The study aims to investigate the presence of a substance in the blood called prokinecitine, which is released by the heart when a heart attack occurs. Several venous blood samples at the arm are withdrawn at admission, H6, H12, H24, H48 and H72 in order to measure the concentration of this substance in the blood. The usefulness of this new blood marker is going to be determsined to seek if it would be of help to better diagnose or estimate the gravity of heart infarction after a heart attack.