Microguidewire stiffness for microcatheter and aspiration catheter navigation in tortuous vessels

Abstract

BackgroundEffective catheter navigation and trackability are crucial in neuroendovascular procedures, particularly through tortuous vessels where catheter kickback can potentially delay treatment and worsen patient outcomes. While operational experience suggests that stiffer microguidewires enhance catheter navigation and trackability, this relationship has not been experimentally validated. This study assesses the impact of microguidewire stiffness on targeted catheter delivery using in-vitro vascular models with severe tortuosity.MethodsTwo experiments were conducted using silicone models of the intracranial vasculature to evaluate microguidewires of similar composition but differing stiffness, as defined by greater resistance to bending with the Stryker Synchro Select Soft, Standard, and Support microguidewires. In Experiment 1, 0.021″ microcatheter navigation through an acute angle M2 branch of the middle cerebral artery was assessed. In Experiment 2, 0.071″ aspiration catheter navigation through a severely tortuous internal carotid artery model was tested. Maximum catheter pushing force and microguidewire kickback length were measured in both experiments.ResultsStiffer microguidewires required significantly lower pushing forces and exhibited reduced microwire kickback during both microcatheter and aspiration catheter advancement.ConclusionsMicroguidewire stiffness significantly influences neuroendovascular catheter deliverability. Stiffer microguidewires provide greater system stability, particularly at the distal end, enhancing catheter navigation and advancement through tortuous anatomy.

Keywords: Device navigation; aspiration catheter; microcatheter; microguidewire; tortuous anatomy.

Figure 1.

Microcatheter navigation in the middle cerebral artery (MCA) model with M2 branches. A microguidewire (Synchro Soft, Standard, or Support) with various stiffness was positioned in the prefrontal branch at an acute angle of 70°. The microcatheter was advanced at a rate of 4 mm/sec from the mid-M1 segment over the microguidewire toward the prefrontal branch. Stages of microcatheter advancement: (1) Initial Advancement Stage, as the microcatheter is advanced without resistance; (2) Resistance Stage, as the catheter tip remained stationary due to resistance despite proximal pushing force; (3) Loading Stage, wherein microguidewire kickback occurs while the pushing force gradually increased, and (4) Release and Propulsion Stage, at which point the peak force is reached, with the microcatheter advancing distally. The maximum microguidewire kickback length (L(mc)) in the M2 branch and the maximum pushing force (F(mc)) required to advance the microcatheter were measured.

Figure 2.

Aspiration catheter navigation in the internal carotid artery (ICA) model with severe tortuosity. The microcatheter and microguidewire were positioned in the inferior M2 branch, and the aspiration catheter was advanced at a rate of 4 mm/sec over the inner microcatheter from the ophthalmic segment of the ICA to the distal M1 segment. Stages of aspiration catheter advancement: (1) Initial Advancement Stage: the aspiration catheter is advanced to the ICA terminus without resistance; (2) Resistance Stage: the catheter tip remains stationary due to resistance at the acute bend over ICA terminus and M1 despite hand-side pushing force; (3) Loading Stage: the microguidewire and microcatheter experience kickback while the pushing force increases; and (4) Release and Propulsion Stage: the aspiration catheter advances distally once peak force is reached, accompanied by a decrease in force. The maximum microguidewire kickback length (L(ac)) in the M2 branch and the maximum pushing force (F(ac)) required to advance the aspiration catheter were measured.

Figure 3.

Impact of microguidewire stiffness on microcatheter navigation in the M2 branch with an acute angle. (Left) Kickback length (L(mc)) of the microguidewire in the M2 branch for Soft, Standard, and Support microguidewires during the microcatheter advancement. (Right) Maximum force (F(mc)) required to advance the microcatheter over the microguidewire. Both the kickback length and the maximum force significantly decreased as microguidewire stiffness increased (P < 0.001). Data are presented as mean ± SD, and statistical significance is indicated by **** (P < 0.0001).

Figure 4.

Impact of microguidewire stiffness on aspiration catheter navigation in a tortuous ICA model. (Left) Kickback length (L(ac)) of the microguidewire in the M2 branch for Soft, Standard, and Support microguidewires. (Right) Maximum force (F(ac)) required to advance the aspiration catheter. Both the kickback length and the maximum force significantly decreased as microguidewire stiffness increased (P < 0.05). Data are presented as mean ± SD, with statistical significance indicated by **** (P < 0.0001), ** (P < 0.01), * (P < 0.05), and ns (not significant).