What is a thallium heart scan?
This leaflet describes a type of heart scan known as a thallium myocardial perfusion scan. It is a nuclear medicine test that looks at the blood supply to the muscles of your heart (the myocardium). The test is usually done in two parts. The stress scan is done while your heart is working hard and the rest scan is done while your heart is resting. The two parts of the scans are both done on the same day.
The two scans are compared to look for differences which indicate areas of poor blood flow (which may cause chest pain) or no blood flow (due to a previous heart attack). Sometimes a third part of the scan may be needed on the next day. This can distinguish areas of the heart muscle that are not working but which still have a viable blood flow.
Is it safe for me to have the scan?
For this scan it is necessary to inject a small amount of radioactive tracer, called a radiopharmaceutical, in order to take the pictures. The small risk from this (similar to a CT scan) is outweighed by the information that will be gained by taking the scan. A doctor will have checked the request to make sure this is the appropriate test for you.
If you have any concerns or would like further information, please contact the department where you are having your heart scan. If you don’t understand why you need to have this scan please speak to the doctor who referred you.
For female patients
If you know that you are pregnant, or there is any chance that you may be pregnant, then please contact the department where you will be having your heart scan. Do this as soon as possible as the scan can be postponed if it is not urgent.
Also contact the department if you are breast-feeding, as they may give you special instructions.
Preparation for your scan
The preparation that is required for a heart scan depends on the method that will be used for the stress part. Therefore it is VERY important that you follow the particular instructions that you are given by the department where you are having your scan.
Unless told otherwise have a light breakfast on the day of your scan but do NOT take anything containing caffeine for 24 hours before your appointment. You may drink fresh fruit juice, water or milk. You must NOT drink coffee or tea (even if decaffeinated), cocoa, drinking chocolate, Coca-Cola or diet coke or eat chocolate. Some over-the-counter medicines also contain caffeine, so check the ingredients.
Some heart medicines that you may be taking can also interfere with the test, so take special note of any particular instructions from the nuclear medicine department, as you may be asked to stop some of them temporarily.
Your stress test
For the stress part of the scan you may be asked to walk on a treadmill or pedal an exercise bike. Some ECG electrodes will be attached to your chest to monitor your heart rate. The injection will be given while you are exercising. This is so that it shows the blood flow to your heart while it is working hard.
If you cannot walk or cycle, your heart can be stressed in other ways. You can be given a drug that speeds up your heart and makes it beat stronger, or a different drug that opens up blood vessels in the heart. Both of these drugs produce an effect on the blood flow to your heart similar to exercising.
The person doing the stress test will discuss this with you and explain why the method they have chosen is the best for you.
A tube connected to a small needle will be inserted into a vein in your arm or hand. You may have had a blood test in the past; this is much the same. The ‘pinprick’ of the needle may hurt a bit, but that is all. A small amount of radioactive tracer will be injected through this tube whilst you are being stressed.
The scan pictures will be taken immediately after the injection.
The scans are taken by a special machine called a gamma camera. This is not a tunnel, but the camera detector will come close to you.
There are sensors in the camera which stop it moving if it touches anything, so it cannot hurt you. You will be asked to lie flat on your back with your left arm (or with both arms) above your head. The gamma camera will move round your chest taking pictures all the time.
This is often followed by a quick X-ray CT scan while you are on the same bed. It is very important that you keep still. If you think that you will find this difficult please speak to the nuclear medicine department before your appointment.
Taking the pictures lasts about 20 to 25 minutes.
You will not be left on your own – there will always be someone immediately available.
Your rest test
Sometimes the stress scan can give doctors all the information that they need, but often a rest scan will also be needed and this will be done later the same day.
After the stress scan you will be asked to wait for about 3 hours in order to give time for your heart to return to its resting state. During this time you may be allowed to leave the department if you wish.
The rest part of the scan just involves the same sort of images as the stress scan, but you will not have to exercise again and you won’t need another injection.
In some conditions you may be asked to come back for some further images to be taken the next day. If this is required you may be given another injection but you won’t need the stress again.
After your scan
It is very unlikely that you will feel any side-effects after the scan, but if you think that you have please let the nuclear medicine department know.
You may continue all your normal activities unless you have been advised otherwise.
After your scan there will be some radioactivity left in your body but this will not present a significant risk to other people around you. However, for the rest of the day, we suggest that you try to keep any time that you spend within arm’s length of pregnant women, babies and small children as short as possible; but there is no need to stop giving children essential love and care.
The radioactivity in your body will disappear over the next few days.
It is perfectly safe for you to travel abroad after your scan, but many airports and sea ports are now equipped with very sensitive radiation detectors. So it is possible that the small amount of radioactivity left in your body could set off a detector as you pass through security. Therefore, if you intend to travel abroad within a month following your scan, it could be helpful to take with you something to explain that you have recently had a thallium heart scan. This could be your appointment letter or some other official confirmation from the department where you had your scan.
Your thallium heart scan will be looked at by a specialist doctor, who will issue a report. The report will be sent to the doctor who requested your scan rather than to your GP. This is because the doctor who requested your scan will have all the results from other tests and will be able to tell you how the result of your thallium heart scan affects your care.
Information about you
As part of your care, information will be shared between clinical staff, some of whom you may not meet. It may also be used to help train other staff. Information collected may also be used later on to help the department improve their quality of care, plan services or to research into new developments.
The pictures from your scan may be used to teach other healthcare workers, but your name and all other identification will be removed first. It won’t be possible to identify you from the scan pictures.
All information will be treated as confidential and is not given to anyone who does not need it. If you have any concerns, please discuss these with the department.
All the staff would like to make your visit as pleasant as possible. If you have any concerns please talk to a member of the nuclear medicine staff.