The main clinical examination performed in nuclear cardiology is Myocardial Perfusion Imaging (also known as a Nuclear Stress Test). During a nuclear stress test, a small amount of radioactive tracer is injected intravenously. Two injections are administered: under rest conditions and under stress conditions. Stress conditions are obtained by use of treadmill exercise or medications that simulate the effects of exercise on the heart. This tracer is taken up by areas of the heart muscle receiving normal blood flow. Areas of the heart which are supplied blood by blocked blood vessels will show as decreased uptake or absence of the tracer. Images are acquired with use of a very sensitive Gamma Camera that creates still pictures as well as movies of the heart. These images are displayed in 3-dimensional format.
This technique provides an assessment of the volume of the total heart, which is not obtaining adequate blood supply. The larger the volume of the heart not receiving adequate blood, the more dangerous the situation is for the patient if this decreased blood flow is not corrected.
These cardiac images identify coronary heart disease, the severity of prior heart attacks, and the risk of future heart attacks. These highly accurate measurements of heart size, function and amount of heart muscle at risk of damage, enable cardiologists to better prescribe medications and select further testing like a coronary angiogram, the need for angioplasty and bypass surgery, or devices to optimize treatment outcomes.