About your Nuclear Stress Perfusion Imaging (Nuclear Stress Test)
What is a nuclear cardiology stress test?
The test is a noninvasive way of looking at blood-flow patterns to the muscle of the heart. It is the best noninvasive method we have available to determine if coronary artery disease is the cause of your symptoms. The test is also useful to evaluate the progression of blockage in patients already diagnosed with coronary artery disease. Coronary artery disease produces narrowing and potentially blockages, called stenosis, in the arteries that supply blood to the muscle of the heart. Performing the nuclear stress test will provide your physician with information on the impact the disease has had on blood flow to the heart during exercise/stress.
Are there any special instructions I need to follow prior to the test?
There are certain medications that we may ask you to hold prior to the test. At the time the test is scheduled, your medications will be reviewed and you will be provided with a list of medications to avoid the day prior - these may include theophylline, beta blockers, persantine, and others. If you are a smoker, we ask that you don't smoke for 4 hours prior to the test. It is essential that you hold all products containing caffeine for a full 24 hour period prior to your appointment time. This includes coffee, decaffeinated coffee, tea, soda, chocolate and certain medications for migraine headaches that contain caffeine. The presence of caffeine in your system at the time of imaging can inhibit the medication needed for the stress portion of the study to be effective. If you have had caffeine within 24 hours we may have to reschedule your study.
What happens during the resting portion of the test?
After you have an IV line placed in your arm, you will be placed on the scanning table, and the technician will hook up electrodes to your chest to record your ECG during the scan. This is because the computer software synchronizes to your heartbeat. The technician can help you find a comfortable position to hold your arms, and put pillows under your head and your knees to make you as comfortable as possible during the 15-20 minute scan. The camera head will rotate around your chest during the scan, so it is important to lie as still as possible during the test.
What happens during the stress portion of the test?
The technician will connect you to the stress equipment with electrodes connected to long cables. Patients who exercise will have their heart rate and rhythm, blood pressure, and any symptoms monitored closely by the nuclear technician. When you reach an acceptable level of exercise, the radioactive dose will be injected into your intravenous line. You will need to exercise for one minute after the isotope has been injected in order to allow it to reach your heart. Immediately after exercise, you will be taken to the nuclear camera room.
What if I am unable to exercise?
Patients who are unable to exercise can have the stress test performed through the use of a medication that dilates the arteries of the heart without speeding it up. There are two such medications that we may use - one is called persantine, and the other is lexiscan. These medications are safe, and provide good quality images of the heart muscle without exercising.
What happens during the imaging portion of the exam after the stress test?
The stress-imaging portion of the exam will require you to lie on your back, knees flexed and supported, and your arms raised above your head so the camera can be positioned over your heart. The longer images require the use of EKG leads placed on your chest to allow the imaging equipment to be synchronized with your heartbeat. This is referred to as a "gated" nuclear cardiology study. Once the leads are in place, the camera will be set up to take a series of images of your heart as the camera moves around your body.
How is the exam interpreted?
Even distribution of the radioactive isotope indicates adequate blood flow. The presence of defects indicates restriction in the blood flow. Matching defects at stress and rest show areas of the heart that have been affected by a heart attack or myocardial infarction. Areas that have defects at stress that do not show up at rest are consistent with a diagnosis of ischemia, or impaired blood flow. The images from the test can also tell the cardiologist how your heart contracts. Dr. Saxena will discuss your findings with you when he reviews all your testing. He will show your the images obtained during your stress test.
What happens after the examination?
The nuclear cardiologist will pull together information from prior studies, the current images, your medical history and your response to the stress test itself in order to interpret your test. Dr. Saxena will discuss these findings with you, and give you opportunity to ask questions about the plan he outlines. The results from both the stress and rest portions of the test help to formulate a treatment plan to meet your specific needs. This may include medications, or scheduling a cardiac catheterization.