Comparison of 2-Year Angiographic Outcomes of Stent- and Nonstent-Assisted Coil Embolization in Unruptured Aneurysms with an Unfavorable Configuration for Coiling

Patient Selection

Our institutional review board approved this study. We retrospectively reviewed the clinical and radiologic data of patients with unruptured aneurysms who underwent endosaccular coil embolization between May 2003 and January 2008 at our institute. Because the thrombogenic environment could have affected initial angiographic results, unruptured aneurysms coiled at the same time as a ruptured aneurysm was treated were excluded. In addition, patients who did not undergo a conventional angiographic evaluation at 2 years after coil embolization also were excluded.

In our practice, stent-assisted coiling was used in unruptured aneurysms under the following conditions: >4 mm in neck size and a dome-to-neck ratio of <1.5. However, many aneurysms with these conditions also were coiled without stent assistance, when the aneurysm was expected to be able to contain the coil mass. In cases with a small neck (≤4 mm), surgical obliteration was used if the aneurysm was unfavorable for simple coiling and could be coiled under only stent assistance. For comparison therefore, we included unruptured aneurysms treated by nonstent-assisted coiling, which had the same conditions as those treated by stent-assisted coiling, in this study. Eventually, 126 aneurysms in total in 121 patients were included in this study (Fig 1).

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Fig 1.

Patient flow according to exclusion criteria for this study.

Coil Embolization Procedure

All aneurysm coilings were performed under general anesthesia by using a biplane angiographic unit (Integris Allura; Philips Healthcare, Best, the Netherlands). Stent-assisted coil embolization was used in 40 (31.7%) aneurysms. In the remaining 86 (68.3%) aneurysms, a multiple microcatheter technique (53, 42.1%) or balloon-assisted coil embolization technique (33, 26.2%) was used. Technical details of aneurysm coiling and stent deployment were conventional and have been described in detail previously ^9,10 All aneurysm embolizations were performed by using detachable platinum coils, which included the GDC (Boston Scientific, Fremont, California), MicroPlex (MicroVention, Aliso Viejo, California), Trufill-DCS (Cordis, Miami Lakes, Florida), and Axium (ev3, Irvine, California) coils. Modified coils, such as Matrix (Boston Scientific) and HydroCoil (MicroVention), were not used. The stents used for remodeling were the Neuroform (Boston Scientific; 17 cases, 42.5%) or Enterprise (Cordis; 23 cases, 57.5%) and were successfully deployed to cover the aneurysmal neck in all cases. In no case was a stent overlapping used. In every case, systemic heparinization was performed after placing a femoral introducer sheath. In accord with our embolization protocol, 3000 IUs of heparin was administered as an intravenous bolus injection, and this was followed by an additional 1000 IUs per hour. Heparin was discontinued after embolization in all patients. When stent-assisted coil embolization was planned, we prescribed antiplatelet medication (oral aspirin, 100 mg and clopidogrel, 75 mg) daily for at least 5 days before coiling. If these daily regimens were not followed, aspirin and clopidogrel were administered at loading doses of 300–500 and 300 mg, respectively. For daily antiplatelet medication after stent deployment, 2 drugs (aspirin, 100 mg and clopidogrel, 75 mg) were used for the first 3 months, and then aspirin at 100 mg was continued.

Aneurysmal Characteristics and Initial Angiographic Outcomes

The following aneurysmal characteristics were recorded; aneurysm location (Table 1), aneurysm type (sidewall, bifurcation), diameter, neck size, dome-to-neck ratio, and volume. Aneurysm obliteration grade (0, complete; 1, occlusion ≥90%; 2, occlusion 70%–89%; 3, occlusion 50%–69%; 4, occlusion 25%–49%; and 5, occlusion <25%), contrast filling within the coil mass, and packing attenuation (percentage) were checked to evaluate initial angiographic outcome.¹¹

The following formulas were used to calculate aneurysm volumes and packing densities.

Imaging Follow-Up after Coil Embolization

The imaging tools used for follow-up were skull imaging by using an angiographic unit (working, conventional frontal, and lateral projections), MRA, and DSA. Skull radiographs were taken at 3, 9, 15, and 21 months and MRA at 6, 12, and 18 months postembolization. DSA was performed at 2 years postembolization. Whenever findings were obtained that suggested recanalization on skull images or MRA images, DSA also was performed.

Follow-up DSA images were obtained in the previous working projection and in conventional frontal and lateral projections. Rotational angiography was performed to detect any change in angiographic outcome. DSA also was performed at the projections determined optimal by rotational angiography.

Evaluation of Angiographic Outcomes at 2 Years Postembolization

Changes in angiographic outcome were evaluated by DSA and were classified as follows: stable (no change in coil configuration, obliteration grade, or contrast filling), improved (progressive occlusion or involution of the neck remnant or contrast filling in aneurysm), and recanalized (aneurysm recurrence evident due to neck growth, coil compaction, coil extrusion by aneurysm degradation,¹² or new sac formation).¹¹ In addition, newly visualized or increased contrast filling inside an aneurysm also was considered to indicate recanalization. All radiologic data were reviewed by a neuroradiologist (M.H.H.), who was unaware of clinical results.

Statistical Analyses

Statistical analysis was conducted by using SPSS version 17 (SPSS, Chicago, Illinois). The Mann-Whitney U test was used for continuous variables, and the χ² or Fisher exact test were used for nominal factors. Statistical significance was accepted for P values of <0.05.