Effect of Stent Strut Interval on Neointima Formation After Venous Stenting in an Ovine Model.

OBJECTIVE: The impact of stent design on venous patency is not well studied. The purpose of this study was to investigate the effect of stent material burden on endothelial coverage of stented venous segments, which may contribute to vessel healing and patency. METHODS: Segmented self expanding bare nitinol stents (18 × 50 mm) comprising 5 mm long attached metallic rings separated by 2, 5, or 8 mm gaps were implanted in the inferior vena cava (IVC) of 10 sheep. These stents were designed and manufactured for the purposes of this study. At six, 12, and 24 weeks after implantation the animals were euthanised and the stented vessels harvested for histomorphometric analysis. Three sections from the metallic part as well as the gaps between the struts were reviewed for quantification of endothelialisation after six, 12, and 24 weeks. The intimal thickness over and between the stent struts was measured. The endothelialisation score (graded from 1 for complete luminal endothelialisation to 5 for absence of endothelial cells) was determined. RESULTS: All stents were successfully deployed and all 10 sheep survived until the time of harvesting. Macroscopic inspection after 24 weeks showed only partial endothelialisation over stents with 2 mm and 5 mm skipped segments, whereas the stents with 8 mm skipped segments were totally incorporated into the vein wall. After 24 weeks, the mean (SD) neointimal thicknesses over stent struts with 2 mm, 5 mm, and 8 mm skipped segments were 254.0 (51.6), 182.2 (98.1), and 194.6 (101.1) µm, respectively. Comparison of endothelialisation scores of stents over time showed statistically significantly better endothelialisation over stents with 8 mm gaps after 12 and 24 weeks. CONCLUSION: Stent designs providing structural support to veins with larger gaps between the scaffold material appear to lead to faster and more complete endothelialisation as well as a thinner intimal layer.

Iliocaval Skip Stent Reconstruction Technique for Chronic Bilateral Iliocaval Venous Occlusion.

PURPOSE: To report safety and efficacy of a skip stent technique using nitinol stents in patients with chronic bilateral iliocaval venous occlusions. MATERIALS AND METHODS: A retrospective analysis of 48 consecutive patients (32 men; mean age, 40.7 years; age range, 18-68 years) with chronic bilateral iliocaval obstructions treated using a nonoverlapping stent technique was conducted at a single center. None of the patients had May-Thurner syndrome. Iliocaval confluence was treated by deploying a nitinol stent in inferior vena cava (IVC) and a nitinol stent in each common iliac vein close to the caval stent. Patency of stents was assessed by duplex US at 2 weeks, 3 months, and 6 months and yearly thereafter. RESULTS: Recanalization and stent reconstruction was technically successful in 47 (98%) patients. The sinus-XL venous stent was used to treat IVC (95 [100%]). Common iliac and external iliac veins were treated with sinus-Venous and VENOVO stents (80 [83%] and 16 [17%] limbs, respectively). External iliac and common femoral veins were treated with sinus-Venous and VENOVO stents (83 [92%] and 7 [18%] limbs, respectively). Early thrombosis (< 30 days) of the iliac vein with stent occurred in 2 limbs. Cumulative primary, assisted primary, and secondary patency rates at 30 months were 74%, 83%, and 97%. CONCLUSIONS: Findings of this study suggest that leaving a skipped lesion at the level of iliocaval confluence may not adversely affect stent patency. Patency rates were comparable with other reported techniques of stent reconstruction at the level of iliocaval confluence.

Early clinical outcomes for treatment of post-thrombotic syndrome and common iliac vein compression with a hybrid Oblique self-expanding nitinol stent - the TOPOS study.

Background: Physical attributes of conventional stents used in the ilio-caval territory are often unfavorable in the presence of external compression close to the bifurcation. A hybrid oblique stent was developed for the treatment of common iliac vein compression without compromising the contralateral iliac vein inflow. Patients and methods: The ongoing international monitored TOPOS study enrolled 60 patients with post-thrombotic syndrome (PTS) treated with the sinus-Obliquus stent (optimed) and provisional distal stent extension. At 3-month follow-up, patency rates were obtained from duplex ultrasound, and clinical outcomes were assessed by the Villalta score, revised venous severity score (rVCSS), pain intensity score and chronic venous disease quality of life questionnaire (CIVIQ-20). Results: Mean age was 46.6 ± 14.9 years (68.3 % women). Mean number of implanted stents was 1.9 ± 0.6; 12 (20 %) patients received the hybrid oblique stent only. Forty-eight (80 %) patients had distal stent extension, and 42 (70 %) had stents below the inguinal ligament. Four (7 %) patients (all with stent extension) developed stent thrombosis. Primary and secondary patency rates at 3 months were 93.1 % (95 %CI 83.3-98.1 %), and 100 % (95 %CI 93.8-100 %), respectively. Improvement in Villalta, rVCSS, CIVIQ-20, and pain intensity score from baseline to 3-month follow-up was 6.9 ± 1.4 points (95 %CI 4.1-9.8; p < 0.0001), 3.4 ± 1.0 points (95 %CI 1.3-5.4 points; p < 0.01), 13.6 ± 2.7 points (95 %CI 8.2-19.0 points; p < 0.0001), and 2.4 ± 0.5 (95 %CI 1.4-3.3; p < 0.0001), respectively. At follow-up, 38 (63 %) patients were free from the PTS and none developed contralateral deep vein thrombosis. Conclusions: In patients with PTS and common iliac vein compression, treatment with the hybrid oblique stent with provisional stent extension resulted in high patency rates and improvement in PTS severity and quality of life at 3-month. Two-year results of TOPOS will assess the durability of this treatment.