Use of Reactivated DEFINITY® in Patients Undergoing Stress Echo Purpose of the study: Each patient undergoing a stress echocardiogram uses a full vial of DEFINITY® contrast agent. During infusion, this often condenses back to its liquid phase due to manual pressure applied in the syringe. At this point, it is not optimal to be used at current ultrasound settings for stress echocardiography. This research project will test whether this condensed DEFINITY® can be reactivated by ultrasound using the same transducer used to image the patient.