[Blood coagulation and fibrinolysis in arteriosclerosis]

Thrombus formation at the site of atherosclerotic lesions, especially on a ruptured plaque, plays a central role in the "atherothrombosis" hypothesis. An activation of the hemostasis and a disturbed fibrinolysis are known. These alterations are especially marked in patients with acute coronary syndromes. In stable coronary artery disease, fibrinogen is elevated. Furthermore, minor alterations of the contact phase factor VII and consecutively of the thrombin system are detectable depending on the study population. Thrombin generation and activation become marked in patients with unstable angina pectoris or acute myocardial infarction. Possible reasons for this activation are an activation of the contact phase factor XII system and the release of tissue factor both from the ruptured plaque and from stimulated monocytes. The fibrinolytic system is markedly altered already in patients with stable coronary heart disease. Increased levels of tissue-type plasminogen activator and of urokinase-type plasminogen activator/receptor are measurable in atheromas. Tissue-type plasminogen activator mass concentration is systemically elevated already at early stages of atherosclerosis. Especially in patients with increased risk for acute coronary syndromes, the plasminogen activator inhibitor activity is significantly increased. Furthermore, a hypercoagulative state with increased d-dimer levels and plasmin-antiplasmin complexes can be measured. The alterations of hemostasis and especially of fibrinolysis are detectable for prolonged time period and persist much longer than the clinical symptoms of the patients. The increased plasminogen activator inhibitor activity is associated with the metabolic syndrome and constitutes an (in part genetically determined) disturbance in patients with stable or unstable coronary heart disease. However, the large intra- und interobserver as well as diurnal variability of this marker limits its use as a routine measure for risk stratification in patients. Alterations of the hemostasis and disturbances of fibrinolysis are detectable during the chronic as well as the acute phase of atherosclerosis. These changes are best documented for coronary heart disease, whereas less data are available for other manifestations of atherosclerosis. The use of newly developed molecular markers for single reaction steps of pathways instead of global functional tests and of new molecular biological methods did considerably improve the detailed knowledge on the pathomechanisms of the development of atherosclerosis, making the development of targeted therapies, e.g., against receptors possible. Future studies will investigate the quantitative impact of the various activated pathways (cause or reaction) and the effects of interventions on these pathomechanisms in patients with acute coronary syndromes. Studies will have to focus especially on the meaning of polymorphisms, early changes in the development of atherosclerosis and interactions with inflammatory processes.