Long-term resistance to fracture and/or corrosion of the nitinol wires of the talent stent-graft: observations from a series of explanted devices.

The biodurability of the Nitinol wires used in stent-grafts retrieved from reoperations and autopsy was analyzed to assess the possible causes of fracture and/or corrosion of the stents. The Nitinol wires of six explanted devices presented a corrosion-free surface after in vivo service. The drawing lines in the control wires were still present, but neither burrs nor flakes were observed. Pits and crevices were rare, but some shallow ones were present. Some abrasions of the surfaces of the Nitinol wires were also observed. The chemical composition of the explanted devices showed the presence of organic contamination that covered the thick layer of titanium oxide before reaching the Nitinol itself. The durability of the Nitinol employed in the manufacture of the Talent stent-grafts was confirmed; the results of this study show the Nitinol to be resistant to corrosion. We have also concluded that the fractures of the Nitinol wires in two devices were unique adverse incidents caused by compression and bending related to the sharp angle of the Nitinol wires.

Fatigue and/or failure phenomena observed in the fabric of stent-grafts explanted after adverse events.

In this study, we aimed to investigate changes to the fabric of Talent stent-grafts following implantation of aortic endografts and to determine the possible causes of fatigue and/or failure of the grafts. Six devices were explanted at reoperation (N=5) and autopsy (N=1). Selected segments were assessed nondestructively by gross observation and destructively by analyzing textile characteristics and chemical properties. All of the devices showed a 4/4 twill woven fabric of monofilament polyester. These devices, explanted at reoperation and autopsy, presented different levels of fatigue and/or failure. Numerous holes were found in the fabric of two devices. The minor damage caused by the passage of the sutures through the weave to fasten the Nitinol wires did not progress significantly over time. The sutures remained relatively intact, except for some distortions. The main failure mode was the abrasion of the yarns at the apices of adjacent Nitinol stents. In two devices, this abrasion resulted in fraying of the yarns and holes in the fabric tubes. This short series of explanted devices provides evidence of damage to polyester fabric used in aortic endografts and raises questions regarding their resistance to abrasion and the risk of endoleak associated with monofilament fabric yarn.

Absence of tissue ingrowth through the textile fabric in a series of explanted clinic stent-grafts.

Using the retrieved devices from one autopsy and five reoperations, the biocompatibility of explanted Talent stent-grafts was investigated to highlight the capacity of the fabric to act as an effective scaffold to regenerate a blood conduit. The autopsy device was encapsulated both internally and externally, but the capsules did not penetrate through the fabric structure. The reoperation devices showed discrete patches of compact fibrin and irregularly scattered mural thrombi. Positive staining of α-actin, tissue plasminogen activator (tPA), urokinase (uPA), urokinase receptor (uPAR), and urokinase inhibitors (PAI 1, PAI 2, PAI 3, and protease nexin), and D-dimer was more frequently identified in the autopsy sample than in the reoperation samples. This preliminary assessment shows that the stent-graft retrieved during autopsy was better healed than those explanted at reoperation.

Endovascular treatment for aortic disease: is a surgical environment necessary?

OBJECTIVE: Interventional radiologists, cardiologists, and vascular surgeons are capable of performing endovascular procedures successfully in their respective environments. Suboptimal anatomy or intraoperative technical problems can be encountered, and endovascular management alone is not always suitable. The objectives of this study were to define the incidence of adjunctive surgical techniques, to discuss the rationale for endovascular reconstruction in a well-developed surgical environment, and to assess the effect of experience on the incidence of adjunctive repair. METHODS: All primary aortic and aortoiliac elective, urgent, and emergent endovascular procedures performed at the Peter Lougheed Center and entered into a prospective database from May 25, 1999 to June 01, 2005, were reviewed. All adjunctive surgical techniques to enable stent deployment, enhance attachment site, or solve intraoperative difficulties were captured. The study period was divided into two time periods based on learning curve data to assess the effect of experience on the rate of adjunctive repairs. RESULTS: Four hundred thirty-eight patients underwent elective (80%), urgent (15%), or emergent (5%) endovascular procedures during the study period. These consisted of 101 thoracic and 337 abdominal operations, including the use of 13 fenestrated stents. One hundred thirty-nine patients (31.7%) required 180 open surgical procedures. Complete data were available for the entire patient cohort. The mean follow-up was 793.2 days (SD, 519.1 days). Procedures were necessary for vascular access, arterial dissection/rupture, limb ischemia, and enhancement/elongation of the stent attachment site. The persistent endoleak rate was 5.3%, the late rupture rate was 0.7%, the conversion rate was 1.6%, the 30-day surgical mortality rate was 3.2%, all-cause mortality to date is 7.3%, and the reintervention rate was 4.6%. There was no statistically significant effect of the learning curve on the incidence of surgical adjunctive procedures in either the thoracic group (11/26 [42.3%] for phase 1 vs 17/75 [22.6%] for phase 2) or the abdominal group (14/50 [28.0%] for phase 1 vs 97/287 [33.8%] for phase 2). Overall, 31.5% of patients required adjunctive surgical repair. CONCLUSIONS: Successful endografting requires endovascular expertise in addition to a well-developed surgical environment to increase applicability and decrease patient risk. Despite advances in endovascular technology, hybrid techniques will continue to be required to achieve good overall success rates.