Objective Multiple studies have shown, retrospectively, the inverse relationship between packing density and aneurysm recurrence. Furthermore, it has been shown that prospectively measuring the packing density, by carefully selecting the first coil with the highest resultant initial packing density, yields higher packing densities overall. It is our theory that prospectively measuring packing density in this manner not only increases the final packing density, but also decreases the recurrence rate of intracranial saccular aneurysms.

Methods Prior to 2011, our facility treated endovascular aneurysms by measuring the diameter of the aneurysm, and then choosing coils of that diameter, and gradually decreasing coil sizes until no further coil could be placed. Packing density was not measured during the procedure. In 2011, we began to prospectively measure aneurysm packing density by calculating the coil volume prior to coil placement. In our past experience, achieving a packing density of 15% or less with the first coil was often feasible in smaller aneurysms, but achieving a packing density of 20% or greater is challenging. Thus, a first framing coil would be chosen that yielded a packing density of 15–20%

As such, the first 25 consecutive aneurysms treated at our facility in 2010 were retrospectively evaluated for packing density, as a control arm. This was compared to the first 25 aneurysms treated at our facility in 2011. Final packing density and recurrence rates at one year were calculated.

Results A total of 50 patients were evaluated. There was one mortality in each arm in subjects with ruptured aneurysms. No intra-procedural ruptures were identified in this series.

In the control arm, the average diameter was 6.9 mm (3 mm – 14 mm), with 40% of the aneurysms ruptured at the time of presentation. A final packing density was calculated using angiographic modeling and geometric modeling, yielding 25%. The average packing density of the first framing coil was 9%. Postoperative complete occlusion was calculated at 64%.

In the prospective arm, the average diameter was 7.1 mm (3 mm – 17 mm), with 40% of the aneurysms ruptured at the time of presentation. A final packing density was calculated using angiographic modeling and geometric modeling, yielding 32%. The mean packing density of the first framing coil was 15%. Postoperative complete occlusion was calculated at 60%. Packing densities greater than 15% were unable to be achieved with the first framing coil for any aneurysm 10mm in diameter or larger.

At one-year follow-up, 17 patients in the control arm returned, with complete occlusion in 12 (71%). A neck remnant was seen in 5 subjects, for a recurrence total rate of 29%. In the prospective arm, 16 subjects returned for one-year follow-up. There was complete occlusion in 15 subjects, 94%, with residual filling in 1 subject, for a recurrence rate of 6%.

Conclusion In this small series, attempting to prospectively select a framing coil that yields 15% or greater packing density led to higher final packing densities and decreased recurrence rates.

Disclosures B. Woodward: 2; C; Penumbra, Codman, Covidien.