The NEAT (Novel endovascular access trial) study demonstrates the possibility of using a catheter-based system to create an endovascular arteriovenous fistula (endoAVF) in patients requiring haemodialysis as a first-line reliable option, without the need for open surgery, writes Dheeraj Rajan, Toronto, Canada.
With around three million patients receiving haemodialysis annually, reliable vascular access is mandatory to facilitate adequate therapy. An arteriovenous fistula is the
preferred vascular access for these patients. However, high thrombosis rates, access maturation failure with multiple interventions, and patient refusal plague access usability. Failing access is the leading cause of hospitalisation for patients undergoing haemodialysis and is responsible for US$2.9 billion in annual costs.
The everlinq endoAVF system (TVA Medical) creates a fistula without open surgery or vessel dissection, eliminating trauma to the vessels to minimise the neointimal hyperplasia responsible for failures with surgical fistulas. The procedure uses two magnetic catheters placed in an artery and adjacent vein (venae comitantes) in the ulnar artery/ulnar vein or radial artery/radial vein. When the catheters are inserted, the magnets align the catheters holding the vessels together. Then, radiofrequency energy is delivered from the venous catheter in the vein to the artery, creating a side-to-side anastomosis and the catheters are removed. As a final step, the entry brachial vein is embolised to divert flow to the superficial veins, which are later cannulated for haemodialysis.
NEAT is a prospective, single-arm, multicentre study designed to evaluate the safety and efficacy of the everlinQ endoAVF system to create an endoAVF in patients with end-stage renal disease who require haemodialysis vascular access. The main inclusion criteria were: target vein and artery diameters ≥2mm; life expectancy >1 year; absence of central or ipsilateral upper extremity venous stenosis; or ineligibility for a distal forearm fistula. Patients were followed for 12 months with duplex ultrasound and physical exam. Key outcomes included procedural success, percentage suitable for dialysis by physiologic criteria (brachial artery flow >500ml/min and vein diameter >4mm), functional usability (received dialysis with two-needle cannulation of endoAVF for at least 2/3 of sessions over four weeks), primary, secondary and functional patency, and adverse events (as adjudicated by an independent Clinical Events Committee).
Eighty patients were enrolled at nine centres in Canada, Australia and New Zealand (20 roll-in and 60 participants in the evaluable cohort). EndoAVF was created in 98% of participants; 91% were physiologically suitable for dialysis within three months with mean brachial artery flow of 918ml/min and vein diameters 5.2mm in cephalic, 5.9mm in median cubital and 6mm in basilic veins. EndoAVF functional usability was 67% in participants who received dialysis, with only 12% of usable endoAVF requiring an intervention to achieve usability. The 12-month primary and cumulative patencies were 68.6% and 83.5%, respectively, with functional patency of 89.4%. There was one serious device-related event that occurred in one patient (1.7%). When compared to a propensity-score matched Centers for Medicare and Medicaid cohort of surgical AVF, the endoAVF required fewer post-creation procedures (0.6 per patient year vs. 3.4), with fewer event rates for angioplasties, thrombectomies, catheter placements, arteriovenous graft creations, new surgical AVF creations, and vascular access-related infections.
The NEAT study demonstrates the possibility of the endoAVF as a first-line reliable AVF creation option for patient without the need for open surgery. Given the cutoff 2mm vessel sizes and unique locations of the endoAVF, more patients may be candidates for the procedure compared to those meeting surgical criteria. Furthermore, the roll-in patient group demonstrated that a physician with endovascular skills can easily learn the procedure. Most importantly, outcomes of endoAVF are higher when compared to other reported studies for surgically created fistulas: maturation (91% vs. 53–76%) and patency (83.5% vs. 68–72%) with a statistically lower post creation intervention rate. These clinical outcomes may translate into lower long-term costs, improved patient acceptance and a fundamental change in current standards of practice.
Dheeraj Rajan is head and professor, Division of Vascular and Interventional Radiology, Department of Medical Imaging, University of Toronto, Toronto, Canada. He is an equity holder at TVA Medical.
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