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Home > Vascular Annual Meeting > PP35. Assessment of Self-Expanding Nitinol Stent...

PP35. Assessment of Self-Expanding Nitinol Stent Deformations Implanted into the Femoropopliteal Artery

Alexander Nikanorov1, Martin Schillinger2, Hugh Zhao1, Erich Minar2, Lewis B. Schwartz1
1Abbott Vascular, Santa Clara, CA; 2Medical University of Vienna, Vienna, Austria

OBJECTIVES: Endovascular stenting has emerged as a promising therapy for femoropopliteal occlusive disease, but stent fractures remain a safety concern. The aim of this study was to quantify the degree of deformations encountered by nitinol stents when implanted into patients.

METHODS: Patients undergoing femoropopliteal endovascular stenting were eligible for study. Stent deformations were assessed by measurement of stent length, deflection angle and bending radius via lateral view radiograms obtained two days and six months following implantation with the patient in three positions: neutral standing (knee/hip flexion 0°/0°), simulated ambulation (knee/hip flexion 70°/20°) and simulated stair climbing (knee/hip flexion 90°/90°).

RESULTS: Nineteen stent implantations in seventeen patients were assessed. Stents were confined to the superficial femoral artery (SFA) in eleven cases, extended to the proximal popliteal artery (SFA/prox pop) in two cases (defined as terminating at least 3 cm above the intercondylar fossa) and crossed the knee joint (popliteal) in six cases. Single stents of 80 or 100 mm length were implanted in sixteen cases; overlapped stents were required in three cases. Leg flexion was associated with 5-10% shortening (compression) of the stent, the greatest amount being observed for stents implanted into the popliteal artery (SFA 3.1%±1.8%, SFA/prox pop 5.3±0.5%, popliteal 8.6%±3.2%). Profound stent bending (deflection angle 64°±16°, bending radius 22±2 mm) was observed in the popliteal artery, with slight bending in the SFA stents (SFA 5°±2°, 138±53 mm; SFA/prox pop 8°±4°, 55±10 mm). Follow-up examinations were performed in fourteen stent implantations of thirteen patients after a mean follow-up of 7.1±1.3 months. In these patients, the degree of stent deformation during leg flexion was essentially unchanged as compared to immediate post-procedure levels.

CONCLUSIONS: In patients with femoropopliteal occlusive disease, indwelling nitinol stents are routinely bent and compressed during leg flexion. Stent bending is considerably more pronounced after implantation into the popliteal artery as compared to the SFA. As the observed levels of compression and bending were unchanged after six months, short-term vascular remodeling appears to have no effect on stent deformation.

AUTHOR DISCLOSURES: A. Nikanorov, Abbott Laboratories; M. Schillinger, consulting fees; H. Zhao, Abbott Laboratories; E. Minar, consulting fees; L.B. Schwartz, Abbott Laboratories.