Salvage of thrombosed dialysis access grafts with venous anastomosis stents

BACKGROUND: Thrombosis of arteriovenous (AV) grafts caused by stenosis at the venous anastomosis is a well-described problem. Surgical thrombectomy and conventional angioplasty with mechanical thrombectomy have provided good success rates in achieving immediate graft patency but with generally dismal graft survival rates in the range of 11% to 36% at 6 months' follow-up. The role of intravascular stents in patients who have failed angioplasty or surgical revision at the venous anastomosis has not been fully elucidated, particularly in older grafts that have previously undergone multiple procedures. METHODS: In this series, 34 patients had self-expanding nitinol stents placed at the venous anastomosis following graft thrombectomy and angioplasty procedures. Patients were selected for stent placement if conventional angioplasty alone was unsuccessful due to immediate elastic recoil or residual stenosis. All patients were followed after stent placement and evaluated for duration of graft patency and need for repeated endovascular procedures. RESULTS: The average graft age at the time of stent placement was 17.9 months. Eight-eight percent of grafts were functioning at 6 months' follow-up, and 63% of the entire group had survived without the need for additional procedures. Among those with need for repeat interventions, 81% had new lesions outside of the stent, and 57% had new lesions within the stent. In 38% of cases, new stenoses were located both outside and within the stent. Among grafts no longer being used, only 19% of the time was it due to disease recurring within the stent. CONCLUSION: Polytetrafluoroethylene (PTFE) graft longevity is improved when venous anastomosis stenoses are treated with stents in selected cases of older grafts that would have normally undergone abandonment or surgical revision.     

Prospective randomized comparison of surgical versus endovascular management of thrombosed dialysis access grafts

Purpose: Salvage of thrombosed prosthetic dialysis shunts can be performed using surgical or endovascular techniques. A prospective randomized trial was designed to compare the efficacy of these two methods in restoring dialysis access function.Methods: One hundred fifteen patients with thrombosed dialysis shunts were randomized prospectively to surgical (n = 56) or endovascular (n = 59) therapy. In the surgical group, salvage was attempted with thrombectomy alone in 22% and with thrombectomy plus graft revision in 78%. In the endovascular group, graft function was restored with mechanical (82%) or thrombolytic (18%) graft thrombectomy followed by percutaneous angioplasty.Results: Stenosis limited to the venous anastomotic area was the cause of shunt thrombosis in 55% of patients, and long-segment venous outflow stenosis or occlusion was the cause in 30%. In 83% of the surgical group and in 72% of the endovascular group, graft function was immediately restored ( p = NS). The postoperative graft function rate was significantly better in the surgical group ( p < 0.05). Thirty-six percent of grafts managed surgically remained functional at 6 months and 25% at 12 months. In the endovascular group, 11% were functional at 6 months and 9% by 12 months. Patients with long-segment venous outflow stenosis or occlusion had a significantly worse patency rate than those with venous anastomotic stenosis ( p < 0.05).Conclusions: Neither surgical nor endovascular management resulted in long-term function for the majority of shunts after thrombosis. However, surgical management resulted in significantly longer primary patency in this patient population, supporting its use as the primary method of management in most patients in whom shunt thrombosis develops.     

Effect of tapered grafts on hemodynamics and flow rate in dialysis access grafts

AIM: Aside from the high incidence of venous stenosis, high-output failure and peripheral steal syndromes remain serious problems of vascular access. Meanwhile commercial tapered grafts are available to address this topic, but little is known about its effect neither on graft flow nor on hemodynamics. METHODS: Anastomotic models were constructed using a clear silicon elastomer. The arterial anastomosis was shaped in two ways: 1) like a direct connection of artery and 7-mm graft and 2) with a 4-mm diameter segment between artery and graft. Hemodynamic measurements were performed in a pulsatile flow circuit to simulate blood flow at physiological conditions. Flow patterns were obtained by direct dye injection. Additionally, the correlation between the length of narrow segment and mean arterial pressure was investigated. RESULTS: In all models using a 4-mm segment, the oscillating anastomotic vortex was disappeared. This vortex was shifted to the area behind the well-rounded expansions of the graft demonstrating a new separation region, but the flow direction was constant during the whole simulated cycle. At identical pressure rates and waveforms the length of narrow segment determined the graft flow rate directly (e.g., at mean pressure 100 mmHg, flow reduction up to 28% in 4-mm segments, and up to 55% in 3-mm segments). CONCLUSION: These findings indicate that taper is an important consideration in the design of vascular access grafts.     

