Mechanical versus pharmacomechanical thrombolysis for the treatment of thrombosed dialysis access grafts

Endovascular Thrombectomy of Arteriovenous Dialysis Access: A Feasible Treatment?

INTRODUCTION

There is no single best treatment for arteriovenous vascular access thrombosis, with comparable patency rates for both surgical and endovascular treatment. This study aims to evaluate the results of endovascular thrombectomy in our center and analyze the patency rates in different groups.

MATERIAL AND METHODS

We retrospectively selected patients referred to our vascular access treatment unit due to arteriovenous access thrombosis from June 2017 to February 2022. All patients were submitted to endovascular manual thromboaspiration. Patient demographic data, comorbidities and clinical data were collected from medical records for further analysis.

RESULTS

Out of the 96 patients selected, 45 (47%) had AV grafts and 51 (53%) had AV fistulas. The mean age was 74 (±15) years and 54% were males. The overall success rate of interventions was 85.4% (n = 82), while the reintervention rate stood at 59.8% (n = 49). AV grafts exhibited superior secondary patency compared to AV fistulas (92.4% vs. 78.0% and 85.3% vs. 74.1% at 6 and 12 months, respectively; p = 0.047). Forearm fistulas demonstrated enhanced primary patency (72.7% vs. 41.5% and 58.2% vs. 23.1% at 6 and 12 months, respectively; p = 0.017), better assisted primary patency (81.8% vs. 55.8% and 81.8% vs. 42.0% at 6 and 12 months, respectively; p = 0.025), and a lower reintervention rate (27.3% vs. 63.3%; p = 0.040) compared to upper arm fistulas.

CONCLUSIONS

Endovascular manual thromboaspiration seems to be an alternative technique for salvaging thrombosed vascular accesses. Forearm fistulas had the best assisted primary patency, which consolidates the rationale of giving primacy to its construction over other options.

Interventions for thrombosed haemodialysis arteriovenous fistulas and grafts

BACKGROUND

Patients who present with problems with definitive dialysis access (arteriovenous fistula (AVF) or arteriovenous graft (AVG)) become catheter dependent (temporary access), a condition that often carries a higher risk of infections, central venous occlusions and recurrent hospitalisations. For AVG, primary patency rates are reported to be 30% to 90% in patients undergoing thrombectomy or thrombolysis. According to the National Kidney Foundation-Kidney Disease Outcomes Quality Initiative (NKF-KDOQI) guidelines, surgery is preferred when the cause of the thrombosis is a stenosis at the site of the anastomosis in thrombosed AVF. The European Best Practice Guidelines (EBPG) reported that thrombosed AVF may be preferably treated with endovascular techniques, but when the cause of thrombosis is in the anastomosis, surgery provides better results with re-anastomosis. Therefore, there is a need to carry out a systematic review to determine the effectiveness and safety of the intervention for thrombosed fistulae.

OBJECTIVES

This review aims to establish the efficacy and safety of interventions for failed AVF and AVG in patients receiving haemodialysis (HD).

SEARCH METHODS

We searched the Cochrane Kidney and Transplant Register of Studies up to 28 January 2024 through contact with the Information Specialist using search terms relevant to this review. Studies in the Register are identified through searches of CENTRAL, MEDLINE, EMBASE, conference proceedings, the International Clinical Trials Registry Portal (ICTRP) Search Portal and ClinicalTrials.gov.

SELECTION CRITERIA

The review included randomised controlled trials (RCTs) and quasi-RCTs in people undergoing HD treatment using AVF or AVG presenting with clinical or haemodynamic evidence of thrombosis. Patients had to have used an AVF or AVG at least once.

DATA COLLECTION AND ANALYSIS

Summary estimates of effect were obtained using a random-effects model, and results were expressed as risk ratios (RR) and their 95% confidence intervals (CI) for dichotomous outcomes. Confidence in the evidence was assessed using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach.

MAIN RESULTS

Our search strategy identified 14 eligible studies (1176 randomised participants) for inclusion in this review. We included three types of interventions for the treatment of thrombosed AVF and AVG: (1) types of thrombectomy, (2) types of thrombolysis and (3) surgical procedures. Most of the included studies had a high risk of bias due to a poor study design, a low number of patients and industry involvement. Overall, there was insufficient evidence to suggest that a specific intervention was better than another for the outcomes of failure, primary patency at 30 days, technical success and adverse events (both major and minor). Primary patency at 30 days may improve with surgical compared to mechanical thrombectomy (3 studies, 404 participants: RR 1.36, 95% CI 1.07 to 1.67); however, the evidence is very uncertain. Death, access dysfunction, successful dialysis, and SONG (Standards Outcomes in Nephrology) outcomes were rarely reported. The current review is limited by the small number of available studies with a limited number of patients enrolled. Most of the studies included in this review have a high risk of bias and a low or very low certainty of evidence. Further research is required to define the most effective and clinically appropriate technique for access dysfunction.

AUTHORS' CONCLUSIONS

It remains unclear whether any intervention therapy affects the patency at 30 days or failure in any thrombosed HD AV access (very low certainty of evidence). Future research will very likely change the evidence base. Based on the importance of HD access to these patients, future studies of these interventions among people receiving HD should be a priority.

Sirolimus-coated balloon angioplasty in maintaining the patency of thrombosed arteriovenous graft: 1-year results of a prospective study

BACKGROUND

A prospective, pilot study was designed to test the feasibility of using sirolimus-coated balloon (SCB) to treat graft vein junction of thrombosed arteriovenous graft (AVG) following successful pharmacomechanical thrombectomy. The present report provides the 1-year results of this study.

METHODS

This is a 1-year follow-up of a single, prospective, single-arm study that was conducted from 2018 to 2019 in 20 patients who presented to a tertiary institution with thrombosed AVG. The recruited patients received SCB angioplasty at the graft-vein junction following successful endovascular thrombectomy of a thrombosed AVG. One year after recruitment, there were three deaths, one AVG revision, and one AVG explantation among the participants recruited. The outcomes of 15 subjects at 1-year following the index procedure obtained from electronic medical records were re-examined.

