Radiological Intervention to Maintain Vascular Access

Development and validation of a risk score to prioritize patients for evaluation of access stenosis

Background

Access flow dysfunction, often associated with stenosis, is a common problem in hemodialysis access and may result in progression to thrombosis. Timely identification of accesses in need of evaluation is critical to preserving a functioning access. We hypothesized that a risk score using measurements obtained from the Vasc‐Alert surveillance device could be used to predict subsequent interventions.

Methods

Measurement of five factors over the preceding 28 days from 1.46 million hemodialysis treatments (6163 patients) were used to develop a score associated with interventions over the subsequent 60 days. The score was validated in a separate dataset of 298,620 treatments (2641 patients).

Results

Interventions in arteriovenous fistulae (AVF; n = 4125) were much more common in those with the highest score (36.2%) than in those with the lowest score (11.0). The score also was strongly associated with interventions in patients with an arteriovenous graft (AVG; n = 2,038; 43.2% vs. 21.1%). There was excellent agreement in the Validation datasets for AVF (OR = 2.67 comparing the highest to lowest score) and good agreement for AVG (OR = 1.92).

Conclusions

This simple risk score based on surveillance data may be useful for prioritizing patients for physical examination and potentially early referral for intervention.

Time to thrombectomy is associated with increased risk for dialysis catheter placement

BACKGROUND

Arteriovenous dialysis access, fistulae (AVF) or grafts (AVG), are associated with significant rates of thrombosis. Timely thrombectomy may have a significant impact on immediate and long-term access survival. However, switching to a catheter is associated with higher rates of morbidity and mortality compared with those who have an AVF or AVG.

OBJECTIVES

The goal of this study was to evaluate whether time to thrombectomy increases the risk for loss of dialysis access and subsequent placement of a dialysis catheter at hospital discharge, at 6 months, 12 months, and data at any time after discharge.

METHODS

Using retrospective data, 444 patients were identified as having undergone thrombectomy for dialysis access dysfunction between January 2008 and April 2015, with 122 hospital admissions primarily for thrombectomy.

RESULTS

The mean age was 60.4 years, 65% were male, and 44.3% had an arteriovenous fistula as their dialysis access. The mean time to thrombectomy was 10.8 hours, and 14 patients utilised a catheter for haemodialysis as primary access upon discharge. After adjustment for prior access intervention, access type, and time to thrombectomy, the adjusted odds ratios (AOR) of a one-day delay in thrombectomy was associated with a twofold increase in requirement for catheter at discharge and at 6 months. This association remained present at any time after discharge.

CONCLUSION

In this study of patients cared for within an academic health system, a single day delay in thrombectomy nearly doubled the risk of needing a dialysis catheter at hospital discharge, 6 months, or any time after discharge.

Sentinel vascular access monitoring after endovascular intervention predicts access outcome

BACKGROUND AND OBJECTIVES

The vascular access pressure ratio test identifies dialysis vascular access dysfunction when three consecutive vascular access pressure ratios are >0.55. We tested whether the magnitude of the decline in vascular access pressure ratio 1-week post-intervention could alert of subsequent access failure.

DESIGN, SETTING, PARTICIPANTS, AND MEASUREMENTS

The retrospective study included all vascular access procedures at one institution from March 2014 to June 2016. Data included demographics, comorbidities, vascular access features, %ΔVAPR = ((Pre-Post)/Pre] × 100% assessed within the first 2 weeks post-percutaneous transluminal balloon angioplasty, time-to-next procedure, and patency. The log-rank test compared the area under the curve, receiver operating curve, Kaplan-Meier arteriovenous graft and arteriovenous fistula survival curves. A multivariable Cox proportional hazard (CP) model was used to determine the association of %ΔVAPR with access patency.

