Time-related alterations in shape, position, and structure of self-expanding, modular aortic stent-grafts: a 4-year single-center follow-up.

PURPOSE: To report the nature and ramifications of structural and positional changes over time in tube and modular bifurcated aortic stent-grafts.
METHODS: Two hundred ninety-one patients received endovascular aortic grafts (primarily Stentor/Vanguard) between August 1994 and August 1998. Follow-up surveillance (clinical and laboratory examination, biplanar noncontrast radiography, and contrast-enhanced computed tomography) has been maintained on all patients for 4 years. Changes in the configuration and position of endografts have been noted and their sequelae charted.
RESULTS: Three types of endograft shape changes have been documented: mild -- slight distortions visible on plain radiographs (n = 90, 31.0%), significant -- angulations reaching 60 degrees to 90 degrees (n = 65, 22.3%), and severe -- angulations > or = 90 degrees (n = 10, 3.4%). Changes in position never gave rise to late migration at the proximal attachment site, whereas at the distal ends, the endograft easily retracted from the iliac arteries (n = 8). Structural alterations (rupture of the stent frame, sutures, or fabric, and total graft disintegration) were more common in the original Stentor model. Shape, position, and structural alterations were mutually dependent and led to secondary endoleaks (n = 26) and graft limb thrombosis (n = 37). Late surgical conversion was necessary in 3 (1.0%) patients.
CONCLUSIONS: Tortuosity of the native vessels is a source of complication in long-term follow-up just as it is during implantation. Given the late appearance of complications in this patient cohort, it would seem that the durability of an endograft cannot be evaluated with < 3 years of follow-up.