Introduction

Recanalization remains a limitation of aneurysm coiling (1, 2). Bioactive coils such as Matrix (Boston Scientific, Fremont, CA) were designed to reduce recanalization. However, controversy still exists about its efficacy (3–9). Our objective was to evaluate the long-term anatomical results in 90 intracranial aneurysms treated with polymer polyglycolic-lactic acid (PGLA)-coated coils.

Materials and methods

Patient selection

From 2002 to 2010, 587 aneurysms were selectively treated with either bare platinum coils (GDC, Boston Scientific, Fremont, CA) or PGLA-coated coils (Matrix, Boston Scientific, Fremont, CA) exclusively. All patients were referred to us from other institutions for endovascular treatment. Only aneurysms with long-term angiographic follow-up (≥12 months) were considered for the purpose of this study.

Definition endpoint

All aneurysms were saccular. Aneurysm occlusion was classified as described by Roy (10). Aneurysm dimensions were determined on 3D images derived from rotational angiography. The same reader reviewed follow-up angiograms, and aneurysm recurrence was dichotomized as absent or present.

Follow-up protocol

Angiographic images obtained immediately after endovascular treatment were compared with those obtained at each follow-up examination. All follow-up angiograms were obtained with catheter digital subtracted angiography. The standard angiographic follow-up protocol consisted of a first angiographic follow-up performed 1 to 6 months after endovascular treatment, a second angiographic follow-up performed 1 year after the first follow-up, and a third angiographic follow-up performed 2 years after the second follow-up. In case of angiographic recurrence and/or associated aneurysms left untreated, the follow-up was continued on a yearly basis.

Data collection and statistical analysis

Aneurysm status (ruptured versus unruptured), patient’s gender, use of balloon remodeling technique, use of stent-assisted coiling technique, initial total angiographic occlusion, and angiographic recurrence were noted and evaluated for statistical significance using a two-tailed Fisher exact test. Patient ages, size of aneurysms, packing densities (the ratio between the volume of the inserted coils and the volume of the aneurysm), duration of follow-up, and time to recurrence were compared by using the Mann–Whitney U and unpaired t tests. A stepwise multivariate logistic regression analysis was performed to control for potential confounders in aneurysm characteristics and in the occurrence of angiographic recurrence. A P value of <0.05 was considered statistically significant. Statistical tests were performed with SAS Release 8.2 (SAS Institute Inc., Cary, NC).

Results

Rebleeding

Among the 187 ruptured aneurysms treated with GDC, four rebled (three within a few days after coiling, the other one 57 months after initial treatment) leading to the patients’ death in three cases and a vegetative state in one patient. Among the 74 ruptured aneurysms treated with Matrix, one rebled 4 days after coiling leading to the patient’s death.

Followed aneurysms

Overall, 397 (67.6%) aneurysms were followed, 248 (90 Matrix, 158 GDC) having been followed for at least 12 months (Table 1). Among these 248 aneurysms, 35 (14.1%) aneurysms (26 GDC, 9 Matrix) had only one follow-up digital subtraction angiography (DSA) (mean cumulative follow-up of 18 and 25 months for GDC and Matrix, respectively). One hundred thirty-four aneurysms (86 GDC, 48 Matrix) had only two follow-up DSAs (mean cumulative follow-up of 22 months for both GDC and Matrix). Seventy-nine aneurysms (46 GDC, 33 matrix) had three (75 aneurysms) or four (4 aneurysms) follow-up DSAs (mean cumulative follow-up of 42 months for both GDC and Matrix). Among these 79 aneurysms, 57 aneurysms (36 GDC, 21 Matrix) were followed by a third DSA after a 2-year interval without follow-up.

Table 1 Summary of the 248 aneurysms with follow-up ≥12 months
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Recurrence rates

The overall recurrence rates are shown in Table 1. Recurrence rates were similar for both groups. A hemorrhagic presentation was the lone factor affecting angiographic recurrence in the multivariate analysis (Table 2). There were significantly more late (at the third or fourth follow-ups) recurrences detected in the GDC group (P = 0.0007; odds ratio, 3.571) than in the Matrix group (P = 0.4974; odds ratio, 0.6917). There were five major recurrences in the Matrix group of aneurysms, two were retreated, and the three remaining were managed conservatively. There were ten major recurrences in the GDC group of aneurysms, eight were retreated, and the two remaining were managed conservatively.

Table 2 Logistic regression for factors affecting angiographic recurrence
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Discussion

Our series is the unique series assessing the long-term anatomical results of aneurysms treated exclusively with Matrix coils. Previous studies reported the mid-term anatomical result of aneurysms treated with Matrix in conjunction with bare platinum coils. The duration of angiographic follow-up is a known important factor; the longer the follow-up, the higher the rate of recurrence. This is why we specifically focused on aneurysms that had been followed at least for 1 year. Our recurrence rate of 35.6% with Matrix coils was within the range of the previously published series (9, 11). Similarly, the recurrence rate of 31.0% with GDC coils was in accordance with the historical series (2). The rates of major recurrence requiring retreatment were also similar in both groups, showing no superiority of Matrix coils.

The correlation between embolized volume and stability of aneurysm occlusion had been a source of controversy in the literature (12, 13). In this series, packing density did not interfere with the recurrence rates for both types of coils. Packing densities of aneurysms treated with Matrix were higher than those of aneurysms treated with GDC. This was due to the bigger section of the Matrix coils, giving more volume of coils for a given length. In our series, aneurysms that were treated with Matrix were larger than those treated with GDC coils. Nevertheless, aneurysm size was not found as a key factor in the multivariate analysis for recurrence since the difference in aneurysm sizes between the two groups was modest. In the multivariate analysis for recurrence, a hemorrhagic presentation was the most important factor affecting recanalization. This is in keeping with previous published series dealing with aneurysm coiling (2, 12).

Conclusions

The use of Matrix coils did not influence the long-term recanalization rate of aneurysms. Consequently, there is definitely no evidence to recommend the use of Matrix over GDC bare platinum coils.