RESULTS

Analysis of 138 subjects (females 51%; Black 87%) included 64 arteriovenous fistulas with 104 angioplasties and 74 arteriovenous grafts with 134 angioplasties. The area under the receiver operating characteristic curve for fistula failure at 3 months was 0.59, with optimal screening characteristics of 33.3%, sensitivity of 56.1%, and specificity of 63.2%. Arteriovenous fistula with <33.3% decline compared to >33.3% required earlier subsequent procedure (136 vs 231 days), lower survival on Kaplan-Meier analysis (P = 0.01), and twofold greater risk of failure (P = .006). Area under the receiver operating characteristic for arteriovenous graft failure at 3 months had a sensitivity of 52.3% and specificity of 67.4%. Arteriovenous graft with a post-intervention vascular access pressure ratio decline of <28.8% also required earlier subsequent procedure (144 vs 189 days), lower survival on Kaplan-Meier (P = 0.04), and a 59% higher risk for failure. The area under the receiver operating characteristic curve for combined access failure (arteriovenous fistula + arteriovenous graft) at 3 months had an optimal cut-point value of 31.2%, a sensitivity of 54.6%, and a specificity of 63.1%. Access with a <31.2% drop had a 62% increase in the risk of failure (hazard ratio 1.62; confidence interval 1.16, 2.27; P = 0.005).

CONCLUSION

The magnitude of post-intervention reduction in vascular access pressure ratio provides a novel predictive measure of access outcomes.

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.

Long-term outcomes of bovine pericardial patch angioplasty for recurrent stenosis in vascular access: A UK single-centre experience

INTRODUCTION:

Stenosis of an arteriovenous fistula or arteriovenous graft for dialysis is a common problem. Stenosis may lead to a number of problems including failure of the fistula. Treatment of stenosis is commonly with percutaneous angioplasty or surgical patch angioplasty with autologous vein or synthetic graft or patch. Here we report the use of bovine pericardial patch angioplasty as an alternative mode of patch angioplasty when percutaneous intervention has failed.

METHODS:

Patients with fistulae treated with bovine patch angioplasty between 2013 and 2016 were identified from a prospectively maintained renal access database (Cyberren^®). Patient records were reviewed, noting type and location of access, patency, re-interventions and complications post bovine pericardial patch.

RESULTS:

A total of 40 patients were identified as having undergone bovine pericardial patch angioplasty between January 2013 and April 2016. The median time from fistula formation to bovine pericardial patch was 15 months (interquartile range (IQR): 5-43). Median duration of follow-up was 14 months (IQR: 5-18). Primary patency at 6, 12, 18 and 24 months was 91%, 66%, 61% and 54%, respectively. Secondary patency was 94%, 91%, 80% and 77% at the same time points, respectively. In total, 15 patients required 23 re-interventions post bovine pericardial patch. There has been no report of infection or aneurysm formation.

CONCLUSION:

Bovine pericardial patch angioplasty for recurrent stenosis in arteriovenous fistulae for dialysis access provides a robust alternative to other surgical patches with the added advantage of allowing early needling and relative resistance to infection. Rates of restenosis and failure post bovine pericardial patch are low.

A Hybrid Approach to Salvage a Failing Long-Standing Autogenous Aneurysmal Fistula in a Hemodialysis Patient

Very few studies have addressed the repair of autogenous and prosthetic-related false arteriovenous access (AVA) aneurysms in hemodialysis patients. Surgical management of complicated AVA-related aneurysms remains the gold standard method although covered stents have recently been introduced for the exclusion of such aneurysms, offering a minimally invasive therapy. In this paper, we describe a combination of open and endovascular repair for treating an anastomotic and a puncture-site aneurysm to salvage a failing long-standing autogenous radial-cephalic fistula in the wrist. Resection of the anastomotic aneurysm and reconstruction of the anastomosis proximally was initially performed. Via the first cm of the anastomosis, a Fluency® stent graft (SG) was inserted and it successfully excluded the mid-outflow vein false aneurysm. Such hybrid therapies may be the future of AVA revisions and this trend should not be overlooked by nephrologists and vascular surgeons.

