Stent Grafts May Outperform Balloon Angioplasty

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Stent grafts may be more effective than balloon angioplasty in prolonging the function of stenosed arteriovenous access grafts and in lowering the likelihood of requiring additional interventions, according to a large prospective controlled study.

“This study should really change our perspective on grafts,” said lead investigator Ziv Haskal, MD, Chief of Vascular and Interventional Radiology at the University of Maryland Medical Center in Baltimore.

“For the first time, clinicians have compelling evidence that we can significantly improve outcomes over balloon angioplasty in this underserved and difficult-to-treat patient population. The durable benefit we observed in the trial, as demonstrated by superior patency and freedom from repeat interventions, strongly supports a fundamental change in how we care for hemodialysis patients.”

The study involved 13 sites and enrolled 190 patients (69 men and 121 women) with a mean age of 60 years. All patients had failing arteriovenous grafts. A total of 97 patients received stent grafts made of expanded polytetrafluoroethylene (the FLAIR Endovascular Stent Graft) and 93 underwent percutaneous transluminal angioplasty (PTA). The two groups were similar with respect to demographics or relevant medical history.

At six months, the treatment area of patients who received the stent grafts was more than twice as likely to be functioning compared with patients who received PTA alone (50.6% primary patency versus 23.3% for the PTA group), Dr. Haskal's group reported in The New England Journal of Medicine (2010;362:494-503).

The incidence of binary restenosis at six months was significantly greater in the balloon-treated group than the stent-treated group (78% vs. 28%). At 210 days, the treatment area in the stent group was far less likely to require additional interventions. Treating physicians had a nearly 94% success rate at implanting the stent grafts. The incidence of adverse events was similar with both approaches.

“What we've done is arguably supersede the results of surgery by improving the flow dynamics beyond those achievable with an operation,” Dr. Haskal said. “Stent grafts overwhelmingly performed better than balloon angioplasty for maintaining access in dialysis patients, providing superior patency and freedom from repeat interventions.”

Balloon angioplasty has been the “gold standard” for treating this patient population even though it was known for its poor durability that often led to repeat procedures. As many as 25% of U.S. end-stage renal disease (ESRD) patient hospital admissions result from complications related to vascular access, with an estimated cost of $1 billion per year.

These new findings are important because of the growing numbers of patients requiring dialysis in the United States. The numbers jumped by approximately 25% from 2004 to 2010 and the trend is expected to continue. More than 485,000 Americans currently are being treated for ESRD and among these patients 341,000 are dialysis patients.

“This is the result of six years of hypothesis-driven work and the findings are quite significant,” Dr. Haskal told Renal & Urology News. “The stent graft is encapsulated in the same material that is in the access graft. So it prevents the trans stent tissue growth that occurs with bare stents. But even more importantly, we change the surgical end-to-side anastomosis to an end-to-end one. The resultant laminar flow reduces shear stress and turbulence, and that dramatically mutes the stimulus to redevelop adjacent neo-intimal hyperplasia. Experimental models suggest that the unique fluted design that the majority of patients received even further magnifies this effect.”

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