Hemodialysis Grafts Research Articles

Pulmonary Hypertension in Hemodialysis Patients Following Repeated Endovascular Thrombectomy.

The prevalence of pulmonary hypertension is unusually high in Taiwanese patients with end-stage renal disease. Thrombosis of hemodialysis grafts is common and pulmonary embolism has been reported after endovascular thrombectomy. The aim of this study was to evaluate the relationship between pulmonary hypertension and endovascular thrombectomy of hemodialysis grafts. One hundred and ten patients on hemodialysis via arteriovenous grafts were enrolled in our study. The mean pulmonary artery pressure (PAP) was measured by right heart catheterization. Clinical information was collected by review of medical records. Comorbid cardiopulmonary disease was evaluated by echocardiography and chest X-ray. The history of patient vascular access thrombosis was reviewed from database, hemodialysis records, and interviews with staff at hemodialysis centers. Fifty-two participants (47%) had pulmonary hypertension diagnosed by right heart catheterization. There was no difference in the number of thrombectomy procedures between patients with and without pulmonary hypertension. Based on multivariate analysis, the number of prior endovascular thrombectomy procedures did not correlate with mean PAP (F-value = 1.10, p = 0.30) nor was it associated with pulmonary hypertension (odds ratio = 0.92, p = 0.17). Prior endovascular arteriovenous graft thrombectomies were not associated with pulmonary hypertension or increased mean PAP in end-stage renal disease patients on maintenance hemodialysis.

A two-year experience with a rapid access, self-sealing, polycarbonate urethane nanofiber vascular access graft for hemodialysis.

Evaluating the safety and efficacy of the AVflo™ graft in terms of patency and complications (early and late) over 2 years. Twelve end-stage renal disease (ESRD) patients (age: mean 68.5 ± 10 years) were followed up for a mean period of 946 ± 570 days after receiving an implantation of the graft for HD. The grafts were implanted at the lower arm (loop configuration), upper arm (straight configuration) and the thigh (loop configuration). First dialysis was performed at day 7 (3-21) following implantation. After a mean follow up of 24 months, the primary patency was 56% and the secondary patency was 82%. In this group, AVflo™ shows similar if not superior efficacy and safety to that of available grafts in terms of safety, complications, and long-term patency.

Heparin-bonded expanded polytetrafluorethylene grafts in hemodialysis access.

When options for autologous arteriovenous (AV) fistulas have been fully exhausted, AV grafts continue to play an important role in access creation for hemodialysis, offering long-term hemodialysis access that is a better alternative to central vein catheters. The drawbacks of AV grafts are their poor patency, infection and higher cost. Their main advantages are that they are widely available, are easy to create, and mature early. In the context of the "Fistula First" initiative, many patients with low quality veins suffer from fistula failure and non-maturation resulting in prolonged catheter days that would otherwise be prevented by initial creation of an AV graft. Endeavors to improve graft patency include administration of pharmacological agents, changing graft configuration, altering graft biology, and altering the graft surface. In this review, the current status of heparin-bonded AV grafts for hemodialysis is discussed.

New hybrid procedures in treating occluded arteriovenous hemodialysis grafts.

The use of arteriovenous graft is indicated in patients if the subcutaneous venous bed is exhausted or unsuitable for arteriovenous fistula creation. The leading cause of failure of a prosthetic arteriovenous hemodialysis-access graft is venous anastomotic stenosis causing thrombosis of the graft. A number of surgical techniques and endovascular tools have been used to treat this stenosis and thrombosis. None have yet proven to be ideal. This study was designed to evaluate the results of hybrid treatment of arteriovenous graft thrombosis associated with venous anastomotic stenosis. Over the period 2013-2014, we treated 16 AVG occlusions. Immediately after the diagnosis of occlusion was made, the patients underwent thrombectomy using a Fogarty catheter. After thrombectomy, a diagnostic fistulogram was performed and if VAG stenosis was confirmed, it was treated with balloon angioplasty and stent graft introduction. Lesions were dilated to reduce the stenosis in the treated area to less than 25%. Primary patency after 12 months was 32.8%. Primary assisted patency was 44.7%, secondary patency was 47.6%. Restenosis of the stent graft was seen in two patients. Recurring AVG occlusion was observed in four patients. The average number of interventions to maintain AVG patency was 1.18 per patient/1 year of dialysis. Treatment of AVG thrombosis due to VAG stenosis by hybrid procedure proved to be effective and improved secondary patency.