Radiological Central Vein Treatment in Vascular Access

In the last decades, the percutaneous interventional approach for the treatment of central venous obstructions (CVO) has become increasingly popular as the treatment of first choice because of its minimal invasiveness and reported success rates. CVOs are caused by a diverse spectrum of diseases which can be broadly categorized into two principal eliciting genera, either benign or malignant obstructions. The large group of benign venous obstructions includes the increasing number of end-stage renal disease patients with vascular access related complications. Due to the invasiveness and complexity of thoracic surgery for benign CVOs, the less invasive percutaneous interventional therapy can generally be considered the preferred treatment option. Initially, the radiological intervention consisted of balloon angioplasty alone, subsequently additional stent placement was applied. This was advocated as either primary placement or secondary in cases of elastic recoil or residual stenosis after percutaneous transluminal angioplasty (PTA). The efficacy of angioplasty of CVO in patients with vascular accesses, either with or without stenting, has been addressed by various studies. Overall, reports indicate an initial technical and clinical success rate above 95% and satisfactory patency rates. However, systematic follow-up and frequent re-interventions are necessary to maintain vascular patency to achieve long-term success.

Post-operative arterio-venous fistula blood flow influences primary and secondary patency following access surgery

PURPOSE

Primary arteriovenous fistula arterio venous fistula (AVF) formation has proven to be the best and optimal vascular access for the majority of haemodialysis patients. At present there are limited data to suggest which haemodynamic parameters most correlate with the likelihood of early failure. The aim of this study is to identify the haemodynamic predictors of early failure, hence identify which fistulae may benefit from timely pre-emptive intervention.

MATERIAL AND METHODS

Retrospective analysis of data was performed of 201 patients undergoing native AVF creation over a one year period. Demographic details, co-morbidity, preoperative vessel calibre were collected. Flow was measured by duplex ultrasound post operatively.

RESULTS

Preoperative vein calibre (p = 0.01) and fistula flow (p < 0.001) positively affected primary patency. Age, gender, ethnicity, type of fistula, hypertension and preoperative arterial calibre did not influence outcome. Regression analysis showed that the strength of correlation between early postoperative fistula flow and patency decreased progressively with time. Six week flow predicts early, but not late, failure. ROC analysis identified 300 ml/min flow as the best predictor of patency. Fistulae with flow above 300 ml/min were more likely to remain patent over the next 12 months (p < 0.001, HR = 7.4).

CONCLUSION

Postoperative fistula flow of less than 300 ml/min identifies AVFs at high risk of early failure. These may be candidates for early intervention with balloon assisted maturation. The findings of this retrospective cohort study strongly support the need for a more robust prospectively designed trial identifying haemodynamic factors that can predict mid and long-term AVF patency.

Does pre- and post-angioplasty Doppler ultrasound evaluation help in predicting vascular access outcome?

BACKGROUND

Kidney Disease - Improving Global Outcomes (KDIGO) recommends post-percutaneous transluminal angioplasty (PTA) <30% residual stenosis (RS) and hemodynamic parameters improvement. Primary end point: how post-PTA access blood flow (ABF) improvement predicts vascular access (VA) outcome. Secondary: compare Doppler ultrasound (DU) and angiography diagnostic accuracy; determine how other factors predict outcome.

METHODS

Eighty patients. DU evaluation performed pre- and post-PTA. Several parameters recorded. Secondary patency verified after 6 months.

RESULTS

Initial ABF 537 ± 248 mL/min; final ABF 1013 ± 354 mL/min. Number and location of stenosis was highly correlated between DU and angiography (p<0.001); central vessels mismatching. First semester overall survival was 63%; significantly better for fistulas (76%) than grafts (51.7%), p 0.044. Final RS>30% associated to better survival, p 0.038. Initial ABF<500 mL/min and multiple stenosis did not affect outcome (p>0.05). A >2-fold ABF increase had no significant impact on fistulas (p>0.05) but was significantly associated with worst outcomes in grafts (23.1% vs. 73.5%, p 0.009). Grafts had lower survival (HR 3.3, p 0.034).

CONCLUSIONS

Although less accurate for central lesions, DU has a key role on VA surveillance, allowing a morphologic and hemodynamic assessment. Angioplasty is effective in preserving VA; however, it may increase restenosis due to accelerated neointimal hyperplasia. Current parameters are not useful. Trials addressing this issue are needed.

