The stress testing will be conducted at the Duke Cardiology Diagnostic Unit Laboratory. Following a 20-minute calibration-rest period, participants will be asked to complete a series of 3 mental stress tasks. There are 3 mental stress tasks to be used for this study, i.e., (1) Mental arithmetic: during this test, patients will be asked to perform a series of serial subtractions beginning at a given number which will be different for each repeated test and will be chosen by the tester from a fixed list of various numbers, with encouragement to perform calculations as quickly as possible; (2) Public speaking with anger recall: during this test, patients will be asked to give a speech on a recent situation in which they experienced anger to an audience of observers (two to three) after 1 minute of preparation. Prior to the speech, subjects are told that their speech will be evaluated on their description of the situation, as to what happened, what they thought, felt, what they did, and what happened as a result. If they run out of things to say, the research tech will prompt them with questions to elicit more content until the three minutes are up; (3) Mirror trace: during this test, patients will be asked to outline, as quickly as possible, a star from its reflection in a mirror. Each task will last 3 minutes and there will be a 6-minute rest period between tasks.