Patients undergoing previously scheduled stress echocardiography with the primary investigator as the supervising physician will be identified and consented. The standard stress echocardiography procedure will be performed. Definity® will be removed from refrigeration and agitated for 45 seconds to vaporize into its gaseous phase. One mL of Definity® will then be diluted in 29 mL of isotonic, sterile saline. Patients will undergo baseline echocardiography followed by stress with either dobutamine or exercise. Standard Definity® will be injected intravenously into the subject via peripheral intravenous access obtained prior to the study by a registered nurse at the end of the stress portion of the procedure coinciding with image acquisition. Contrast enhanced echocardiography by standard acoustic acquisition will be performed following stress for the indicated diagnostic purpose of the test. By the end of the exam, the gaseous Definity® will have undergone manual compression via manual pressure and condensed back to its liquid phase. At this point, the compressed Definity® will be given intravenously with repeated transthoracic echocardiography. During this second round of image acquisition, real time (RT) imaging (35 Hertz) and 1:1 triggered (Tr) end systolic imaging at various mechanical indices (MI's) up to 1.2 will be performed in standard transthoracic echocardiography windows. Acoustic Intensity (AI) within the left ventricular (LV) cavity, the anterior myocardium (AM) and inferolateral myocardium (ILM) at end systole will be obtained at each MI setting with real time or triggered imaging. Differences in AI between Tr and RT imaging within the AM and ILM at each MI will be used to quantify bubble activation/destruction. Following image acquisition, the patient will be observed for 30 minutes by echo lab staff with nearby resuscitative equipment per current protocol. If no adverse events are noted, the patient will then be dismissed.