Nanotechnology Poised to Transform Fistula Creation
With the help of nanotechnology, interventionalists might soon be able to create an immediate and permanent percutaneous arteriovenous fistula that has patency and maturation rates comparable to or better than surgically created fistulas, a multicenter trial shows.
"Despite the arteriovenous fistula being the preferred route of access for hemodialysis, somewhere from 40% to 60% of patients still receive dialysis through a central venous catheter," said Jeffrey Hull, MD, from the Richmond Vascular Center in Virginia.
But "catheters have markedly higher morbidity and mortality rates than arteriovenous fistulas," he pointed out.
"So we developed an ultrasound-guided, percutaneous arteriovenous fistula for hemodialysis using tissue fusion, a nanotechnology that welds the collagen fibers of the artery and veins together in an immediate and permanent connection," he told Medscape Medical News. "The procedure takes, on average, 23 minutes."
The Ellipsys Vascular Access System, from Avenu Medical, was designed to replace the sutured anastomosis and create a fistula in the proximal radial artery, which is normally quite well preserved in patients requiring hemodialysis. By connecting the artery and the vein, surgeons create a low-resistance circuit, so that the rate of flow can be increased approximately 10 times.
"To do this procedure, patients are given either conscious sedation or a block. We access the cubital vein just below the elbow," Dr Hull explained. Operators travel down that vein, under ultrasound guidance, to the artery, and cross into the artery to engage the arterial wall.
A sheath is then introduced and a thermal resistance anastomosis device is advanced between the artery and the vein, where it clamps them together and fuses the tissue. When the jaws of the device close, the anastomosis is complete, the device is removed, and the puncture wound is covered with a bandage.
To assess the efficacy and safety of the device, Dr Hull, an interventional radiologist, and seven interventional nephrologists who had never created a fistula before conducted the procedure in office-based settings on an outpatient basis.
Dr Hull presented results from the intent-to-treat population — 107 patients who were on dialysis or about to start — here at Kidney Week 2017.
The anatomic requirements for the percutaneous approach are the same as for the surgical approach — an artery and a vein 2 mm in diameter — plus an outflow vein 2 mm in diameter where patients will receive dialysis is required.
"We had excellent technical success: 95% of patients got a fused anastomosis," Dr Hull reported.
The cephalic vein was the target vein for dialysis in almost three-quarters of the patients and, aside from a few exceptions, the basilica vein was the target for the rest.
"All patients required one of a number of maturation procedures," Dr Hull noted. "But these fistulas have all the benefits of a surgical proximal radial artery fistula, including preserving veins and multiple outflow options."
The primary efficacy end point — standard brachial artery flow of at least 500 mL/min and a target vein of at least 4 mm in diameter — was achieved in 86% of patients (P = .0001). There were no device-related serious adverse events.
Average blood flow at 90 days was 1000 mL/min. Average time to needle cannulation was 100 days, which is less than the standard 136 days with a surgically created arteriovenous fistula.
Cumulative patency was 87% at 12 months, which compares favorably with reports in the literature for surgically created arteriovenous fistulas.
Functional patency — a measure of how well the fistula works once a patient starts using it — was over 90%.
Other Advantages
One advantage of the new procedure, aside from little or no infection risk, is that patients with stage 4 chronic kidney disease are often reluctant to undergo the surgery they need to create an arteriovenous fistula.
"At stage 4, patients often don't feel that bad, so we think that patient acceptance of the percutaneous route will be better," Dr Hull said.
The other main advantage to the percutaneous approach is that patients are guaranteed a continuum of care.
"I do your mapping in the office with ultrasound, which tells me if you have the right kind of arteries and veins for the procedure, and then we schedule the procedure and release you for dialysis," he explained.
"Patients see the same person; they don't have to go to the hospital to see the surgeon or the cardiologist to get ready for surgery. We are cutting out a huge amount of cycle time for patients," Dr Hull pointed out.
A large proportion of dialysis patients have poor vascular circulation, which makes achieving a functional arteriovenous fistula difficult, said session cochair Janice Lea, MD, professor of medicine at Emory University in Atlanta.
