What is HELPS?

A randomised controlled trial of hydrocoil versus bare platinum in the endovascular coil treatment of intracranial aneurysms. We aim to compare the following in patients allocated hydrocoil versus patients allocated bare platinum:

Primary outcome	Major aneurysm recurrence on follow-up angiography at 3-6 and 15-18 months.
Secondary outcomes	Aneurysm packing density; clinical outcome at 3 and 18 months post-coiling (measured by the modified Rankin scale); coil length deployed (per mm of aneurysm dome); re-bleed and re-treatment rates.

Background

Endovascular treatment is now the preferred treatment option for many intracranial aneurysms. However, aneurysm recurrences and rebleeds are more frequent after endovascular treatment than neurosurgical clipping. Therefore follow-up imaging is mandatory and important to the ongoing patient management. Major recurrences following endovascular treatment are associated with both a high retreatment rate (58.8% overall in one prospective series) and with a substantially increased risk of aneurysmal rebleed- increased 20-fold in recurrent aneurysms in another prospective series. Major recurrences occur in 15% to 19% of cases by 3-6 months, rising to 20% at a mean of 16 months of follow-up.

An endovascular treatment that substantially reduced the major recurrence rate would be expected to reduce both the rebleed rate and the retreatment rate, which would be to the benefit of patients and health care systems alike. As the hydrogel coating hydrocoils can fill small interstices that bare platinum coils cannot, the hydrocoil system offers the prospect of improved aneurysm packing and angiographic outcomes with the added advantage that overall a lesser length of coil might be deployed.

One study (HEAL) has already examined the role of hydrocoil. However, this was a much smaller, company run, non-randomised study with no control arm. This cannot provide robust scientific evidence on which to advocate widespread use of HES in preference to bare platinum. HELPS will enable neurointerventionists to show conclusively, in an independent randomised controlled trial whether hydrocoil usage results in a substantially reduced recurrence rate plus a significantly increased packing density and whether such an approach is largely cost neutral.

Trial Design

Randomised controlled trial of 500 patients (includes allowing for 20% drop out rate by 18 months)

• Trial powered with 80% power (b) to detect significant difference at the 5% level of major recurrence rate of 10% with hydrocoil compared with 20% in control group. Minimisation algorithm employed on randomisation into the trial to ensure balance between the groups on those parameters that directly relate to endovascular coiling.
• Independent core angiographic lab based in Montreal, Canada [Drs Raymond and Roy].
• Clinical status is recorded (using Modified Rankin Score) at 3 months and 18 months post coiling as a secondary endpoint. This is done using questionnaires sent out with prepaid envelope. By sending these direct to the patient rather than getting an assessment done in clinic by the team treating the patient, we will reduce bias and get an independent, valid assessment of clinical outcome.
• Data analysis will be performed by the Trial Steering Committee in collaboration with the trial statistician at the Neurosciences Trials Unit, Edinburgh University. Trial data will be presented according to the CONSORT guidelines. Oversight of the trial is by an independent Data Monitoring Committee according to UK Medical Research Council guidelines.

NB Microvention, have no control over the running of the trial or access to the data. The Protocol was also developed independently.