Carotid stent mobility with regard to head movements: in vitro analysis

Given that considerable motion of the carotid artery is present during head movements, we hypothesized that a flexible stent with low torsion might be favorable to avoid stress imparted to the stent and carotid artery. Therefore, we evaluated the flexibility of different expanded carotid stents before and after deployment in a carotid artery in vitro. Subsequently, we evaluated torsion of the bare expanded stents. Five stents (Wallstent [Boston Scientific Corp., Natick, MA], Acculink [Guidant Corp., Indianapolis, IN], Precise [Cordis Corp., Johnson & Johnson Company, Warren, NJ], Carotid SE [Medtronic AVE, Santa Rosa, CA], and Protégé [EV3, Plymouth, MN]) were tested. Flexibility was determined using a three-point bend test recording the bending load (BL) in grams required to flex the stent 25 degrees. Increased BL implies decreased flexibility. Torsion was measured by recording the rotation load (RL) in grams required to rotate the stents 30 degrees along its axis. Increased RL implies increased torsion. In the bare expanded state, the median BL was 6 g (range 1-22 g). The BL increased to 38 g (range 20-41 g) after deployment in a carotid artery, with the Carotid SE (21 g) and Wallstent (36 g) showing significantly lower BL (p < .0001 and p = .0016, respectively). Overall, the RL was 11 g (range 1-76 g). Significantly higher RL was required to rotate the Wallstent (73 g) and Precise (20 g) stents (p < .0001). The flexibility of the currently used stents decreases after deployment in a carotid artery irrespective of its flexibility in the bare state. Two stents showed increased torsion compared with the other stents. Limitations in both flexibility and torsion might influence the long-term performance of carotid angioplasty stenting.