Cardiac Resynchronisation Therapy (CRT)

What is Cardiac Resynchronisation Therapy (CRT)?

Cardiac Resynchronisation Therapy (CRT) is a procedure in which a therapy device is implanted and connected to the heart to help it beat in a more coordinated (synchronised) manner. It is specifically designed for people with heart failure to help their heart beat as efficiently as possible. The goal of the procedure is to make the heart’s chambers squeeze (contract) in a more organised and efficient way, improving the quality of life for heart failure patients.



In a CRT procedure, the small device is implanted in your chest, under your skin, during minor surgery performed by a specialised cardiologist. The device that is implanted is called ‘cardiac resynchronisation device’ (CRT-D). It can also be referred to as a ‘biventricular pacemaker’ or a ‘CRT pacemaker’ device. It has leads that are connected to each chamber of the heart to deliver the therapy.

The device sends electrical signals to both lower chambers of the heart (right and left ventricles). The signals are timed to trigger the ventricles to contract in a more coordinated way, which improves the pumping of blood out of the heart. This synchronised contraction can improve the efficiency of damaged or weakened heart muscle in some heart failure patients.

What is the difference between a CRT and a pacemaker?

A pacemaker and Cardiac Resynchronisation Therapy (CRT) are similar – they are both medical devices that are implanted in the chest to help regulate the heartbeat. However, there are some important differences between the two devices. A pacemaker is primarily used to treat slow heart rhythms by delivering electrical signals to help the heart beat at more normal speeds. A CRT device is often used to treat heart failure by delivering electrical signals to both sides of the heart in a better coordinated manner that makes it more efficient and reduces symptoms of heart failure.

How does Cardiac Resynchronisation Therapy (CRT) procedure work?

In some heart failure patients, the cause of the inefficient or uncoordinated beat is that part of the heart’s conduction system is not working well – there is a ‘conduction delay’ in part of the heart. This is most commonly due to a ‘left bundle branch block’ (LBBB) – which means that this major branch of nerves that carry the signals to the ventricles are not able to keep in rhythm with the rest of the heart. As a result, the heart’s ventricles are not coordinated and the heartbeat overall is less efficient. For a heart already in heart failure, this further reduction in efficiency can cause excessive strain.

The CRT aims to restore the coordinated contraction of the ventricles and improve the efficiency of the heart’s pumping action. During the CRT procedure, wires from the device are connected to the ventricles on both sides of your heart. The CRT uses electrical impulses to coordinate the contraction of the left and right ventricles. For this reason, CRT is sometimes called “biventricular pacing”.

There are two different types of CRT:

  • Single Therapy System or Bi-ventricular / CRT Pacemaker

Provides CRT therapy in the form of pacing only using three pacing leads. Two are positioned inside the heart in the right atrium and the right ventricle. The third is placed within a vein that lies on the outside surface of the left ventricle.

  • Combined Therapy System or Bi-ventricular ICD / CRT Defibrillator (CRT-D)

Provides CRT pacing therapy as above, but is also capable of treating a fast or irregular heart beat (ventricular tachyarrhythmia). This is achieved by implanting a defibrillator lead in the right ventricle.

The CRT device or CRT machine has two components:

  • Pulse Generator

The Pulse Generator is a small computerised device that runs on a battery. It generates the electrical impulses that are delivered to the heart. The device is small enough to fit in your hand.

  • Leads

The leads are insulated wires that transmit information to and from the heart. The leads carry the electrical impulses from the pulse generator to the heart. They also provide information for the device about your heart rhythm.

How to prepare for a CRT procedure

You will be required to fast for six hours before the CRT procedure.

You may require: 

  • A blood test
  • An ECG
  • Male patients have their chest shaved
  • An antiseptic shower
  • IV drip inserted into your arm
  • You may be given a tablet such as Valium to help you relax

What happens during a CRT procedure

On return to the ward you will be monitored overnight and will remain resting in bed until the following morning. You may be required to stay in hospital for a number of days following the procedure for monitoring.

The morning of discharge your CRT device will be tested by your doctor or a pacemaker technician. The monitoring leads will be removed once your CRT device has been checked and ensured it is programmed correctly. You may still experience some mild pain at the insertion site. This should be eased by taking some paracetamol.

