The purpose of the study is to procure blood samples from patients who present to the Emergency Department with suspected ACS (Acute Coronary Syndrome).

This is a prospective, multi-center, observational, and sample procurement study of adult subjects presenting to an Emergency Department (ED) in whom ACS is in the differential diagnosis. Subjects must present to one of the participating EDs within 6 hours or less from the time of symptom onset, and must have experienced at least 30 minutes of chest discomfort. Those ED patients with possible ACS who meet the inclusion/exclusion criteria will be approached for study enrollment by trained research personnel.

The patient's diagnostic work-up and treatment will continue per the standards of the treating institution. As indicated by their clinical presentation, all subjects in the study will have objective cardiac testing for evidence of coronary artery disease (CAD) during or in close proximity to the index ED visit or hospital admission. For this study, objective cardiac testing will consist of one of the following tests: exercise treadmill, coronary angiography, myocardial stress imaging, stress magnetic resonance imaging (MRI), sestamibi scan, or dobutamine echocardiogram. Cardiac events and procedures, such as angioplasty-stenting and coronary artery bypass surgery (CABG), will be recorded during the index ED visit, hospitalization and post-hospital follow-up period. Subjects will have a 30-day and 6-month follow-up contact by phone to collect this information on cardiac events, procedures, and survival.

Inclusion Criteria:

• Age 18 years or older at time of enrollment
• Patient presenting to the ED within 6 hours or less from symptom (chest discomfort consistent with possible ACS) onset
• Patient experiencing at least 30 minutes of chest discomfort, consistent with possible ACS, from time of symptom onset; patients who have symptoms of shorter duration due to pharmacologic intervention may be included
• Physician plans to perform objective cardiac testing as defined by the protocol

Exclusion Criteria:

• Patient (or legal representative) unable or unwilling to provide informed consent
• Patient (or legal representative) refusal of medical record review or telephone follow-up at 30 days or 6 months
• Patient (or legal representative) refusal of multiple blood sample collection over the study period
• Prisoners or other institutionalized individuals

Patients presenting the to the ED within 6 hours with symptoms consistent with ACS.