Exercise testing alone can miss some patients with coronary artery blockages, typically when the blockages are relatively mild. Some patients will also have abnormal ST segment responses on the electrocardiogram that do not reflect coronary artery disease. To deal with these limitations, heart imaging studies have been developed to enhance the diagnostic capability of exercise or pharmacologic stress testing. These tests are also more proficient in identifying abnormalities within specific arteries, and thereby can be helpful in monitoring changes in patients with established coronary artery disease.