Nuclear tests are a method for diagnosing coronary artery disease, which means discovering the precise spot where the artery is affected and identifying a course of treatment according to the results.
What is thallium (cardiolyte)?
These are two substances that are injected during a stress test. As they find their way into the bloodstream, they make artery blockage visible. They attach to different cells in the body, while the patient is connected to an image camera that helps detect radioactivity. The device will render the image of the muscle that has thallium and cardiolyte attached to it so that your doctor can see if an artery is totally or partially blocked.
The benefits of a thallium (cardiolyte) scan
The major benefit of such a scan is that it can pinpoint the exact location where the coronary arteries are narrow or blocked. Such a scan is typically performed in three situations:
- When patients show signs of stable angina, this scan can reveal the location of artery blockages.
- When patients have already received angina treatment, the thallium scan can check if there are any signs of improvement. The scan is quite common for determining if a patient’s angina treatment is working and if they should continue with it. If the blockage is still there, the doctor can suggest other approaches, like inserting a stent or performing bypass surgery.
- When doctors need to see if the heart muscle is still viable going past a coronary artery blockage. If it’s viable, then the heart muscle will light up on the imaging monitor, and doctors will likely choose to perform bypass surgery or insert a stent to improve the heart’s function.
The risks of a thallium (cardiolyte) scan
Typically, there are no risks or complications of a thallium scan, but when they do occur, you can expect:
- Having an allergic reaction to the substances injected in your bloodstream.
- While extremely rare, one must never exclude the possibility of a heart attack.
- In some cases, this test can lead to abnormal heartbeats (arrhythmias), but these are usually regulated once the test is finished.
- Chest pain can also be the result of a stress test.
- Because of the physical intensity of a nuclear stress test, some people experience a drop in blood pressure, which can cause dizziness.
What happens during a thallium (cardiolyte) scan?
The first step of the test is mostly just lying on a table so that the monitor can record images while your heart is resting. Electrodes (tiny patches that will connect your body to the image monitor) are also attached to your limbs and chest. These are connected to an electrocardiogram machine. If you’ve ever done an EKG, you know what to expect.
The doctor will place a cuff on your arm, to monitor your blood pressure during the test, but may also ask you to breathe into a tube, to monitor your breathing pattern during the test.
At this point, patients will be required to put their heart to the test by performing a physical exercise which is typically riding a stationary bike or walking on a treadmill. The intensity of this exercise will increase as the test progresses because the purpose is to push the heart to see how it reacts in more strenuous conditions.
If a patient is unable to perform the physical activity required during the test, the doctor will inject a drug that increases the heart’s blood flow, so that they can recreate the heart’s activity during exercise. The side effects are similar to those of actually working out: shortness of breath and flushing.
Prior to the exercise, you and your doctor will discuss safety limits, and keep in mind that you can stop the test whenever you feel like you can’t continue.
The exercise part of the test continues until the heart rate reaches a certain threshold, or when:
- You start feeling dizzy.
- You experience arrhythmia.
- You have very high or very low blood pressure.
- You experience shortness of breath.
- You have mild to severe angina.
- You start showing signs that you can’t continue.
- There are changes in the electrocardiogram.
Otherwise, when your heart rate peaks, the doctor will administer another injection and ask you to wait for another 20 to 40 minutes. After that, they will record the second set of images of your heart muscles. It is at this point that the doctor determines if there are areas of your heart which aren’t receiving enough blood. By comparing the “before” and “after” images, the doctor will know more about your coronary artery disease.
The results of a thallium (cardiolyte) scan
The results of this test can reveal one of four things:
- A constant and normal blood flow before and after the test.
- Normal blood flow when resting, abnormal blood flow during exercise. This means that under stress, there are parts of your heart which aren’t receiving enough blood, which could mean that you have coronary artery disease.
- Low blood flow when resting and exercising. This typically indicates a previous heart attack or severe coronary artery disease.
- A radioactive dye is not present in parts of your heart. This means that a heart attack has caused tissue damage, preventing the dye from reaching certain heart areas.
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