Fatigue and in vivo validation of a peritoneum-lined self-expanding nitinol stent-graft.

PURPOSE: To assess the fatigue and in vivo performance of a new stent-graft incorporating bovine peritoneum lining that is designed for application in peripheral vascular occlusive disease. METHODS: Bovine peritoneum-lined stent-grafts were subjected to accelerated in vitro pulsatile fatigue and axial/torsional fatigue testing designed to simulate 10 years of physiological strain on the devices. At specified times the devices were evaluated for stent fracture, suture failure, or tissue tearing. Seven dogs underwent bilateral common iliac artery (CIA) balloon angioplasty injury with unilateral placement of the peritoneum-lined stent-graft. Angiography and intravascular ultrasound were performed prior to treatment, after treatment, and prior to sacrifice at 30 days. Vessels were perfusion fixed and histologically evaluated at 5 regions: above stent, proximal stent, mid stent, distal stent, and below stent. RESULTS: No evidence of stent, suture, or tissue failure was present during or after pulsatile and axial/torsional fatigue testing. At 30±0.3 days after implantation, all vessels were patent. The average lumen area at explantation across stented vessels was 25.45 mm(2). Lumen areas tended to be reduced above (23.57 mm(2)) and below (24.17 mm(2)) the stent. Lumen areas were consistent across stented regions at explantation (proximal stent 27.80 mm(2), mid stent 25.88 mm(2), and distal stent 25.81 mm(2)). The mean neointimal area in peritoneum-lined stents was 2.02±1.52 mm(2), with a neointima:media ratio of 1.03±0.50. These values were significantly lower in the above and below stent areas than in the stented regions, but there was no difference in either measure within the proximal, mid, or distal stent. CONCLUSION: The custom-designed peritoneum-lined stent-graft is promising for clinical peripheral applications due to its ability to resist relevant long-term physiological stresses and outstanding short-term patency rates in canine implantations.

Results from the Endologix PowerLink multicenter trial.

The Endologix PowerLink system is a one-piece, bifurcated, fully supported endoluminal graft for the treatment of abdominal aortic aneurysms (AAA). In a recently completed multicenter trial, the device has proven to be effective with a high technical success rate, low morbidity and mortality rates, and a mean decrease in AAA size over time. A 16-month mean follow-up has found low endoleak and migration rates. There have been no ruptures to date. The Endologix PowerLink device compares favorably with previously published results of other endoluminal grafts.

Evaluation of the Crux IVC Filter in an animal model.

PURPOSE: To determine the safety and performance of a new inferior vena cava (IVC) filter in an ovine model and evaluate the retrievability at 5 weeks. METHODS: The Crux Vena Cava Filter (VCF) is composed of 2 nitinol spiral supports with a polymeric filter suspended between them. Retrieval tails on each end facilitate retrieval. Twelve filters were placed in the infrarenal IVCs of 12 sheep. The vessels were imaged pre and post deployment to assess acute device performance. At 5 weeks, the vessels were re-imaged to evaluate continued device performance and vessel integrity. Nine of 12 filters were retrieved, and the animals were returned to their housing. The other 3 animals were sacrificed, and the filters and vessels were processed for gross and histological examination. At 9 weeks, 4 weeks after filter retrieval, vessel integrity of the remaining 9 animals was again assessed under fluoroscopy. The animals were sacrificed, and the IVCs were explanted for study. RESULTS: All 12 filters were implanted without complications at the intended deployment site and remained fixed over the implantation period. At 5 weeks, the filters intended for recovery were successfully retrieved, with a mean capture time of 9.6+/-13.7 minutes. There were no complications during the 4-week follow-up after filter retrieval. Post-retrieval imaging at 5 and 9 weeks showed no visible signs of vessel wall damage. Histological study of 3 explanted vessels and filters revealed slight neointima encapsulation of the filter elements and minimal incorporation. Gross examination of the post-retrieval vessel walls after the 4-week healing period showed minimal superficial vessel damage; histology showed minimal residual signs of hemorrhage, with little to no inflammatory reaction. CONCLUSION: The Crux VCF was deployed and safely retrieved without incident at 5 weeks in an animal model. There was no significant damage seen to the IVCs 1 month after filter retrieval.

Results of a multicenter trial for the treatment of traumatic vascular injury with a covered stent.