Management of complications of endovascular dialysis access procedures

Endovascular procedures are becoming the standard of care for the management of hemodialysis (HD) vascular access dysfunction. As with any type of medical procedure, these techniques result in procedure-related complications. The expected frequencies are low. The most frequent procedure-related complication seen in association with angioplasty that dictates the need for intervention is tearing of the vein or vein rupture. The clinical significance of this complication is variable, ranging from none to disaster for the access. The difference lies in the severity of the tear. Management depends on the clinical presentation, ranging from symptomatic measures alone to the need to occlude the graft. Since endovascular thrombectomy is a combined procedure including angioplasty, all of the complications of that procedure can occur with this procedure as well. The major unique procedure-related complication requiring interventional therapy is the occurrence of a symptomatic peripheral artery embolus. This complication can generally be managed successfully by mechanical endovascular means. It is essential that the interventionalist be prepared to manage these complications appropriately when they are encountered.     

Novel repair of venous aneurysms secondary to arteriovenous dialysis fistulae

This report describes the surgical management of 12 hemodialysis patients with arteriovenous fistulae in whom non-infected, fusiform venous aneurysms developed that compromised access for dialysis. The venous aneurysmal changes were too extensive to permit excision and primary veno-venous anastomosis. To avoid the use of synthetic interpositional grafts, the venous aneurysms were left in situ and reduced in size to match the diameters of the veins entering and exiting the aneurysms. After decompression, the lumens of the venous aneurysms were reduced by firing staple lines along the longitudinal axes of the venous aneurysms and excision of the aneurysmal tissue anterior to the staple lines. Twenty-eight aneurysms were repaired by this method of reduction aneurysmoplasty, in 15 operations on 12 patients over the past 10 years. There were no wound infections or dehiscences and no bleeding or hematomas. After the operations, the arteriovenous fistulae were used continuously for hemodialysis until the patients died (7 patients for 36 months -/+ 28 SD), were lost to follow-up (1 patient at 30 days postoperatively), until the arteriovenous fistulae thrombosed following revision of the arteriovenous anastomosis (1 patient at 41 months postoperatively), or until the arteriovenous fistulae was ligated to relieve pain in the upper arm (1 patient at 6 months postoperatively). Two patients continue to use their arteriovenous fistulae until and including the time of this report at 10 and 11 months, respectively. Reduction aneurysmoplasty as described in this report offers an effective and low-risk option for the management of venous aneurysms secondary to arteriovenous fistulae in hemodialysis patients.     

Angioplasty for arteriovenous grafts and fistulae

The technique of percutaneous transluminal angioplasty (PTA) has become routinely used in the management of hemodialysis access dysfunction. It is used for the management of problems that affect both AVF and grafts. In the case of fistulae, it is used for treatment of early failure caused by juxta-anastomotic stenosis and late failure related to venous stenosis. In the case of AVGs, it is used primarily for the management of venous stenosis secondary to neointimal hyperplasia. The technique has been shown to be safe, easily performed, and effective. Details of the procedure, supplies used, complications and their management, and results are reviewed in detail.     

