to use the mid-forearm site before considering a more proximal site in the upper arm for future needs. The approved devices are catheter-based systems used to create a side-to-side anastomosis using the deep vessels in the mid to proximal forearm; the 2 devices are the Ellipsys (Medtronic) and the WavelinQ (Becton, Dickinson and Co.) systems. Both of these FDA-approved systems require prescreening assessment of the forearm vessels with ultrasonography and a multidisciplinary approach to select patients who may be at high risk for distal AVF maturation failure. Every member of the team needs to be well informed about the differences between endoAVF and surgical AVF. Working as a team, the proceduralist and the surgeon can select suitable patients and effectively manage unexpected complications. The nephrologist and the dialysis teams can educate patients and learn the subtle points to assess for endoAVF maturation and cannulation techniques. The eligibility factors for an ideal recipient of an endoAVF include life expectancy of at least 1 year, vessels that are unsuitable to surgically create a distal AVF, a compressible proximal radial/ulnar artery without intimal calcification, an inflow brachial artery ≥2 mm, an outflow cephalic and/or basilic vein ≥2.5 mm, procedural access vessels >2 mm, a perforator ≥2 mm and not tortuous, and an adequate creation site with ulnar and/or radial target vessels >2 mm (Box 1).17Wasse H. Alvarez A.C. Brouwer-Maier D. et al.Patient selection, education, and cannulation of percutaneous arteriovenous fistulae: an ASDIN white paper.J Vasc Access. 2019; 21: 810-817Crossref PubMed Scopus (8) Google Scholar The access is created between paired ulnar or radial artery and a perforator vein. A physician trained in this technique performs the ultrasound and selects the site for endoAVF. Patient selection is critical to preserve the valuable vasculature for future needs as outlined in the “life-plan” concept in the KDOQI vascular access guideline.13Lok C.E. Huber T.S. Lee T. et al.on behalf of the National Kidney Foundation. KDOQI clinical practice guideline for vascular access: 2019 update.Am J Kidney Dis. 2020; l75: S1-S164Abstract Full Text Full Text PDF Scopus (273) Google ScholarBox 1Ideal Patient Characteristics for Using an Innovative Device for Hemodialysis Vascular AccessEndoAVF•Minimum life expectancy of 1 year•Unsuitable vessels to surgically create a distal AVF•Compressible proximal radial/ulnar artery without intimal calcification•Luminal diameter of ≥ 2 mm of the artery and adjacent perforating vein•Patent proximal draining veinsBioengineered graft•Small veins (<2 mm)•Individuals with obesity•Age > 70 years old•Women with small veins•Exhausted vasculature from multiple failed accesses•Minimum life expectancy of 6 months•Treatment of aneurysm/pseudoaneurysm•May be as a hybrid with HeRO deviceEarly cannulation graft•Avoidance of central venous catheter•Initiating urgent hemodialysis therapy•As a hybrid with HeRO device•Age > 70 years old•Individuals with obesity•Women with small veins•Exhausted vasculature from failed multiple accesses but patent artery•Treatment of aneurysm/pseudoaneurysmInside-out device•Total central vein occlusion•Avoid lower extremity access•Thoracic outlet syndromeStent grafts•Recurrent graft vein stenosis•Cephalic arch stenosis•Elastic recoil post balloon angioplasty in noncannulation zone•Possibly recurrent central vein stenosisDrug-coated balloon•Further studies neededAbbreviations: AVF, arteriovenous fistula; EndoAVF, endovascular arteriovenous fistula; HeRo, hemodialysis reliable outflow. EndoAVF•Minimum life expectancy of 1 year•Unsuitable vessels to surgically create a distal AVF•Compressible proximal radial/ulnar artery without intimal calcification•Luminal diameter of ≥ 2 mm of the artery and adjacent perforating vein•Patent proximal draining veins Bioengineered graft•Small veins (<2 mm)•Individuals with obesity•Age > 70 years old•Women with small veins•Exhausted vasculature from multiple failed accesses•Minimum life expectancy of 6 months•Treatment of aneurysm/pseudoaneurysm•May be as a hybrid with HeRO device Early cannulation graft•Avoidance of central venous catheter•Initiating urgent hemodialysis therapy•As a hybrid with HeRO device•Age > 70 years old•Individuals with obesity•Women with small veins•Exhausted vasculature from failed multiple accesses but patent artery•Treatment of aneurysm/pseudoaneurysm Inside-out device•Total central vein occlusion•Avoid lower extremity access•Thoracic outlet syndrome Stent grafts•Recurrent graft vein stenosis•Cephalic arch stenosis•Elastic recoil post balloon angioplasty in noncannulation zone•Possibly recurrent central vein stenosis Drug-coated balloon•Further studies needed Abbreviations: AVF, arteriovenous fistula; EndoAVF, endovascular arteriovenous fistula; HeRo, hemodialysis reliable outflow. The Ellipsys is a single-catheter system, also called a thermal resistance anastomosis device (TRAD), that uses a single venous catheter placed under ultrasound guidance to create an anastomosis using heat and pressure.18Hull J.E. Jennings W.C. Cooper R.I. Waheed U. Schaefer M.E. Narayan R. The pivotal multicenter trial of ultrasound-guided percutaneous arteriovenous fistula creation for hemodialysis access.J Vasc Interv Radiol. 