Covered stents were found to be effective in TASC C and D lesions in the findings of the COBEST randomised, multicentre trial comparing Atrium’s proprietary Advanta V12 balloon expandable covered stent to bare metal stents commonly prescribed for iliac occlusive vessel disease.
Patrice Mwipatayi, Royal Perth Hospital, Australia, reported the final results of COBEST to delegates at LINC 2010. To date, he said, there have been no trials comparing any type of stent in iliac occlusive vessel disease. One hundred and twenty three patients (167 limbs) were included in the study, with 83 limbs randomised to the Advanta V12 covered stent group and 84 to the bare metal stent group. The Advanta V12 covered stent group had significantly less binary restenosis than the bare metal stent group and greater freedom from stent occlusion compared to bare metal stents. At 18 months 95.4% of the Advanta V12 covered stent group were free of binary restenosis compared with 82.2% for the bare metal stent group. At 18 months, 94.2% of the covered stent group showed clinical improvement, compared with 76.7% in the bare metal stent group. There were fewer amputations and a lower complication rate in the covered stent group (4.8%) vs. the bare stent group (10.7%). No deaths were reported.
There were fewer patients with TASC D lesions in the bare stent group (7%) compared to the covered stent group (16.1%). However, TASC C lesions were equally distributed in both groups. There were also differences in restenoses locations, Mwipatayi reported, with restenosis predominantly occurring at the ends or outside the stent in the covered stent group but occurring within the stent in the bare metal stent group.
Concluding, Mwipatayi said in TASC C and D aorto-iliac occlusive disease, there was a difference in restenosis/freedom from occlusion. The Advanta V12 covered stent was clearly superior in these cases. However, there was no significant difference in overall patency rate with patients with type B lesions. Target lesion revascularisation was statistically different between the two groups with less binary restenosis at 12 and 18 months.
In a critical comment, Stefan Müller-Hülsbeck, radiologist, Kiel, Germany, pointed out that in the COBEST trial, double the patients in the TASC C and D groups were treated with the V12 stent compared to bare metal stents, which may have lead to a bias in the trial. Müller-Hülsbeck looked back to the COVENT trial, dealing with covered self-expanding stents, which had exceptional patency rates over six and 12 months (over 90%). “COBEST did even better,” Müller-Hülsbeck said, “But the difference may be due to the stent design.”
The ongoing, multicentre VIBRANT study is designed to compare the safety and patency of Gore’s ViaBahn endoprosthesis with a bare nitinol stent graft. One hundred and forty eight patients were randomly assigned to receive either the prosthesis or a bare nitinol stent in the superficial femoral artery. Gary Ansel, Riverside Methodist Hospital, Columbus, Ohio, USA presented the interim data at LINC 2010.
Ansel described the goals that led toward the conception of VIBRANT. The investigators aimed to gather “real world data on femoro-popliteal lesions, real world data on world device use, with stent overlaps allowed. We wanted core lab controlled data with longer term results included, clinical application of various duplex velocities and to evaluate potential predictors of patency,” he said. They treated claudicants with long diffuse disease and found it was clinically safe and effective at one year. They also found that stent grafts restenosed only at the edges, while bare metal stents restenosed diffusely. Primary patency appeared to be suboptimal, Ansel reported, but secondary patency was better, even in the diffuse lesions. “Even the more flexible stents had high fracture rate in the long lesions, and this may be associated with the vessel restenosis”, Ansel added. Fracture of the ViaBahn stent was very rare, and surveillance appears to be important.
Ansel emphasised that the average new lesion of those included in the study was around 19cm. Severe calcification was slightly higher in the stent graft group, at 62%. There was no difference in 30-day safety between the two groups. Looking at the one-year interim data, technical success was high in both groups, primary patency was 53% for the stent graft and 58% for the bare metal stent group. Freedom from target lesion revascularisation was 73% for the stent graft and 69% for the stent group. Secondary patency was close to 90% for both groups. Despite worries that stent grafts would have more acute limb ischaemia, this was not found in this trial.
The VIBRANT study is designed to take place over three years, with plans to report the primary patency rate data in 2011.