RESULTS

The 1-year access circuit primary patency rate was 40%, while assisted primary and secondary patency rates were 46.7% and 73.3%, respectively. A total of 16 interventions (4 angioplasties, 12 thrombectomies) were performed in 9 patients over the 12 months. Four AVGs were abandoned. The median number of interventions per patient was 1 (0-3) per year. Using Kaplan-Meier analysis, the mean estimated post-intervention access circuit primary patency was 230 (95% CI: 162-300) days, while access circuit assisted primary patency was 253 (95% CI: 187-320) days, and access circuit secondary patency was 292 (95% CI: 230-356) days. Sub-group analysis did not show a significant difference in the mean estimated primary patency between AVG with de novo and recurrent stenosis (245 days, 95% CI: 151-339 vs 210 days, 95% CI: 113-307; p = 0.29).

CONCLUSIONS

SCB may help sustain the patency of thrombosed AVG following successful thrombectomy.

Mechanical thrombectomy of inferior vena cava filter-associated caval thrombosis using FlowTriever and ClotTriever systems

OBJECTIVE

Chronically indwelling inferior vena cava filters (IVCFs) can have multiple adverse sequelae, including IVCF-associated thrombosis. The Inari ClotTriever and FlowTriever mechanical and aspiration thrombectomy systems (Inari Medical) can be used for acute caval thrombosis associated with IVCFs if appropriate proximal IVCF protection is used intraprocedurally. The present study reports a single institution's outcomes after ClotTriever and FlowTriever thrombectomy of acute IVCF-associated iliocaval thrombus.

METHODS

A retrospective review was conducted of all patients who underwent ClotTriever or FlowTriever thrombectomy for IVCF-associated caval thrombosis. The patient demographics, clinical characteristics, and postprocedural outcomes of a 15-patient cohort were compiled and described.

RESULTS

A total of 15 patients were identified as presenting with acute IVCF-associated caval thrombosis and having undergone intervention with either the ClotTriever or FlowTriever system from 2019 to 2022. Of the 15 patients in the cohort, 3 (20%) had presented with a threatened extremity (phlegmasia cerulea dolens), and 12 had presented with severe, debilitating, but non-limb-threatening, lower extremity edema. The preprocedural clot burden was significant and involved the cava, iliac veins, and femoropopliteal veins in 7 of 15 patients (47%) in the cohort. The procedure was technically successful in 11 patients (73.33%). Resolution of acute symptoms was noted in 100% of the technically successful procedures. The 30-day mortality rate was 13% (2 of 15 patients). One intraprocedural death occurred from pulmonary embolism, and one patient died of malignancy complications. The surviving patients not lost to follow-up experienced stable or improving venous disease, with only one patient presenting with post-phlebitic syndrome.

CONCLUSIONS

Mechanical and aspiration thrombectomy of IVCF-associated thrombus with the FlowTriever and ClotTriever systems have good technical success and resulted in significant improvement in acute symptoms with adequate clot clearance. Proximal embolic protection maneuvers for pulmonary embolism prophylaxis and preexisting filter protection are required intraprocedurally.

Comparison of Clinical Outcomes in Patients Undergoing a Salvage Procedure for Thrombosed Hemodialysis Arteriovenous Grafts

Background

The major limitation of arteriovenous graft access is the high incidence of thrombotic occlusion. This study investigated the outcomes of our salvage strategy for thrombosed hemodialysis arteriovenous grafts (including surgical thrombectomy with balloon angioplasty) and evaluated the efficacy of intragraft curettage.

Methods

Salvage operations were performed for 290 thrombotic occluded arteriovenous grafts with clinical stenotic lesions from 2010 to 2018. Of these, 117 grafts received surgical thrombectomy and balloon angioplasty from 2010 to 2012 (group A), and 173 grafts received surgical thrombectomy and balloon angioplasty, with an additional salvage procedure using a curette and a graft thrombectomy catheter, from 2013 to 2018 (group B). Outcomes were described in terms of post-intervention primary patency and secondary patency rates.

Results

The post-intervention primary patency rates in groups A and B were 44.2% and 66.1% at 6 months and 23.0% and 38.3% at 12 months, respectively (p=0.003). The post-intervention secondary patency rates were 87.6% and 92.6% at 6 months and 79.7% and 85.0% at 12 months, respectively (p=0.623). Multivariate Cox regression analysis demonstrated that intragraft curettage was a positive predictor of post-intervention primary patency (hazard ratio, 0.700; 95% confidence interval, 0.519-0.943; p=0.019).

Conclusion

Surgical thrombectomy and balloon angioplasty showed acceptable outcomes concerning post-intervention primary and secondary patency rates. Additionally, intragraft curettage may offer better patency to salvage thrombotic occluded arteriovenous grafts with intragraft stenosis.

Comparison of Peritoneal Catheter Survival with Fistula Survival in Hemodialysis

Objective

To compare continuous ambulatory peritoneal dialysis (CAPD) and hemodialysis (HD) with regard to long-term maintenance of access.

Design

Retrospective study of a four to six-year time period at one center.

Patients

One hundred and twenty-two CAPD patients between December 1988 and December 1992, and 172 HD patients between May 1986 and December 1992.

Main Outcome Measure

Cumulative survival rate of peritoneal catheters and arteriovenous fistulas (AVF) was the main outcome measure. Variables affecting the survival rate including sex, age, presence or absence of diabetes, and type of AVF (autogenous or prosthetic graft) were assessed. The causes of peritoneal catheter failures were analyzed.

Results

The cumulative survival rate of all peritoneal catheters was significantly longer than the AVF survival rate (84% vs 74% at one year; 73% vs 61% at two years; and 63% vs 48% at three years) (p = 0.029). There were no differences in peritoneal catheter survival according to sex, age, or diabetes. Compared with A VF survival, peritoneal catheter survival was significantly longer in male (p = 0.0492), elderly (p = 0.0082), and diabetic (p = 0.0022) patients. Prosthetic graft and old age were risk factors for AVF survival. Of all peritoneal catheter failures, infectious complications were responsible for 75% (33/44) and mechanical complications for 25% (11/44). Peritonitis was the leading infectious complication (21/33) and outflow obstruction was the leading mechanical complication (9/11).

