Introduction As aneurysm treatment transitions towards flow-diversion, coils may become less important. This coupled with the emphasis on healthcare economics requires an assessment of the coil types that may be pertinent in future. We hypothesised that larger coils provide the biggest “bang for the buck” in occluding aneurysms and hence may be more relevant than smaller, shorter coils.

Methodology A retrospective analysis was performed on 402 aneurysms. Aneurysm were divided into: <6mm (n = 167), 6–11 mm (n = 181) and >11 mm (n = 54). Coil-thickness was dichotomized into ≤0.0115” and >0.115”. An analysis of aneurysms with 100% use of either ≤0.0115” or >0.115” coils was performed for each group. The effect of “framing” coils on the final packing density (PD) was also calculated. The financial impact of coil choice was factored into each aneurysm treatment.

Results The mean age was 57.5(±12) years and there were 320(79.6%) female patients. The mean PD was 25%(±13). The PD was 30%(±15) for the <6 mm-group, 22%(±8.6) for the 6–11 mm-group and 17%(±9.8) for the >11 mm-group (p < 0.0001). In aneurysms in which all coils were ≤0.0115”(n = 128), the PD was 22.5%(±9.5) and for aneurysms in which all coils were >0.0115”(n = 160), the PD was 27.4%(±15), (p = 0.002). The final PD was 26%(±14) if the first or “framing” coil was >0.0115 (n = 251), versus a PD of 23%(±11) if the framing coil was ≤0.0115” (n = 148), (p = 0.03). The final PD rose to 27%(±14) if the first two coils were >0.0115 (n = 212), versus a PD of 23%(±11) if the first two coils were ≤0.0115” (n = 172), (p = 0.01). The impact of coil choice (all coils ≤0.0115” versus all coils >0.0115) on PD, number of coils deployed and cost of coils for aneurysms <6 mm and between 6–11 mm is given in Table 1. It shows that for aneurysms <6 mm, a significantly higher PD was achieved with coils >0.0115”. For aneurysms between 6–11 mm, there was no significant difference in PD based on coils used, however to achieve a similar PD, significantly more coils at a significantly higher cost had to be used in the ≤0.0115” group.

Conclusion Flow-diverters are approved for large aneurysms. The potential next target for these devices is aneurysms between 6–11 mm and perhaps smaller. The question is what function coils may have in this emerging era? A potential use is in conjunction with endo-luminal devices – an adjunctive rather than a primary role. If PD is a measure of aneurysm occlusion than certainly coils larger than 0.0115 fare better in either achieving a higher PD than smaller coils or a similar PD with less number of coils and at a reduced cost. This effect is evident even if only the framing coils are >0.0115. We can thus speculate that smaller OD coils will increasingly become irrelevant as the field evolves.

Disclosures A. Rai: 2; C; Stryker Neurovascular, Codman Neuro. B. Cline: None. J. Patterson: None. A. Tarabishy: None. J. Carpenter: None.