The purpose of this study is to determine whether the combination of copeptine and troponin adds diagnosis information to that provided by troponin alone or the combination of troponin and myoglobin.

Hypothesis : If the values of troponin and copeptin are not elevated, diagnosis of acute myocardial infarction can be ruled out without prolonged monitoring and serial blood sampling.

Patients older than 18 years with pain suggestive of Acute Coronary Syndrome, with onset within the last 12 hours, presenting to the Emergency Department of the University Hospital Gabriel Montpied (Clermont-Ferrand, France) and the General Hospital Henri Mondor (Aurillac, France) are enrolled.

Upon admission to the hospital, all patient underwent an initial clinical assessment, including medical history, temperature, respiratory rate, cardiac frequency, blood pressure, pulse oxymetry, 18-lead ECG, chest X-ray and screening blood test including C reactive protein, natremia, Troponine T, myoglobin, creatin kinase and copeptine.

Patients with hyponatremia < 135 mmol/L or troponin > 1 μg/L are released study.

Blood sampling are taken for Troponine T, myoglobin, creatin kinase and copeptine analysis and 18-lead ECG was performed after 2, 4, 6 and 12 h.

Copeptin and myoglobin are measured at the end of the patients inclusion, after to be centrifugrd end frozen at -80°C at each time point.

The treatment of patients is not modified by the study. At 90 days, clinicals and paraclinicals events are collected.

Inclusion Criteria:

• Chest pain suggestive of Acute Coronary Syndrome
• Chest pain with onset within the last 12 h
• Patients older than 18 years

Exclusion Criteria:

• ST-Elevation Myocardial infarction
• Legal incapacity
• Sepsis
• Hyponatremia < 135 mmol/L
• Shock
• Lung neoplasms
• life expectancy of less than 6 months
• Refuse to consent