Coronary Sinus Reducer Objective Impact on SymptoMs, Ischaemia and miCrovascular Resistance in Non-obstructive Hypertrophic CardioMyopathy

This study is looking for adults aged 18 or over who have a specific type of hypertrophic cardiomyopathy (HCM). You would be considered if your heart muscle is thickened but the blood flow out of your heart is not significantly blocked. You also need to be experiencing ongoing symptoms, even with your current medication, and a special heart MRI scan should show that parts of your heart muscle aren't getting enough blood flow when under stress.

There are certain reasons why you might not be able to join. For instance, if you have very weak heart muscle, severe kidney problems, or if your heart has very high pressure in one of its chambers. Also, if you have another significant heart condition that blocks your arteries, or if you can't have certain types of MRI scans or contrast dyes, you wouldn't be able to take part. Women who are pregnant also cannot participate.

If you've been on certain new medications for HCM in the last six months, or if you can't take blood-thinning medicines, this study might not be right for you. The researchers will check all these details carefully to make sure the study is safe and suitable for everyone involved.

If you decide to take part, the study will involve several steps over about six months. Firstly, you'll have an initial assessment including symptom questionnaires and you'll be set up with a smartphone app to record your daily symptoms. You'll use this app for two weeks to make sure your symptoms are consistent. If you don't have any symptoms during this time, you won't continue in the study.

Next, you'll have a procedure in a hospital lab. You'll be given medicine to make you feel very relaxed (sedated), and headphones to help you stay calm and unaware of what's happening. You will then be randomly chosen to receive either the coronary sinus reducer device or a dummy procedure. You won't know which one you've had. During this procedure, the doctors will take some measurements from a vein in your neck and also take blood samples from your heart.

Some participants will also have an extra, more detailed heart examination where doctors look at your heart's blood vessels using thin wires and special measurements. This extra check happens before you have the device or dummy procedure. After the procedure, you will continue to use the smartphone app to report your symptoms daily for six months. At the end of the six months, you'll return for repeat questionnaires and another special heart MRI scan. If you had the extra heart examination at the start, you'll be invited to have it again at six months to see if there have been any changes.