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Experimental Nitinol Stent Improves Haemodialysis Graft Access: Presented at SIR

By Peggy Peck

SALT LAKE CITY, UT -- April 3, 2003 -- An experimental stent appears to work better at opening blocked haemodialysis access grafts than balloon angioplasty. In a small prospective study, a nitinol Smart stent maintained median primary patency of polytetrafluorethylene (Teflon) grafts for 325 days compared to 130 days for patients treated with balloon angioplasty alone. Stenosis was also significantly reduced in patients who received stents, 7% compared to 15% (p=0.006).

Patrick V.M. Vogel, MD, of Carmichael, CA, USA presented these results March 29^th at the 28^th Annual Scientific Meeting of the Society of Interventional Radiology.

Compromise of vascular access by stenosis or thrombosis is one of the major problems facing haemodialysis patients. Placement of a stent is one strategy being tested for improving vascular access. Nitinol is a flexible nickel-titanium alloy that retains its shape after deformation and is used for many kinds of biomaterials.

The Smart stent was used under a US Food and Drug Administration investigational device exemption. Indications for stent placement in patients who failed angioplasty were residual stenosis of more than 30% following angioplasty, rapidly recurrent stenosis, a mid-graft systolic pressure ratio of more than 0.4 with a localized venous obstruction, or venous rupture.

The endpoint of primary patency of the treated obstruction was defined as functioning access without elevated venous pressure, arm swelling, recurrent thrombosis or low access flow.

Seven patients received stents for post-angioplasty stenosis of more than 30%, 3 for rapidly recurrent peripheral venous stenosis, and 1 for venous rupture following angioplasty.

Factors such as graft age or incidence of diabetes did not differ between the angioplasty and stent groups, but upper arm grafts were positively associated with stenting. The treated stenosis was at the venous anastomosis in 96% of patients retreated with angioplasty and 91% of patients given stents.

Vogel said stented lesions were longer and had more severe stenosis than lesions that responded to angioplasty—3.3 cm versus 2.2 cm, and 74% blocked versus 65%.

There was no significant difference in mid-graft systolic pressure between the two interventions. Vogel said this could reflect the small numbers in this ongoing trial--only 11 of 36 patients with dysfunctional Teflon grafts received stents.


[Study title: SMART Stent Use Following Angioplasty Failure in Dialysis Access Venous Stenoses. PVM Vogel. Abstract: 79]

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