Distal-tip shape-consistency testing of steam-shaped microcatheters suitable for cerebral aneurysm coil placement

Abstract

Background and purpose: Although the selection of microcatheter for endovascular aneurysmal treatment is one important factor in patient outcome, the use of steam shaping for achieving safe entry and stability during coil placement has not, to our knowledge, been systematically evaluated. The goal of this study was to compare the durability of distal microcatheter steam shaping in five different catheters with typical intraprocedural stresses that are similar to those encountered during aneurysm coil placement.

Methods: Distal tips of microcatheters were shaped into a 90 degrees turn with distal straight-segment lengths of 3, 5, or 7 mm by using steam, performed according to the instructions for use included with each catheter. In a water bath kept at body temperature, the changes in catheter tip angle were recorded and measured following microcatheter insertion into a guiding catheter, microguidewire insertion through the microcatheter, and Guglielmi detachable coil (GDC) placement through the microcatheter.

Results: The degree of distal microcatheter straightening with typical intraprocedural manipulations was more pronounced on braided microcatheters and on microcatheters with 3- or 5-mm distal-shaped segments. The degree of spontaneous recovery of the initially steamed shape was more pronounced with nonbraided catheters. The most significant single variable contributing to straightening of a steam-shaped catheter tip was the effect of microguidewire insertion. The catheter-tip straightening effect encountered with inserting GDCs was less than that encountered with microguidewire insertion. We demonstrated that the decreased catheter-tip angle encountered with a large-magnitude straightening stress spontaneously recovered once the stress was removed or when it was reduced to a smaller magnitude stress.

Conclusion: Our study shows that, although braided microcatheters are suitable for maintaining durable configurations when long distal-tip lengths are permissible, nonbraided microcatheters demonstrate the most durable distal-tip configurations when short distal-tip lengths are called for. This may be one of significant factors in catheter choice for endovascular treatment of aneurysm.

Fig 1.

Excel 14 catheter, demonstrating 7-mm length and manually steam-shaped 90° angle curve. Although the initial measured tip angle measured 98° (I), the tip angle decreased to 75° following coaxial microcatheter insertion through a guiding catheter (CI). The tip angle was further reduced to 46° following guidewire manipulation (GW). The tip angle recovered to approximately 60° after the second (C2) and fifth GDC withdrawals and insertions (C5). The change rate of the catheter-tip angles, once exposed to straightening forces, is graphically depicted as a percentage straightening when compared with the initial baseline-shaped angle.

Fig 2.

Change rate without stress on 5- and 7-mm lengths of steam-shaped catheter tip. After insertion through a guiding catheter (CI), measurement was performed at 5, 15, and 30 minutes. Exc14 indicates Excel 14; Fas10, FasTracker 10; I, initial measurement; Prow14, Prowler 14; ProwPS, Prowler 14 Preshaped; and SL10, Excelsior SL 10.

Fig 3.

Change rate with stress on 3-, 5-, and 7-mm lengths of steam-shaped catheter tip. CI indicates coaxial microcatheter insertion through a guiding catheter; C2, after second GDC insertions and withdrawals; C5, after fifth GDC insertions and withdrawals; Exc14, Excel 14; Fas10, FasTracker 10; GW, microguidewire manipulation; I, initial measurement; Prow14, Prowler 14; ProwPS, Prowler 14 Preshaped; and SL10, Excelsior SL 10.