Looking after your heart


What is cardiac resynchronisation therapy (CRT)

CRT is a therapy that is sometimes required to maximise the pumping function of the heart inpatients with underlying poor ventricular function, for example patients with heart failure. Often the two lower chambers of the heart, the ventricles, become uncoordinated, making the heart less efficient. A normal pacemaker usually only has wires (leads) in the right side of the heart. CRT requires an extra wire to be placed into the left ventricle to enable both sides to beat together (resynchronisation).

Making the lower chambers of the heart work together can improve the overall function of the heart as a pump and reduce the symptoms of breathlessness and fatigue. Your doctor has decided that you may benefit from CRT as you have been noted to have reduced ventricular pump function or reduced ejection fraction (EF).


Other tests

Your doctor is likely to suggest you have a number of tests before the decision is taken to implant a CRT device.

You may have an angiogram (cardiac catheter) to check the blood supply to the heart. Due to a blockage or narrowing in one of the coronary arteries (vessels that supply the heart muscle with blood) you may have a reduced blood flow to the heart. This can cause ischaemia (lack of oxygen to the heart muscle), which can reduce the pump function of the heart. If the blockages or narrowings can be treated by angioplasty, which is the inflation of a balloon catheter to widen the narrowed artery or by cardiac surgery, you may no longer require CRT therapy as normal blood flow is returned to the heart.

Some patients will need to have a magnetic resonance imaging (MRI) to look in a very detailed way at the structures and muscle of the heart. However if you already have a device implanted, for example a pacemaker or ICD, you will not be able to have an MRI scan, this is because the MRI scanner uses magnetic fields to generate the images.


Risks of the procedure

CRT implantation is safe. However, as with any procedure, there are potential risks. The risks will be fully explained by your doctor before you have your procedure. CRT implantation is performed safely in both children and adults.


Further information

The following websites also provide useful information:






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Heart Rhythm Clinic is based at Spire Southampton Hospital but also consults in Lymington, Sarum Road (Winchester) and the Nuffield Hospital, Southampton.