Which cardiac test uses radioactive tracers to assess blood flow?

• A. Electrophysiology study
• B. Echocardiogram
• C. Myocardial perfusion imaging (MPI)
• D. Stress test

Answer: (C)

Myocardial perfusion imaging (MPI) is a cardiac test that utilizes radioactive tracers to provide images of blood flow to the heart muscle. During the MPI procedure, a radioactive substance is injected into the bloodstream, which then travels to the heart. Special gamma cameras are used to capture images of the heart as the tracer distributes itself, allowing for the assessment of blood flow during different states, such as at rest and during stress.

The primary purpose of MPI is to identify areas of the heart that may not be receiving adequate blood supply, which can be indicative of conditions like coronary artery disease. This technique is particularly valuable because it non-invasively visualizes the perfusion (or blood flow) to the heart muscle, aiding in both diagnosis and treatment planning for cardiovascular conditions.

In contrast, an electrophysiology study focuses on the electrical activity of the heart, while an echocardiogram uses sound waves to create images of the heart's structure and function. A stress test, which can be done with or without imaging, primarily assesses the heart's response to physical stress rather than directly measuring blood flow using radioactive tracers. Thus, MPI stands out as the correct answer for assessing blood flow using radioactive materials.