Immediate Anatomic Results after the Endovascular Treatment of Ruptured Intracranial Aneurysms: Analysis in the CLARITY Series

Discussion

The ISAT showed that in patients with ruptured aneurysms suitable for neurosurgical clipping and endovascular coiling, endovascular coiling was more likely to result in independent survival at 1 year (absolute risk reduction of 7.4%).¹ However, as outlined in the ISAT publication, a crucial issue for endovascular coiling is the uncertainty about the long-term durability of aneurysm occlusion and protection from further aneurysm rupture.

The CARAT study was conducted in a cohort of 1010 patients treated with coil embolization or surgical clipping at 9 hospitals in 8 high-volume centers in the United States and showed that the risk of rerupture tended to be greater after coil embolization compared with surgical clipping.³ The degree of aneurysm occlusion was strongly associated with the risk of rerupture (cumulative risk: 1.1% for complete occlusion, 2.9% for 91%–99% occlusion, 5.9% for 70%–90% occlusion, and 17.6% for occlusion <70%). In fact, as was demonstrated in both ISAT and CARAT, the degree of occlusion was different in the coiling and clipping groups.^1,3 In ISAT, angiographic occlusion was complete in 66% of aneurysms treated by coiling and in 82% of aneurysms treated by clipping; subtotal in 26% and 12%, respectively; and incomplete in 8% and 6% respectively. Similar results were reported in the CARAT study: complete occlusion in 38.6% of the coiling group and 91.5% in the clipping group; a small residual neck in 43.4% and 6.4%, respectively; a residual neck in 13.9% and 1.4%, respectively; and a partial occlusion in 4.1% and 0.7%, respectively. As demonstrated in ISAT and CARAT, the difference in aneurysm occlusion in the coiling and clipping groups is partially explained by the fact that postoperative evaluation is not always performed by using DSA after surgery.

Therefore, the quality of aneurysm occlusion after endovascular treatment must be precisely evaluated by using the appropriate scale and an independent core lab.⁴ Most published series reporting anatomic results of endovascular treatment of ruptured and/or unruptured aneurysms do not include independent evaluation. In ISAT, the rate of occlusion was assessed by the local investigator,¹ and in CARAT, aneurysmal occlusion was abstracted from procedural reports.³ Similarly in another large series published by Gallas et al,⁵ anatomic results were evaluated by the performing physician. In a recent series published by Holmin et al,⁶ which assessed long-term clinical follow-up in relation to morphologic treatment results, how the anatomic analysis was performed is not clearly indicated.

More recent published reports have shown that self-reported evaluations by the performing physician vary significantly from those performed by an independent core lab (or blinded reader), with a tendency toward better anatomic results reported by the treating physician. For example, in a series dealing with the endovascular treatment of intracranial aneurysms with Matrix coils, analysis performed by the treating neuroradiologist reported complete occlusion in 61.5% of aneurysms, neck remnant in 33.2% of aneurysms, and aneurysm remnant in 5.3% of aneurysms, whereas results from the independent core lab were complete occlusion in 44.0%, neck remnant in 25.0%, and aneurysm remnant in 31.0% of aneurysms.⁷

Anatomic results in the CLARITY series were evaluated by an independent core lab, which included 2 experienced neuroradiologists with a combined treatment experience of >10 years, to ensure precise analysis. Analysis was conducted by using the Montreal Scale, which is currently used in most endovascular published reports. A new scale was also used by the core lab (the CLARITY scale) but will be presented in another article.

As previously shown, the anatomic results in CLARITY are different when evaluated by the treating physician and the independent neuroradiologists.⁷ The rate of complete occlusion was reported higher by the treating neuroradiologist (75.8%) than by the core lab (47.3%). On the other hand, neck and aneurysm remnants (41.9% and 10.7%, respectively) were more frequently depicted by the core lab than by the treating neuroradiologist (18.8% and 5.4%, respectively). In fact, results are very heterogeneous with a low interobserver agreement between the performing physician and the core lab (κ = 0.395). For example, what was defined as a complete occlusion by the core lab was sometimes classified as a neck remnant or aneurysm remnant by the treating neuroradiologist (Fig 1). The interobserver agreement by the 2 independent neuroradiologists of the core lab was good (κ = 0.905).

The comparison of our series with other previously published large series is difficult due to the methodologic heterogeneity previously outlined (Table 7).^1,5,8–11 Including our series, the rate of postoperative complete occlusion was between 49.1% and 72.6%. More important, aneurysm remnants were reported to be between 1.9% and 12.2%. The lower rate of complete occlusions and the higher rate of aneurysm remnants observed in our series are likely due to the methodology we used. Effectively, the evaluations reported by the treating physicians in our series (complete occlusion, 75.1%; neck remnant, 18.2%; aneurysm remnant, 6.7%) are very close to those reported in other large series in which anatomic evaluations were also self-reported. According to CARAT (see below), the risk of rebleeding is primarily a risk for aneurysm remnants (aneurysm occlusion <90%). Thus, accumulation of all complete occlusion and neck remnants resulted in an overall high rate of satisfactory occlusion (89.3% in CLARITY and 92.2%–98.1% in other series, Table 7). Comparison with surgical series is much more difficult because the postoperative evaluation is rarely performed by using DSA but visually during neurosurgery as was the case in ISAT and CARAT.

In the analysis of factors that may affect anatomic results, only age was significant (P = .021), as was previously reported in ATENA.⁴ In patients older than 65 years, the rate of complete occlusion was lower compared with that in younger patients (respectively 39.0% and 48.9%). On the other hand, aneurysm remnants were more frequent in patients older than 65 years (17.1%) compared with younger patients (9.5%); this outcome is likely due to less aggressive treatment in older patients to reduce the risk of complications. Anatomic results were not significantly affected by anatomic factors (aneurysm location, aneurysm size, dome-to-neck ratio). In ATENA, the quality of aneurysmal occlusion was linked to 2 anatomic factors: aneurysm size and dome-to-neck ratio. Finally, results were slightly better in those aneurysms in which the balloon remodelling technique was used compared with aneurysms treated by coiling alone (complete occlusion achieved in 50.0% and 46.9% of aneurysms, respectively; aneurysm remnants in 5.1% and 11.5% of aneurysms, respectively). Anatomic results were not significantly different according to the type of coils used (GDC or Matrix). The number of patients in this series may be too small to depict some clinical or morphologic factors that can affect immediate postoperative anatomic results.