"Evaluation of the impact of the dose of heparin on the occurrence of DWI ischemic lesions after embolization of unruptured intracranial aneurysm" "HARMONI"
A brain aneurysm is a weak bulge in a blood vessel wall. When doctors treat an aneurysm before it bursts, they often use a keyhole technique called embolisation to seal it off safely. During this procedure, a blood thinner called heparin is given to stop blood clots from forming. However, finding the perfect balance is crucial: too little blood thinner can allow tiny clots to travel to the brain, while too much can cause bleeding. This study, called the HARMONI trial, compares different doses of heparin to find out which works best. Participants will have their planned aneurysm treatment with one of the study doses. An MRI scan 24 hours later will check for any tiny, often harmless areas of reduced blood flow. By taking part, patients help doctors make aneurysm surgery safer for everyone in the future.
At a glance
What is this study about?
A brain aneurysm is a small blister-like bulge that forms on a blood vessel in the brain. If an aneurysm has not burst (unruptured), doctors often recommend treating it to prevent future problems. The most common treatment is embolisation, a gentle keyhole procedure where doctors guide tiny coils or stents through a blood vessel to seal off the bulge.
During this procedure, the body's natural response is to try to form blood clots around the medical devices. To stop this from happening, doctors routinely use a blood-thinning medicine called heparin. While heparin prevents dangerous clots from forming, giving too much can increase the risk of bleeding in the brain. Doctors want to find the safest balance between preventing clots and avoiding bleeds.
This clinical study, named HARMONI, is testing different doses of heparin during aneurysm treatment. The team wants to find out if adjusting the dose reduces the chance of tiny, quiet areas of reduced blood flow—known as ischemic lesions—which can show up on scans even if they do not cause noticeable symptoms.
About 24 hours after the keyhole procedure, each patient has an MRI brain scan. This scan allows researchers to check for any microscopic spots where blood flow was temporarily reduced. The findings will help doctors choose the safest, most effective dose of blood thinner for future patients worldwide.
Key takeaways
- The trial tests different doses of the blood thinner heparin during keyhole brain aneurysm surgery.
- The goal is to find the dose that best stops clots without raising the risk of bleeding.
- Participants have a routine MRI scan 24 hours after their procedure to check their brain vessels.
- Participation lasts for your normal hospital stay (about 24 to 48 hours).
- Joining the study is completely voluntary and does not change your right to standard treatment.
Who may be eligible?
This trial is open to adults aged 18 and older who are already scheduled to have keyhole treatment (embolisation) for an unruptured brain aneurysm. Men and women can both take part.
To be suitable, your aneurysm must not have burst, and you must be able to have standard brain imaging, including a routine MRI scan after your procedure. You will also need to be able to safely receive common blood-thinning medications used during this type of surgery.
People whose aneurysms have already burst or bled, or those who cannot safely have an MRI scan (for example, due to certain metallic implants), will not be able to join the study. Your hospital care team will check your full medical history to confirm if this trial is right for you.
Could this study suit you?
Answer these quick questions to see if you may be eligible. This is a guide only — the research team makes the final call.
- I am aged 18 or older.
- I have been diagnosed with an unruptured brain aneurysm.
- I am scheduled to have keyhole repair (embolisation) for my aneurysm.
- I am able to safely have an MRI scan.
- I can safely take standard blood-thinning medications.
What does participation involve?
If you decide to take part, your planned hospital stay will feel very similar to standard NHS care. On the day of your aneurysm treatment, you will receive the keyhole procedure as planned. As part of the study, the medical team will give you a specific dose of heparin through an intravenous drip, alongside standard protective medicines like aspirin.
Throughout the procedure, doctors will closely monitor your blood and brain vessels. The main extra step is a special MRI brain scan roughly 24 hours after your surgery. A doctor will also carry out a gentle neurological check (checking your speech, vision, and movement) to ensure you are recovering well.
Your active involvement in the trial is short, usually lasting around 24 to 48 hours while you are in the hospital. The research team will review your recovery before you go home and may check your medical notes as part of your normal post-surgery follow-up.
Potential risks and benefits
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Common questions
What is an unruptured brain aneurysm?
It is a small, intact bulge in a brain artery that has been discovered before it has leaked or burst. Treating it prevents it from bursting in the future.
What is an ischemic lesion?
It is a tiny area of tissue that temporarily received less blood flow. During keyhole surgery, microscopic clots can cause these spots, which often show up on MRI scans without causing any noticeable symptoms.
Will taking part delay my planned surgery?
No. The study is built directly into your planned procedure, so your surgery should take place on your scheduled date as normal.
Will I know which dose of heparin I receive?
This is usually determined by a computer process to keep the study fair and unbiased. Your surgical team will always know exactly what medicine you are receiving so they can keep you safe.
Do I have to pay anything to take part?
No. All study medicines and extra checks, such as the 24-hour MRI scan, are provided at no cost to you.
How to find out more
Always speak to your GP or specialist before deciding to take part in a study.
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