Vessel Deformations and Restenosis After Stenting of the Popliteal Artery

Overview

The femoro-popliteal (FP) artery is the most frequently treated vascular segment in patients with symptomatic peripheral artery disease (PAD), for which endovascular therapy became an established treatment option during the last decades. However, loss of primary patency and consecutive clinically driven target lesion revascularization (TLR) limit this procedure. Moreover, in the popliteal artery (PA), evidence about the best treatment strategy to prevent loss of patency and TLR is limited to only a few randomized controlled trials (RCT). Arterial deformations of the PA with its unique anatomical properties during leg flexion might explain the poor technical and clinical outcomes in this segment. Generally, a "leave nothing behind" strategy in the PA is preferred, but cannot be avoided in all cases due to e.g. flow limiting dissections or re-coil after balloon angioplasty. Basically two different self-expandable nitinol-based stent designs are available on the market. An interwoven nitinol and laser-cut nitinol stent. The interwoven nitinol stent has a higher radial force in comparison to the laser-cut stent and reveals higher patency rates in the FP arteries. However, a head-to-head comparison of these stents is missing and it remains unknown in which way different stent designs affect the deformation and hemodynamic behaviors of the PA during knee flexion.

Randomized trial to investigate the impact of different stent designs on the target lesion restenosis rate in femoro-popliteal arteries. Immediately after stent implantation, sets of three orthogonal angiographic views (separated by an angle of \> 25°) of the stented region (TL) will be obtained with the leg in supine position. This will be followed by intra-arterial imaging using Optical Coherence Tomography (OCT). OCT images (one pullback if the lesion length is \< 75 mm, 2 pullbacks otherwise) of the TL will be acquired using the Dragonfly catheter. In addition, duplex ultrasound (DU) of the TL will be performed, including the arterial segments 10cm at proximal and distal edge of the TL. Thereafter, a bending cast will be used to obtain a knee/hip flexion of approximately 70°/20°. In this position the angiographic, OCT, and DU measurements will be repeated. The OCT images will provide the shapes of the arterial lumen which will be used to generate 3D surface models (in .stl format). The X-ray images will be utilized to construct the 3D arterial centerline for the supine and flexed leg positions. These arterial centerlines will be used to quantify the axial deformation (in mm), twisting (in °), and curvature changes (in mm-1) along the length of the investigated segment. Additionally, the lumen profiles obtained from OCT images will be used to accurately estimate the radial deformations (in mm) in the lumen and define instances of arterial pinching during leg flexion (as the difference in lumen diameters between straight and flexed leg positions). The geometries of the arterial lumens will be combined with their corresponding 3D arterial centerlines to generate patient-specific arterial models. Along with patient-specific boundary conditions obtained from DU measurements, these models will be transferred to a commercial software, to perform Computational Fluid Dynamics analyses. The changes in these parameters due to leg flexion, as well as due to different stent designs, will be quantified.