Written by Dimitrios Vrachatis, Specialist Cardiologist, PhD, National and Kapodistrian University of Athens.
What is biventricular pacing?
A cardiac resynchronisation therapy device (CRT) delivers electrical impulses to both ventricles with carefully coordinated timing. The aim is to resemble the natural spread of electrical activation as closely as possible.
It is device-based treatment rather than medication, used at an advanced stage of treatment for heart failure when symptoms persist despite the maximum tolerated medication.
How does it work?
CRT aims to replace a functioning but poorly coordinated conduction system for as much of the day as possible. It can also act as a pacemaker when the natural system fails to maintain an adequate rate.
The main purpose is to reproduce the electrical activation of a healthy conduction system, improving mechanical contraction and symptoms.
When is CRT needed?
This advanced treatment is used in selected patients with heart failure and ECG features such as left or right bundle branch block with marked QRS widening, indicating poor coordination between the ventricles.
CRT should therefore coordinate ventricular activation for as much of the 24-hour period as possible. Otherwise its effectiveness decreases.
Conventional pacing, by contrast, treats an inadequate heart rate and ideally acts only as backup for severe bradycardia, operating as little as possible.
How does a CRT device differ?
Like pacemakers and defibrillators, CRT systems have a generator, electronic circuitry and leads.
The generator is somewhat larger than a standard pacemaker.
An additional lead is used for the left ventricle. A system usually has a right atrial lead and always has a right ventricular lead plus a lead in the coronary sinus.
The coronary sinus is the heart’s large vein. A lead placed within it can directly pace the left ventricle because of its anatomical proximity.
How is CRT implanted?
Although technically more demanding, implantation is broadly similar to conventional pacemaker or ICD implantation and carries comparable risks.
What if I also need a defibrillator?
If there is an additional indication for a defibrillator, an appropriate CRT device can provide this function. It is called CRT-D, while CRT-P has no defibrillation capability.
Can an existing pacemaker or ICD be upgraded?
Yes. An existing pacemaker or ICD can be upgraded by adding a lead and replacing the generator with a CRT generator.
How long is the hospital stay?
Usually 24 hours if there are no complications.
How often is the device checked?
As with other pacing or defibrillation devices, routine checks are annual, with additional checks for clinical indications or after a shock from a CRT-D device.
When do I need urgent assessment after implantation?
Immediate assessment is needed for fever lasting more than 24 hours, chest pain at rest or on deep breathing, breathlessness, fainting, marked inflammation with pain, redness or swelling, or a haematoma at the device pocket. Your cardiologist will provide instructions.
Can I have an MRI?
More models are becoming MRI-compatible. Your device card identifies the exact model and its capabilities.
What precautions should I take?
Avoid strong magnetic fields, such as those encountered in airport security checks, because they may affect device function, although this is less common with newer models. Keep mobile phones away from the pocket and use them on the opposite side.