Prospective, randomized, multicenter clinical study comparing a self-expanding covered stent to percutaneous transluminal angioplasty for treatment of upper extremity hemodialysis arteriovenous fistula stenosis.

Use of a covered stent after percutaneous transluminal angioplasty (PTA) was compared to PTA alone for treatment of upper extremity hemodialysis patients with arteriovenous fistula (AVF) stenoses. Patients with AVF stenosis of 50% or more and evidence of AVF dysfunction underwent treatment with PTA followed by randomization of 142 patients to include a covered stent or 138 patients with PTA alone. Primary outcomes were 30-day safety, powered for noninferiority, and six-month target lesion primary patency (TLPP), powered to test whether TLPP after covered-stent placement was superior to PTA alone. Twelve-month TLPP and six-month access circuit primary patency (ACPP) were also hypothesis tested while additional clinical outcomes were observed through two years. Safety was significantly non-inferior while six- and 12-month TLPP were each superior for the covered stent group compared to PTA alone (six months: 78.7% versus 55.8%; 12 months: 47.9% versus 21.2%, respectively). ACPP was not statistically different between groups at six-months. Observed differences at 24 months favored the covered-stent group: 28.4% better TLPP, fewer target-lesion reinterventions (1.6 ± 1.6 versus 2.8 ± 2.0), and a longer mean time between target-lesion reinterventions (380.4 ± 249.5 versus 217.6 ± 158.4 days). Thus, our multicenter, prospective, randomized study of a covered stent used to treat AVF stenosis demonstrated noninferior safety with better TLPP and fewer target-lesion reinterventions than PTA alone through 24 months.

Prospective, Multicenter Clinical Study of the Covera Vascular Covered Stent in the Treatment of Stenosis at the Graft-Vein Anastomosis of Dysfunctional Hemodialysis Access Grafts.

PURPOSE: To study the use of the self-expanding Covera covered stent for the treatment of stenotic lesions at the venous anastomosis of hemodialysis arteriovenous grafts (AVGs). MATERIALS AND METHODS: A total of 110 patients with AVG venous anastomotic stenosis of ≥50% and access dysfunction were treated at 14 centers in the United States using percutaneous transluminal angioplasty followed by covered stent placement. The primary end points were 30-day safety and 6-month target lesion primary patency (TLPP). The secondary measures included access circuit primary patency, circuit cumulative patency, and the number of reinterventions through 24 months. RESULTS: Freedom from a primary safety event at 30 days was 96.4% while the 6-month TLPP rate was 70.3%. Seventy-five patients completed 24-month follow-up (68.2%). The TLPP rates were 54.2% at 365 days and 36.9% at 730 days while the access circuit primary patency rates were 16.7% at 365 days and 7.8% at 730 days (Kaplan-Meier analysis). The access circuit cumulative patency rates were 85.4% at 12 months and 73.6% at 24 months. The number of reinterventions to maintain the patency of the access circuit was 3.6 ± 3.1 at 24 months (1.6 ± 1.9 at the target lesion). CONCLUSIONS: Use of the Covera covered stent for hemodialysis graft-vein anastomotic stenosis provided a safe treatment option with a TLPP rate of 70.3% at 6 months and TLPP and cumulative access circuit patency rates of 36.9% and 73.6% at 2 years.

Evaluation of a Novel Spun Polytetrafluoroethylene Stent Graft in an Ovine External Iliac Artery Model.

PURPOSE: To evaluate the patency, cellular response, and thrombogenicity of a novel vascular stent graft. MATERIALS AND METHODS: Test stent grafts, incorporating luminal spun polytetrafluoroethylene and a nonpermeable fluoropolymer layer, and control stent grafts, constructed of permeable expanded polytetrafluoroethylene, were implanted in the external iliac arteries of 14 adult sheep with a median weight of 73.4 kg ranging from 60.6-86.8 kg for 30 (n = 4), 90 (n = 4), and 180 (n = 6) days. Angiographic patency and percent diameter stenosis (%DS) were assessed at termination. Excised stent grafts were fixed and stained for histopathologic analysis, including neointimal coverage (NC) assessment. RESULTS: Test and control device migration occurred in 1 animal, resulting in test device thrombosis. Both devices were excluded from analysis. Mean %DS in test and control implants was 4.6% and 8.2% (P = .563), 2.0% and 10.9% (P = .363), and 2.1% and 10.3% (P = .009) at 30, 90, and 180 days, respectively. Median NC scores at 30, 90, and 180 days were significantly lower in middle test device sections (P < .05). Proximal and distal test and control sections exhibited similar median NC scores at all time periods (P > .05). When present, test and control devices exhibited no neointimal detachment from the graft surface. Except for the migrated test device, no thrombus was observed. Transgraft cellular migration was absent in test devices but present in control devices with tissue accumulation around the stent struts. CONCLUSIONS: Test and control devices demonstrated excellent patency in an ovine model. Compared to the control, test devices exhibited significantly lower %DS values at 180 days and significantly lower mid-device NC scores at 30, 90, and 180 days.

