The Era of Flow Diverters in Aneurysm Treatment

Jabbour, Pascal; Chalouhi, Nohra

doi: 10.1227/NEU.0000000000000255

Philadelphia, Pennsylvania

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To the Editor:

We read the article by Arrese et al1 published in Neurosurgery as well as the accompanying comment requesting a “health warning” label for the use of flow diverters. The authors criticize the quality of evidence supporting the use of flow diverters and close the article with a provocative and erroneous statement that “in the absence of reliable evidence, the use of flow diverters in patients eligible for more conventional treatments should be restricted to controlled clinical trials.” Although efforts to review and summarize complex data are encouraged, drawing wrong, unfounded conclusions about revolutionary devices in aneurysm treatment is a great disservice to our patients. The authors criticize the quality of the literature but do not realize that their study has even more serious limitations because it combines heterogeneous data from mostly retrospective studies and pools the biases and limitations of individual studies into 1 analysis. To add further heterogeneity, the authors throw data on both the Silk and the Pipeline Embolization Device (PED) into their analysis as if the 2 devices were identical. This is not to mention that the meta-analysis is largely outdated (by at least 1.5 years) and reflects the initial experience of a few centers while these centers were in their learning curve. As will be discussed below, the study is out of touch with the reality about flow diverters, in general, and the PED, in particular, and we worry that it is sending the wrong message to the neurointerventional community.

Although we agree that flow diverters are associated with some risks—which is the case for any endovascular technology—recent studies have shown that flow diverters are an excellent treatment option. We will dedicate the present discussion to the PED, which is the only device approved for use in the United States. First, the authors disregard the Pipeline for Uncoilable or Failed Aneurysms (PUFS) trial (the results of which were available before the publication of their study) which led to the US Food and Drug Administration approval of the PED. The PUFS was a multicenter international trial that included 108 patients treated with the PED and reported a major complication rate of only 5.6% and an occlusion rate of 74%. Also, in the largest reported series on the PED with 251 treated aneurysms, Saatci et al2 reported a 6-month occlusion rate of 91% with a combined morbidity-mortality rate as low as 1.5%. Again the authors disregard this study, which was published online in July 2012 (ie, more than a month before the submission of their manuscript). Likewise, several other studies since then have confirmed the safety and high efficacy of the PED,3-10 and it is beyond the scope of this report to summarize them.

Because the authors voice their concern about the lack of studies comparing flow diversion and conventional strategies (which they use as an argument for concluding that flow diverters should only be used when conventional techniques are contraindicated), we would like to highlight the results of 2 recent studies. First, in an article published in the August issue in Stroke, our group compared the periprocedural, angiographic, and clinical outcomes of flow diversion and coiling in unruptured, large and giant (≥10 mm) aneurysms.5 The complication rate was 7.5% in both groups, and clinical outcomes were similar at follow-up. The aneurysm occlusion rate was significantly higher (86% vs 41%) with the PED and the re-treatment rate was also better with flow diversion (2.8% vs 37%). In multivariable analysis, the odds of achieving occlusion of large aneurysms were more than 10 times higher with flow diversion than with coiling. These results show that the PED is a preferred option for large and giant aneurysms and should be considered a first-line option in this setting. In another study, we sought to determine whether flow diversion was a similarly safe strategy for small aneurysms (<10 mm), a subgroup in which conventional endovascular techniques have generated very favorable clinical and angiographic results.11 Indeed, flow diversion was undertaken with no additional morbidity and similar clinical outcomes compared with coiling. Additionally, there was a trend toward higher occlusion rates with the PED (80% vs 70%), although the study was likely underpowered to detect small differences in angiographic outcomes. Clearly, these 2 comparative studies show that the PED is a better option for large aneurysms and at least no worse of an alternative for smaller aneurysms in which conventional techniques are lauded as the safest and most effective. Thus, in contrast to the conclusion of the meta-analysis, the use of flow diverters can and probably should be extended to patients eligible for more conventional treatments.

At our institution, we have treated more than 240 aneurysms with the PED since its US Food and Drug Administration approval, and we have noted a dramatic decrease in the complication rate after an initial learning curve phase.6 The Pipeline procedure is also much more simple than coil embolization or stent-assisted coiling and requires significantly shorter fluoroscopy and procedure times.12 Moreover, flow diversion is more economical than conventional strategies with a 27% reduction in the cost per millimeter of aneurysm treated.13 The safety, practicality, ease of use, high efficacy, and cost benefit of the PED have all led to a dramatic decline in the use of coils at our institution. Basically, we and several other institutions are now offering coiling only for freshly ruptured aneurysms. In other terms, this is a new era, one that belongs to flow diverters.

Although the authors are to be commended for their effort, we thank the editors of Neurosurgery for allowing us to respond to unfounded statements that may potentially affect patient care.

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Dr Jabbour has served as consultant for ev3, Codman Neurovascular, and Mizuho. Dr Chalouhi has no personal, financial, or institutional interest in any of the drugs, materials, or devices described in this article.

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