So what is Cardiac Resynchronisation Therapy also known as CRT-P / CRT-D

This page deals with CRT devices CRT-P, CRT-D and ICD

CRT stands for Cardiac Resynchronisation Therapy, the “D” for defibrillator and the “P” for pacing. Often when people have heart failure their heart is weak and may be damaged in places. This means that the heart does not beat effectively and the electrical system may be damaged. A biventricular pacemaker has 3 leads, one is situated in the top chamber of your heart and the other two pacing leads are positioned at each side of your heart and pace it simultaneously from the bottom with tiny electrical impulses.

The amount of blood pushed out of your heart in one beat is known as your EF (ejection fraction) usually expressed as percentage e.g. 30%.  This, along with other factors, is used as a clinical indicator of heart failure. The CRT device is there to increase your heart function. In the UK NICE (National Institute for Care and Health Excellence) recommends patients with an ejection fraction of less than 35% may be eligible for CRT devices.

See the NICE guidelines here

Read our CRT and ICD pre implant toolkit

Single / Dual Chamber Pacemakers

It is important not to get confused between CRT devices and single or dual chamber pacemakers which have one or two leads and send an electrical impulse so the heart beats at a normal rate, however if the heart muscle is not working properly like in heart failure then this is not the optimum treatment.

A CRT-D device

The image is that of a CRT-D device. Notice the 3 leads on the top. They are marked RA (Right atrial) LV (left ventricle) and RV (right ventricle).

Image provided courtesy of Boston Scientific. © 2015 Boston Scientific Corporation or its affiliates. All rights reserved”



Helps resynchronise the heart function, makes it work better at pumping the blood around the body


Does the same as the CRT-P but in addition has defibrillation therapy to protect you if you are at risk of a dangerous rhythm

So who gets one?

If your condition is not improving whilst you are on medication then your cardiologist may recommend having a CRT-D or a CRT-P. There are many reasons why you may be fitted with a CRT-P or CRT-D but it will always be to improve your heart function.  If you are at risk of developing an abnormal heart rhythm then you may be recommended to have a CRT-D. This means that if your heart develops a dangerous heart rhythm then the device would defibrillate (shock) the heart back to a normal rhythm. Around 75% of people who have a CRT-P or CRT-D see an improvement in their heart function. For a variety of reasons up to 25% may not have a significant improvement in their heart function.

This is a video that demonstrates what happens when a healthy heart moves towards a heart with heart failure.

“Video provided courtesy of Boston Scientific. © 2015 Boston Scientific Corporation or its affiliates. All rights reserved”

So what's it like to have one put in?

You will be sedated to make you feel comfortable. The surgery is generally carried out using local anaesthetic. An incision is made in your upper chest area. The leads are very thin and are pushed through a vein and into your heart. Once the two leads are inserted into the two top chambers (atria) the other lead is inserted into a vein that encircles your left ventricle and then inserted into the left ventricle. The other end of the lead is then inserted into the device.The surgeon will usually try and create a little pocket under your skin or muscle and place the device in this pocket. The device will then be tested and once it is working optimally you will be taken to recover. The procedure may require an overnight stay in hospital. It is natural you will be sore for a couple of weeks after the surgery. You will have to be careful not to lift your arm on the side the device has been put in above shoulder height until the leads have healed.

This is a video that demonstrates how a CRT device is implanted.

“Video provided courtesy of Boston Scientific. © 2015 Boston Scientific Corporation or its affiliates. All rights reserved”

What's it like to live with a CRT device?

Although a CRT-P is no bigger than a matchbox a CRT-D is slightly larger they are getting smaller as newer models come out. They are comfortable and you will get used to it in a relatively short while after surgery. Some of the new devices attach to a remote home monitoring system whereby information is sent securely to the hospital where your device is remotely monitored. This allows your cardiologist to see how you are doing on a day by day basis. The information will be used to “tweak” your device so it gives you the optimum performance. For other devices without remote monitoring you will generally have to go to hospital once every 6 months to get your device checked however as you should have access to a Heart Failure Nurse then your health can be managed at more regular intervals. Your check-up will be carried out by a cardiac physiologist who will wirelessly connect your device to a specialist computer that downloads all the data from your device. This allows the technician to see how your heart has been working with the device and if it has recorded anything which may require the device to be “tuned”. It’s a bit like having your car in for a service! To tune your CRT device doesn’t require any further surgery.  Modern devices can last for up to 10 years and are very reliable, it’s worth asking your cardiologist how long your device will last for? Eventually the battery will run down and you will need to have a replacement fitted. Your consultant will be able to tell you when you need to replace the device and that there will be a warning to tell you when the batteries are running low and what to do when this happens. On receiving this warning the device will not automatically stop. The procedure is usually scheduled as day surgery. It is a quicker operation as the leads generally do not have to be replaced each time the device is changed so it is just a matter of changing the ‘box’.

This video only relates to a CRT-D. It demonstrates what happens when the heart goes into an abnormal rhythm and the device shocks the heart back into a normal rhythm.

“Image provided courtesy of Boston Scientific. © 2015 Boston Scientific Corporation or its affiliates. All rights reserved”

So what do I need to be aware of?

Some electrical devices may interfere with your device and should be avoided. You should be given a booklet from your device manufacturer with a list of things to avoid.

It is important you avoid magnets near the device including MRI scanners and airport security scanners. You should receive a card which you can present to airport security which will allow you to bypass the body scanner.

Implantable devices cannot be damaged by using properly operating household appliances, such as microwave ovens, electric blankets and most power tools. Your doctor can advise you if you have questions about using certain electrical equipment or tools. You can also contact the device manufacturer for guidance. Most manufacturers have engineers who can determine if the electrical field generated by the equipment can interfere with the CRT device.

Will people be able to see it?

You will have a small scar on your chest area which will usually fade to a thin line but this may be more obvious for women as it may be visible if wearing a lower cut top. Depending on body composition there may be a slight lump under the skin but for most people it is not visible.

My perspective of having gone through this?

My name is Lorna and I am one of the patient educators at the Pumping Marvellous Foundation and I have written this to help you understand why I would recommend you to consider this type of therapy if offered. I know it can be very scary being told that you need a device implanted. You will have lots of questions however don’t be afraid to ask. Below you can have a look at some of the questions I would ask now.

It helps to have someone with you at appointments as you can feel overwhelmed, as they say a problem shared is a problem halved.

It can also help to write down any questions you want answered before hand, treat it like a job interview, the information is not just a one way street, you need to know and be in control of what’s going on as well.

It also may help to speak to someone who already has a device fitted and you can do this by speaking to your heart failure nurse who may be able to put you in touch with someone locally or you could contact us at the Pumping Marvellous Foundation and we can put you in touch with one of our patient educators like me who has one.

Contact us by clicking or tapping here.

If you require more detailed information then please download our Marvellous guide to having a cardiac device fitted.

Listen to patients talking about their devices


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