Because of concern about the percentage of enlarging abdominal aortic aneurysms (AAAs) after endovascular repair with the Excluder device (W.L. Gore & Assoc, Inc, Sunnyvale, Calif), the graft material was modified to reduce its permeability and released for commercial use in mid-2004. We studied all AAA repairs with Excluder endografts performed at our institution, including the original-permeability (OP) version (n = 99) and the low-permeability (LP) version (n = 48).Methods:
All patients were followed up with serial computed tomography (CT) angiography and three-dimensional (3D) reconstruction. Morphologic measurements, including AAA diameter and 3D volume, were prospectively entered into a database to evaluate changes in AAA size over time. Owing to the length of available follow-up for the LP version, the primary end point was AAA size change at 6 and 12 months, evaluated by Mann-WhitneyUtest for unpaired samples.Results:
Preoperative and postoperative anatomy was similar in the two groups, including AAA diameter (OP, 5.6 ± 1 cm; LP, 5.8 ± 2 cm;P= .3), aortic neck length (OP, 21 ± 1 mm; LP, 22 ± 2 mm;P= .9), postoperative aortic seal zone (OP, 18 ± 1 mm; LP, 16 ± 1 mm,P> .1) and iliac seal zone (OP, 33 ± 1 mm, LP 31 ± 1 mm,P= .2). The rate of sac shrinkage differed significantly. Orthogonal diameter measurements showed a significant difference in the rate of shrinkage by 12 months postoperatively (OP, −2.1 ± 1 mm; LP, −5.1 ± 1 mm;P= .01). By 3D volume, the rate of shrinkage was considerably different between the two groups at both 6 and 12 months (12 months: OP, −6% ± 1%; LP, −20 ± 4%;P= .0006). There was no enlargement by diameter in either group at 6 or 12 months postoperative. By standard volume criteria, however, 12 of 99 patients in the OP group and one of 48 patients in the LP group had significant AAA enlargement ≤12 months (P= .04). Of these, four of 12 patients in the OP group had enlargement without apparent endoleak, even on delayed-contrast CT. The remainder had persistent type II endoleaks (8/12 in the OP group and 1/1 in the LP group). Multivariate analysis revealed graft permeability (P< .0001) and endoleak (P< .0001) as independent factors in aneurysm size change. In the OP group long-term, the average AAA enlarged at later time points compared with the prior scan: 24 months, −0.2%; 36 months, +0.2%; 48 months, +2%; and 60 months, +2% (P< .0002).Conclusions:
In early follow-up, the low-permeability Excluder device is associated with a significantly greater aneurysm shrinkage rate than the original version. Clinically important enlargement also appears significantly different within 1 year of implantation. Despite these promising results, longer follow-up is needed to determine whether these differences will persist.