2018; 29: 149-158Abstract Full Text Full Text PDF PubMed Scopus (54) Google Scholar An immediate balloon angioplasty of the anastomotic site is performed to prevent stenosis. The WavelinQ system is a dual-catheter system that involves placing a separate arterial and venous catheter in adjacent vessels using ultrasonographic and fluoroscopic guidance. The catheters are aligned by activating the magnets under fluoroscopic guidance, and an anastomosis is created by using radiofrequency energy. The resulting fistula drains into multiple outflow veins that generally requires additional coil embolization of the brachial vein to direct the blood flow into superficial veins for future cannulation during HD.19Lok C.E. Rajan D.K. Clement J. et al.Endovascular proximal forearm arteriovenous fistula for hemodialysis access: results of the Prospective, Multicenter Novel Endovascular Access Trial (NEAT).Am J Kidney Dis. 2017; 70: 486-497Abstract Full Text Full Text PDF PubMed Scopus (62) Google Scholar The prospective single-arm study using the Ellipsys system enrolled 107 patients, in whom an AVF was created in 105 patients. The primary end points of brachial arterial flow of >500 mL/min and fistula luminal diameter of >4 mm were achieved in 92 of 107 patients (86%).18Hull J.E. Jennings W.C. Cooper R.I. Waheed U. Schaefer M.E. Narayan R. The pivotal multicenter trial of ultrasound-guided percutaneous arteriovenous fistula creation for hemodialysis access.J Vasc Interv Radiol. 2018; 29: 149-158Abstract Full Text Full Text PDF PubMed Scopus (54) Google Scholar In the pivotal Novel Endovascular Access Trial (NEAT) study published in 2017, the Everlinq (now WavelinQ) system was used to create 59 percutaneous AVFs in 60 patients.19Lok C.E. Rajan D.K. Clement J. et al.Endovascular proximal forearm arteriovenous fistula for hemodialysis access: results of the Prospective, Multicenter Novel Endovascular Access Trial (NEAT).Am J Kidney Dis. 2017; 70: 486-497Abstract Full Text Full Text PDF PubMed Scopus (62) Google Scholar A successful AVF was created in 87% of those patients, with a mean brachial arterial flow of 918 mL/min and a mean fistula luminal diameter of 5.2 mm, achieving the KDOQI-suggested target luminal diameter range of 4-6 mm. The primary and cumulative patency rates at 12 months were 69% and 84%, respectively. The procedure-related complications were low but significantly differed between the 2 systems. The single-catheter device study reported no major procedure-related complications, including vessel perforation, dissection, or distal embolization. Two cases with small hematomas, 1 case resulting in technical failure and 1 case requiring manual compression were the only other adverse events reported. The dual-catheter device–related complications included 1 case of dissection of the brachial artery and 2 cases each with pseudoaneurysm and thrombus formation in the brachial artery. Eight adverse events in 5 patients were attributed to the procedure. Secondary interventions (including transpositions, coil embolizations, and angioplasties) needed to create a functional AVF were required in 99 of 107 patients (92.5%) in the Ellipsys study and 19 of 59 patients (32%) in the NEAT study. The endoAVF approach requires additional dialysis clinic personnel education and training. The cannulation of an endoAVF can be relatively difficult as the conventional physical examination findings are absent or diminished.20Vachharajani T.J. Hemodialysis vascular access care in the United States: closing gaps in the education of patient care technicians.Semin Dial. 2011; 24: 92-96Crossref PubMed Scopus (8) Google Scholar A subtle difference in the physical examination findings of endoAVF, such as the absence of surgical scar and softer thrill due to low blood flows (<1,000 mL/min), necessitate learning new cannulation skills. The question as to who will provide this training and how long it will take to learn these new skills become crucial issues during the early planning phase of building an endoAVF program. Recently, a multicenter retrospective study reported 2-year cumulative patency rates for endoAVFs created in 105 cases, which at 6, 12, and 24 months were 97%, 94%, and 93%, respectively.21Beathard G.A. Litchfield T. Jennings W.C. Two-year cumulative patency of endovascular arteriovenous fistula.J Vasc Access. 