What are the risks in having a myocardial perfusion scan?

Minimal : There is a small amount of radiation from the scan but it is less than from a cat scan. If you do an exercise stress test, there is a small risk from the exercise portion but you are continuously monitored for any problems. Your job is to report any difficulties or symptoms during the test.

About 5 in 10,000: The risk of a resting only perfusion scan is close to zero, the only risks being an allergic reaction to the tracer, pain from the iv, and discomfort from lying still for about 20 minutes. The real risk is from performing the treadmill (or pharmacologic) stress test itself. The historical risk of an adverse event from this is about 5 in 10, 000 but probably now much lower given modern equipment.

Stress associated : A myocardial perfusion scan is performed in two steps. One injection of a radiotracer at rest and another at stress ( either treadmill or pharmacological stress test with adenosine, regadenoson, dobutamine, dipyridamole). Only few skin reactions have been reported with the radiotracer injection. Risks are more associated with the stress used for the test such has angina, headache, nausea...