 There will be two groups of 20 subjects recruited in a collaborative effort by UWHC and University of Pennsylvania. This project will require one visit approximately 3-5 hours in length. The subject will fill out a symptom questionnaire. A small gauge angiocath will be place to establish intravenous access. Single-lead ECG and blood pressure are monitored for the duration of the protocol. Tonometry non-invasive measurement of the pulse and echocardiographic images will be obtained at baseline. After baseline data are obtained, dobutamine will be infused at escalating doses of 2, 4, 8, and 16 μgkgmin IV at 30-minute intervals. After 5 minutes of infusion at each dose, echocardiographic and tonometry data will be recorded. If 85 or more of predicted target heart rate is reached, the final study data collection and safety imaging will be performed and the dose not increased further. 