Arteriovenous graft for hemodialysis, graft venous anastomosis closure - current state of knowledge. Minireview

Backround. The use of artificial vascular grafts (arteriovenous graft, AVG) is indicated in patients in hemodialysis programs if the subcutaneous venous bed is exhausted or unsuitable for arteriovenous fistula (AVF) creation. The native fistula should be the hemodialysis access of first choice: AVF has better results in terms of function and potential complications. However, the use of AVG is necessary in some patients. In these patients, extensive clinical examination, color duplex sonography and angiography should be performed prior to indication. The technique of graft implantation requires respect for geometric relations for the graft anastomoses to minimize the formation of intimal hyperplasia mainly on the venous anastomosis. The main complications of AVG are stenosis on the venous anastomosis (VAG), causing closure of graft and graft infection. The cumulative function of AVG is 59-90% in the first year and 50-82% in the second year. Arteriovenous graft stenosis leading to thrombosis is a major cause of complications in patients undergoing hemodialysis. The purpose of this review is to summarise current knowledge of the diagnostics and treatment of graft thrombosis and discuss the issue in combination with relevant publications via Pubmed database.

CONCLUSION

The most frequent cause of failure of AVG for hemodialysis is stenosis and closure by VAG. AVG closure can be addressed surgically, endovascularly (amenable to thrombectomy by radiological or surgical means) and by hybrid performance.

Is Repeat PTA of a Failing Hemodialysis Fistula Durable?

Purpose. Our objective was to evaluate the outcome of percutaneous transluminal angioplasty (PTA) and particularly rePTA in a failing arteriovenous fistula (AV-fistula). Are multiple redilations worthwhile? Patients and Methods. All 159 stenoses of AV fistulas that were treated with PTA, with or without stenting, during 2008 and 2009, were included. Occluded fistulas that were dilated after successful thrombolysis were also included. Median age was 68 (interquartile range 61.5-78.5) years and 75% were male. Results. Seventy-nine (50%) of the primary PTAs required no further reintervention. The primary patency was 61% at 6 months and 42% at 12 months. Eighty (50%) of the stenoses needed at least one reintervention. Primary assisted patency (defined as patency after subsequent reinterventions) was 89% at 6 months and 85% at 12 months. The durability of repeated PTAs was similar to the durability of the primary PTA. However, an early primary PTA carried a higher risk for subsequent reinterventions. Successful dialysis was achieved after 98% of treatments. Nine percent of the stenoses eventually required surgical revision and 13% of the fistulas failed permanently. Conclusion. The present study suggests that most failing AV-fistulas can be salvaged endovascularly. Repeated PTA seems similarly durable as the primary PTA.

Pictorial essay: Interventional radiology in the management of hemodialysis vascular access - A single-center experience

Chronic kidney disease (CKD) is a worldwide public health problem and is associated with high morbidity and mortality. The majority of patients with CKD stage 5 (CKD-5), who cannot undergo renal transplant, depend on maintenance hemodialysis by surgically created access sites. Native fistulae are preferred over grafts due to their longevity. More than half of these vital portals for dialysis access will fail over time. Screening procedures to select high-risk patients before thrombosis or stenosis appears have resulted in aggressive management. These patients are referred for angiographic evaluation and/or therapy. We present the patterns of dialysis-related interventions done in our institution.

Surgical Treatment Modalities for Complicated Aneurysms and Pseudoaneurysms of Arteriovenous Fistulas

Purpose

This study was designed to determine the clinical presentation, characteristics, and management of aneurysm/pseudoaneurysm formation (APF) in dialysis access fistulas.

Methods

The treatment methods and outcomes of 31 patients who underwent surgery for APF in dialysis access fistulas were retrospectively reviewed over a 9-year period.

Results

We performed 1558 operations for arteriovenous fistulas (AVFs) between 2000 and 2009 at our centre. Of the 1558 operations, 35 were carried out for APFs (2.2%) on 31 patients. Thirty of these operations were restorative. Twenty-two (71%) of these patients had their original access done elsewhere, and all corrective surgeries were performed at our hospital. Approximately 52% of the subjects were female, with a mean age of 45.7 ± 17 years. The mean duration of end-stage renal disease was 70.2 ± 51.5 months. The mean number of AVFs per patient was 2.2 ± 1.5. Synthetic grafts were used in five patients (16.1%). Most of the procedures were left-sided (67.7%) and brachial-cephalic fistulas (48.3%). Among 31 complications, 22 were arterial/venous aneurysms (71%) and nine were pseudoaneurysms (29%). Fourteen patients (46.6%) were treated by excision of the aneurysm and primary suture repair. The post-intervention primary patencies for all revised APFs were 68%, 56%, and 52% at 1, 6, and 12 months, respectively. Dysfunction of AVF (16.1%) and bleeding (12.9%) were the most encountered complications after aneurysmectomy.