Patency of the Viabahn stent graft for the treatment of outflow stenosis in hemodialysis grafts

BackgroundTo evaluate arteriovenous graft patency when failing grafts are treated with Viabahn covered stents vs percutaneous angioplasty (PTA) alone. MethodsA retrospective review of all patients that underwent endovascular interventions for failing grafts at a single institution between January 2010 and July 2013 was performed. Forty-four patients were identified who were treated with PTA alone (11) and with Viabahn stent grafts (33) for stenoses in the venous to graft anastomoses. Patient demographics, procedural success, and intraoperative complications were recorded as well as graft patency at 3, 6, and 12 months. Graft patency was reviewed and compared with PTA alone. ResultsThere was no statistically significant difference between the 2 groups regarding gender, frequency of diabetes, hypertension, coronary artery disease, or peripheral arterial disease. Primary technical success defined as residual stenosis 10% or less was achieved in 100% of the cases. Follow-up was determined by flow velocities during dialysis and ultrasound imaging in the vascular laboratory. At 12 months 87.8% (29/33) grafts with stents were functional vs 36.4% (4/11) of those with PTA alone. Primary patency of the stent group was 61%, 52%, and 42% at 3, 6, and 12 months respectively vs the PTA group 64%, 45%, and 9%. ConclusionsGrafts treated with Viabahn covered stents for outflow stenosis have a superior patency to PTA alone, 12 months after treatment; although earlier post treatment results are comparable.

Emergency Hybrid Repair of an Infected Pseudo-aneurysm of an Axillary Dialysis Necklace Graft

Excision of infected synthetic haemodialysis grafts with arterial repair can be extremely challenging due to friable vessels. We present a case of an infected pseudo-aneurysm of a synthetic necklace dialysis graft, where surgical repair of the axillary artery was attempted but not technically feasible. Emergency endovascular covered stenting was performed and the patient has now been free of complications for 4 years. Placing covered stents at infected sites remains controversial but we support endovascular treatment as a viable alternative in the emergency management of infected pseudo-aneurysms related to synthetic grafts and report long term good results in this case.

Enfekte Hemodiyaliz Greftinin Nadir Bir Komplikasyonu:Politetrafloroetilen Vasküler Protezin Dermal Erozyon ve Protrüzyonu

Enfekte Hemodiyaliz Greftinin Nadir Bir Komplikasyonu:Politetrafloroetilen Vasküler Protezin Dermal Erozyon ve Protrüzyonu

A Comparison of Patency and Interventions in Thigh versus HeRO Grafts for Chronic Hemodialysis

A Comparison of Patency and Interventions in Thigh versus HeRO Grafts for Chronic Hemodialysis

Catheter intervention in thrombosed hemodialysis graft

Catheter intervention in thrombosed hemodialysis graft

Results of repeated percutaneous interventions on failing arteriovenous fistulas and grafts and factors affecting outcomes

