HEAT: Hydrogel Coil Superior to Standard Coil for Aneurysm

Pauline Anderson

February 08, 2019

HONOLULU — Compared to receiving a standard platinum coil during an endovascular procedure, patients getting the second-generation hydrogel coil had a significantly lower rate of aneurysm recurrence, and had a similar level of adverse events, new research shows.

"This study adds more credibility to the argument that gel coils result in less recanalization," study author Bernard R. Bendok, MD, Chair, Department of Neurological Surgery at the Mayo Clinic in Phoenix, Arizona, told Medscape Medical News.

"This study suggests, strongly, that using gel coils likely results in better durability of treatment without increasing adverse outcomes."

Dr Bernard Bendok

Results of the Hydrogel Endovascular Aneurysm Treatment (HEAT) trial were presented here at the International Stroke Conference (ISC) 2019.

Intracranial aneurysms may cause neurologic injury and can be life-threatening. "You want treatments to be low risk and durable and effective," said Bendok. He added that if an aneurysm recurs, it can cause rehemorrhage. "As people are living longer, it's important that these treatments last, for a lifetime hopefully."

The US Food and Drug Administration-approved device used in this study, called the HydroCoil Embolization System, consists of platinum coils coated with a hydrogel that expands in the body.

The HEAT postmarket clinical trial included 600 subjects ages 18 to 75 years (mean age about 57 years) from 46 sites in the US and Canada; almost 80% were female.

Participants had to have an untreated aneurysm of between 3 mm and 14 mm in size. Most had an unruptured rather than ruptured aneurysm.

"They had an aneurysm that everyone agreed should be treated," said Bendok.

During an endovascular procedure, subjects randomly received either the standard platinum coil or the new system. The two groups had similar baseline characteristics.

Patients were assessed before their surgery and at regular visits afterward. They were followed for 18 to 24 months (mean follow-up, 21 months). Bendok noted that most studies of coils continue for only a year.

Aneurysm Recurrence

The primary outcome was aneurysm recurrence, defined as any progression on the three-level Raymond-Roy Aneurysm Occlusion Scale. Raymond-Roy 1 indicates complete occlusion; 2 is residual neck; and 3 is residual aneurysm.

Researchers also rated aneurysms using the Meyer Aneurysm Occlusion Scale. This scale includes progressively more serious grades of recanalization, from Grade 1 to Grade 5.

A secondary outcome included packing density as measured by volumetric filling of the aneurysm. "How much of the aneurysm you fill can affect the chance of recurrence," noted Bendok.

Other secondary outcomes included adverse events related to the procedure and/or the device, mortality rate, modified Rankin Score (mRS), and various quality-of-life measures.

Staff at the imaging core lab were blinded to coil type, site, and site evaluation, but practitioners were not blinded.

The analysis included 231 in the bare platinum group and 222 in the hydrogel group at 18 to 24 months.

The primary endpoint of recanalization occurred in 15.4% of the bare platinum coil group and in 4.4% in the hydrogel group on the Raymond-Roy Scale (P < .001).

The hydrogel coil was beneficial in patients with both ruptured and unruptured aneurysms, although this was not an endpoint and therefore did not have a P value, said Bendok. Among the unruptured group, the percentages for recanalization were 11.9% for the bare platinum coil and 3.2% for the hydrogel coil. For the ruptured group, the percentages were 23.5% for the bare platinum coil and 7.9% for the hydrogel coil.

On the Meyer scale, recanalization occurred in 27% in the bare platinum group and 13% in the hydrogel group (P < .001).

Packing density was 24.7% for the bare platinum coil and 32.5% for the hydrogel coil (P < .001).

"Hydrogel, by expanding in the aneurysm, fills more of the dead space," commented Bendok.

"When you put coils in an aneurysm, even when you get complete angiographic occlusion, you're only hitting about 30% volumetric fill of the aneurysm; but with hydrogel you can push that up by 10 to 20%."

Initial complete occlusion occurred in 28% for the platinum coil vs 18% for hydrogel coil (P = .003), but there was progressively more occlusion at 3 to 12 months and 12 to 24 months.

Retreatment was required in 8% of the bare platinum coil and in 5% of the hydrogel coil groups (P = .162).

Similar Side Effects

There were no significant differences in mortality rate (3% for the standard and 2% for the hydrogel) or in adverse events such as bleeding related to the coil or procedure (25% for bare platinum and 22% for hydrogel).

There was no significant difference in mRS scores between the two groups.

Interestingly, quality of life improved similarly in both groups. "This may be one of the first studies in the literature to show that treating an aneurysm improves quality of life, although we don't fully know the reasons for that," said Bendok.

Commenting on the study for Medscape Medical News, Mark Alberts, MD, chief of neurology at Hartford Hospital in Connecticut, complimented the authors.

"This was a large, well-done study, and the outcomes are clinically relevant," said Alberts, who was not involved with the research. "I think it will change what the endovascular people and neurosurgeons do because it looks like this hydrogel coil worked better than the standard therapy and it was safe and well tolerated, and had a good clinical outcome."

For people who perform this sort of aneurysm surgery "for a living," these new results are "a big deal," said Alberts.

The study was funded by MicroVention. Bendok has disclosed no relevant financial relationships.

International Stroke Conference (ISC) 2019: Abstract LB20.
Presented February 7, 2019.

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