Harvard Heart Letter

Ask the doctor: Do I need a thallium stress test every year?

Ask the doctor

Do I need a thallium stress test every year?

Q. Ever since my bypass operation in 1996, my cardiologist has me take a thallium stress test every year. I haven't had any heart-related trouble since the bypass, and the test results are always fine. I'm worried that the radiation from these tests is going to give me some kind of radiation-related cancer. What does this test tell my cardiologist? Do I really need it?

A. The danger from the minuscule amount of radiation involved in a thallium stress test isn't something you should worry about. No one has ever demonstrated that nuclear cardiology tests increase the risk for cancer, so the danger is trivial, if it exists at all. That's the good news. The bad news is that the need for you to have this test every year is probably equally nonexistent.

The use of a radioactive tracer like thallium during an exercise test allows a special camera to make clear pictures of heart tissue before, during, and after exertion. The images can show the extent of artery blockage, zones of damaged heart muscle, and whether angioplasty or a stent continues to hold open a once-narrowed coronary artery.

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