Fibrin sealant facilitates hemostasis in arteriovenous polytetrafluoroethylene grafts for renal dialysis access

A prospective randomized study was performed to evaluate the efficacy of fibrin sealant (FS) in patients undergoing upper-extremity polytetrafluoroethylene (PTFE) graft placement for dialysis. This procedure appears to be a reproducible and clinically relevant model for evaluating FS in vascular surgery. Consenting adult patients (n = 28) undergoing placement of a PTFE graft (6 mm) were randomized to either the treatment group using FS (Hemaseel APR, Haemacure Corp., Sarasota, FL) or control comparator groups (four) of bovine thrombin (T) (Thrombogen, GenTrac Inc., Middleton, WI), pressure (P), bovine thrombin (Thrombogen, GenTrac Inc.) -soaked cellulose sponges (TG) (Gelfoam, Upjohn Co., Kalamazoo, MI), or oxidized regenerated cellulose (S) (Surgicel, Johnson & Johnson, New Brunswick, NJ). All patients received heparin (3000 IU intravenous push) before placement of vascular clamps. The mean time to hemostasis was 29.3 seconds for FS, 147.4 seconds for T, 872.2 seconds for P, 346 seconds for TG, and 1044.5 seconds for S. There were no significant adverse events. FS appeared to be a superior hemostatic agent in these vascular procedures. No complications from FS were noted.     

True venous aneurysms and arterial "steal" secondary to arteriovenous fistulae for dialysis.

In patients requiring hemodialysis, arteriovenous fistulae may be created using autogenous vessels or prosthetic grafts. Complications of such operations include thrombosis, infection, venous hypertension, pseudoaneurysm, congestive heart failure, true venous aneurysms, and arterial "steal" syndrome. Of these the last two are the least common. On reviewing the English literature (Medline search: 1969-1991) we found only 8 reported cases of true venous aneurysms secondary to creation of an arteriovenous fistulae for dialysis. Hemodynamic assessment has shown that arterial "steal" is frequently present distal to an arteriovenous fistula. However, these patients rarely have ischemic symptoms. Over the last 7 years 236 patients had arteriovenous fistulae created for hemodialysis at our institution. Three of these patients (1.2%) developed true venous aneurysms. One of these 3 patients (0.4%) also had severe hand claudication due to arterial "steal". All of these patients were treated successfully without any complications. The etiology and various therapeutic options for these rare complications are discussed.     

Transluminal angioplasty of venous stenoses in polytetrafluoroethylene vascular access grafts

Since 1984, percutaneous transluminal angioplasty (PTA) utilizing high pressure balloon catheters has been used as an initial approach to restore patency of PTFE (polytetrafluoroethylene, GORE-TEX) hemodialysis vascular access grafts. Seventeen stenotic lesions detected by fistulogram underwent elective PTA. Twelve of these lesions were detected after thrombectomy and five were detected because of increased venous pressures during dialysis. Fourteen attempts at PTA were completely successful in restoring functional patency to the vascular graft. Three attempts were unsuccessful; two of these three grafts were subsequently repaired surgically. Venous stenoses that extended far greater than 6 cm were not considered for PTA. We conclude that PTA is a technique of promise in the non-surgical salvage of failing PTFE grafts. PTA can prolong the useful life of PTFE vascular access grafts and can be performed on an outpatient basis, eliminating the hospitalization that is usually required for surgical revision.     

A pig model of venous neoinitimal hyperplasia in polytetrafluoroethylene dialysis grafts

Purpose: Vascular access dysfunction is a major cause of morbidity and hospitalization in the hemodialysis population. In the United States, $1 billion per year is spent managing the vascular complications of hemodialysis. Venous neointimal hyperplasia (VNH), with subsequent venous stenosis and thrombosis at the graft-vein anastomosis, constitutes 75% of failed polytetrafluoroethylene vascular grafts. To understand both the pathogenesis and potential therapeutic interventions of VNH, we have validated a model of arteriovenous graft stenosis in pigs.Methods: Goretex loop grafts, 7 cm long × 4 mm ID, were placed bilaterally from the femoral artery to the femoral vein in 12 pigs, using standard operative vascular techniques. Grafts were harvested at 2-, 4-, 7-, 14-, and 28-day time points, and H&E-stained specimens were evaluated for neointimal encroachment into the graft. Immunohistochemistry was performed to demonstrate the expression of factor VIII, smooth muscle α-actin, and Ki67 (a marker of cell proliferation).Results: Venous neointimal hyperplasia was present postoperatively within 14 days at the graft-vein anastomosis and within the proximal vein. It was characterized by prominent angiogenesis within the thickened neointima, a perigraft macrophage layer, extracellular matrix components, and the proliferation of smooth muscle cells and myofibroblasts.Conclusion: The pathognomonic features of VNH visualized in the pig specimens are similar to those identified in human hemodialysis patients, which demonstrates the clinical relevance of this model. Each of these characterized lesions represents a potential site for novel prophylactic and therapeutic interventions, which will diminish the significant human and economic costs associated with dialysis graft dysfunction.     

