For patients who are physically incapable of exercising on a treadmill, stress testing can be performed by causing pharmacologic agents to simulate some aspects of exercise. The two medications used by the BryanLGH Heart Institute are dobutamine and Adenosine.  These medications usually do not cause ST segment changes and symptoms by themselves. Heart rate and blood pressure changes are not as meaningful as with exercise. Therefore, they are always used with imaging tests. Dobutamine is infused in increasing doses through an intravenous catheter during the exam. This drug increases the heart rate and pumping strength of the heart muscle. This requires an increase in blood flow to the heart, but if inadequate blood flow is present due to a blocked artery, changes are seen in the imaging pictures. Adenosine dilates heart arteries, but diseased arteries are unable to dilate. This produces abnormalities in the nuclear perfusion pictures. It less commonly produces abnormalities in echocardiogram pictures, and is rarely used in this country with echocardiography.