This is a national multi-center, prospective surveillance study in patients with suspected acute coronary syndrome. Eligible patients must present to one of the participating Emergency Departments within 24 hours from the time of symptom onset. Approximately 2000 patients >18 and <85 years of age are planned to be enrolled.

Upon enrollment in the Emergency Department, a venous blood sample will be obtained from each patient for analysis. The patient's diagnostic work-up, treatment and disposition will continue per the standards of the treating institution. Results will be recorded for ECGs, any cardiac biomarkers measured at the site and any follow-up cardiac objective tests performed for evidence of coronary artery disease and/or myocardial damage (exercise treadmill, coronary angiography, cardiac thallium or technetium scintigraphy, etc).

The Principal Investigator at each site will evaluate the results of the diagnostic cardiac tests performed for that patient to determine whether each patient enrolled at their site has a final diagnosis of ACS.

The status of each patient will also be assessed at 1 month and 6 months after enrollment for intercurrent Major Adverse Cardiac Events (MACE), including myocardial infarction, cardiac revascularization and death.

Inclusion Criteria:

• Only patients who are able to give consent. This has to be carefully verified in each case, by the doctors leading the study
• Men or women >18 and <85 years of age
• Patients with chest discomfort within last 24h and suspected Acute Coronary Syndrome (STEMI, NSTEMI and unstable angina)
• Patient experiencing at least 30 minutes of chest discomfort or other symptoms consistent with possible ACS; (Note: Patients who have symptoms of shorter duration that resolved due to pharmacologic intervention may be included.)
• Written informed consent

Exclusion Criteria:

• Age <18 or >85 years
• Inpatient in the hospital prior to onset of symptoms.
• Obvious traumatic disease
• Prisoners or other institutionalized or vulnerable individuals
• Major surgery within last 4 weeks
• Patients with cardiogenic shock
• Other significant laboratory abnormalities that the investigator feels may compromise the patient's safety by participation in the study
• Women who are pregnant or breast feeding
• Obvious iv drug abuse
• Refusal to provide written informed consent
• Unavailability of a telephone number and insufficient contact information as well as permanent residence abroad
• Unreliability as a study participant as based on the investigator's prior knowledge of the patient, such as the inability or willingness to participate in or complete the study or the presence of concurrent physical or psychological disorders that may make it impractical for the patient to participate in or complete the study

This study will focus on patients presenting to the ED within 24 hours of the onset of chest pain. Both patients then discharged to home as well as patients subsequently admitted to the hospital are eligible for the study and may be enrolled.