Conclusion

In terms of long-term maintenance of access, CAPD is superior to HD, especially in the elderly or diabetics. Prevention and proper management of peritonitis may prolong the peritoneal catheter survival.

Spanish Clinical Guidelines on Vascular Access for Haemodialysis

Vascular access for haemodialysis is key in renal patients both due to its associated morbidity and mortality and due to its impact on quality of life. The process, from the creation and maintenance of vascular access to the treatment of its complications, represents a challenge when it comes to decision-making, due to the complexity of the existing disease and the diversity of the specialities involved. With a view to finding a common approach, the Spanish Multidisciplinary Group on Vascular Access (GEMAV), which includes experts from the five scientific societies involved (nephrology [S.E.N.], vascular surgery [SEACV], vascular and interventional radiology [SERAM-SERVEI], infectious diseases [SEIMC] and nephrology nursing [SEDEN]), along with the methodological support of the Cochrane Center, has updated the Guidelines on Vascular Access for Haemodialysis, published in 2005. These guidelines maintain a similar structure, in that they review the evidence without compromising the educational aspects. However, on one hand, they provide an update to methodology development following the guidelines of the GRADE system in order to translate this systematic review of evidence into recommendations that facilitate decision-making in routine clinical practice, and, on the other hand, the guidelines establish quality indicators which make it possible to monitor the quality of healthcare.

Comparison of surgical and radiological interventions for thrombosed arteriovenous access

INTRODUCTION:

To compare open surgical and radiological interventions for thrombosed arteriovenous access for dialysis.

METHODS:

A retrospective analysis of access procedures and dialysis episodes from 1 December 2002 to 30 November 2015 with follow-up up to 1 August 2016. Hospital records and dialysis database interrogated for further interventions and length of functional use.

RESULTS:

Some 128 surgical and 27 radiological thrombectomies were compared. Radiological treatment was successful in 24 (89%) cases and surgical interventions in 65 cases (51%; p < 0.001). In all, 82 (64%) of the 128 surgical thrombectomies had no additional treatment, 43 (34%) had a surgical revision and 3 cases (2%) had an on-table balloon angioplasty. All 27 interventional thrombectomies had an additional balloon angioplasty. Success rate was significantly increased after a surgical revision (74%) or balloon angioplasty (87%) compared to no adjuvant procedure (38%; p < 0.001). There was a trend towards higher primary failure rates of arteriovenous fistula thrombectomies in the upper arm (57%) compared to the arteriovenous fistula thrombectomies in forearm (40%) and arteriovenous graft thrombectomies (33%; p = 0.056). Assisted primary patency was better after interventional treatment compared to surgery (p = 0.02) and significantly better after thrombectomy with additional treatment (p = 0.005). Patency after surgical revision or balloon angioplasty of the access was similar (p = 0.15). More procedures were required to maintain the access after balloon angioplasty than after surgical revision, and intervention-free survival was better after surgical revision (p = 0.02).

CONCLUSION:

Revision procedures significantly increase success rate of access thrombectomies. Radiological thrombectomies have higher success rates but lower intervention-free survival and need more additional procedures to maintain patency.

Hemodialysis Tunneled Catheter Noninfectious Complications

Noninfectious hemodialysis catheter complications include catheter dysfunction, catheter-related thrombus, and central vein stenosis. The definitions, causes, and treatment strategies for catheter dysfunction are reviewed below. Catheter-related thrombus is a less common but serious complication of catheters, requiring catheter removal and systemic anticoagulation. In addition, the risk factors, clinical manifestation, and treatment options for central vein stenosis are outlined.

Percutaneous treatment of thrombosed hemodialysis arteriovenous fistulas: use of thromboaspiration and balloon angioplasty

Background

Endovascular strategies have been used to manage patients with thrombosed vascular access for hemodialysis. We analyzed primary success rate and patency rates of balloon angioplasty following mechanical thrombectomy for the treatment of thrombosed native arteriovenous fistulas.

Methods

This was a retrospective study of 24 patients with thrombosed native arteriovenous fistulas who were referred for treatment in the intervention unit of the Radiology Department. All patients had been performed percutaneous thrombo-aspiration and balloon angioplasty. Technical and clinical success rates as well as the 6th and 12th months primary and secondary patency of fistulas were evaluated.

Results

Technical and clinical success was 83%. In the 6 of 20 patients, early re-thrombosis were detected. Patent AVF with primary and secondary patency rates at 6 and 12 months was 55%-40%. The secondary patency rates at 6 and 12 months were 75% and 70%.

Conclusion

Mechanical thrombectomy with balloon angioplasty is a minimally invasive and effective procedure for the treatment of thrombosed native arteriovenous fistula. Advantages of this technique are minor complication rates, cost effectiveness, high technical success rate.

Advances in Endovascular Techniques to Treat Failing and Failed Hemodialysis Access

During the decade since JEVT was inaugurated, we have witnessed the growing application of endovascular techniques for arteriovenous (AV) access in parallel with the evolution of endovascular therapy for arterial pathology. To date, few if any technologies have compared with balloon angioplasty for treating venous anastomotic stenosis, the most common cause of access failure. Only one device, which incorporates the principles of access graft design and self-expanding stent technology, has been uniquely conceived for this pathology. The encapsulated polytetrafluoroethylene stent-graft has achieved reasonable preliminary results, but randomized data is forthcoming. Technology to clear the clot from a thrombosed graft continues to evolve, but will never be as cost-effective as simple balloon thrombectomy. However, the pressure placed on providers to perform all percutaneous interventions and move away from open techniques continues to fuel interest in this component of treatment. Finally, the pursuit of a completely percutaneous AV access continues. As with endovascular procedures in general, whether or not the procedure is cost-effective or time-consuming seems to take a back seat to the all-percutaneous approach that so many seem to converge upon. Moreover, as most autogenous fistulas and AV grafts can be created with minimal incisions under local anesthesia, the pursuit of a completely percutaneous access system seems more like an academic exercise than a practical application of technology. We must try and avoid the tendency to “minimize invasiveness” with technology that is maximally intensive (and expensive), such as limiting ourselves to only percutaneous methods. Given the increasing pressure to have an all autogenous access program, current techniques that apply well in prosthetic grafts will need to be modified to accommodate the different biology of a native fistula. Clearly, the enlarging end-stage renal disease population will continue to provide endovascular specialists with clinically challenging problems requiring new and revolutionary technology.

