Echocardiography in stress testing uses sound waves to create pictures of the heart muscle as it is working. The motion of the muscle can be described for all the segments of the left ventricle. Images of the heart are taken at rest, and then exercise or dobutamine stress testing is performed. Additional images are obtained immediately following exercise (or during dobutamine infusion). A normal study shows all segments moving or contracting well both at rest and stress. In the presence of a "tight" heart artery blockage, the function of the muscle worsens during stress, reflecting inadequate blood flow to that segment. This is termed a "regional wall motion abnormality". In muscle that has suffered a heart attack, the motion of the segment is reduced or absent both on the rest and stress images.