Stress echocardiography combines stress testing with an echocardiogram (cardiac ultrasound) obtained immediately after exercise. Exercise is usually carried out on a treadmill. Alternatively a bicycle (either upright or lying down) may be used to provide the exercise stress. This measures the pump function of the heart under stress and can be used to prove or disprove the presence of coronary artery disease and evaluate the functional significance and severity of angiographically identified coronary narrowing. Sometimes a medication, dobutamine, is used to accelerate the heart rate in patients who are unable to exercise. Echocardiography is used to measure the pump function of the heart before and during this pharmacologic (medication induced) stress test and identify lack of blood supply to the heart muscle. Side effects of dobutamine include angina and cardiac arrhythmias.