Cardiovascular disease are a leading cause of mortality and morbidity in the Western world. Platelets play an important role in the development of cardiovascular disease, not only in the acute... Show moreCardiovascular disease are a leading cause of mortality and morbidity in the Western world. Platelets play an important role in the development of cardiovascular disease, not only in the acute onset of thrombosis after atherosclerotic plaque rupture but also in the initiation and progression of atherosclerosis and plaque formation. In recent years, the awareness has grown that platelet function may vary among individuals and that high platelet reactivity may increase the risk of cardiovascular events. This thesis addresses variation in platelet reactivity in relation to occurrence of cardiovascular events. We show that high platelet reactivity in subjects with cardiovascular disease using aspirin or clopidogrel as well as in antiplatelet drug-na_ve healthy subjects is related to the risk of cardiovascular events. We also revealed several genetic and clinical risk factors of high platelet reactivity. Moreover, we show that the 110-year old antiplatelet drug aspirin has interesting time-dependent pleiotropic effects on various pressor systems underlying blood pressure. As discussed in this thesis, although promising results have been published, routine platelet reactivity testing in daily clinical practice would currently be premature. Future studies are warranted to further investigate the clinical applicability of platelet reactivity testing in subjects at risk for cardiovascular events. Show less