Low-Permeability Stent May Prevent AAA Sac Enlargement

By Jeff Evans 

WASHINGTON -- The low-permeability version of the Gore Excluder stent graft appears to reduce the volume and diameter of abdominal aortic aneurysms at 1 year significantly more than the older, more permeable model, according to results of a prospective study comparing the two.

The high rate of failure with the original Gore Excluder stent graft, in which the mean maximum abdominal aortic aneurysm (AAA) diameter increased at least 5 mm in 36% of patients after 5 years, prompted the manufacturer to add a new low-permeability layer between the device's expanded polytetrafluoroethylene layer and its reinforcing membrane, Dr. Manish Mehta said at the annual meeting of the Eastern Vascular Society.

In a series of 428 patients who received the new or the old Excluder for AAA treatment during 2001-2005 at the Institute for Vascular Health and Disease at Albany (N.Y.) Medical College, Dr. Mehta and his colleagues compared the outcomes of 214 patients who had CT angiography imaging results available 1 year later.

The CT angiograms revealed that 114 consecutive patients with the low-permeability stent had significantly greater declines in mean AAA volume than 100 consecutive patients with the original type of stent (163 mL to 141 mL vs. 156 mL to 160 mL). The percentage of patients with more than a 5% drop in AAA volume also was significantly greater in patients with the new stent (52%) than in those with the old stent (6%), reported Dr. Mehta, a vascular surgeon at the institute. In the 5-year trial with the original Excluder stent, 23% of patients experienced a decline in AAA volume of more than 5% after 1 year. Dr. Mehta said that he did not have an explanation for why a lower percentage of patients with the old Excluder stent had at least a 5% decline in AAA volume in the current study, noting that two observers performed all AAA measurements.

Compared with recipients of the old stent graft, significantly fewer patients with the new device had more than a 5% increase in AAA volume (12% vs. 2.6%).

A significantly greater percentage of patients with the low-permeability stent had at least a 5-mm decrease in maximum AAA diameter (25% vs. 8%). The mean preoperative maximum AAA diameter was similar among the patients with the new (5.4 cm) or old Excluder (5.3 cm).

"I think we need a lot longer studies and further analysis to really try to make some sense" of these data, Dr. Mehta said.