2020; 21: 350-356Crossref PubMed Scopus (23) Google Scholar Even though these results are encouraging, the study failed to provide details on the patient selection process. The high success rate could be attributed to the atypical patient population included in that study, which is younger (mean age, 56 years), leaner (mean body mass index, 31 kg/m2), and with a higher prevalence of White men (74%) than populations with a high maturation failure rate with surgical AVF creation. The study also omits key information on comorbidities such as diabetes, cardiovascular disease, and peripheral arterial disease. Around the same time, Shahverdyan et al published a single-center and single-surgeon experience-based retrospective review comparing endoAVF outcomes in 100 patients using the WavelinQ (n = 35) and the Ellipsys (n = 65) devices.22Shahverdyan R. Beathard G. Mushtaq N. Litchfield T.F. Nelson P.R. Jennings W.C. Comparison of outcomes of percutaneous arteriovenous fistulae creation by Ellipsys and WavelinQ devices.J Vasc Interv Radiol. 2020; 31: 1365-1372Abstract Full Text Full Text PDF PubMed Scopus (16) Google Scholar AVF maturation rates at 4 weeks using the WavelinQ and Elipsys devices were 54.3% and 68.3%, respectively. Twelve-month primary patency rates of 33% and 32% (hazard ratio [HR], 0.92 [95% CI, 0.53-1.59]) and secondary patency rates of 60% and 82% (HR, 0.42 [95% CI, 0.19-0.97]) were reported for the WavelinQ and Ellipsys devices, respectively. Access failure occurred in 37% and 15.4% of patients with the WavelinQ and Ellipsys devices, respectively. Overall, there are definite advantages to creating an endoAVF compared to an open surgical AVF. The endoAVF can be created in an office-based practice with the patient under conscious sedation using local anesthetics, thereby reducing the scheduling delays and interim dependence on a CVC that are often experienced with a surgical technique. The configuration of the side-to-side anastomosis is believed to support more optimal flow dynamics, reducing shear stress and neointimal hyperplasia, which may ultimately reduce the incidence of stenosis in the juxta (peri)-anastomotic region. Furthermore, an endoAVF avoids surgical dissection, minimizes vessel wall trauma, and eliminates the need to use sutures, thereby reducing local inflammation. An endoAVF may offer the added advantage of avoiding surgical scars and improving aesthetics and acceptance of the procedure by the patient. The high success rate in these early studies is certainly exciting but warrants long-term randomized controlled studies before endoAVF can become a mainstream option. Biosynthetic materials such as bovine arterial grafts and ovine (sheep) collagen grown around a polyester mesh endoskeleton have been used with limited success since the early 1970s. Arterial allografts are plagued by chronic rejection as demonstrated in rat studies showing lymphocyte infiltration in the endothelium, intimal thickening, aneurysmal changes, and thrombi resulting in graft failure.23Allaire E. Guettier C. Bruneval P. Plissonnier D. Michel J.B. Cell-free arterial grafts: morphologic characteristics of aortic isografts, allografts, and xenografts in rats.J Vasc Surg. 1994; 19: 446-456Abstract Full Text Full Text PDF PubMed Scopus (149) Google Scholar In addition to xenografts, cryopreserved deceased donor cadaveric vascular grafts from the femoral vein and iliac arterial allograft have been used in patients to create a vascular access.24Matsuura J.H. Johansen K.H. Rosenthal D. Clark M.D. Clarke K.A. Kirby L.B. Cryopreserved femoral vein grafts for difficult hemodialysis access.Ann Vasc Surg. 2000; 14: 50-55Abstract Full Text PDF PubMed Scopus (46) Google Scholar Korean investigators harvested aortoiliac arterial allografts from brain death donors and used a liquid nitrogen cryopreservation method to cool the graft to −196°C for storage. When the allograft was needed, it was warmed and placed in the upper arm of patients deemed to have failing or failed nonsalvageable vascular accesses.25Ha T.Y. Kim Y.H. Chang J.W. et al.Clinical outcomes of cryopreserved arterial allograft used as a vascular conduit for hemodialysis.J Korean Med Sci. 2016; 31: 1266-1272Crossref PubMed Scopus (7) Google Scholar Complications encountered included early aneurysm formation and high access failure rate (30% in the cryopreserved group vs 18% in the polytetrafluoroethylene [PFTE] group). There is cautious hope and enthusiasm in the development and clinical application of tissue-engineered vascular conduits in patients with CKD. The potential niche for bioengineered grafts is in patients who would qualify for a synthetic AVG over that of an AVF. The hope is that bioengineered grafts will be more durable and less prone to infection, stenosis, thrombosis, and aneurysms than conventional synthetic grafts. One potential concern is the immunogenic response that may occur with bioengineered grafts as it relates to the integrity of the vascular structure but even more broadly to sensitizing a potential kidney transplant recipient. In 2016, promising results were published for a phase 2 trial of Humacyl (Humacyte), a completely biologically engineered human acellular vessel (HAV).26Lawson J.H. Glickman M.H. Ilzecki M. et al.Bioengineered human acellular vessels for dialysis access in patients with end-stage renal disease: two phase 2 single-arm trials.Lancet. 