Hemodialysis Tunneled Catheter Noninfectious Complications

Noninfectious hemodialysis catheter complications include catheter dysfunction, catheter-related thrombus, and central vein stenosis. The definitions, causes, and treatment strategies for catheter dysfunction are reviewed below. Catheter-related thrombus is a less common but serious complication of catheters, requiring catheter removal and systemic anticoagulation. In addition, the risk factors, clinical manifestation, and treatment options for central vein stenosis are outlined.

Initial clinical use of a novel mechanical thrombectomy device, XCOILTM, in hemodialysis graft and fistula declot procedures

PURPOSE

We aimed to evaluate the safety and effectiveness of a novel catheter-based mechanical thrombectomy device, XCOILTM, as a first line therapy to restore patency of thrombosed dialysis grafts and fistulae.

METHODS

In 2010, 18 consecutive/sequential patients (11 male, 7 female; median age, 52 years; age range, 32-69 years) with occluded arteriovenous grafts (n=15) or fistulae (n=3) were treated with XCOILTM (NexGen Medical Systems Inc.) without adjunctive thrombolytic drugs. XCOILTM was advanced distal to the thrombus within the outflow vein as well as distal to the arterial inflow platelet thrombin plug, using a 4F angiographic catheter. The percentage of thrombus cleared, primary patency, procedure time, and XCOILTM performance were documented.

RESULTS

Thrombosis occurred 1-30 days prior to the procedure. Thrombosed segments of graft/fistula measured 10-50 cm. Pre- and postprocedure angiography demonstrated that in 15 of 18 cases (83%) XCOILTM removed 80%-100% of the venous outflow thrombus. In 11 of 14 cases (79%), the platelet thrombin plug was also removed. Thrombectomy procedure time averaged 8 min, with one to three passes with the XCOILTM required. No evidence of distal embolization or graft/vessel injury was found on angiography following clot removal. In four cases in whom patency was not restored with XCOILTM, subsequent use of other clot removal devices also failed to restore patency. In one case with severe venous stenosis, the device failed to deploy and the thrombus was not captured. No intraprocedural complications related to XCOILTM use occurred.

CONCLUSION

XCOILTM is an effective and safe first-line therapy option for the treatment of thrombosed hemodialysis grafts/fistulae. Rapid removal of intact thrombus and platelet thrombin plug can be achieved without adjunctive thrombolytics.

Pre-emptive correction for haemodialysis arteriovenous access stenosis

BACKGROUND

Guidelines recommend routine arteriovenous (AV) graft and fistula surveillance (technology-based screening) in addition to clinical monitoring (physical examination) for early identification and pre-emptive correction of a stenosis before the access becomes dysfunctional. However, consequences on patient-relevant outcomes of pre-emptive correction of a stenosis in a functioning access as opposed to deferred correction, i.e. correction postponed to when the access becomes dysfunctional, are uncertain.

OBJECTIVES

We aimed to evaluate 1) whether pre-emptive correction of an AV access stenosis improves clinically relevant outcomes; 2) whether the effects of pre-emptive correction of an AV access stenosis differ by access type (fistula versus graft), aim (primary and secondary prophylaxis), and surveillance method for primary prophylaxis (Doppler ultrasound for the screening of functional and anatomical changes versus measurement of the flow in the access); and 3) whether other factors (dialysis duration, access location, configuration or materials, algorithm for referral for intervention, intervention strategies (surgical versus radiological or other), or study design) explain the heterogeneity that might exist in the effect estimates.

SEARCH METHODS

We searched the Cochrane Kidney and Transplant Specialised Register to 30 November 2015 using search terms relevant to this review.

SELECTION CRITERIA

We included all studies of any access surveillance method for early identification and pre-emptive treatment of an AV access stenosis.

DATA COLLECTION AND ANALYSIS

We extracted data on potentially remediable and irremediable failure of the access (i.e. thrombosis and access loss respectively); infection and mortality; and resource use (hospitalisation, diagnostic and intervention procedures). Analysis was by a random effects model and results expressed as risk ratio (RR), hazard ratio (HR) or incidence rate ratio (IRR) with 95% confidence intervals (CI).