ASDIN white paper: Assessment and management of hemodialysis access-induced distal ischemia by interventional nephrologists.

Although not common, hemodialysis access-induced distal ischemia is a serious condition resulting in significant hemodialysis patient morbidity. Patients with signs and symptoms suggestive of hand ischemia frequently present to the general and interventional nephrologist for evaluation. In order to care for these cases, it is necessary to understand this syndrome and its management. Most cases can be managed conservatively without intervention. Some cases requiring intervention may be treated using techniques within the scope of practice of the interventional nephrologists while other cases require vascular surgery. In order for the interventional nephrologists to evaluate and manage these cases in a timely and appropriate manner, practice guidelines are presented.

An Economic Analysis of Stent Grafts for Treatment of Vascular Access Stenosis: Point-of-Care and Medicare Perspectives in the United States.

PURPOSE: To conduct an economic analysis on the impact of increased stent graft (SG) use for treatment of arteriovenous graft (AVG) anastomotic stenosis or arteriovenous fistula (AVF)/AVG in-stent restenosis (ISR) from United States point-of-care (POC) and Medicare perspectives. MATERIALS AND METHODS: The analyses compared initial device and reintervention costs over 2 years between current and projected treatment mixes, including percutaneous transluminal angioplasty (PTA), bare metal stents (BMSs), and SGs. In projected scenarios, the absolute increase in SG use was approximately 3%. Costs included procedure reimbursement rates (Medicare) and device list prices (POC) for index procedures and reinterventions. Reintervention rates and types were informed by the RENOVA and RESCUE randomized trials. Reinterventions were primarily PTA only; however, stent use occurred a proportion of the time. BMS reintervention rates were assumed to be identical to PTA based on observational data. A population size of 1,000 patients was assumed. RESULTS: To the POC (n = 1,000), increased SG use was predicted to result in cost savings ranging from $4,106 to $34,420 for AVG anastomotic stenosis. For AVF/AVG ISR, increased SG use was predicted to result in either a cost increase of $17,187 or a cost savings of $13,159. To Medicare (n = 1,000), increased SG use was predicted to save costs for both populations, with savings ranging from $57,401 to $169,544. CONCLUSIONS: The use of SG for treatment of AVG anastomotic stenosis and AVF/AVG ISR appears to be economically favorable for POC providers and Medicare. Further data on reintervention rates are required from other SG trials to validate findings.

Training in dialysis access - charting future success.

PURPOSE: Medical education and training in dialysis access skills remains complex and inadequate as learners come from diverse backgrounds and from various specialties so that appropriate training is limited. As a result, a system of progressive education including live lectures, and hands on training has emerged, but there is controversy as to what constitutes the best educational model. METHODS: Presently there is no recognized or structured training in vascular access during residency or fellowships. Here we present a model of dialysis access training for beginner to advanced surgeons. RESULTS: A structured hands-on and didactic surgery training certification course consisting of a one week curriculum with 49 hours of ACCME credit hours has been in effect for one year. The learning impact and the performance outcome are high but with limited attendance capacity. Pre- and post- training test results attest to training effectiveness. To increase access, an off-site training curriculum has been initiated, entailing 1-2 days (8-15 credit hours) consisting of didactic lectures and surgical training. This teaching module has moderate learning impact for 50-100 attendees.Finally, a tiered, web-based training curriculum (10 ACCME credit hours) can accommodate an unlimited number of learners, but has a lower skills learning impact. CONCLUSIONS: The future dialysis access training must also accommodate learners with diverse individual backgrounds, and different levels of professional (skill) development. To be effective and accessible, a variety of educational system, for example on site or web based is needed. Collaborative initiatives for global dialysis access training are currently underway.

Training and certification in dialysis access.