Repeated percutaneous interventions on failing arteriovenous fistulas (AVFs) and arteriovenous grafts (AVGs) for hemodialysis are common, but the outcomes are largely unknown. We sought to determine the results of the second percutaneous intervention on failing AVGs and AVFs and to identify factors associated with loss of patency. For the purpose of this study, the second percutaneous intervention was identified as the index procedure. We reviewed the second percutaneous interventions on failing AVFs and AVGs at a single institution between 2007 and 2013. Patient comorbidities, graft or fistula configuration, lesion characteristics, and procedural characteristics of the intervention performed were analyzed with respect to technical success, primary patency, primary assisted patency, and secondary patency. Patency was defined per Society for Vascular Surgery recommended reporting standards and was determined from the time of the index procedure. Cox proportional hazards multivariable modeling was performed to identify independent determinants of loss of patency. Among 91 patients, 96 second-time percutaneous interventions were performed on 52 AVFs and 44 AVGs. Patients included 56% men and 44% women with a mean age of 64 ± 17 years. The lesions intervened on were primarily located along the accessed portion of the outflow in AVFs and within the length of the graft and at the venous anastomosis in AVGs. Transluminal angioplasty alone was performed in 82 procedures (85%), and uncovered or covered stents were placed in 15 procedures (16%). Pharmacomechanical thrombectomy was performed in 32 patients (34%) and was more commonly performed in AVGs compared with AVFs (53% vs 17%; P = .0002). Technical success was achieved in 90 procedures (97%; n = 92). One-year primary patency, assisted primary patency, and secondary patency rates were 35%, 86%, and 86%, respectively. One-year primary patency did not differ between AVFs and AVGs, but secondary patency was lower for AVG in comparison to AVF (P = .04). On multivariable analysis, only the need for pharmacomechanical thrombectomy significantly predicted failure of primary patency (hazard ratio, 2.6; 95% confidence interval, 1.6-4.3). The presence of an AVG rather than an AVF independently predicted failure of secondary patency (hazard ratio, 2.9; 95% confidence interval, 1.0-8.2). The second percutaneous interventions on AVFs and AVGs are associated with excellent technical success but poor primary patency. The need for pharmacomechanical thrombectomy predicts the need for additional percutaneous intervention to maintain patency. With additional interventions, acceptable secondary patency out to 5 years can be achieved, although AVGs have inferior secondary patency to AVFs. To develop optimal practice management algorithms, the effectiveness of repeated percutaneous interventions for failing AVGs and AVFs vs creation of a new access should be further investigated.

Abstract 13903: Application of in vivo Tissue-engineered, Autologous “Biotube” Vascular Grafts, Prepared Using a Less Invasive Device, for Hemodialysis Access in a Canine Model

Purpose: When arteriovenous (AV) fistula is not feasible for vascular access in most patients on hemodialysis, the second choice is interposition AV fistula using synthetic graft. However, the grafts pose risks such as infection and low patency. Therefore, we created in vivo tissue-engineered “Biotube” vascular grafts formed with autologous tissue, based on the tissue encapsulation phenomenon. Previously, we confirmed that vascular-like structure was reconstructed in implanted Biotubes with year-ordered patency in vivo. In this study, we evaluated whether Biotubes could replace vascular access grafts for hemodialysis in the cervical vessels of beagles. Methods and Results: The mold for Biotube preparation was assembled by inserting a silicone rod (external diameter 4 mm; length 50 mm) into an acrylate tubular cover (internal diameter 6 mm; length 50 mm with several longitudinal slits). The molds were embedded into the dorsal subcutaneous pouches of beagles (n=3) for 4 weeks, after which they were harvested by a minimally invasive technique from the same incision (width ca. 20 mm). After removing the molds, Biotubes formed by tissue migration to a silicone surface through the mold slits (internal diameter 4 mm; length 45 mm; wall thickness ca. 1 mm) were obtained. Biotubes were then bypassed between the carotid artery (side-to-end anastomosis) and jugular vein (end-to-end anastomosis) of anesthetized beagles. Following placement of Biotubes, continuous thrill was felt by palpation and ultrasound showed turbulent blood flow. After one month, angiography showed no stenosis, elongation, or hemorrhage in any Biotubes. Percutaneous puncturing with a needle, blood removal and resupply from the needle, and astirction within several minutes were feasible. Conclusions: In our beagle model, Biotubes successfully created an AV shunt that maintained steady blood flow, suggesting that Biotubes have potential clinical use in maintaining vascular access for hemodialysis.