MAIN RESULTS

We identified 14 studies (1390 participants), nine enrolled adults without a known access stenosis (primary prophylaxis; three studies including people using fistulas) and five enrolled adults with a documented stenosis in a non-dysfunctional access (secondary prophylaxis; three studies in people using fistulas). Study follow-up ranged from 6 to 38 months, and study size ranged from 58 to 189 participants. In low- to moderate-quality evidence (based on GRADE criteria) in adults treated with haemodialysis, relative to no surveillance and deferred correction, surveillance with pre-emptive correction of an AV stenosis reduced the risk of thrombosis (RR 0.79, 95% CI 0.65 to 0.97; I² = 30%; 18 study comparisons, 1212 participants), but had imprecise effect on the risk of access loss (RR 0.81, 95% CI 0.65 to 1.02; I² = 0%; 11 study comparisons, 972 participants). In analyses subgrouped by access type, pre-emptive stenosis correction did not reduce the risk of thrombosis (RR 0.95, 95% CI 0.8 to 1.12; I² = 0%; 11 study comparisons, 697 participants) or access loss in grafts (RR 0.9, 95% CI 0.71 to 1.15; I² = 0%; 7 study comparisons; 662 participants), but did reduce the risk of thrombosis (RR 0.5, 95% CI 0.35 to 0.71; I² = 0%; 7 study comparisons, 515 participants) and the risk of access loss in fistulas (RR 0.5, 95% CI 0.29 to 0.86; I² = 0%; 4 studies; 310 participants). Three of the four studies reporting access loss data in fistulas (199 participants) were conducted in the same centre. Insufficient data were available to assess whether benefits vary by prophylaxis aim in fistulas (i.e. primary and secondary prophylaxis). Although the magnitude of the effects of pre-emptive stenosis correction was considerable for patient-centred outcomes, results were either heterogeneous or imprecise. While pre-emptive stenosis correction may reduce the rates of hospitalisation (IRR 0.54, 95% CI 0.31 to 0.93; I² = 67%; 4 study comparisons, 219 participants) and use of catheters (IRR 0.58, 95% CI 0.35 to 0.98; I² = 53%; 6 study comparisons, 394 participants), it may also increase the rates of diagnostic procedures (IRR 1.78, 95% CI 1.18 to 2.67; I² = 62%; 7 study comparisons, 539 participants), infection (IRR 1.74, 95% CI 0.78 to 3.91; I² = 0%; 3 studies, 248 participants) and mortality (RR 1.38, 95% CI 0.91 to 2.11; I² = 0%; 5 studies, 386 participants).In general, risk of bias was high or unclear in most studies for many domains we assessed. Four studies were published after 2005 and only one had evidence of registration within a trial registry. No study reported information on authorship and/or involvement of the study sponsor in data collection, analysis, and interpretation.

AUTHORS' CONCLUSIONS

Pre-emptive correction of a newly identified or known stenosis in a functional AV access does not improve access longevity. Although pre-emptive stenosis correction may be promising in fistulas existing evidence is insufficient to guide clinical practice and health policy. While pre-emptive stenosis correction may reduce the risk of hospitalisation, this benefit is uncertain whereas there may be a substantial increase (i.e. 80%) in the use of access-related procedures and procedure-related adverse events (e.g. infection, mortality). The net effects of pre-emptive correction on harms and resource use are thus unclear.

Influence of drugs on arteriovenous vascular access dysfunction

Vascular access dysfunction, due to venous stenosis at the vein-artery anastomosis in arteriovenous fistulas and vein-graft anastomosis in synthetic arteriovenous grafts, is a major cause of morbidity and mortality in dialysis patients. The two overarching approaches to prevent and treat vascular access dysfunction are from systemic or local (including endovascular and perivascular) routes. However, there are currently very few effective therapies to treat vascular access dysfunction. This article will review major studies evaluating systemic, endovascular, and perivascular therapies for vascular access dysfunction. Ongoing research to evaluate novel innovations to prevent and/or manage vascular access dysfunction appears promising.

Use of Hybrid Vascular Grafts in Failing Access for Hemodialysis: Report of Two Cases

Purpose

Vascular access morbidity represents one of the most common indications for readmission in patients with end-stage renal disease (ESRD). We report the use of hybrid grafts in two patients for revision of failed vascular access for hemodialysis (HD).

Case Presentations

The first patient was a 45-year-old woman with ESRD who presented with an arteriovenous graft (AVG) that had required multiple interventions for maintenance in whom much of the graft was lined with covered stents. The patient presented with erosion of a stent in the AVG through the skin to the emergency department. The second patient was a 41-year-old man with ESRD who also had an AVG that had required multiple interventions for maintenance. He presented to clinic with chronic bleeding from the AVG after HD sessions. Both patients were taken to the operating room for salvage of part of the AVG through the use of hybrid vascular access grafts. The patients have passed six and three months from the procedure, respectively, without needing additional interventions.

Conclusions

This technique demonstrates successful use of hybrid vascular access grafts, specifically inside existing grafts in locations that contain stents utilizing the existing venous resources in that arm to carry out the surgical repair, thereby preserving venous capital.

In-center thrombolysis for clotted AV access: a cohort review

Thrombosis is the leading cause of arteriovenous (AV) access failure for hemodialysis patients requiring frequent interventions. We describe a novel approach to the lyse-and-wait technique in thrombosed AV access using nurse-administered thrombolytics in a hospital-based hemodialysis unit. All patients at a single-center, large, urban, tertiary care hospital, who underwent in-center thrombolysis via alteplase instilled directly into a thrombosed AV access by inpatient hemodialysis unit staff between January 1, 2003 and December 31, 2007, were eligible. Included subjects were at least 18 years old and did not have known or suspected infection or trauma to the AV access site. Primary outcome measure was successful thrombolysis defined as hemodialysis performed immediately or after the interventional radiology (IR) procedure. Adverse events related to the procedure were collected. A total of 321 procedures, performed on 145 subjects (77 (53%) male, 68 (47%) female) remained for analysis. Successful instillation occurred in 317 of 321 procedures (98.8%). Successful thrombolysis occurred in 237 of 321 procedures (73.8%). Adverse events (8 major and 10 minor) occurred in 18 procedures, yielding a complication rate of 5.6%. In-center thrombolysis with alteplase administration by hemodialysis unit nursing staff under physician supervision is safe and effective with an adverse outcome rate similar to the literature. Thus, this modified lyse-and-wait protocol can be adopted with appropriate IR and surgical backup in place.

Treating thrombotic prosthetic arteriovenous access with cross-balloon occlusive thrombolysis and angioplasty

OBJECTIVE

Clot embolism remains a concern due to flushing of clot and thrombolytic agent centrally in the process of percutaneous pharmacomechanical thrombolysis (PMT) for a thrombosed prosthetic arteriovenous access (PAVA), which might be reduced by a modified technique.

METHODS

We retrospectively review this modified technique that uses two balloon-catheters in crisscross fashion and occludes both ends of PAVA during thrombolysis. Underlying stenotic lesions were dilated simultaneously with balloon angioplasty when needed.

