CIRSE 2019: New data show high chronic outward force causes significantly more restenosis

Pulsar stent (Biotronik)

Twelve-month results of the BIOFLEX COF trial have demonstrated that the implantation of stents with low chronic outward force (COF) was associated with less neointimal hyperplasia, consequently resulting in less restenosis. Patients treated with Biotronik’s low COF, Pulsar stent, showed significantly lower restenosis rates than patients treated with the high COF, LifeStent implant.

Martin Funovics, Medical University of Vienna, Austria, presented the full-cohort primary endpoint data at the Annual Scientific Meeting of the Cardiovascular and Interventional Radiological Society of Europe (CIRSE 2019; 7–11 September, Barcelona, Spain).

BIOFLEX-COF is the first randomised controlled trial (RCT) to investigate differences in clinical outcomes of nitinol stents with high versus low COF in de novo superficial femoral artery (SFA) occlusive arterial lesions. The low-COF Pulsar stent had a mean restenosis rate of 26%, while the high-COF LifeStent implant showed 35%, as measured on CT angiography (CTA) at one year (p<0.001, t-test & Mann-Whitney U test).

“We initiated the BIOFLEX COF trial to close the gap on how COF impacts the human neointima,” explained Funovics, the study’s principal investigator. “These RCT data support our hypothesis that high COF leads to increased neointimal hyperplasia, which causes restenosis and increases the risk of repeat interventions for the patient. Our results suggest that COF impacts clinical outcomes and should therefore be an important factor in the choice of the stent.”

Self-expanding nitinol stents must be oversized by at least a minimal amount to ensure contact with the vessel wall and prevent migration. Once the stent is deployed, it exerts a continuous force upon the vascular wall, termed COF. While an animal study has found increased neointimal hyperplasia, inflammation and injury scores in vessels treated with high COF stents, human data were not available until now.

The investigator-initiated BIOFLEX-COF RCT enrolled 83 patients with symptomatic peripheral arterial lesions eligible for endovascular stent implantation. The patients were randomized 1:1 to either a high COF group or a low COF group. The trial’s primary endpoint is the amount of in-stent restenosis at one and two years as assessed by contrast-enhanced CTA.


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