Preexisting venous calcification prior to dialysis vascular access surgery

Vascular calcification is present in arterial vessels used for dialysis vascular access creation prior to surgical creation. Calcification in the veins used to create a new vascular access has not previously been documented. The objective of this study was to describe the prevalence of venous calcification in samples collected at the time of vascular access creation. Sixty‐seven vein samples were studied. A von Kossa stain was performed to quantify calcification. A semi‐quantitative scoring system from 0 to 4+ was used to quantify the percentage positive area for calcification as a fraction of total area (0: 0; 1+: 1–10%; 2+: 11–25%; 3+: 26–50%; 4+: >50% positive). Twenty‐two of 67 (33%) samples showed evidence of venous calcification. Histologic examination showed varying degrees of calcification within each cell layer. Among the subset of patients with calcification, 4/22 (18%), 19/22 (86%), 22/22 (100%), and 7/22 (32%) had calcification present within the endothelium, intima, media, and adventitia, respectively. The mean semi‐quantitative scores of the 22 samples with calcification were 0.18 ± 0.08, 1.2 ± 0.14, 1.6 ± 0.13, and 0.36 ± 0.12 for the endothelium, intima, media, and adventitia, respectively. Our results demonstrate that vascular calcification is present within veins used to create new dialysis vascular access, and located predominately within the neointimal and medial layers.     

Tapered arteriovenous grafts do not provide significant advantage over nontapered grafts in upper extremity dialysis access

ObjectiveAlthough tapered dialysis access grafts are often used in an effort to prevent ischemic steal, their efficacy is uncertain. Our goal was to use real-world data to assess the performance of these grafts with respect to primary patency and ischemic steal.MethodsThe Vascular Quality Initiative database was queried from 2010 to 2017 for all patients undergoing tapered dialysis grafts in the upper arm. Multivariable analysis was performed to analyze primary patency, ischemic steal, and reinterventions.ResultsWe identified 3608 patients who received dialysis access grafts, 1473 tapered grafts and 2135 nontapered grafts. The mean age was 64.8 years, and 43.4% of the patients were male. Tapered grafts were used more often in female patients (60.5% vs 54%), nonwhite patients (53.3% vs 47.7%), patients with no previous access (28% vs 26.3%), grafts with an antecubital brachial artery origin (50% vs 44.4%), and grafts with an antecubital cephalic vein target (7.4% vs 3.7%; P < .05). Three-month outcomes between tapered and nontapered grafts were similar for wound infection (1.4% vs 2%; P = .31), ischemic steal (4.1% vs 4.6%; P = .58), and arm swelling (3.5% vs 2.9%; P = .38). Multivariable analyses revealed that in comparison to nontapered grafts, tapered grafts did not affect primary patency rates (hazard ratio [HR], 1.17; 95% confidence interval [CI], 0.96-1.42; P = .11), ischemic steal (HR, 1.03; 95% CI, 0.64-1.65; P = .92), difference in endovascular reintervention (HR, 1.08; 95% CI, 0.74-1.16; P = .5), or operative reintervention (HR, 1.25; 95% CI, 0.86-1.82; P = .24).ConclusionsTapered grafts for upper extremity arteriovenous access do not affect primary patency, development of steal, or endovascular reintervention in comparison to nontapered grafts. Our findings do not support the routine use of these grafts in dialysis access to improve outcomes.