Early cannulation grafts for haemodialysis: a systematic review.

Arteriovenous grafts have advantages compared with central venous catheters for dialysis access and guidelines suggest their use as second choice after arteriovenous fistulas. Standard practice with expanded polytetrafluoroethylene (ePTFE) grafts has been to avoid cannulation for 2 weeks following placement, but new generation grafts have been marketed for their early cannulation properties allowing use as an alternative to central venous catheters for prompt access. The aim of this review is to search the current literature for evidence of early cannulation of new generation grafts and to assess their patency and complication rates. Electronic databases were searched for studies assessing the use of early cannulation grafts for dialysis in accordance with PRISMA. The primary outcomes for this study were primary patency rate, primary-assisted patency rate and secondary patency rate. Secondary outcomes were timing of first cannulation, rates of access thrombosis, steal syndrome, pseudo-aneurysm and infection. Following strict inclusion/exclusion criteria by two reviewers, 15 studies were included in our review and divided into the different types of graft. Flixene, Avflo, Rapidax and Acuseal grafts showed that early cannulation within 72 h was possible; there was no evidence of the use of Vectra within 2 weeks of placement. All grafts showed similar patency and complication rates as previously published data on standard ePTFE grafts. Our review showed that early cannulation is possible without detriment, but data did not allow specific graft recommendations. Therefore, we feel that a multicentre, randomised controlled trial is necessary to compare early cannulation grafts.

Clinical success rate of percutaneous management in thethrombosed hemodialysis graft at King ChulalongkornMemorial Hospital

Clinical success rate of percutaneous management in thethrombosed hemodialysis graft at King ChulalongkornMemorial Hospital

NUMERICAL SIMULATION OF THE EFFECT OF VENOUS NEEDLE'S FLOW RATE AND ANGLE ON FLOW PARAMETERS OF A HEMODIALYSIS GRAFT

Arterio-Venous grafts, which are used for hemodialysis, frequently develop intimal hyperplasia in venous anastomosis which ultimately leads to graft failure. It is observed in different studies that the wall shear stress can be correlated to intimal hyperplasia development. Although high Arterio-Venous access blood flow has been implicated in the pathogenesis of graft stenosis, the role of needle's angle and flow rate during the hemodialysis procedure are relatively unexplored. Since the flow field in the region of the venous needle may be a source of damage, in the current study, a numerical investigation of the effect of venous needle's angle and flow rate on hemodynamic parameters of the flow inside a hemodialysis graft has been carried out. Five cases of different needle angles and flow rates with graft flow rate of 500 ml/min have been investigated. Results indicate that in lower angle and lower flow rates the risk of damage is less because of lower wall shear stress and more uniform shear stress distribution on graft wall.

Risk Evaluation of Immediate Surgical Failure During Thigh Hemodialysis Graft Placement by Sonographic Screening.

The purpose of this study was to determine whether preoperative sonographic evaluation of vascular diameters and calcification identifies patients at risk for immediate technical failure of thigh hemodialysis grafts. A retrospective analysis of 143 chronic hemodialysis patients who underwent thigh graft placement was performed. All patients underwent preoperative sonography to assess arterial and venous waveforms and vascular diameters. The degree of arterial calcification was assessed retrospectively. Patient characteristics and graft outcomes were examined. Statistical analyses were performed, with P< .05 considered clinically significant. Sonography identified no or mild arterial calcification in 113 of 143 patients (79%) and moderate to severe calcification in 30 of 143 patients (21%). Primary surgical technical failure occurred in 23% of patients (7 of 30) with moderate to severe calcification, compared to 3.5% (4 of 113) of those with no or mild calcification (hazard ratio, 6.59; 95% confidence interval, 2.06-21.05; P = .002). Cumulative graft survival (time to permanent failure) was shorter in patients with moderate to severe arterial calcification (3-year graft survival, 37% versus 56%; hazard ratio, 2.32; 95% confidence interval, 1.48-6.69; P= .003) but was not significantly associated with venous (P= .82) or arterial (P = .43) diameters. Preoperative sonographic assessment of thigh vessel diameters and calcification can identify patients who may be at risk for immediate technical graft failure and decreased cumulative graft survival. The use of sonography as a screening examination may improve preoperative assessment and surgical planning of hemodialysis thigh grafts.

