Patients are advised to refrain from eating or drinking for about four to six hours before the test. Physicians find it easier to evaluate the heart’s performance when the patient’s stomach is empty, and patients are less likely to experience nausea or cramping during exertion. Physicians may also advise patients to refrain from taking caffeine and certain medications in the days or hours leading up to the test. These items can affect the results of the test. Patients are advised to wear comfortable, loose clothing and appropriate exercise shoes. Also, it may be necessary for the patient to sign a consent form before beginning the test.

Aside from the quick, minor discomfort that patients may feel when injected with the radionuclide substance, this test is considered to be relatively safe and painless. It can take place in a physician’s office, hospital or outpatient medical facility.

Before the nuclear component of the nuclear stress test is performed, preparations are made for the standard stress test. First, the patient is prepared for an electrocardiogram (EKG). The patient removes his or her clothes from the waist up, and a nurse or technician thoroughly cleans about a dozen small areas on the patient’s body – usually on the chest, arms and legs. Usually, the technician will apply a conductive gel to these areas. About 10 to 12 small metal devices (electrodes) are then taped to those clean areas of the skin and attached by wires to the electrocardiograph machine.

The next step varies, depending on the facility where the test is done and whether the patient is scheduled for an exercise stress test (which involves physical exertion) or a pharmacological stress test (which involves a medication that mimics the effects of exertion on the heart).

Regardless of how the heart rate is elevated, all patients will have pictures taken after stress has been placed on the heart through either exercise (usually on a treadmill) or medication. Once the desired heart rate has been reached, the thallium (or technetium or sestamibi) is injected. The patient will then be taken to another room to lie down on a table under a gamma camera that will take pictures of the heart. The first part of the test takes about 15 to 30 minutes.

After a few hours, when the heart rate is back to normal, additional pictures of the heart are taken. This measures the redistribution of thallium through the heart muscle.

Alternatively, the facility may first inject the patient with one substance, take resting pictures, increase the patient’s heart rate (through exercise or medication) and then inject the person with another substance before taking pictures again. In all, the test may take a total of two to two and a half hours.

At other facilities, patients may be asked to complete the exercise/medication component and take pictures on one day, then come back on another day to take pictures of the heart at rest. In some cases, a second injection of thallium will be administered, in conjunction with oral nitroglycerin, to improve the accuracy of the test. To plan their time accordingly, patients are encouraged to speak with their physician about how long the test will take.

The reason for the pause between testing and additional images is to improve the test. Studies have shown that the period of time between the exercise and the imaging will affect the test results. Some studies have shown that the best results are obtained when three image sets are taken: during stress, during the post-stress redistribution period, and after reinjection. By comparing the three sets of images, physicians can tell which parts of the heart muscle absorbed the isotope and how deeply it penetrated.

After the test, the patient is usually advised that he or she can eat, drink and resume normal activities immediately.

A physician may be able to provide the patient with a preliminary report at the end of the test, and a more complete report within a day. Based on the physician’s evaluation of how efficiently the heart is able to regulate blood flow at rest and during physical stress, a diagnosis can be made. The physician will then discuss his or her treatment plan for the patient, which may include additional procedures or tests (e.g., cardiac catheterization).