Conclusion

Reformative operations should be considered in cases of urgency and irresponsiveness to endovascular surgery rather than closing the fistulas directly, as it prolongs the duration of AVF patency.

Outcomes of AngioJet® Thrombectomy in Hemodialysis Vascular Access Grafts and Fistulas: Pearl I Registry

Purpose

Results are reported from the PEARL I Registry for procedures where a mid-length AngioJet catheter was used for thrombosed hemodialysis arteriovenous grafts and fistulae.

Methods

The PEARL I Registry was a prospective, multicenter, observational database collecting information on the AngioJet procedures for a variety of thrombotic conditions. Patient demographics, procedural information, outcome data, and safety information were collected through 3 months postprocedure on AngioJet procedures. This paper describes the data collected for subjects presenting with hemodialysis access thrombosis.

Results

A total of 72 (16%) of the 452 subjects enrolled in the PEARL 1 Registry had thrombosed hemodialysis access sites. Procedural success was reported in 66/72 subjects (92%); surgical interventions were required in 6/72 subjects (8%). There was a statistically significant improvement (p<0.0001) in vessel occlusion from baseline to final angiography. Eighty-eight percent of access sites were patent at the end of the procedure and 97% of vessels showed improved occlusion status of ≥1 grades. Among prosthetic grafts, 53% (20/38) remained patent at the 3-month follow-up, 18% (7/38) were restenosed, and 29% (11/38) rethrombosed. Among autologous fistulas, 86% (18/21) remained patent without intervention at the 3-month follow-up; 3 fistulas rethrombosed. Four subjects (5%) died; none of the deaths were considered related to the AngioJet device or procedure.

Conclusions

Outcomes from the PEARL I registry corroborate other studies of AngioJet thrombectomy and the overall literature of endovascular thrombectomy procedures. A high procedural success rates with acceptable near-term patency rates and low rates of adverse events are achieved with AngioJet thrombectomy.

The primary patency of percutaneous transluminal angioplasty in hemodialysis patients with vascular access failure

Background and Objectives

Dysfunction of arteriovenous fistulas (AVFs) and arteriovenous grafts (AVGs) contributes significantly to morbidity and hospitalization in the dialysis population. We evaluated the primary patency of AVFs following percutaneous transluminal angioplasty (PTA) in haemodialysis patients.

Subjects and Methods

We performed 231 interventions in 118 patients with a mean age of 62.1±12.9 years. We performed 122 interventions in 53 AVG patients (44.9%), and 109 interventions in 65 AVF patients (55.1%). If there was thrombosis of the vascular access, urokinase was administered and/or thrombus aspiration was performed. The stent was inserted when balloon dilatation did not expand sufficiently or elastic recoil occurred.

Results

For the 118 patients, the median patency time was 10.45±10.29 months at 92 months of follow-up. The primary patencies for stenotic AVFs at 6, 12, 24, 36, 48, and 60 months were 63.4%, 41.4%, 17.0%, 9.7%, 7.3%, and 2.4%, respectively. The primary patencies for AVGs at 6, 12, 24, and 36 months were 36.9%, 19.5%, 10.8%, 2.1%, respectively, and were obtained by means of the Kaplan-Meier analysis (log rank=6.42, p<0.05). The median patency time was 11.0 months and 4.45 months in the non-thrombus and thrombus groups, respectively. The complication rate was 1.73% (4/231); two cases of pseudoaneurysms and two cases of extravasation were detected. All therapy failures (5/231) occurred in thrombotic lesions of AVGs and were treated surgically.

Conclusion

PTA is an efficacious method for the correction of stenosis of AVFs for hemodialysis, thus prolonging the patency of the fistulas.