Inclusion Criteria:  Adults ≥ 18 years old; diagnosed with myocardial infarction, unstable angina, or undergoing percutaneous coronary intervention or coronary artery bypass graft surgery; and speak and read English.  Exclusion Criteria:  The following exclusion criteria are in place for Aims 1 and 3 because they affect HRV: having a pacemaker or implanted cardioverter-defibrillator, chronic arrhythmia, history of or current valvular disease, history of organ transplant, current use of immunosuppressive medications, or diabetic autonomic insufficiency