Decreasing and eliminating the gaps in knowledge, skills, and effective communication are the mainstays for a successful dialysis access training program curriculum and at the core of the human factors training philosophy. Many of these skills can be learned in the simulation environment. Education and training will reduce gaps in knowledge and technical skills, before exposing patients to procedure-related risk. For dialysis access, a reliable workplace environment depends upon a culture where safety and accountability are balanced to recognize the human contribution to success or failure in the complex care of patients with end-stage renal disease. Rigorous testing and certification adds value to the participants and validates the training program.

Long-term follow-up of TIPS created with expanded poly-tetrafluoroethylene covered stents.

BACKGROUND: Transjugular intrahepatic portosystemic shunts (TIPS) created with expanded poly-tetrafluoroethylene-covered stents have largely replaced bare metal stents. Short-term shunt patency is typically assessed with protocol Doppler ultrasound (US), while little information exists with regard to long-term patency. AIM: We investigated the value of Doppler US in assessing TIPS patency as well as long-term clinical outcomes. METHODS: A retrospective analysis of 59 patients with covered stents used for TIPS between January 2001 and December 2011 was performed. RESULTS: Fifty-four patients had early (median 9 days) Doppler US follow-up. Seven of eight patients with an abnormal baseline US required stent revisions. None of the 46 patients with normal baseline Doppler US required revisions within the first 6 months; six of these patients subsequently had a portogram because of symptoms, but all TIPS were patent. Fifty-two patients survived for long-term (>6 months) follow-up, averaging 654 days and three Doppler US exams. Five of six patients with abnormal follow-up Doppler US required revisions, whereas none of the 46 patients with normal follow-up US had revisions. The recurrence of symptoms of portal hypertension and/or hepatic encephalopathy (HE) was low (4/52 patients). No significant predictors of long-term stenosis were identified. Post-TIPS HE was independent of pre-TIPS HE or Child-Pugh score. CONCLUSIONS: Short-term patency and that at approximately 2 years after TIPS placement was 87 and 77 %, respectively. We conclude that Doppler US at least 1 week after TIPS is warranted, but repeated Doppler US follow-up is probably not necessary in the absence of clinical symptoms.

Virtual reality: emerging role of simulation training in vascular access.

Evolving new technologies in vascular access mandate increased attention to patient safety; an often overlooked yet valuable training tool is simulation. For the end-stage renal disease patient, simulation tools are effective for all aspects of creating access for peritoneal dialysis and hemodialysis. Based on aviation principles, known as crew resource management, we place equal emphasis on team training as individual training to improve interactions between team members and systems, cumulating in improved safety. Simulation allows for environmental control and standardized procedures, letting the trainee practice and correct mistakes without harm to patients, compared with traditional patient-based training. Vascular access simulators range from suture devices, to pressurized tunneled conduits for needle cannulation, to computer-based interventional simulators. Simulation training includes simulated case learning, root cause analysis of adverse outcomes, and continual update and refinement of concepts. Implementation of effective human to complex systems interaction in end-stage renal disease patients involves a change in institutional culture. Three concepts discussed in this article are as follows: (1) the need for user-friendly systems and technology to enhance performance, (2) the necessity for members to both train and work together as a team, and (3) the team assigned to use the system must test and practice it to a proficient level before safely using the system on patients.

Successful Salvage of a Renal Allograft after Acute Renal Vein Thrombosis due to May-Thurner Syndrome.

A 68-year-old Caucasian female with a past medical history of a deceased donor kidney transplant four months prior was admitted with a two-day history of anuria and acute kidney injury. A renal ultrasound demonstrated thrombus in the transplanted kidney's renal vein that extended into the left iliac vein as well as into the left femoral venous system. Catheter-guided tissue thrombolytics were infused directly into the clot. Within twelve hours of initiating thrombolytic infusion, there was brisk urine output. Interval venography demonstrated decreasing clot burden. At the time of discharge her creatinine was 0.78 mg/dL, similar to her baseline value prior to presentation. The patient was noted to have May-Thurner syndrome on intravascular ultrasound (IVUS). Angioplasty followed by stent placement was done. Unique to our case report was the timing of the presentation of renal vein thrombosis (four months after transplant) and the predisposing anatomy consistent with May-Thurner syndrome, which was diagnosed with IVUS and successfully treated with local thrombolytics.

Salvage of angioplasty failures and complications in hemodialysis arteriovenous access using the FLUENCY Plus Stent Graft: technical and 180-day patency results.

