Abstract WP195: The Impact of Tortuosity on Microwire Torquability

Abstract

Introduction: Navigation of a microguidewire through the intracranial vasculature is crucial for the success and safety of neuroendovascular procedures. Its navigation is influenced by a combination of patient factors, such as vessel tortuosity, and device factors, such as microwire torquability. In this study, we compared the torquability of microwires in two vascular models of differing tortuosity. Methods: We tested torquability of three 0.014” nitinol microwires (Synchro Select Soft, Standard, or Support, Stryker Neurovascular, Fremont, CA) docked in either a moderate tortuosity silicone flow model of the middle cerebral artery (MCA), or a severe tortuosity model of the anterior cerebral artery (ACA). Tortuosity was determined by measuring the length of the centerline/straight length (MCA 1.28, ACA 2.22). The microwires were rotated proximally at a constant rate of 180 degrees per second, seven times clockwise and seven times counterclockwise. Rotation at the distal tip was quantified by measuring the change in angle every 0.2 seconds over 6 seconds. To quantify the deviation of distal tip motion from the ideal, the difference between the distal degrees measured and the proximal degrees rotated were summed and compared between wires. Results: In the severe tortuosity ACA model, the distal tip of the stiffer Support wire displayed significantly larger deviation from ideal than either the Standard (p<0.0001) or Soft (p<0.0001) wires. There was no significant difference amongst the three wires in the moderate tortuosity MCA model (p=0.598). Discussion: Our results demonstrated that increased vessel tortuosity decreased the torquability of the stiffer Support microwire. This was observed as “whip” motions of the Support wire in the severe tortuosity model, likely due to its higher bending rigidity. In cases of distal vessel selection or tortuous vasculature, our results suggest a Soft or Standard microwire should be utilized in place of a stiff wire.