In New Zealand MRIs for people with congenital heart conditions are mainly done in Auckland, Christchurch and Wellington, but sometimes more straightforward scans can be done elsewhere. This means that  you may need to travel to a different hospital in order to have your scan.

This is because cardiac MRI is a specialised procedure which requires specific software to allow the scanner to take pictures of the heart. The radiologist or cardiologist doing the scan also needs to have specific training and expertise in analysing cardiac MRI scans.

The picture shows what a cardiac MRI scanner looks like. The circular part is a powerful magnet which allows the scanner to produce the MRI pictures. MRI uses magnetic fields and radio waves to generate the pictures instead of x-rays: this is thought to be a safe way of generating the pictures without needing to use the small amount of x-ray radiation that is required for CT scans.

You will lie on the bed that you can see in the picture. This is then moved into the MRI machine so that you are lying inside the circular part of MRI scanner while the pictures are taken.

Sometimes we use MRI contrast to improve the pictures that we obtain. This is a clear liquid that is injected into a vein and it contains a substance called gadolinium. The gadolinium appears bright on the MRI pictures and can help to show up blood vessels and also helps to demonstrate areas of abnormal heart muscle.

The length of the scan depends on your heart diagnosis and exactly what information the doctors need from the MRI scan. If there is a lot of information required it may take over an hour, but usually it’s between 30 minutes and an hour for most people.

It is a bit boring, but you do need to try to lie still for the scan and not move around. You will be able to listen to music through headphones for at least part of the scan.

Usually MRI is a very safe test, but there are some situations where MRI is not safe. This is usually related to metal implants or injuries involving metal fragments, particularly if these involve the eyes. Because the magnetic field is very powerful this can make the scan unsafe.

As far as we know gadolinium is a safe substance and it has been administered to many millions of people around the world. We know that a very small amount of gadolinium remains in the brain long after scans have been done, but there is no evidence that this causes any problems.

There are a few situations where gadolinium is not advised because it can cause complications. The most important one is in people with major kidney dysfunction, so we may ask you to have a blood test to check your kidney function prior to the scan.

If you need to have a gadolinium injection for the scan, there is a small risk of allergic reactions. These can include itching and skin flushing, or skin rashes or hives. More severe reactions including difficulty breathing or anaphylaxis can occur, but are very rare. There are appropriate medicines available in the MRI facility to treat reactions and even resuscitation equipment if this is required.

You’re at greater risk of an allergic reaction to MRI contrast if you’ve had a previous reaction. Let the medical team know if this is the case. Sometimes you can be given medicines prior to the scan which will reduce the risk of a reaction.

The scan itself is not painful. If you need contrast for the scan you will need a small intravenous line so that the contrast can be injected into a vein: often the iv line will be put in before you start the scan.

The scanner is quite noisy and you will be given headphones to wear. It’s also quite a small space in the scanner, so some people feel a bit claustrophobic. For most people this is something they can put up with, but for a small number of people it can be more of a problem. If this is a big deal for you, then you may be able to have some sedation before the scan, but this will usually need to be organised in advance.

Cardiac pacemakers can also be a reason why some people cannot have an MRI scan, although the more modern pacemakers have been specifically designed to be MRI compatible. If you do have a pacemaker it is important to check with your cardiologist to make sure that your pacemaker is suitable for MRI scans.

When you come for your MRI scan you will usually be asked not to eat prior to the scan. The amount of time during which you need to avoid eating will usually be specified on the appointment letter that you receive in the mail.

You also need to avoid caffeine for 24 hours prior to your scan, so this means no coffee or tea and no chocolate for the day before the scan (sorry!).

MRI scanning is safe for pregnant women, but in most cases gadolinium contrast will be avoided.