Cardiac Resynchronisation Therapy (CRT) is an implantable device specifically designed for people with heart failure. CRT is similar to a pacemaker implantation, but paces both ventricles simultaneously to produce a coordinated pumping action. This synchronised contraction can improve the efficiency of damaged or weakened heart muscle in certain groups of patients.
CRT is not a substitute for medication. Anyone receiving this therapy should continue to take the medications prescribed by their cardiologist.
How does CRT work?
Conduction of electrical impulses through the heart can be slowed in some patients with heart failure. The most common cause of conduction delay in heart failure patients is left bundle branch block. The signal is delayed in the left bundle branch, resulting in the contraction of the ventricles in an uncoordinated and less efficient manner.
CRT aims to restore synchronised contraction of the ventricles and improve the efficiency of the heart's pumping action. This is achieved by overcoming the delays in electrical impulse conduction and can decrease the symptoms of heart failure.
CRT uses electrical impulses to coordinate the contraction of the left and right ventricles. For this reason, CRT is sometimes called "biventricular pacing".
The CRT system has two components
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.
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.
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 3 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 defibrillation lead in the right ventricle.
You will be required to fast for 6 hours before the 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 will be given a tablet such as Valium to help you relax.
The procedure should take approximately 2 hours. It is performed in the Cardiac Catheter Theatre where the leads are implanted through a vein (transvenously). The leads are introduced into a vein in the left upper chest region. The lead is then threaded through the vein to the appropriate chamber in the heart.
After the leads are in position, they are secured and connected to the pulse generator, which is positioned on the left side of your upper chest. During the procedure the CRT device is tested to ensure it works successfully.
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 will be tested by your doctor or a pacemaker technician. The monitoring leads will be removed once your CRT device has been checked. You may still experience some pain at the insertion site. This should be eased by taking some paracetamol.
By the time you are discharged, you may leave feeling emotionally and physically drained and perhaps depressed. This is quite normal, and will improve as you recover. Most people adapt very well to their CRT device and return to most of their normal previous activities.
You will have regular routine check-ups that will be scheduled; the first after 3 months and then 6 monthly thereafter. These will take place either in the QCG rooms, or via our Remote Monitoring Service.
Your CRT device will monitor and treat your heart automatically, but you must make an effort to follow your doctor's instructions, and maintain regular check-ups.
Follow Up Visits and Remote Home Monitoring
An important feature of your CRT device is the information that it stores about your heart function between check-ups. This vital information assists your doctor in your ongoing treatment.
Information gathered may include:
- How your device has performed since your last check-up.
- Any irregular heart rhythms or events that may have occurred.
- Checking the battery to see how much energy remains. The battery life is able to be calculated accurately and the device is replaced well before the battery is flat.
If you have any questions or concerns, do not hesitate to talk to your doctor, pacemaker technician or nurse.
Who do I call?
Phone your cardiologist on 07 3016 1111 during office hours if you:
- Notice any redness, swelling, warmth or fluid drainage from your wound site.
- Develop a fever that does not go away after 2-3 days.
- Have any questions about your CRT device, heart rhythm or medications.
- Plan to travel or move.
- Notice anything unusual or unexpected such as new symptoms.
How will CRT affect my life?
The response to CRT varies between patients. Improvements may be experienced quickly but can occur over a number of months. Patients may notice fewer symptoms, improvement in exercise capacity and improved quality of life.
You will receive a booklet produced by the manufacturer of the CRT 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.
Although your device may replace some medications, you may still need to continue with others. Some medications work with your CRT device to support heart pump function and to treat abnormal rhythms. Make sure you talk to your doctor to understand why you are taking these medications, and always take them as directed.
Airport Screening Devices
May detect the pacemaker's metal case. It will be necessary to present your device ID card to obtain clearance.
CRT devices are protected from most interference produced by electrical appliances. You can safely use common household appliances if it has been properly grounded and maintained in good repair. This includes microwave ovens, televisions, computers and portable phones etc.
For Patients with a CRT-ICD Device
An electrical current from poorly grounded equipment could cause your CRT device with defibrillator function to deliver a shock, even if the current is too small to be noticed.
Take precautions when using electrical equipment in damp or wet conditions. If you feel a tingle when touching anything metal, such as an electrical appliance, immediately let go and have the cause investigated and corrected by a qualified person.
If you receive a shock from your CRT-ICD
- Stay calm.
- Move to a comfortable place where you can lie or sit down.
- One shock from your ICD – providing you are feeling, there may not be any need for immediate medical assistance.
- If you receive a series of shocks or symptoms persist – call an ambulance, DIAL 000.
- If you receive more than one shock in 24 hours notify your cardiologist.
Avoid strong electric or magnetic fields
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 - use on the opposite ear to the side of the ICD (see below).
- 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.
Studies have indicated that there may be some potential interaction between mobile phones and CRT devices with or without defibrillator function. This may be due either to the radiofrequency signal or the magnet housed within the phone. The effect is temporary, and may include preventing or delivering an extra therapy when the phone is within close proximity (15cm).
- Maintain a minimum distance of 15cm between your device and your mobile phone.
- Hold the phone to the ear opposite your device.
- Don't carry your phone in your breast pocket.
Always tell your health professional that you have an ICD and show your ID card. Most medical procedures are unlikely to interfere with your pacemaker. An MRI scanner may interfere if your device is not MRI compatible.
What should my friends and family know about my CRT device?
Your friends and family should be encouraged to learn about your CRT 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 as a precaution. You can contact the local ambulance service or St John's Ambulance service for more information.
For more information read about Conduction System.