BACKGROUND: The safety and efficacy of endovascular treatment of arterial trauma using the Wallgraft Endoprosthesis was evaluated in a subgroup analysis of a prospective, multicenter, nonrandomized registry trial with a historical control to surgical management. Endpoints were exclusion success at procedure and at 12-months, primary patency and freedom-from-bypass at 12-months, and major adverse events. METHODS: Sixty-two patients were treated for arterial trauma from October 1997 to June 2003. The anatomic locations of the injuries were: iliac (33), subclavian (18), and femoral (11) arteries. Indication for treatment was perforation/rupture (33), acute pseudoaneurysm (10), AV fistula (16), and dissection (3). Exclusion and patency were assessed using arteriography, duplex ultrasound, CT, or MRA at postprocedure and 12-months. Major adverse event and mortality rates were compared with surgical intervention of arterial trauma using literature based objective performance criteria. RESULTS: The Wallgraft Endoprosthesis achieved postprocedure exclusion in 58 of 62 cases (93.5%). One-year exclusion rates were 91.3% iliac, 90.0% subclavian, and 62.3% femoral. One-year primary patency rates were 76.4% iliac, 85.7% subclavian, and 85.7% femoral. Freedom-from-bypass was achieved in 74.3% iliac and 100% femoral and subclavian injuries. The most common adverse events were stenosis (4.8%) and occlusion (6.5% early, 1.6% late). There were no device- or procedure-related deaths. Analysis of the literature revealed the rates and severity of complications are less than those associated with surgical repair. CONCLUSION: The Wallgraft Endoprosthesis for the treatment of traumatic arterial injuries offers a promising alternative to conventional operative repair with comparable patency and less major morbidity and mortality.

Explant analysis of AneuRx stent grafts: relationship between structural findings and clinical outcome.

OBJECTIVE: We reviewed the structural findings of explanted AneuRx stent grafts used to treat abdominal aortic aneurysms, and relate the findings to clinical outcome measures. METHODS: We reviewed data for all bifurcated AneuRx stent grafts explanted at surgery or autopsy and returned to the manufacturer from the US clinical trial and worldwide experience of more than 33,000 implants from 1996 to 2003. Devices implanted for more than 1 month with structural analysis are included in this article. Explant results were analyzed in relation to cause of explantation and pre-explant evidence of endoleak, enlargement, or device migration. RESULTS: One hundred twenty explanted stent grafts, including 37 from the US clinical trial, were analyzed. Mean implant duration was 22 +/- 13 months (range, 1-61 months). Structural abnormalities included stent fatigue fractures, fabric abrasion holes, and suture breaks. The mean number of nitinol stent strut fractures per explanted device was 3 +/- 4, which represents less than 0.2% of the total number of stent struts in each device. The mean number of fabric holes per explanted device was 2 +/- 3, with a median hole size of 0.5 mm(2). Suture breaks were seen in most explanted devices, but composed less than 1.5% of the total number of sutures per device. "For cause" explants (n = 104) had a 10-month longer implant duration (P =.007) compared with "incidental" explants (n = 16). "For cause" explants had more fractures (3 +/- 5; P =.005) and fabric holes (2 +/- 3; P =.008) per device compared with "incidental" explants, but these differences were not significant (P =.3) when adjusted for duration of device implantation. Among clinical trial explants the number of fabric holes in grafts in patients with endoleak (2 +/- 3 per device) was no different from those without endoleak (3 +/- 4 per device; P = NS). The number of fatigue fractures or fabric holes was no different in grafts in clinical trial patients with pre-explant aneurysm enlargement compared with those without enlargement. Pre-explant stent-graft migration was associated with a greater number of stent strut fractures (5 +/- 7 per device; P =.04) and fabric holes (3 +/- 3 per bifurcation; P =.03) compared with explants without migration. Serial imaging studies revealed inadequate proximal, distal, or junctional device fixation as the probable cause of rupture or need for conversion to open surgery in 86% of "for cause" explants. Structural device abnormalities were usually remote from fixation sites, and no causal relationship between device findings and clinical outcome could be established. CONCLUSIONS: Nitinol stent fatigue fractures, fabric holes, and suture breaks found in explanted AneuRx stent grafts do not appear to be related to clinical outcome measures. Longer term studies are needed to confirm these observations.