What is a Myocardial (heart muscle) Perfusion (blood flow) nuclear stress test, also known as a Myocardial Perfusion Scan (MPS)?

From the Guidelines

A Myocardial Perfusion Scan (MPS) is a nuclear stress test that evaluates blood flow to the heart muscle during rest and stress conditions, utilizing a radioactive tracer and pharmacological stress to detect areas with reduced blood flow. This test is particularly useful for patients who cannot perform adequate physical exercise for a standard stress test, as it provides detailed information about coronary artery disease, heart function, and potential areas of damaged heart muscle 1.

Key Components of MPS

• The test involves intravenous injection of a radioactive tracer, such as technetium-99m, during some form of cardiovascular stress 1.
• Pharmacological stress, using a vasodilator such as adenosine or a beta sympathetic agonist such as dobutamine, allows patients who cannot achieve maximal cardiovascular stress on a treadmill to be studied 1.
• Single-photon emission tomographic imaging (SPET) is the preferred imaging technique, providing a semi-quantitative assessment of regional tracer uptake and comparison with databases of normal appearances allows objective assessment of the presence, depth, and extent of abnormalities 1.

Diagnostic Accuracy and Limitations

• The diagnostic accuracy for detection of obstructive CAD of exercise and pharmacological stress nuclear MPI has been studied extensively, with uncorrected diagnostic sensitivity ranging from 82% to 88% for exercise and 88% to 91% for pharmacological stress nuclear MPI 1.
• Diagnostic image quality is affected in obese patients, as well as in women and men with large breasts, but reductions in breast tissue artifact have been reported with the use of the Tc-99m agents as well as with attenuation-correction algorithms or prone imaging 1.

Clinical Applications

• MPS is valuable for evaluating coronary artery disease, heart function, and potential areas of damaged heart muscle, while minimizing the time patients need to spend in the imaging department 1.
• The test typically takes 3-4 hours to complete, and patients should avoid caffeine for 24 hours before the test and may experience brief side effects from pharmacological stress agents such as shortness of breath, headache, or flushing 1.

From the FDA Drug Label

Regadenoson injection is a pharmacologic stress agent indicated for radionuclide myocardial perfusion imaging (MPI) in patients unable to undergo adequate exercise stress. A Myocardial Perfusion Scan (MPS), also known as a Myocardial (heart muscle) Perfusion (blood flow) nuclear stress test, is a type of test that uses a small amount of radioactive material to evaluate the blood flow to the heart muscle.

• It is used to diagnose and assess coronary artery disease.
• The test involves using a pharmacologic stress agent, such as regadenoson, to increase blood flow to the heart muscle, which is then imaged using a special camera.
• The images are used to identify areas of the heart muscle that have reduced blood flow, which can indicate blockages in the coronary arteries 2.

From the Research

Myocardial Perfusion Scan (MPS) Overview

• A Myocardial Perfusion Scan (MPS), also known as a nuclear stress test, is a diagnostic procedure used to assess coronary artery disease (CAD) by evaluating blood flow to the heart muscle [ 3, 4,5 ].
• The test involves the use of a small amount of radioactive tracer, such as technetium-99m sestamibi, which is injected into the bloodstream and taken up by the heart muscle 6, 7.
• The tracer's distribution is then imaged using a gamma camera, allowing for the visualization of areas with reduced blood flow, which may indicate CAD 3, 5.

Types of Stress Tests

• There are two main types of stress tests used in conjunction with MPS: exercise stress tests and pharmacological stress tests 3, 4, 5.
• Exercise stress tests involve physical exercise, such as walking on a treadmill, to increase heart rate and blood flow 3, 4.
• Pharmacological stress tests use medications, such as adenosine or dipyridamole, to increase blood flow and simulate exercise 3, 4, 5.

Pharmacological Stress Testing

• Pharmacological stress testing is a widely used noninvasive method for assessing patients with known or suspected CAD 5.
• The test has high accuracy for diagnosing CAD and excellent safety records with acceptably low occurrences of side effects 5.
• Vasodilating agents, such as adenosine and dipyridamole, are commonly used for pharmacological stress testing, and have been shown to be effective in detecting CAD 3, 4, 5.

Image Acquisition and Interpretation

• Image acquisition for MPS typically occurs 15-60 minutes after the stress test 6.
• However, some studies suggest that early imaging, such as 6-8 minutes after the stress test, may be more sensitive for detecting CAD 6.
• The lung to heart ratio (LHR) of technetium-99m sestamibi has been shown to be a predictor of adverse cardiac events and extensive CAD 7.