A nuclear stress test is performed to diagnose the presence of obstructive coronary artery disease or to determine if there is a lack of blood flow to your heart muscles. This is done by taking images of your heart using nuclear medicine (isotope) after a rest injection and after an exercise or pharmacologic stress test a second injection occurs.
This test involves the injection of an isotope into the bloodstream during a normal resting state and during the stress test (treadmill or pharmacologic). Two images are taken of your heart with a gamma camera within two hours of having each injection. A comparison is made between the two images which helps determine whether or not you have adequate blood flow to your heart muscle. It also allows your physician to see how well the pumping function is of your heart.
You will receive detailed instructions with the specifics about not eating or drinking prior to the test and about bringing your medications and a snack with you. In general, do not eat or drink for 6 hours before the test. DO NOT HAVE items that contain caffeine, which is found in coffee, tea, sodas, chocolate, and some over-the-counter pain relievers. Also, be sure to ask your doctor about any medicines you are taking and whether you should stop taking them before the test. There are certain medications that can interfere with testing and should be held 24 to 48 hours prior to testing. The nuclear stress test takes between 4 and 6 hours to complete.
The day of the test, you will initially have your medication bottles reviewed, discuss the test, sign an informed consent, and have your height and weight recorded. Staff will start an IV and administer a resting injection of the radioisotope (nuclear medicine). It is not a dye and will not make you feel differently. After that, you will take your medications if they do not interfere with the test, and eat. You will be sent to the lobby to eat, drink, and take medicines as instructed by staff. YOU CAN NOT HAVE CAFFEINE UNTIL TESTING IS COMPLETED.
After approximately 1 hour, a resting image is taken. You will either sit up or lie down on a gamma camera and have a 15 minute scan of your heart. You must remain very still during this image or it will have to be repeated.
Then, there will be a waiting period before the stress test. You will be connected to a 12 lead EKG machine for the stress test whether you walk on the treadmill or have a pharmacological stress test.
Alcohol is used to clean the areas of your skin where the electrodes will be. The alcohol may feel cold. Next, staff will place electrodes on your chest. The electrodes attach to an electrocardiograph machine, which records your heart’s electrical activity. A healthy person’s electrocardiogram has a certain pattern, and changes in that pattern can tell doctors if there is a problem with your heart. You will also wear a blood pressure cuff around your arm, which will watch your blood pressure during the test.
Before the stress test, your blood pressure and pulse will be checked. They will also record your heart’s electrical activity before you start exercising (called a resting EKG).
If you have the exercise test, you will walk on a treadmill to achieve a target heart rate. Once that heart rate is achieved a second injection of the radioisotope (nuclear medicine) will be given. You will need to walk at least one minute following the injection to let it circulate before stopping.
The nurse or exercise physiologist with you during the stress test will increase the speed and slope of the treadmill every third minutes. He or she will look for changes in the EKG patterns and blood pressure levels, which may tell doctors that your heart is not getting enough oxygen.
If your doctor would rather you not exercise, medication can be administered with you lying on a stretcher to achieve the stress test. It may be best to do a pharmacological(medicine) stress test as opposed to exercise if you are not able to walk safely on the treadmill, have certain EKG patterns, a pacemaker, or a defibrillator. In addition, if you try the treadmill and cannot achieve the target heart rate, then a pharmacologic(medicine) stress test will be necessary. The radioisotope (nuclear medicine) is administered during this test at a certain time.
At the end of the test, you will have a recovery phase and will need to drink something cold prior to the last scan of your heart. That scan will be on the same gamma camera you were on for the rest scan.
After completing the entire test, you may eat, drink, and take all medications (including those that you may have held prior to testing). You can resume your normal activities.