Multi-Center Two-Year Patency Outcomes of Endovascular Arteriovenous Fistulas (endoAVF) Created with a 4 French System.

PURPOSE: To assess multicenter two-year patency outcomes of endovascular arteriovenous fistulas (endoAVF) created with the WavelinQ device. MATERIALS AND METHODS: Patients who had fistulas created at three centers from January 2018 to December 2020 were included in this retrospective study. In total, 112 patients underwent endoAVF creation [40 females, 72 males; mean age 60 years (range 18-88)]. Data collected included patient demographics, location of fistula creation, interventions performed, and brachial artery flows pre- and post-creation. Two-year cumulative patency, functional patency, and primary patency were assessed with Kaplan-Meier methodology. Factors affecting patency and maturation were examined using the Cox proportional hazards model. RESULTS: Technical success defined as angiographically successful endoAVF creation was 97.3% (109/112). In 11 patients the fistula did not mature for dialysis use. For 98 patients (87%) with endoAVF maturation, 12- and 24-month cumulative patency was 94.3% and 91.7%. Functional patency (two-needle cannulation) at 12 and 24 months was 95.7% and 92.7%, respectively. Median maturation time is 95 days (IQR 51-231 days). Male gender and brachial vein coiling at the time of endoAVF creation were predictive of maturation. There were 34 censored events (four patients undergoing renal transplantation; 30 patients deceased). Number of reinterventions per patient year was 0.73 where 43 were maturation procedures and 101 were maintenance procedures. One Grade 3 complication occurred of arterial access puncture site pseudoaneurysm. CONCLUSION: A high two-year functional and cumulative patency following endoAVF creation with the WavelinQ device was observed in this multicenter real-world experience Level of Evidence: 3 Level of Evidence III.

Two-Year Cumulative and Functional Patency after Creation of Endovascular Arteriovenous Hemodialysis Fistulae.

PURPOSE: To assess 2-year cumulative and functional patency of endovascular arteriovenous fistulae (endoAVF) created with the WavelinQ device. MATERIALS AND METHODS: Patients who had fistulae created at a single center from December 2019 to December 2020 were included in this retrospective study. Forty-three patients underwent endoAVF creation (22 females, 21 males). Data collected included patient demographics, location of fistula creation, interventions performed, and brachial artery flow before and after creation. Two-year cumulative and functional patency rates were assessed with Kaplan-Meier method, and variables that affected patency and maturation were examined using Cox proportional hazards model. RESULTS: Technical success was 95% (41/43), and in 4 patients, the fistula did not mature for dialysis use (9.7%). For the remaining 37 patients with endoAVF maturation, 25 had ulnar-ulnar fistulae, 10 had radial-radial fistulae, and 2 had interosseous artery-vein fistulae. Mean maturity time was 73 days, and brachial artery flow of >886 mL/min was predictive of maturation. Mean tunneled dialysis catheter removal time was 133 days. Number of interventions per patient-year was 0.38, where 8 were maturation procedures (5 vein elevations/transpositions and 3 coil embolizations) and 21 were maintenance angioplasties. Two-year cumulative/secondary and functional patency rates were 89.4% and 92.1%, respectively, with a mean follow-up of 665.7 days. Examined variables did not impact cumulative or functional patency. One adverse event was migration of coil to the heart, which was successfully retrieved at time of procedure. CONCLUSIONS: Two-year patency of 89.4% and functional patency of 92.1% were observed after endoAVF creation with WavelinQ device.

Outcomes of Wrist-Access Deep Venous Embolization Following Percutaneous Fistula Creation: A Two-Year Single Center Experience.

PURPOSE: During percutaneous arteriovenous (pAVF) fistula creation, deep venous embolization is recommended to encourage superficial venous flow development. The safety of crossing adjacent to the newly formed fistula from wrist venous access has not been established. The purpose of this study was to evaluate the safety and efficacy of antegrade deep venous embolization after creation of the pAVF. MATERIALS: A retrospective analysis was performed of all procedural data related to pAVF creation using the Wavelinq device from October 2019 to November 2021. Patient data from the hospital information systems were collected where the venous access for fistula creation was from the wrist-access (ulnar or radial vein) and where deep venous embolization was performed after forming the fistula and crossing adjacent to the anastomosis. Thirty-nine patients were identified. RESULTS: Twenty pAVFs were created from wrist ulnar vein access and 19 from radial vein access. The accessed veins were used for embolization of the brachial veins central to the newly created anastomosis. No pAVFs were lost by crossing adjacent to the anastomotic area to perform deep venous embolization at time of creation. There were no major complications, specifically bleeding, infection, pseudoaneurysm formation. Rates of minor complications consisted of two coil migrations to the right atrium requiring uneventful retrieval (5%). Follow-up ultrasound data showed no evidence of delayed complications. CONCLUSION: In this single center experience crossing alongside the anastomosis of a newly formed percutaneous fistula from an antegrade venous approach was safe with no risk of loss of the pAVF.

Effects of turbulent stresses upon mechanical hemolysis: experimental and computational analysis.

