Is used when a patient has an abnormal resting ECG result or is unable to walk safely. A dye with a nuclear isotope is used to enhance the image of the echocardiogram. The patient will be given the dye shortly before receiving IV medication to stimulate the heart and simulate exercise. Being able to visualize the relative amounts of radioactive isotope within the heart muscle makes nuclear stress tests more accurate in detecting regional areas of decreased blood flow. Though the medicine is radioactive, it’s still safe for patients. However, pregnant women should avoid the test because of potential risk to the child.