Stent graft migration after XXXX repair: importance of proximal fixation.

@entity1 @entity135 @entity439
OBJECTIVE: We reviewed the incidence of stent-graft migration after @entity439 repair in a prospective multicenter trial and identified factors that may predispose to such migration. METHODS: All @entity1 who received treatment during the course of the multicenter AneuRx clinical trial were reviewed for evidence of stent-graft migration over 5 years, from 1996 to 2001. Post-deployment distance from the renal arteries to the proximal end of the stent graft and the proximal fixation length (length of the infrarenal neck covered by the stent graft) were determined in @entity1 for whom pre-procedure and post-procedure computed tomography scans were measured in an independent core laboratory. RESULTS: Stent-graft migration was reported in 94 of 1119 @entity1 , with mean time after device implantation of 30 +/- 11 months. Freedom from migration was 98.6% at 1 year, 93.4% at 2 years, and 81.2% at 3 years (Kaplan-Meier method). Subset (n = 387) analysis revealed that initial device deployment was lower in 47 @entity1 with migration, as evidenced by a greater renal artery to stent-graft distance (1.1 +/- 0.7 cm), compared with 340 @entity1 without migration (0.8 +/- 0.6 cm; P =.006) on post-implantation computed tomography scan. Proximal fixation length was shorter in @entity1 with migration (1.6 +/- 1.4 cm) compared with @entity1 without migration (2.3 +/- 1.4 cm; P =.005). There was significant variation in migration rate among clinical sites (P <.001), ranging from 0% to 30% (median, 8%), with a greater than twofold difference in migration rate between the lowest quartile (6%) and the highest quartile (15%) clinical sites. Univariate and multivariate analysis revealed that renal artery to stent-graft distance (P =.001) and proximal fixation length (P =.005) were significant predictors of migration, and that each millimeter increase in distance below the renal arteries increased risk for subsequent migration by 5.8% and each millimeter increase in proximal fixation length decreased risk for migration by 2.5%. @entity135 , neck diameter, degree of device oversizing, correct versus incorrect oversizing, device type (stiff vs flexible), placement of proximal extender cuffs at the original procedure, and post-procedure endoleak were not significant predictors of migration. Migration was treated with placement of extender modules in 23 @entity1 and surgical conversion in 7 @entity1 ; 64 @entity1 (68%) with migration have required no treatment. CONCLUSIONS: Stent-graft migration among @entity1 treated in the AneuRx clinical trial appears to be largely related to low initial deployment of the device, below the renal arteries, and short proximal fixation length. Significant variation in migration rate among clinical sites highlights the importance of the technical aspects of stent-graft deployment. Advances in intraoperative imaging and deployment techniques that have been made since completion of the clinical trial facilitate precision of device placement below the renal arteries and should increase proximal fixation length. Whether this, together with increased iliac fixation length, will result in lower risk for migration remains to be determined in long-term follow-up studies.
