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Diagnostic Tests – Sestamibi Testing
What Is Sestamibi Testing?
Sestamibi testing—often referred to by its tracer name Tc-99m sestamibi—is a form of nuclear stress testing used to evaluate myocardial perfusion. It involves injecting a radiopharmaceutical (technetium-99m) that accumulates in healthy, well-perfused myocardial tissue. Because the tracer depends on both blood flow and viable cardiac cells, areas of ischemia or infarction appear as perfusion defects on imaging. Like other nuclear stress tests, it helps determine whether chest pain or abnormal EKG findings are due to underlying coronary artery disease.
How Is the Test Performed?
During the procedure, Tc-99m–labeled compounds are injected into the bloodstream during both stress and rest phases. A gamma camera then captures images of tracer uptake in the myocardium.
Healthy tissue receives adequate blood flow and shows normal tracer uptake, whereas diseased, ischemic, or infarcted myocardium demonstrates reduced uptake. The pattern of defect behavior is key:
- Reversible defect: reduced uptake during stress but improved at rest → ischemia (viable myocardium that becomes underperfused during stress).
- Fixed defect: reduced uptake on both stress and rest images → infarcted or scarred myocardium.
This allows clinicians to distinguish between viable, at-risk myocardium and areas of permanent damage.
When Should You Choose Sestamibi Testing?
The most practical “Kaplan-style” indication is that Tc-99m sestamibi is the preferred nuclear stress test in certain patient populations where standard imaging methods are limited by technical barriers. It is particularly useful in:
- Obese patients, where ultrasound penetration for stress echocardiography is poor
- Female patients with large breasts, where breast tissue can interfere with echo imaging or make exercise EKG less reliable
Because sestamibi imaging provides clearer results in these scenarios, it is often selected when other stress modalities may produce nondiagnostic images or false results.
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