HOUSTON – Hydrogel coils significantly outperformed bare platinum coils in treating patients with medium-sized intracranial aneurysms, reducing the incidence of adverse outcomes by about 9% in an open-label, randomized trial.

Compared against the platinum coils, the self-expandable, hydrophilic coils scored significantly better on a composite endpoint of aneurysm recurrence at 18 months, re-treatment by 18 months, serious morbidity that prevented angiographic follow-up, and death, Christian Taschner, MD, said at the International Stroke Conference sponsored by the America Heart Association.

The coils are manufactured by MicroVention, Tustin, Calif., which also sponsored the trial. They consist of a platinum helical core coated with a hydrophilic acrylic polymer, which softens and expands on contact with any liquid. The company makes three varieties of the coil; Dr. Taschner’s study examined two of them: Hydrosoft, which is intended to deliver hydrogel at the aneurysm neck, and Hydroframe, which is intended for aneurysms with complex morphology.

These are the company’s second-generation products, said Dr. Taschner, a neuroradiologist at University Hospital Freiburg (Germany). The initial hydrogel-coated coils were not well received because they were too stiff, he said in an interview.

The 18-month study comprised 513 patients and was conducted in 15 centers in France and 7 in Germany. Patients with medium-sized aneurysms (4-12 mm) were randomized to coiling with either the hydrogel coils or bare platinum coils and followed for 18 months. The cohort was stratified by rupture status in the analysis.

Angiographic images of the aneurysm were obtained before treatment, immediately after treatment, at 6 months, and at 18 months. All images were reviewed by an independent laboratory that was blinded to the treatment.

In addition to the primary composite outcome, the study assessed secondary endpoints of modified Rankin Scale (mRS) score at 18 months and coil packing density.

The final analysis included 484 patients. They were a mean of 52 years old, and about 70% were women. The aneurysms were ruptured at baseline in about 43% of cases. The mean aneurysm size was 7 mm, and the mean neck size, 3.5 mm. The dome-to-neck ratio was less than 1.5 in about a third of the group. Most lesions (89%) had anterior circulation.

Most patients needed some kind of adjunctive endovascular-assisting device during the procedure. These included balloon remodeling, which was necessary in about 50% of cases to help keep the coils from extruding into the parent vessel, and stents in 22%.

Intraoperative adverse events were uncommon in both groups. They were numerically, but not significantly, less common in the hydrogel group. These included thromboembolism (8 vs. 12), intraoperative rupture (3 vs. 7), parent vessel occlusion (1 vs. 3), and vessel perforation (one in each group). There were no vessel dissections.

By 18 months, 20% of the hydrogel group and 29% of the platinum coil group had experienced the composite primary endpoint. The 9% absolute difference was statistically significant. It was largely driven by the subcomponents of major recurrence (12% vs. 18%) and re-treatment (3% vs. 6%).

An mRS of 3-5 was used as the proxy for patients whose clinical status prevented them from having angiographic follow-up. That endpoint occurred in three patients in the hydrogel group but in none of the platinum coil group. Dr. Taschner said that difference was not statistically significant.

In an analysis that stratified by baseline rupture status and by aneurysm size, the hydrogel coils were largely superior to bare platinum. However, the hydrogel coils were not significantly more effective than the platinum coils for aneurysms 10 mm or larger, Dr. Taschner noted.

There was no significant difference in the secondary endpoint of mRS at 18 months. Most patients (85% vs. 86%) did well, with an mRS of 0. Scores of 1-2 were seen in 9% of each group. An mRS of 3-5 occurred in 3% of the hydrogel group and 1% of the platinum coil group. There were 17 deaths: 7 in the hydrogel group and 10 in the platinum coil group (3% vs. 4%). This was not a significant difference.

Patients whose aneurysms were unruptured at baseline did significantly better than did those with ruptured lesions, although the mRS scores did not vary significantly between treatment groups. Among those with intact lesions, 90% of the hydrogel and 94% of the platinum coil group achieved an mRS of 0, and 2% of each group died. Among those with ruptured lesions at baseline, 78% of the hydrogel group and 75% of the platinum coil group achieved an mRS of 0. Five patients in the hydrogel group and seven in the platinum coil group died.

On the technical outcome of coil volume, hydrogel did somewhat better (0.041 cm³ vs. 0.038 cm³). The mean packing density was significantly higher (39% vs. 31%).

Dr. Taschner said the study provides good support for using the hydrogel coils in medium-sized aneurysms, and that other recent data reaffirm this.

“A recent trial in Canada and the U.S. looked at hydrogel coils in aneurysms 12 mm or larger, with broad necks, and it failed to show a benefit of the hydrogel coils.”

Additionally, a study published in January found that hydrogel coils were no better than platinum coils in 250 patients with large or recurrent aneurysms (AJNR Am J Neuroradiol. 2017 Jan 12. doi: 10.3174/ajnr.A5101).

“I myself would use them in medium-sized aneurysms with an unfavorable dome-to-neck ratio, and in those that have a broad neck. In those instances, I do think that hydrogel coils have their place. I wouldn’t use them in really large aneurysms. I don’t think they are well suited for that. In those cases, I would probably use platinum coils in combination with a flow diverter. That really provides very stable aneurysm occlusion with acceptable complication rates.”

Dr. Taschner said that he received research support from MicroVention during the study.

msullivan@frontlinemedcom.com

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Hydrogel coils improve outcomes in medium-sized intracranial aneurysms