PURPOSE: To review technical and 180-day clinical outcomes when stent grafts were used to treat dysfunctional arteriovenous (AV) hemodialysis access circuits. MATERIALS AND METHODS: The FLUENCY Plus Stent Graft (Bard Peripheral Vascular, Tempe, Arizona) was used to salvage percutaneous transluminal angioplasty (PTA) technical failures and complications in AV access circuits over 2 years. There were 106 patients treated with 138 stent grafts. Indications for stent graft use included residual stenosis after PTA (n = 81), extravasation after PTA (n = 22), early recurrent stenosis (n = 14), pseudoaneurysms (n = 4), and "other" (n = 4). Data were retrospectively analyzed for complications and outcomes. RESULTS: Technical success was achieved in all patients, and clinical success was achieved in 104 (98%) of 106 patients. At 180 days, postintervention primary patency (PIPP) was 47%, and postintervention secondary patency (PISP) was 79%. PIPP was 62% for autogenous fistulas (AVFs) and 35% for prosthetic grafts (AVGs) (P = .010). The 180-day PIPP for stent grafts 9-10 mm in diameter was 63% versus 38% for stent grafts 6-8 mm in diameter (P = .012). Implants that did not cross the elbow had a 180-day PIPP of 47% compared with 25% for implants across the elbow (P = .032). Technical complications were periprocedure AVG thromboses (n = 2), intraprocedural stent graft dislodgment (n = 1), venospasm (n = 2), and contrast agent-related hives (n = 1). One patient returned at 2 months with an infected AVG and stent graft in the outflow vein. CONCLUSIONS: The FLUENCY Plus Stent Graft was effective for maintenance of hemodialysis access circuit patency and was comparable or better than historical outcomes for PTA and bare stents. Factors that favored improved patency included larger diameter devices, use in AVFs, and avoiding placement across the elbow joint.

Traumatic occlusion and dissection of the main renal artery: endovascular treatment.

PURPOSE: To report experience with endovascular treatment of traumatic injuries of the main renal artery. MATERIALS AND METHODS: A retrospective review of traumatic injuries to the main renal artery was performed in three major trauma institutions. Eight patients (age range, 17-46 y; mean age, 27 y) presented with main renal artery occlusion (n = 7) or dissection (n = 1) after major blunt abdominal trauma. Associated injuries were present in the majority of patients. The mean time from injury to intervention was 5 hours (range, 2-8 h). RESULTS: Recanalization of the occluded renal artery with stent placement was successfully achieved in six patients. In two of the eight patients, interventions resulted in extravasation of contrast medium, and embolization of the main renal artery was performed. At follow-up 2-24 months after injury, four patients had kidney atrophy (two treated with embolization and two with stents), two had proven stent patency with functional kidneys, one was normotensive with unknown stent patency, and one was lost to follow-up. One of the patients with an occluded stent developed severe renal hypertension and required nephrectomy. CONCLUSIONS: The majority of occlusions and dissections of the main renal artery after major blunt abdominal trauma can be successfully treated with recanalization and stent placement. However, long-term kidney salvage is not always achieved, and there is a potential of development of renovascular hypertension, which may require late nephrectomy.

The safety and effectiveness of the retrievable option inferior vena cava filter: a United States prospective multicenter clinical study.

PURPOSE: To evaluate the safety and effectiveness of the retrievable Option inferior vena cava (IVC) filter in patients at risk for pulmonary embolism (PE). MATERIALS AND METHODS: This was a prospective, multicenter, single-arm clinical trial. Subjects (N = 100) underwent implantation of the IVC filter and were followed for 180 days; subjects whose filters were later removed were followed for 30 days thereafter. The primary objective was to determine whether the one-sided lower limit of the 95% CI for the observed clinical success rate was at least 80%. Clinical success was defined as technical success (deployment of the filter such that it was judged suitable for mechanical protection from PE) without subsequent PE, significant filter migration or embolization, symptomatic caval thrombosis, or other complications. RESULTS: Technical success was achieved in 100% of subjects. There were eight cases of recurrent PE, two cases of filter migration (23 mm), and three cases of symptomatic caval occlusion/thrombosis (one in a subject who also experienced filter migration). No filter embolization or fracture occurred. Clinical success was achieved in 88% of subjects; the one-sided lower limit of the 95% CI was 81%. Retrieval was successful at a mean of 67.1 days after implantation (range, 1-175 d) for 36 of 39 subjects (92.3%). All deaths (n = 17) and deep vein thromboses (n = 18) were judged to have resulted from preexisting or intercurrent illnesses or interventions and unrelated to the filter device; all deaths were judged to be unrelated to PE. CONCLUSIONS: Placement and retrieval of the Option IVC filter were performed safely and with high rates of clinical success.