From the Guidelines
A nuclear stress test, also known as Myocardial Perfusion Imaging (MPI), is a diagnostic test that uses small amounts of radioactive material to evaluate blood flow to the heart muscle during rest and stress.
Key Components of a Nuclear Stress Test
- Stress: can be induced by exercise or pharmacological agents, such as vasodilators (e.g., adenosine, dipyridamole) or adrenergic stimulants (e.g., dobutamine) 1
- Imaging: uses a gamma camera to detect the radioactive material, which is typically a technetium-99m (Tc-99m) agent, such as sestamibi or tetrofosmin 1
- Rest and Stress Images: compared to evaluate changes in myocardial perfusion, with areas of reduced uptake indicating hypoperfused or ischemic myocardium 1
Diagnostic Endpoints
- Reduction in myocardial perfusion: after stress, indicating ischemia or infarction 1
- Nonperfusion high-risk markers: include markedly abnormal ECG, extensive stress-induced wall motion abnormalities, reduced post-stress left ventricular ejection fraction (LVEF), transient ischemic LV dilation, increased lung or right ventricular uptake, or abnormal coronary flow reserve with myocardial perfusion PET 1
Diagnostic Accuracy
- Sensitivity: ranges from 82% to 91% for exercise and pharmacological stress nuclear MPI 1
- Specificity: ranges from 70% to 90% for exercise and pharmacological stress nuclear MPI 1
Limitations and Considerations
- Image quality: affected in obese patients, as well as in women and men with large breasts, but can be improved with attenuation-correction algorithms or prone imaging 1
- Radiation exposure: a consideration, particularly with serial perfusion imaging, but can be reduced with newer technologies and protocols 1
From the Research
Definition of Nuclear Stress Test
A nuclear stress test, also known as Myocardial Perfusion Imaging (MPI), is a diagnostic technique used to assess coronary artery disease (CAD) [ 2 ].
Purpose of Nuclear Stress Test
The purpose of a nuclear stress test is to evaluate the blood flow to the heart muscle, both at rest and during stress, to identify any areas of reduced blood flow [ 3 ].
Types of Stress Tests
There are different types of stress tests used in MPI, including:
- Exercise stress test, such as treadmill test [ 2 ]
- Pharmacologic stress test, such as adenosine stress test [ 2 ]
Key Points of Nuclear Stress Test
Some key points to note about nuclear stress tests include:
- The test involves the use of a small amount of radioactive tracer to visualize the heart muscle [ 4 ]
- The test can be performed using a stress-first approach, which can save time and reduce radiation exposure [ 4 ]
- The test results can be used to diagnose and manage CAD [ 5 ]
- The test has been shown to be safe and effective in a variety of patient populations [ 6 ]
Criteria for Adequate Cardiac Stress
The criteria for adequate cardiac stress during a nuclear stress test include:
- Expenditure of 5 metabolic equivalents of energy
- Production of symptoms, such as fatigue or shortness of breath
- Attainment of 85% of the maximum predicted heart rate [ 3 ]