Endovascular Coiling of Cerebral Aneurysms Using “Bioactive” or Coated-Coil Technologies: A Systematic Review of the Literature

Abstract

SUMMARY: Second-generation coils have been available since 2002. We wanted to assess their performance and appraise available evidence. Therefore we performed a systematic review of the literature from 2002 to 2007. There were 27 studies with a total of 2390 patients that met pre-specified inclusion criteria. All studies were classed as having a high risk of bias. There were no randomized trials and for most studies results were not independently assessed and follow-up periods were short (mean 7 months). There were large differences in demographic and aneurysm characteristics, making comparisons between coil cohorts difficult. Procedure-related morbidity and mortality were similar for all coil types. Hemorrhagic events during follow-up were few, in the range of 1%/year for all coil types. The available literature is of poor quality and clinical series provide very little evidence in favor of second-generation coils. Positive randomized trial results are needed to justify routine clinical use. This systematic review illustrates the failure of the industry, the regulatory authorities, and the neurointerventional community combined to provide a reliable and prudent approach to the introduction of new devices. Since 2002, several coil manufacturers have introduced a variety of controlled detachment coil types specifically designed "to promote aneurysm healing" following cerebral aneurysm coiling or to improve the durability and angiographic results of coiling. Although they have been submitted to various regulatory agencies as "similar to a predicate device," once on the market, these coils were often claimed to be substantially different from or better than standard platinum coils. These devices include coils using polyglycolic (PGA) or combined polyglycolic/polylactic acid (PGLA), nylon/Dacron (DuPont, Wilmington, Del)/PGLA fibers, and hydrogel coating. None of these products were subjected to randomized controlled trial evaluation before being marketed extensively, 1,2 and many were not even seriously tested in appropriate animal models. 3 Many were sold at a substantial cost premium despite the lack of grade 1 evidence for equivalent safety, let alone of improved efficacy compared with the proved bare platinum coil technology. 4,5 Several years later, randomized controlled trials are underway, but it will be some months before the first of these, the HydroCoil Endovascular Aneurysm Occlusion and Packing Study trial, 6 reports follow-up results and approximately 1-6 years before the others report. In an effort to clarify and critically appraise the existing published literature of case series, prospective single-or multicenter studies, and national or international registries, we have undertaken a systematic review. Such reviews reliably determine the quality and quantity of published work and can help direct/prioritize future research. 7 Materials and Methods Search StrategyWe performed a systematic review of the literature (paper/electronic) from 2002 to 2007 inclusive. A computerized search strategy of MEDLINE...

HydroCoils, Occlusion Rates, and Outcomes: A Large Single-Center Study

“…20 HydroCoils are safe, and initial procedural results from the HELPS study showed no significant difference in the complication rate in a properly controlled study. 21 This study agrees with ours in demonstrating a low risk of adverse procedure-related clinical complications.…”

“…[9][10][11][12][13][14][15][16][17][18][19] These same articles were recently the subject of an evidence-based review of bioactive coils by White and Raymond,20 which revealed that on the evidence-based hierarchy, the published data were inadequate, only achieving a Cochrane level C. The downfall of many of these studies as described by the authors of this latter publication was the inaccurate and incomplete reporting of data. We have attempted to overcome some of the deficiencies highlighted by the way we have reported our data.…”

Embolization of Intracranial Aneurysms with HydroSoft Coils: Results of the Korean Multicenter Study

“…Systematic review of endovascular coiling of cerebral aneurysms by using coated coils demonstrated 4.7% and 2.9% morbidity-mortality rates in PGLA-coated and hydrogel-coated groups, respectively. 17 Immediate angiographic results of the HydroSoft coil were complete occlusion in 69%, residual neck in 19%, and residual sac in 12%. The HydroCoil Endovascular Aneurysm Occlusion and Packing Study showed complete immediate occlusion in 47% and residual neck in 31%.…”

Long-Term Follow-Up of 1036 Cerebral Aneurysms Treated by Bare Coils: A Multicentric Cohort Treated between 1998 and 2003

“…Results of these new devices, however, are sometimes disappointing, and it remains to be proved that modified coils provide better results. [24][25][26] One of the limitations in our study, which began in 1998, is the absence of an independent core laboratory to analyze our results. However, in each of the 5 participating centers in our study, the physician who collected and reviewed all of the aneurysms was independent of the treating physician.…”