About a cardiac MRI scan
A cardiac (heart) MRI uses a strong magnetic field, radio waves and a computer to make detailed still and moving pictures of the heart. It does not use X-rays. It shows the size and shape of the heart’s chambers, how well the heart muscle is pumping, the heart valves, the sac around the heart (pericardium) and the large blood vessels nearby.
Cardiac MRI is especially good at showing the heart muscle itself. With a contrast injection, it can show scarring of the heart muscle after a heart attack, and changes caused by inflammation (myocarditis) or by conditions that affect the muscle, such as cardiomyopathy. It is usually requested by a cardiologist, often after an echocardiogram (heart ultrasound) or ECG.
For an overview of heart scans, see our Cardiac MRI Scan page.
What happens during the scan
Small sticky pads (ECG electrodes) are placed on your chest so the scanner can time the pictures with your heartbeat, and a coil is placed over your chest. You lie on your back on the scanner bed, and the scanner is loud, so you will wear ear plugs or headphones. You will be asked to hold your breath many times, for up to about 20 seconds each, while pictures are taken, so that breathing movement does not blur them. The radiographer can see, hear and talk to you throughout.
Most cardiac MRI scans include an injection of contrast dye (gadolinium) through a small cannula in your arm. Where contrast is needed, it is charged separately.
What the scan can show
A cardiac MRI can help to look at:
- how well the heart is pumping, and the size of its chambers
- scarring of the heart muscle after a heart attack, in coronary artery disease
- cardiomyopathies, including hypertrophic cardiomyopathy, and conditions such as cardiac amyloidosis and sarcoidosis
- inflammation of the heart muscle (myocarditis)
- heart valve leaks (regurgitation) and narrowing (stenosis)
- the causes of abnormal heart rhythms or unexplained fainting
- the pericardium, the sac around the heart
- heart conditions present from birth, before and after surgery
- tumours and masses in or around the heart
- the aorta and the arteries to the lungs, including pulmonary hypertension
MRI is not the best test for looking at the coronary arteries themselves; a CT coronary angiogram or a catheter angiogram is usually used for that.
Preparing for your scan
You can usually eat, drink and take your normal medicines. Bring a list of your medicines and any previous heart test results, such as echocardiogram or ECG reports. If you have a pacemaker or implanted defibrillator, tell us when you book: some devices can be scanned, but they need to be checked first and may need adjusting.
You can usually eat, drink and take your normal medicines unless the scanning centre tells you otherwise. Wear loose, comfortable clothing without metal zips or buttons, and leave jewellery at home. You will be asked to remove metal items such as hair clips, hearing aids, coins and keys, and you may be asked to change into a gown.
Before the scan you will complete a safety questionnaire. Tell the team if you have a pacemaker, any metal implant, surgical clips or other device, if you have kidney problems or allergies, or if you are, or might be, pregnant or breastfeeding. If you feel anxious in enclosed spaces, let us know when you book. Some centres can offer a relaxant, and if you take one you will need someone to take you home and must not drive for 24 hours.
Frequently asked questions
Why do I need to hold my breath during a cardiac MRI?
The heart moves as you breathe. Holding your breath for short periods, usually up to about 20 seconds, keeps it still so the pictures are sharp. The radiographer will tell you exactly when to breathe in, out and hold.
Can I have a cardiac MRI if I have a pacemaker?
Sometimes. Many modern pacemakers and defibrillators are MRI-conditional, but the device must be checked and may need to be adjusted, and your heart is monitored during the scan. Tell us about any device when you book, before your appointment is confirmed.
What is the difference between a cardiac MRI and a stress cardiac MRI?
A standard cardiac MRI looks at the structure and pumping of the heart and any scarring. A stress cardiac MRI also uses a medicine to make the heart work as if you were exercising, to show whether parts of the heart muscle are short of blood supply because of narrowed coronary arteries.
Will I need a contrast injection?
Usually, yes. Contrast dye helps show scarring and inflammation in the heart muscle. It is given through a small cannula in your arm and is charged separately.
Sources
The information on this page has been gathered from various sources and is provided for general information only. It is not medical advice. TOP MRI is not liable for the accuracy or completeness of this information. Please speak to your doctor or the scanning centre about your own situation.