Force characterization of intracranial endovascular embolization: coil type, microcatheter placement, and insertion rate.

Background: Intraoperative rupture (IOR) is a rare, but potentially morbid complication of endovascular aneurysm coil embolization. Yet, IOR predictors have remained relatively uninvestigated in relation to coil design.
Objective: To develop a novel in vitro aneurysm model to characterize forces exerted by coils of different design on the aneurysm during endovascular embolization that are hypothesized to contribute to IOR.
Methods: A 3-mm saccular aneurysm model was developed with flat latex membrane at the dome apex. Membrane deflection was observed throughout simulated embolization and converted to force measurement. Simultaneous coil insertion and force measurement were accomplished with a compression strength-testing machine. Membrane and insertion forces across coil type, microcatheter tip placement, and insertion rate were evaluated.
Results: Insertion force and force directly on the aneurysm wall exhibited a difference, with framing coils exerting greatest force, followed by filling and finishing coils. Regarding microcatheter placement, a similar graded response in membrane and insertion forces was observed with positioning in the top-third of the aneurysm generating the greatest force compared with central and bottom-third placement. Insertion rate was also a factor with the slowest rate (10 mm/min) exhibiting the greatest membrane force, followed by lower forces at 30 and 50 mm/min. A multiple linear regression model was created to assess the contributions of each factor toward aneurysm forces.
Conclusion: Increased force on the aneurysm is associated with framing coil use, microcatheter placement proximal to aneurysm dome, and slow insertion rate. Further characterization remains necessary to reduce IOR risk, especially concerning the contributions of insertion rate.