About a stress cardiac MRI scan
A stress cardiac MRI, also called a stress perfusion MRI, is a heart MRI scan that shows how well blood flows into the heart muscle. Rather than exercising on a treadmill, you are given a medicine, usually adenosine, through a drip in your arm. This makes the heart’s blood vessels widen as they would during exercise, and contrast dye is then injected so that the scanner can show the blood supply to each part of the heart muscle.
If a coronary artery is narrowed, the part of the heart muscle it supplies receives less blood under stress, and this shows up on the pictures. The scan is used to investigate chest pain that may be angina, and to help decide whether a narrowed artery needs treatment such as a stent. It also includes the standard cardiac MRI pictures, showing the heart’s pumping, valves and any scarring.
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.
Partway through the scan, the stress medicine is given through a cannula in one arm while your heart rate, blood pressure, oxygen level and ECG are monitored throughout. The medicine can cause temporary sensations such as flushing, breathlessness or chest discomfort, which settle quickly once it is stopped. Contrast dye is then injected through a cannula, and more pictures are taken.
What the scan can show
A stress cardiac MRI can help to:
- show whether parts of the heart muscle are short of blood supply under stress (ischaemia), a sign of narrowed coronary arteries
- investigate chest pain that may be angina
- help decide whether a narrowed coronary artery needs treatment such as a stent or bypass
- show scarring from a previous heart attack, and how much healthy muscle remains
- assess the heart’s pumping, chambers and valves at the same time
Preparing for your scan
No caffeine for 24 hours before your scan. Caffeine blocks the effect of the stress medicine and can make the results invalid. Avoid tea, coffee (including decaffeinated), green tea, cola and other fizzy drinks, energy drinks, chocolate and chocolate-flavoured foods, and some painkillers and cold remedies that contain caffeine (check the label). Water, milk, fruit juice and squash are fine.
Continue your usual medicines unless told otherwise, but some heart medicines, such as dipyridamole (Persantin) and nicorandil (Ikorel), usually need to be stopped for 24 hours beforehand. Check with your doctor or the scanning centre. Bring any sprays or inhalers and a list of your medicines. If you have asthma or other breathing problems, tell us when you book, as this affects whether the stress medicine can be used. Avoid wearing nail polish and eye make-up.
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 can’t I have caffeine before a stress cardiac MRI?
Caffeine blocks the effect of adenosine, the medicine used to stress the heart. If you have had caffeine in the 24 hours before the scan, the test may not work properly and may need to be rebooked.
Will I need to exercise?
No. Instead of exercise, a medicine given through a drip makes the heart’s blood vessels respond as if you were exercising. Its effects wear off quickly once it is stopped.
What does the stress medicine feel like?
Some people feel flushed, short of breath or have chest discomfort while the medicine is running. These feelings pass quickly once it is stopped, and staff monitor you closely throughout.
Can I have it if I have asthma?
Please tell us if you have asthma or another breathing condition when you book. The team will check whether the stress medicine is suitable for you before your appointment is confirmed.
Sources
- Alliance Medical – Cardiac MRI stress perfusion patient guide
- University Hospital Southampton NHS – MRI cardiac stress scan (adenosine) factsheet
- RadiologyInfo.org – Cardiac MRI
- NHS – MRI scan
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.