2016; 387: 2026-2034Abstract Full Text Full Text PDF PubMed Scopus (171) Google Scholar The HAV is created by obtaining smooth muscle cells harvested from deceased human organs and tissue donors and grown in a nutrient medium. After cell expansion, the cells are seeded on a biological scaffold placed in a bioreactor. The bioreactor provides a pulsatile flow of nutrient-rich fluid to expose cells to shear stress, which promotes cell differentiation. After 8 weeks, the graft is decellularized to remove antigens while leaving behind the nonimmunogenic collagen tube (Fig 2). In the phase 2 trial from 2016,26Lawson J.H. Glickman M.H. Ilzecki M. et al.Bioengineered human acellular vessels for dialysis access in patients with end-stage renal disease: two phase 2 single-arm trials.Lancet. 2016; 387: 2026-2034Abstract Full Text Full Text PDF PubMed Scopus (171) Google Scholar a total of 60 patients, 20 from the United States and 40 from Poland, who were deemed unsuitable for AVF creation underwent bioengineered graft insertion. Fifty-nine of the participants received a placement of a brachial artery-to-axillary vein anastomosis and were followed for 16 months. Cannulation was permitted after 8 weeks (n = 50) but was later liberalized to 4 weeks after implantation (n = 10). At 6 and 12 months, the primary patency (intervention-free access survival) rates were 63% and 28%, respectively; primary assisted patency (durability of an intervention until the first episode of thrombosis) rates were 73% and 38%, respectively; and secondary patency (durability of intervention until the access is abandoned) rates were 97% and 89%, respectively. Interventions to maintain patency were required 1.89 times per patient-year. Only 1 vessel became infected, which was corrected with a surgical revision and later used. Investigators analyzed panel-reactive antibodies (major histocompatibility complex I and II), serum immunoglobulin G levels, and biopsied the vessels at 16 weeks, which were negative for CD20 (B-lymphocyte marker) and CD3 (T-lymphocyte marker), confirming the absence of systemic immune or inflammatory response. One of the most interesting aspects of that study was the identification of CD68 and CD31 cells on the procured sections of the HAV graft near the venous anastomosis site and at previous cannulation sites as early as 16 weeks and also as late as 55 weeks. The histological presence of those cells implies that the HAV graft was being repopulated by surrounding connective tissue cells, resulting in re-endothelialization of the graft and creation of a truly “living tissue” capable of “healing itself” after cannulation. Due to the success of the early trial and with the goal of Humacyl becoming a first-line treatment for HD patients, Humacyte has now completed enrollment of a multicenter, randomized, controlled phase 3 trial comparing HAV to the gold standard AVF in 240 HD patients. The study is expected to be completed in June 2024. The questions that remain unanswered for long-term patency outcome are whether this “living tissue” will heal with fibrosis and result in stenosis, and if so, how often it may need interventions. Also to be determined is whether these problems will be any different from those encountered currently with native AVFs. Early cannulation grafts have a trilayer design incorporating an elastomeric “self-sealing” membrane that allows cannulation as early as 48-72 hours after the implantation. These grafts offer an option to either skip the use of a CVC or minimize the duration of its use.27Aitken E. Thomson P. Bainbridge L. Kasthuri R. Mohr B. Kingsmore D. A randomized controlled trial and cost-effectiveness analysis of early cannulation arteriovenous grafts versus tunneled central venous catheters in patients requiring urgent vascular access for hemodialysis.J Vasc Surg. 2017; 65: 766-774Abstract Full Text Full Text PDF PubMed Scopus (35) Google Scholar In a review of 15 studies, several different early cannulation grafts (Flixene [Getinge]; AVflo [Nicast]; Rapidax [Terumo Aortic]; Vectra [Becton, Dickinson and Co.]; and Acuseal [W.L. Gore]) were reported to have equivocal results in patency and complication rates compared to standard PTFE grafts.28Al Shakarchi J. Houston G. Inston N. Early cannulation grafts for haemodialysis: a systematic review.J Vasc Access. 2015; 16: 493-497Crossref PubMed Scopus (47) Google Scholar Twelve-month pooled primary and secondary patency rates ranged between 43.3%-63.7% and 70.5%-85%, respectively. The long-term patenc" @default.
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