RESULTS

Among the 23 patients treated, 21 (91.3%), 10 (43.5%), and seven (30.4%) presented significant stenosis at the outflow, intragraft, and inflow segments of PAVA, respectively. The median duration of follow-up was 310.0 (range, 288.0-327.0) days. Anatomic success was achieved in 12 out of 23 (52.2%). Clinical success for successful dialysis was achieved in all patients. The median primary patency and secondary patency were 126.0 days (range, 7.0-316.0) days and 308.0 days (range, 84.0-327.0), respectively.

CONCLUSION

We believe this method is safe and effective in dissolving PAVA thrombus as well as treating culprit stenosis. It may reduce concerns of flushing of clot and thrombolytic agent into the central circulation in the process of PMT.

Cardiac Arrest Secondary to Bilateral Pulmonary Emboli following Arteriovenous Fistula Thrombectomy: A Case Report with Review of the Literature

Number of patients with End Stage Renal Disease (ESRD) is growing worldwide. Hemodialysis remains the main modality of renal replacement therapy for ESRD patients. A patent hemodialysis access (arteriovenous fistula or arteriovenous graft) plays a key role in successful delivery of hemodialysis. Common vascular access issues encountered by patients and nephrologists are thrombosis and infection. The thrombosed access is declotted by various percutaneous techniques these days by multiple outpatient access centers in a timely fashion. Thrombolysis can give rise to various complications, a few of which can be life threatening. A young hemodialysis patient underwent percutaneous thrombolysis of his clotted arteriovenous fistula. Outpatient access thrombectomy was complicated immediately afterwards with cardiac arrest requiring cardiac resuscitation in the recovery room. The patient was admitted to intensive care unit after life sustaining care. Work up revealed multiple pulmonary emboli to both lung fields on CT scan of the chest. Patient was anticoagulated and discharged from the hospital. Thrombolysis of clotted hemodialysis access is associated commonly with occurrences of pulmonary embolic which are usually asymptomatic. Massive pulmonary embolization due to access thrombolysis is rare. Nephrologists and radiologists should be aware of this dangerous complication particularly in patients with preexisting cardiopulmonary disease.

Thrombectomy of prosthetic dialysis grafts using mechanical plus "no-wait lysis" approach requires less procedure time and radiation exposure

In spite of the existence of various strategies, dialysis graft thrombectomy remains time-consuming and requires substantial radiation exposure. The authors report a new approach for graft thrombectomy, "no-wait lysis", with the objective to examine its effect on procedure time and radiation exposure. Based on the use of tissue plasminogen activator (tPA), the 88 retrospectively reviewed graft thrombectomies were divided into "no-tPA" group (n = 35) and "no-wait lysis" group (n = 53). Fogarty thrombectomy and balloon angioplasty were used similarly in both groups. In the "no-wait lysis" group, small-dose tPA was added directly into the graft during the procedure. Comparing the "no-wait lysis" group with the "no-tPA" group, the procedure time was reduced: 27.2 ± 10.2 vs. 55.5 ± 19.9 minutes (p < 0.0001), and the radiation exposure time was decreased correspondingly: 159.4 ± 61.6 vs. 243.9 ± 101.9 seconds (p < 0.0001). Multivariate regression analysis revealed that the use of "no-wait lysis" approach was the major significant predictor for shorter procedure time and radiation exposure time. In conclusion, our data support that the use of "no-wait lysis" approach for dialysis graft thrombectomy substantially reduces procedure time and radiation exposure, and it may serve as an efficient and economical alternative to other existing approaches.

The history of interventional nephrology

Visionary nephrologists in the early 1960s invented the dialysis machine, constructed arteriovenous shunts and fistulas, and designed vascular and peritoneal catheters to provide their patients with long-term dialysis. As the number of dialysis patients grew, the construction and care of vascular access was abandoned by nephrologists to surgeons and radiologists. There was a decline in the number of fistulas and an increase in grafts in the United States. Vascular access was not the first priority for the nonnephrologists, and this set the stage for the emergence of diagnostic and interventional nephrologists. These self-taught nephrologists trained others, resulting in a critical mass of subspecialists who founded the Society of Diagnostic and Interventional Nephrology. This review traces the origin of this exciting field from its pioneers to the society as it exists today. The future of this society depends on academic nephrology fellowship programs fostering training and research in this field.

Hemodialysis vascular access monitoring: current concepts

Most arteriovenous grafts fail due to irreversible thrombosis, and most clotted grafts have an underlying stenotic lesion. These observations raise the plausible hypothesis that early detection of graft stenosis with preemptive angioplasty will reduce the likelihood of graft thrombosis. A number of noninvasive methods can be used to detect hemodynamically significant graft stenosis with a high positive predictive value. These tests include clinical monitoring, as well as surveillance by static dialysis venous pressures, flow monitoring, or duplex ultrasound. However, these surveillance tests have a much lower positive predictive value for graft thrombosis in the absence of preemptive angioplasty. In other words, none of the currently available surveillance tests can reliably distinguish between stenosed grafts destined to clot, and those that will remain patent without intervention. As a consequence, any program of graft surveillance necessarily results in a substantial proportion of unnecessary angioplasties. Moreover, a substantial proportion of grafts thrombose despite a normal antecedent surveillance test. Numerous observational studies have found an impressive reduction of graft thrombosis after implementation of a stenosis surveillance program. In contrast, 5 of 6 randomized clinical trials failed to show a reduction of graft thrombosis in patients undergoing graft surveillance, as compared with those receiving only clinical monitoring. The lack of benefit of surveillance is largely attributable to the rapid recurrence of stenosis after angioplasty. Thus, routine surveillance for graft stenosis, with preemptive angioplasty, cannot be recommended for reduction of graft thrombosis. Future research should be directed at pharmacologic interventions to prevent graft stenosis.

Is surgical salvage of arteriovenous grafts feasible after unsuccessful percutaneous mechanical thrombectomy?

