Postinsertion iliac vein stent position and relationship to contralateral deep vein thrombosis after unilateral iliac vein stenting

OBJECTIVE: Nitinol stents designed for the treatment of iliac venous obstructive lesions were expected to improve shortcomings associated with previously available stents, including accuracy of deployment at the iliac confluence and insufficient stent expansion at the site of compressive obstruction. Comparative studies to measure these characteristics have not been reported. This study was performed to measure the position of venous stents after insertion and the effect of coverage of the contralateral iliac orifice, comparing nitinol venous (NV) stents to Elgiloy stents (Boston Scientific Corporation; WALLSTENT Endoprosthesis). METHODS: Patients with a history of iliac venous stent insertion where the proximal end of the stent was placed at the iliac confluence were identified retrospectively. Patients studied with a poststent computed tomography/magnetic resonance scan that allowed examination of the position of the previously placed stent were selected for study inclusion. Imaging was reviewed using three-dimensional reconstructions to determine the accuracy of stent deployment at the iliac confluence and the position of the stent relative to the contralateral iliac orifice. The incidence of residual iliac obstruction after stent insertion, and the incidence of poststent ipsilateral or contralateral thrombosis was determined. RESULTS: One hundred sixty-three patients with iliac vein stent were identified with poststent axial imaging with a median age of 61 years. In total, 66.3% patients were female, and 73.6% were Caucasian. Stent insertion was performed on the left side in 87.1% of cases. Stenting was performed with Elgiloy stents in 36.8% of cases and NV stents in 63.2% with median follow-up of 3.3 ± 3.4 years. In 64 cases (39.3%), stents completely extended across the entire (100%) contralateral iliac orifice, with no significant difference in incidence between Elgiloy stents (31.7%) and NV stents (43.7%). Persistent stent compression >25% at the confluence was seen in 9.8% of Elgiloy stents and 6.8% of NV stents. Contralateral iliac vein thrombosis after stenting occurred in 8.0% of patients at 5 years and was statistically more frequent in those where the iliac stent was placed completely across the contralateral iliac orifice (P = .046). On Cox regression adjusted for limb laterality, each 10 percentage-point increase in orifice obstruction was associated with a 61% increase in the hazard of contralateral deep vein thrombosis (hazard ratio, 1.61; 95% confidence interval, 1.20-2.15; P = .001). Stent type was not associated with the incidence of contralateral iliac deep vein thrombosis. CONCLUSIONS: Complete coverage of the contralateral iliac orifice was found in almost 40% of patients after unilateral iliac vein stenting. The use of NV stents did not result in a decreased incidence of contralateral coverage. Contralateral iliac vein thrombosis was more frequent after complete coverage of the contralateral iliac orifice suggesting that this should be avoided at the time of stent insertion. Long-term follow up is required to fully determine the incidence of this complication and its relationship to stent type or stent positioning.