By the time you are discharged, you may feel emotionally and physically drained. This is quite normal, and will improve as you recover. Most people can return to their usual activities after a few days, although driving and heavy lifting might be restricted for a time. 

You will have regular routine check-ups that will be scheduled; the first after three months and then six monthly thereafter. These will take place either in the Queensland Cardiovascular Group offices, or via our Remote Monitoring Service.

Your CRT device will monitor and treat your heart automatically, but you must ensure you follow your doctor’s instructions, and maintain regular check-ups.

Remote Monitoring Service

QCG offers a remote monitoring service that enables ‘virtual check-ups’ for your implanted device. This allows you to directly and securely transmit data from your device to your cardiologist from the comfort of your own home. This enables us to detect significant events such as an abnormal heart rhythm, monitor the performance of your device such as battery life, and optimise your care through device programming or medication change.

Your participation in remote monitoring allows us to follow your device function between visits, and in some situations, it may replace office visits. This means less time spent at the doctor’s office for regular checks, faster time to treatment if your cardiologist detects a medical problem and faster troubleshooting if a problem is detected with your device. Research evidence has shown that early detection of issues through remote monitoring leads to improved health outcomes and a reduced risk of hospital admission. It also allows you to monitor your own heart rhythm and quickly detect any irregularities or arrhythmias.

For more information visit Remote Monitoring Service.

CRT Frequently Asked Questions

While both pacemakers and CRT devices are implantable devices used to treat certain heart conditions, pacemakers are primarily used to regulate the heart’s rhythm, while CRT devices are specifically designed to treat heart failure by improving the coordination of the heart’s contractions. The choice of device will depend on the specific heart condition being treated and the individual needs of the patient.

A cardiac resynchronisation therapy defibrillator is an implantable device that combines the functions of a cardiac resynchronization therapy (CRT) device and an implantable cardioverter defibrillator (ICD). It is used to improve heart function in patients with heart failure and also provide a life-saving shock to treat a cardiac arrest.

Your friends and family should be encouraged to learn about your cardiac resynchronisation therapy device and how they can continue to support you at home. Your device can be a source of security for you and your family and can be viewed as a positive development. This will help you all to be more comfortable with your device when you are away from emergency care.

Some friends or family members may also want to learn more about CPR (cardiopulmonary resuscitation) as a precaution. You can contact the local ambulance service or St John’s Ambulance service for more information.

Strong electric or magnetic fields which may interfere with the device function. Observe all warning notices addressed to people with pacemakers and implantable cardioverter defibrillators.

Probable sources of electrical interference include:

Mobile phones
Magnetic underlays used to alleviate the pain of arthritis.
MRI scanners.
TENS machines used by physiotherapists.
Electrical arc welding equipment.
Dielectric heaters used in industry to bend plastic.
Electric steel furnaces.
CB radio antennas.
Some battery powered tools.

The risk of interaction between your mobile phone and your cardiac device is a low.
The safe distance between your mobile phone and your device is 15 cm.
You may talk with your mobile phone at your ear on the same side that you are device is implanted.
Do not put your mobile phone in a breast pocket or jacket pocket on the same side that your cardiac device is implanted.

You will receive a booklet produced by the manufacturer of the cardiac resynchronisation therapy device, along with a device ID card. Always carry your ID card with you to alert medical and security personnel that you have an implanted device. Your ID card provides information that may be needed if you require emergency treatment

Yes. It is very safe to fly on a plane if you have a cardiac resynchronisation therapy device implanted.

Be aware that the airport security walk-through metal detectors will likely detect your pacemaker and alarm.

At the security checkpoint you should declare you have an implanted cardiac device.
You may be asked to bypass the walk-through metal detectors and be security checked via a handheld metal detector.

Security checks at the airport are safe and will not damage your implanted cardiac device.

Carry your pacemaker ID card: Make sure you carry your implanted cardiac device ID card with you at all times. The card will identify you as genuinely having an implanted cardiac device and provide information about your device, which could be useful in case of an emergency.

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