Treatment of thrombosed dialysis ateriovenous (AV) grafts in the radiology interventional suite requires percutaneous mechanical thrombectomy, along with angioplasty of the underlying stenotic lesion. We analyzed the anatomic reasons for unsuccessful percutaneous thrombectomy of AV grafts, and assessed the feasibility of surgical salvage. The radiologic reports of all thrombosed AV grafts undergoing unsuccessful percutaneous mechanical thrombectomy during a 5-year period were analyzed for the specific problem precluding restoration of graft patency. We also compared the features of patients with unsuccessful graft thrombectomy to those with successful thrombectomy. Of 77 AV grafts undergoing unsuccessful percutaneous thrombectomy, only six (or 8%) could be revised surgically. Inability to salvage the graft surgically was because of: severe draining vein occlusion or stenosis (30 patients); severe central vein lesion (12); multiple intragraft stenoses (11); large pseudo-aneurysms (six); venous anastomotic occlusion (six); and arterial anastomotic occlusion (four). When compared with 211 patients with successful graft thrombectomy, those with unsuccessful thrombectomy were more likely to have a forearm graft (53% vs. 27%, p < 0.001), and more likely to have a lesion in the draining vein (42% vs. 10%, p < 0.001), the central vein (17% vs. 3%, p < 0.001), or within the graft itself (23% vs. 1%, p < 0.001). An unsuccessful percutaneous graft thrombectomy is more likely in forearm than in upper arm grafts, and more likely if there is a lesion in the draining vein, central vein, or within the graft itself. Surgical salvage of a thrombosed AV graft after an unsuccessful percutaneous intervention is rarely feasible. Most patients have a severe anatomic lesion that cannot be repaired, and require creation of a new vascular access.

Current management of vascular access

Optimizing vascular access outcomes remains an ongoing challenge for clinical nephrologists. All other things being equal, fistulas are preferred over grafts, and grafts are preferred over catheters. Mature fistulas have better longevity and require fewer interventions, as compared with mature grafts. The major hurdle to increasing fistula use is the high rate of failure to mature of newly created fistulas. There is a desperate need for enhanced understanding of the mechanisms of failure to mature and the optimal type and timing of interventions to promote maturity. Grafts are prone to frequent stenosis and thrombosis. Surveillance for graft stenosis with preemptive angioplasty may reduce graft thrombosis, but recent randomized clinical trials have questioned the efficacy of this approach. Graft stenosis results from aggressive neointimal hyperplasia, and pharmacologic approaches to slowing this process are being investigated in clinical trials. Catheters are prone to frequent thrombosis and infection. The optimal management of catheter-related bacteremia is a subject of ongoing debate. Prophylaxis of catheter-related bacteremia continues to generate important clinical research. Close collaboration among nephrologists, surgeons, radiologists, and the dialysis staff is required to optimize vascular access outcomes and can be expedited by having a dedicated access coordinator to streamline the process. The goal of this review is to provide an update on the current status of vascular access management.

Outcomes of thrombosed arteriovenous grafts: Comparison of stents vs angioplasty

The usual radiologic approach to thrombosed grafts is a combination of thrombectomy and angioplasty of the underlying lesion. However, the primary (unassisted) graft patency after thrombectomy is quite poor. We evaluated whether graft patency following thrombectomy is improved by placement of a stent in the stenotic lesion. Using a prospective, computerized vascular access database, we identified 14 patients with thrombosed arteriovenous (A-V) grafts treated with a stent at the venous anastomosis (stent group). The outcomes of these grafts was compared to those observed in 34 sex, age-, and date-matched control patients whose thrombosed A-V grafts were angioplastied (control group). Both groups were comparable in age, sex, race, diabetic status, graft age, and number of previous graft interventions. The immediate technical success, as indicated by the post-procedure graft to systemic pressure ratio, was similar in the stent and control groups (0.33+/-0.16 vs 0.41+/-0.17, P=0.14). The primary graft patency (time from thrombectomy to next intervention) was significantly longer for the stent group (median survival, 85 vs 27 days, P=0.02). Assisted or secondary patency (time from thrombectomy to permanent graft failure) was also longer for the stent group (median survival, 1215 vs 46 days, P=0.049). In conclusion, treatment of thrombosed grafts with a stenosis at the venous anastomosis with a stent results in longer primary and secondary graft survival, as compared to treatment with angioplasty. Stent placement may be a useful treatment modality in a subset of patients with thrombosed A-V grafts and stenosis at the venous anastomosis.

Percutaneous declotting of virgin femoral hemodialysis grafts

OBJECTIVE

The objective of our study was to evaluate outcomes of percutaneous declotting procedures in patients with prosthetic femoral dialysis grafts.

MATERIALS AND METHODS

A retrospective review of all pharmacomechanical femoral dialysis graft declotting procedures performed in our hospital between May 11, 1993, and April 30, 2003, was performed. A total of 110 procedures were performed on 25 patients (nine males, 16 females; age range, 17-80 years; mean age, 49 years) with 30 grafts.

RESULTS

Technical success was 97.3%. Using life table analysis, 30-day postinterventional primary patency was 72%, 90-day primary patency was 46%, 180-day primary patency was 25%, and 365-day primary patency was 4%. The 30-day secondary postinterventional patency was 93%, 90-day secondary patency was 86%, 180-day secondary patency was 76%, and the 365-day secondary patency was 51%. An average of 1.96 declotting procedures were performed per year of dialysis.

CONCLUSION

Percutaneous declotting of femoral hemodialysis grafts has technical success and patency rates similar to those for percutaneous declotting in the upper extremities. Results of this series exceeded criteria established by the National Kidney Foundation in the "Dialysis Outcome Quality Initiative" for immediate patency and unassisted 3-month patency.

Vascular Access in Hemodialysis: Issues, Management, and Emerging Concepts

This article (1) identifies the types of hemodialysis access, (2) summarizes the clinical standard of care for dialysis access grafts and fistulae, (3) describes the pathology and pathogenesis of venous stenosis in dialysis access grafts and fistulae, (4) tabulates avail-able therapies for hemodialysis vascular access dysfunction and speculates on the rea-sons for the lack of effective therapies, and (5) discusses the development and application of novel therapeutic interventions for this difficult clinical problem. The possibility that dialysis access grafts and fistulae could be the ideal clinical model for testing novel local therapies to block neointimal hyperplasia is discussed.

