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Effects of anatomic characteristics of aneurysms on packing density in endovascular coil embolization: analysis of a single center’s experience

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Abstract

When embolizing cerebral aneurysms, dense coil packing may prevent recanalization but this may be influenced by the aneurysm morphology. We have analyzed retrospectively the relationship between anatomic features and the volumetric coil packing density. We analyzed 452 aneurysms in 434 patients treated by coil embolization without stenting, expressing packing density as volume embolization ratio (VER, volume of inserted coils/aneurysm volume). Six morphological variables (neck width, height, maximum diameter, dome to neck ratio (DNR), and aspect ratio), aneurysm location, and whether the aneurysm was ruptured or unruptured were analyzed with respect to dense (VER ≥20 %) or loose (VER <20 %) packing densities, using logistic regression analysis and ROC analysis. Among 452 aneurysms, VERs >20 % were achieved for 272 aneurysms, with a mean VER of 24.7 %. The mean VER of the remaining 180 aneurysms was 15.6 %. In univariate analyses, the predictors for dense packing were having an anterior circulation, DNR, aspect ratio, and neck width. In multivariate analysis, the independent predictors were smaller neck width (odds ratio (OR) 0.8735; 95 % confidence interval (CI) 0.7635–0.9993) and larger aspect ratio (OR 1.6679; 95 % CI 1.0460–2.6594). ROC analysis showed optimal cutoff values for an aspect ratio of 1.35 (sensitivity 69.5 %, specificity 51.7 %) and a neck width of 3.13 mm (sensitivity 51.1 %, specificity 27.8 %). Although dense coil packing is still difficult to achieve in wide-necked aneurysms without the use of stents, packing with VER >20 % is expected to be achieved when the height is 1.35 times larger than the neck width.

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Authors and Affiliations

  1. Department of Neurosurgery, Fujita Health University, 1-98 Dengakugakubo, Kutsukake-cho, Toyoake, Aichi, 470-1192, Japan

    Akiyo Sadato, Kazuhide Adachi, Motoharu Hayakawa, Yoko Kato & Yuichi Hirose

Authors
  1. Akiyo Sadato
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  2. Kazuhide Adachi
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  3. Motoharu Hayakawa
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  4. Yoko Kato
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  5. Yuichi Hirose
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Correspondence to Akiyo Sadato.

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Comments

Michael R. Levitt, Louis J. Kim, Seattle, USA

The authors investigated the degree of coil packing density as a function of aneurysm anatomy in aneurysms treated without stent assistance. This single-center experience included 434 patients with 452 aneurysms and determined the factors that influence whether an aneurysm was considered “densely packed” (≥20 %) or “loosely packed” (<20 %), as calculated by three-dimensional rotational angiographic (3D-RA) reconstructions and coil dimensions. The authors sought to define anatomical variables that could predict whether an aneurysm was likely to be densely or loosely packed using area under the curve analyses, with the hypothesis that densely packed aneurysms are less likely to recur. They found that an aneurysm aspect ratio of ≥1.35 was associated with dense coil packing. The manuscript’s strengths include a large number of aneurysms and the use of 3DRA to calculate aneurysm volume (rather than conventional 2D measurements).

Many studies have attempted to relate aneurysm morphological characteristics to clinical events such as rupture risk, though the variability and imprecision of published results reduces confidence in the clinical applicability of such measures. However, the utility of this paper’s conclusions (the predictor of whether dense packing is more likely) can be directly applied to clinical practice. Specifically, by determining whether a particular aneurysm is likely to be densely packed based on pre-treatment morphology, a clinician could judge whether stent assistance (and its accompanying requirement for antiplatelet medications) might be required or avoided. Further prospective study is necessary, however, to validate the predictive value of this analysis, as well as the threshold of 20 % packing density (as determined by 3DRA), as they relate to aneurysm recanalization.

Srinivasan Paramasivam, New York, USA

This is a well-written retrospective single-center review of the assessment of the aneurysm morphology to determine the packing density achievable without the use of stent. Packing density is considered an important aspect of coiling that determines recanalization among other factors. The dome to neck ratio along with aspect ratios as performed in this article can be used as guidance for analyzing an angiogram before coil embolization to determine the need for premedication with anti-platelets and prepare for a stent assistance to achieve a minimum of 20 % packing density. Though similar packing density and remodeling can be achieved with balloon assistance compared to use of stent in most aneurysms, there is a risk of coil prolapse following balloon deflation. Today, with advanced technology, even in patients with lower aspect ratio (<1.35) the strategy may involve balloon remodeling and dense packing of aneurysm followed by placement of stent through the balloon catheter to stabilize the densely packed coil mass if needed.

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Sadato, A., Adachi, K., Hayakawa, M. et al. Effects of anatomic characteristics of aneurysms on packing density in endovascular coil embolization: analysis of a single center’s experience. Neurosurg Rev 39, 109–114 (2016). https://doi.org/10.1007/s10143-015-0658-7

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  • DOI: https://doi.org/10.1007/s10143-015-0658-7

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