Arteriovenous Grafts: Early Ultrasonography Tells Their Fortune

Background: The patency of arteriovenous grafts (AVG) for hemodialysis is mostly limited by growing stenoses that lead to decreasing of blood flow, thromboses and finally to access failure. The aim of this study was to find out if detection of any pathology by duplex Doppler ultrasonography (DDU) early after creation of AVG could identify those with lower survival. Methods: We retrospectively enrolled AVG examined by DDU in our center within 40 days after their creation during the last 10 years. The findings were divided into 4 subgroups: (1a) normal finding, (1b) DDU risk factor (low flow volume, medial calcinosis of the feeding artery, presence of intimal hyperplasia in the venous anastomosis), (2a) non-significant or (2b) significant stenosis. The primary outcome measure was the cumulative survival of people with AVGs, and the secondary was the primary (unassisted) survival. All patients underwent DDU surveillance every 3 months with pre-emptive treatment of significant stenoses. Results: Overall, 340 cases were found; the median follow-up was 565 days. Normal DDU finding had 60% cases, DDU risk factor 18% cases, non-significant stenosis 13% cases and significant stenosis 9% cases. Occurrence of early significant stenosis was associated with high risk of access loss (hazards ratio (HR) 14.73; 95% CI 5.10-42.58; p < 0.0001). Similarly, the presence of a DDU risk factor and of a non-significant stenosis were related to significantly shorter access lifespan (HR 2.86; 95% CI 1.10-7.40; p = 0.03 and HR 2.83; 95% CI 1.12-7.17; p = 0.03, respectively). Conclusion: DDU examination of AVG early after their creation can identify those at higher risk and may contribute to individualize the surveillance strategy.

Higher Patency of Transposed Brachio-Basilic Arteriovenous Fistulas Compared to Brachio-Axillary Grafts for Hemodialysis Patients

We compared outcomes of transposed brachio-basilic arteriovenous fistulas (BBAVF) with brachio-axillary prosthetic grafts (BAPG) for hemodialysis. All consecutive patients who underwent creation of a BBAVF or a BAPG, in one of the two institutions, between January 2008 and December 2013 were retrospectively identified. We assessed functional patency and compared complication rates. Patency was also compared between one-stage and two-stage creation procedures for the BBAVF group. Two hundred and thirty-eight patients underwent the creation of a BBAVF (N = 136) or a BAPG (N = 102). Median follow-up was 17 months (range, 1-79). At 6, 12 and 24 months, patients in the BBAVF group had significantly higher primary patency (80%, 69%, 56% vs. 77%, 56%, 37%, respectively; p = 0.005), assisted primary patency (90%, 80%, 71% vs. 80%, 66%, 48%; p&lt;0.0001) and secondary patency (93%, 84%, 72% vs. 94%, 87%, 62%; p = 0.006). Two-stage BBAVF had a significantly higher secondary patency (98%, 92%, 78% vs. 90%, 80%, 68%; p = 0.04) than one-stage BBAVF. The rate of infectious complications was significantly lower in the BBAVF group than in the BAPG group (0.8% vs. 6.9%; p = 0.03). In this large cohort, BBAVF had a higher functional patency and lower rate of infectious complications than BAPG. After exhaustion of cephalic veins, we suggest creation of a BBAVF instead of BAPG, whenever anatomically feasible. The superiority of one-stage or two-stage BBAVF creation procedure must be further investigated.

