Thirty patients with acute ST-elevation myocardial infarction treated with primary PCI and aspiration of thrombus material from the infarct related coronary artery will be included. Both cellular and non cellular content of the thrombus will be examined with morphological and immunohistochemical methods and related to time from onset of symptoms to PCI, as well as to the degree of myocardial necrosis. Furthermore, mRNA expression of selected signal molecules will be performed. In addition, peripheral venous blood samples will be drawn and analyzed for signalling molecules and corresponding mRNA expression in circulating leukocytes.