Advances in endovascular techniques to treat failing and failed hemodialysis access

During the decade since JEVT was inaugurated, we have witnessed the growing application of endovascular techniques for arteriovenous (AV) access in parallel with the evolution of endovascular therapy for arterial pathology. To date, few if any technologies have compared with balloon angioplasty for treating venous anastomotic stenosis, the most common cause of access failure. Only one device, which incorporates the principles of access graft design and self-expanding stent technology, has been uniquely conceived for this pathology. The encapsulated polytetrafluoroethylene stent-graft has achieved reasonable preliminary results, but randomized data is forthcoming. Technology to clear the clot from a thrombosed graft continues to evolve, but will never be as cost-effective as simple balloon thrombectomy. However, the pressure placed on providers to perform all percutaneous interventions and move away from open techniques continues to fuel interest in this component of treatment. Finally, the pursuit of a completely percutaneous AV access continues. As with endovascular procedures in general, whether or not the procedure is cost-effective or time-consuming seems to take a back seat to the all-percutaneous approach that so many seem to converge upon. Moreover, as most autogenous fistulas and AV grafts can be created with minimal incisions under local anesthesia, the pursuit of a completely percutaneous access system seems more like an academic exercise than a practical application of technology. We must try and avoid the tendency to "minimize invasiveness" with technology that is maximally intensive (and expensive), such as limiting ourselves to only percutaneous methods. Given the increasing pressure to have an all autogenous access program, current techniques that apply well in prosthetic grafts will need to be modified to accommodate the different biology of a native fistula. Clearly, the enlarging end-stage renal disease population will continue to provide endovascular specialists with clinically challenging problems requiring new and revolutionary technology.

Veterinary hemodialysis: advances in management and technology

Hemodialysis (HD) is a renal replacement therapy that can enable recovery of patients in acute kidney failure and prolong survival for patients with end-stage kidney failure. HD is also uniquely suited for management of refractory volume overload and removal of certain toxins from the bloodstream. Over the last decade, veterinary experience with HD has deepened and refined and its geographic availability has increased. As awareness of the usefulness and availability of dialytic therapy increases among veterinarians and pet owners and the number of veterinary dialysis facilities increases, dialytic management will become the standard of advanced care for animals with severe intractable uremia.

Management of thrombosed dialysis access: thrombectomy versus thrombolysis

More than 250,000 patients per year with end stage renal disease are maintained on long-term hemodialysis. Because of this large population, hemodialysis access procedures now account for a large percentage of operative interventions in the United States. Prosthetic arteriovenous access thrombosis is a frequent complication that occurs at a rate of 0.5 to 0.8 episodes per year and is a major source of hospital admissions, increasing hospital costs, patient morbidity, and physician frustration. Thrombosed grafts often require rescue procedures to extend the life of the graft and make the most use of the limited available access sites. Such salvage procedures of thrombosed prosthetic dialysis shunts may be performed with either conventional surgical or endovascular techniques. Many techniques for declotting have been used, including open surgical thrombectomy, percutaneous pharmacologic or mechanical thrombectomy, and pharmacomechanical techniques. Despite the various treatment options, no individual declotting modality has proven itself superior. Long-term patencies after a single revascularization procedure are meager, with a median of less than 90 days. This article will review prosthetic hemodialysis access graft declotting mechanisms and supporting literature.

Pharmacomechanical Thrombolysis of Dialysis Access Grafts Using the MTI Castañeda Over-the-Wire Brush Catheter and Reteplase

Pharmacomechanical thrombolysis (PMT) has emerged as an alternate treatment used in most patients presenting with a thrombosed hemodialysis graft. Although the gold standard, surgical revision of thrombosed hemodialysis grafts is reserved for those cases of recurrent thrombosis despite the use of percutaneous techniques and for complicated cases after PMT. Nevertheless, as for every other procedure, PMT has its own set of limitations and cost issues. New mechanical devices have begun to emerge on the market to help accelerate clot dissolution with or without thrombolytic medications. These devices have decreased the time required to lyse clot and decrease the overall cost of percutaneous treatment. This article describes the use of the Microtherapeutics, Inc. (MTI) Castañeda over-the-wire brush and our experience with this device in the treatment of the clotted hemodialysis graft.

Percutaneous treatment of complications occurring during hemodialysis graft recanalization

INTRODUCTION/OBJECTIVE

To describe and evaluate percutaneous treatment methods of complications occurring during recanalization of thrombosed hemodialysis access grafts.

METHODS AND MATERIALS

A retrospective review of 579 thrombosed hemodialysis access grafts revealed 48 complications occurring during urokinase thrombolysis (512) or mechanical thrombectomy (67). These include 12 venous or venous anastomotic ruptures not controlled by balloon tamponade, eight arterial emboli, 12 graft extravasations, seven small hematomas, four intragraft pseudointimal 'dissections', two incidents of pulmonary edema, one episode of intestinal angina, one procedural death, and one distant hematoma.

RESULTS

Twelve cases of post angioplasty ruptures were treated with uncovered stents of which 10 resulted in graft salvage allowing successful hemodialysis. All arterial emboli were retrieved by Fogarty or embolectomy balloons. The 10/12 graft extravasations were successfully treated by digital compression while the procedure was completed and the graft flow was restored. Dissections were treated with prolonged Percutaneous Trasluminal Angioplasty (PTA) balloon inflation. Overall technical success was 39/48 (81%). Kaplan-Meier Primary and secondary patency rates were 72 and 78% at 30, 62 and 73% at 90 and 36 and 67% at 180 days, respectively. Secondary patency rates remained over 50% at 1 year. There were no additional complications caused by these maneuvers.

DISCUSSIONS AND CONCLUSION

The majority of complications occurring during percutaneous thrombolysis/thrombectomy of thrombosed access grafts, can be treated at the same sitting allowing completion of the recanalization procedure and usage of the same access for hemodialysis.