Experimental and computational studies were performed to elucidate the role of turbulent stresses in mechanical blood damage (hemolysis). A suspension of bovine red blood cells (RBC) was driven through a closed circulating loop by a centrifugal pump. A small capillary tube (inner diameter 1 mm and length 70 mm) was incorporated into the circulating loop via tapered connectors. The suspension of RBCs was diluted with saline to achieve an asymptotic apparent viscosity of 2.0 +/- 0.1 cP at 23 degrees C to produce turbulent flow at nominal flow rate and pressure. To study laminar flow at the identical wall shear stresses in the same capillary tube, the apparent viscosity of the RBC suspension was increased to 6.3 +/- 0.1 cP (at 23 degrees C) by addition of Dextran-40. Using various combinations of driving pressure and Dextran mediated adjustments in dynamic viscosity Reynolds numbers ranging from 300-5,000 were generated, and rates of hemolysis were measured. Pilot studies were performed to verify that the suspension media did not affect mechanical fragility of the RBCs. The results of these bench studies demonstrated that, at the same wall shear stress in a capillary tube, the level of hemolysis was significantly greater (p < 0.05) for turbulent flow as compared with laminar flow. This confirmed that turbulent stresses contribute strongly to blood mechanical trauma. Numerical predictions of hemolysis obtained by computational fluid dynamic modeling were in good agreement with these experimental data.

Blood soluble drag-reducing polymers prevent lethality from hemorrhagic shock in acute animal experiments.

Over the past several decades, blood-soluble drag reducing polymers (DRPs) have been shown to significantly enhance hemodynamics in various animal models when added to blood at nanomolar concentrations. In the present study, the effects of the DRPs on blood circulation were tested in anesthetized rats exposed to acute hemorrhagic shock. The animals were acutely resuscitated either with a 2.5% dextran solution (Control) or using the same solution containing 0.0005% or 5 parts per million (ppm) concentration of one of two blood soluble DRPs: high molecular weight (MW=3500 kDa) polyethylene glycol (PEG-3500) or a DRP extracted from Aloe vera (AVP). An additional group of animals was resuscitated with 0.0075% (75 ppm) polyethylene glycol of molecular weight of 200 kDa (PEG-200), which possesses no drag-reducing ability. All of the animals were observed for two hours following the initiation of fluid resuscitation or until they expired. We found that infusion of the DRP solutions significantly improved tissue perfusion, tissue oxygenation, and two-hour survival rate, the latter from 19% (Control) and 14% (PEG-200) to 100% (AVP) and 100% (PEG-3500). Furthermore, the Control and PEG-200 animals that survived required three times more fluid to maintain their blood pressure than the AVP and PEG-3500 animals. Several hypotheses regarding the mechanisms underlying these observed beneficial hemodynamic effects of DRPs are discussed. Our findings suggest that the drag-reducing polymers warrant further investigation as a potential clinical treatment for hemorrhagic shock and possibly other microcirculatory disorders.

Polyethylene glycol additives reduce hemolysis in red blood cell suspensions exposed to mechanical stress.

Mechanical damage to blood cells is of considerable concern in the development and use of circulatory assist devices and other blood contacting systems. Furthermore, hemodilution with saline, dextran, and other plasma expanders applied during extracorporeal circulation and dialysis increases red blood cell (RBC) susceptibility to the high shear stresses associated with these procedures. In this paper, we present polyethylene glycol (PEG) as a potential erythrocyte protective agent against mechanically induced cellular trauma. Bovine RBCs were subjected to mechanical stress induced by rolling stainless steel shots through RBC suspensions for a constant exposure time. The suspensions were prepared at a hematocrit of 30% in various media: PEG (20,000 molecular weight), autologous bovine plasma, Dextran 40 solution, and phosphate buffered saline (PBS). RBC suspensions in Dextran 40 were prepared at a viscosity similar to the PEG suspensions. We found the hemolysis level of RBCs suspended in plasma and in PEG solutions to be several times lower (p < 0.001) than in the Dextran and PBS solutions. No statistically significant difference was found between the hemolysis that occurred in suspensions of RBCs in autologous plasma and in 2.0% PEG solutions. Even PEG concentration as low as 0.1% reduced hemolysis by more than 40% compared with PBS or the same concentration of Dextran in suspension medium. Our data demonstrate the efficacy of PEG molecules in reducing mechanical trauma to erythrocytes and suggest the potential for using PEG in assisted circulation, dialysis, and other procedures where RBCs are subjected to extensive mechanical stress.

In vitro evaluation of hemolysis and sublethal blood trauma in a novel subcutaneous vascular access system for hemodialysis.

Hemodialysis requires reliable frequent access to the patients' vasculature, with blood flow rates of > 300 ml/min. Currently in the U.S. market, there are three types of hemodialysis access systems: the native arteriovenous fistula, generally using 15G needles; the synthetic arteriovenous (AV) graft, also generally using 15G needles; and the percutaneous catheter. Some of the problems with current vascular access technologies include insufficient blood flow, blood trauma, thrombosis, infection, cardiac load, and venous stenosis. The LifeSite System (Vasca, Inc.) represents an alternative for vascular access, and consists of a subcutaneous valve and 12F cannula accessed by a standard 14G needle. The LifeSite valve is implanted in the upper torso with the cannula generally entering the right internal jugular vein. The purpose of this study was to compare the LifeSite System with two known vascular access systems: the 10F dialysis catheter (Tesio-Cath, MedComp) and the 15G A.V. Fistula Needle Set (JMS Co., Ltd.) with regard to blood damage produced by these devices in use. Mechanical hemolysis and sublethal blood trauma were evaluated by means of in vitro blood pumping through a circulating loop incorporating a hemodialysis vascular access system. Sublethal blood damage was examined by using a hemorheologic assay that included parameters such as erythrocyte mechanical fragility, plasma total protein and fibrinogen concentrations, and blood viscosity. The tests demonstrated that, at both studied flow rates of 300 ml/min and 450 ml/min, the LifeSite produced lower hemolysis and less sublethal damage to blood than either the Tesio-Cath catheter or the A.V. Fistula Needle Set.