A nuclear stress test, also known as a myocardial perfusion imaging (MPI) study, is a medical imaging procedure that assesses blood flow to the heart both at rest and during physical exercise using a small amount of radioactive material known as a radiotracer. Administered through an intravenous (IV) line, this radiotracer is tracked as it flows through the heart's arteries, enabling the detection of areas with poor blood flow or cardiac damage.
Why It's Done
A nuclear stress test is typically conducted for the following purposes
Diagnosing Coronary Artery Disease (CAD)
This test helps diagnose CAD, a condition where the coronary arteries, responsible for supplying the heart with blood, oxygen, and nutrients, become damaged or diseased. It provides insights into the severity of CAD.
For individuals with CAD, a nuclear stress test assists healthcare physicians in evaluating the effectiveness of treatment strategies.
A nuclear stress test is also referred to as a cardiac SPECT study or MPI study.
Patients should adhere to specific preparations outlined by their healthcare physician
Food and Medications
Depending on the physician's instructions, patients may need to refrain from eating, drinking, or smoking for several hours prior to the test. Caffeine consumption should be avoided on the day preceding and the day of the test. Patients should consult their physician regarding the use of medications before the test, as certain drugs can interfere with test results. Inhaler use for respiratory issues should be communicated to the healthcare team.
Clothing and Personal Items
Wearing comfortable, loose-fitting clothing and well-fitting shoes is recommended. The application of oil, lotion, or cream on the skin on the test day should be avoided.
What to Expect
A nuclear stress test involves the use of a radioactive tracer delivered via IV. The test comprises two sets of images of the heart: one at rest and another after exercise.
Before the Test
A medical history assessment and an evaluation of exercise habits are conducted. A physical examination may be performed to identify factors that could influence test results.
During the Test
Blood pressure is monitored with an arm cuff. Electrodes are placed on the chest, and sometimes on the legs and arms, to record the heart's electrical activity (ECG).
An IV line is inserted to inject the radiotracer. After a brief period for absorption, the patient lies still under a gamma camera for the first set of images, assessing blood flow at rest.
Subsequently, exercise is initiated, typically on a treadmill, with gradual increments in intensity. The radiotracer is injected during peak exercise.
If exercise is not possible, a medication administered intravenously increases blood flow to the heart. Patients may experience symptoms similar to those during physical exertion, such as flushing or shortness of breath.
The patient can stop exercising if they experience discomfort or specific symptoms, such as an irregular heart rhythm, dizziness, chest pain, shortness of breath, or abnormal blood pressure.
After exercise, the second set of images is captured, highlighting areas of the heart with inadequate blood flow.
After the Test
Following exercise, patients may briefly stand still and then lie down while healthcare physicians continue monitoring heart rate and breathing.
In most cases, patients can resume their normal activities after the test unless instructed otherwise.
The radioactive tracer is eliminated from the body through urine or stool, and patients are encouraged to drink plenty of water to expedite this process.