Pharmacomechanical Thrombolysis versus Surgical Thrombectomy for the Treatment of Thrombosed Haemodialysis Grafts

The key to treatment of a thrombosed dialysis graft is restoration and maintenance of function as long as possible. The objective of this study was to compare the outcomes of pharmacomechanical thrombolysis and surgical thrombectomy in the treatment of thrombosed haemodialysis grafts. During a 3-year period, 108 patients with 114 thrombosed dialysis grafts were referred to our institute for treatment. Fifty thrombosed dialysis grafts underwent pulse-spray catheter thrombolysis using recombinant tissue plasminogen activator (rt-PA) with angioplasty, and 64 thrombosed dialysis grafts underwent surgical thrombectomy. The procedural success rates, complications and average patency times and patency rates were compared between the 2 procedures. P values less than 0.05 were considered to be statistically significant. There were no statistically significant differences between the pharmacomechanical thrombolysis group and the thrombectomy group in the procedural success rates (94% and 93.8%, P = 0.15) or average patency times (6.24 months and 6.30 months, P = 0.17). The primary and secondary patency rates at 12 months were 28.0% ± 8.4% and 54.3% ± 7.8% for the thrombolysis with angioplasty group, and 30.0% ± 6.3% and 57.0% ± 4.8% for the thrombectomy group, respectively (P = 0.65 and P = 0.49, respectively). There were no procedural-related major complications. Our study found no differences in outcomes between patients treated with pharmacomechanical thrombolysis and surgical thrombectomy for thrombosed haemodialysis grafts. Pharmacomechanical thrombolysis can be considered as an alternative treatment for dialysis graft thrombosis.

Abstract No. 18 - Bare metal versus covered stents for treatment of intragraft stenosis within prosthetic hemodialysis arteriovenous grafts

Angioplasty is the standard method for treatment of intragraft stenosis within prosthetic hemodialysis grafts. While stenting can be performed, there are no comparative data in the literature on various stent types at this location. Therefore, the purpose of this study was to compare post-intervention access patency rates after deployment of bare metal versus covered stents for the treatment of intragraft stenoses. Our procedural database was retrospectively reviewed for all percutaneous interventions on prosthetic hemodialysis grafts over a 7-year period in which a stent was deployed at the site of an intragraft stenosis. 31 stent deployments within 22 patients were identified (15 males, 7 females, mean age 57.4 years). All stents were deployed due to suboptimal results with angioplasty (“bail-out”). Intragraft stents deployed for the treatment of anastomotic stenosis, pseudoaneurysms, or bleeding were excluded. Post-intervention access patencies were calculated using Kaplan-Meier analysis and compared using the logrank test. 21 covered stents and 10 bare metal stents were deployed for the treatment of intragraft stenoses. 90% of the grafts were thrombosed at presentation. The 3 and 6 month post-intervention primary access patency rates for bare metal stents were not significantly different from covered stents: 44% and 22% compared to 45% and 25%, respectively (p=0.92). The 6 and 12 month post-intervention secondary access patency rates were also not significantly different: 50% and 30% for bare metal stents and 80% and 55% for covered stents (p=0.28). The 6 month lesion patency rate was 56% and 70%, respectively (p=0.45). In this retrospective study with limited sample size, bare metal and covered stents deployed to treat intragraft stenosis resistant to angioplasty demonstrated similar primary, secondary, and lesion patency rates.

Abstract No. 16 - Economic evaluation of the Viabahn stent-graft vs. angioplasty for hemodialysis graft stenosis: evidence from the revise clinical trial

Abstract No. 16 - Economic evaluation of the Viabahn stent-graft vs. angioplasty for hemodialysis graft stenosis: evidence from the revise clinical trial