RecruitingInterventional

Comparing three types of specialist pacemakers to improve heart function and reduce rhythm problems in heart failure

This UK study is looking at new ways to help people with heart failure whose hearts don't beat in time. When the heart's electrical signals are delayed, it struggles to pump blood effectively, causing symptoms and shortening life. Doctors can implant special pacemakers to help the heart's left and right sides beat together. Traditionally, this is done with a 'biventricular pacemaker'. This study compares two newer pacemaker approaches — one that uses a single lead to directly connect to the heart's natural wiring (conduction system pacing) and a combination of both. It aims to discover which method is best at improving symptoms, physical ability, heart pumping, and preventing abnormal heart rhythms over six months.

At a glance

Status

Recruiting

Sponsor

Imperial College London

Enrolment target

Start

12 Nov 2025

Estimated completion

01 Oct 2028

Heart failure with reduced ejection fraction and electrical dyssynchrony

What is this study about?

If you have heart failure, it means your heart isn't pumping blood as well as it should. For some people, this is because the electrical signals in their heart are a bit out of sync. Imagine your heart is an orchestra, and the left and right sides are two sections. If they play at slightly different times, the music (your heartbeat) won't be as strong or effective. This can lead to symptoms like breathlessness and tiredness, and can make your heart failure worse.

Doctors can implant special pacemakers, often called 'cardiac resynchronisation therapy' or CRT, to help solve this timing problem. These devices send small electrical pulses to help your heart's left and right sides beat together more effectively. The study wants to find out if newer types of these pacemakers work better than the traditional ones. The traditional pacemaker uses two wires: one on the right side of your heart and one on the outside of the left side. While this helps with timing, the way electricity then spreads through the heart can still be a bit unusual, sometimes leading to abnormal heart rhythms.

Researchers have developed a newer approach where a single wire is placed right into the middle of your heart, connecting to its natural electrical system. This aims to make the heart's electrical signals spread more naturally. This study will compare this 'conduction system pacing' to the traditional method, and also to a combined approach. The main goal is to see which type of pacemaker helps most with heart failure symptoms and rhythm problems over half a year. They'll also look at how these different pacemakers affect your heart's strength and overall function.

Key takeaways

Compares three types of pacemakers for heart failure.
Aims to improve heart function and reduce symptoms.
Involves four hospital visits at Hammersmith Hospital over six months.
Participants are randomly assigned to a pacemaker type.
Information gained could help future heart failure patients.
You can withdraw from the study at any time.

Who may be eligible?

This study is looking for adults who have been referred by their heart doctor (cardiologist) for a special type of pacemaker called cardiac resynchronisation therapy (CRT). This pacemaker helps improve your heart's pumping.

To be considered, you must have heart failure that causes symptoms (meaning it bothers you in daily life), and your heart's main pumping chamber (left ventricle) shouldn't be pumping blood well (doctors call this a reduced ejection fraction of 40% or less). Your doctor will also check electrical readings on your heart (an ECG) to see if the electrical signals inside your heart are delayed or out of sync.

You won't be able to join if you're under 18 years old or unable to understand and agree to take part. If you are a woman who could become pregnant, you'll have a pregnancy test before joining, and if you're pregnant, you won't be able to participate.

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.

Are you an adult (18 or older)?
Have you been referred by your heart doctor for a special pacemaker (CRT)?
Do you have heart failure symptoms?
Has your doctor told you your main heart pumping chamber isn't working at full strength?
Could you be pregnant (if applicable, you'll need a negative test)?
Can you understand and agree to take part in the study?

Answer every question to see your result.

What does participation involve?

If you decide to join this study, you'll need to attend four hospital visits at Hammersmith Hospital over six months. Refreshments will be provided at each visit. The first visit, where you'll learn more and give your consent, will have your travel costs reimbursed (e.g., taxi fare).

Before your pacemaker is fitted, you'll have some routine tests, which will be used for the study. You’ll also do special research tests like a walking test, complete questionnaires about your heart failure, and have a detailed ECG. A special app will be set up on your smartphone (or a friend/family member's phone) for you to record a main heart failure symptom every day for six months. If you don't have a phone or someone to help, the research team can call you daily.

When your pacemaker is implanted, you'll be randomly assigned to one of the three pacemaker types, like drawing lots. You, and the doctors measuring your progress, won't know which type you have until after six months or if you leave the study. You'll wear a special vest for a few hours before and during the procedure for electrical measurements, and you'll have some quick blood pressure and ECG checks. After the pacemaker is fitted, you'll have two more follow-up visits (at 12 weeks and 6 months) which will include standard heart checks along with extra research tests like more walking tests, questionnaires, and electrical heart measurements. At the 6-month visit, you'll also have a low-dose CT scan and wear the special vest again. After six months, there are no more in-person research visits, and your care will return to how it was before the study, with your pacemaker adjusted if needed by your clinical team. The research team will continue to monitor your health remotely for up to three years using your routine medical records.

Potential risks and benefits

There might not be a direct personal benefit for you from taking part in this study. However, the information gathered will help doctors understand which pacemaker type works best for heart failure, potentially leading to better care for others in the future. The risks of having the pacemaker fitted are similar to those for any standard pacemaker procedure. There's a very small risk (less than 1%) from inserting a small tube for blood pressure measurements, including damage to the artery, bleeding, or infection. You'll also have two low-dose CT scans, which involve a small amount of radiation. This slightly increases your lifetime risk of cancer (by about 0.03% above the general population's 50% risk). There are also very small risks of pain or bruising from blood tests. Some questions in the questionnaires might be sensitive. Remember, you can withdraw from the study at any time, for any reason, without it affecting your medical care.

Locations (1)

Some site locations are approximate. We're improving this — please verify with the trial team before travelling.

Imperial College Healthcare NHS Trust
City only
London, England

Common questions

What is heart failure?

Heart failure means your heart isn't pumping blood around your body as efficiently as it should, leading to symptoms like tiredness and breathlessness.

What is a pacemaker?

A pacemaker is a small device placed in your chest that sends electrical pulses to your heart to help it beat regularly and in time.

Will I know which pacemaker I receive?

No, you won't know which type of pacemaker you receive until after the 6-month study period is complete.

How many visits do I need to make?

You'll have four hospital visits over six months, all at Hammersmith Hospital.

Can I leave the study at any time?

Yes, you are free to leave the study at any point without it affecting your usual medical care.

How to find out more

Jack Samways

j.samways@nhs.net +44 020 3313 3000 Official trial record

Always speak to your GP or specialist before deciding to take part in a study.