Thrombosis and cardiovascular disease.

It was only quite recently that the thrombotic component in myocardial infarction and sudden coronary death was generally acknowledged. When attention was eventually paid to it, interest initially centered primarily on platelet function. There is, of course, no doubt about the central role of platelet adhesion and aggregation in thrombogenesis, but still no generally accepted measure of platelet function has been shown to be associated with the later onset of ischemic heart disease (IHD). Epidemiologically, the assessment of coagulability has been more rewarding. Several prospective studies have now shown a strong relationship between the plasma fibrinogen level and the incidence of IHD and stroke. Epidemiologic and laboratory studies have also implicated factor VII and extrinsic pathway activity in the onset of IHD. Other components of the hemostatic system that are probably involved include factor VIII activity and the fibrinolytic system. It is increasingly clear that lipoproteins exert a major influence on coagulability as well as their better known role in atherogenesis. Any further polarization of hypotheses for IHD as being purely atherogenic or purely thrombogenic is therefore counterproductive. At the same time, antithrombotic measures for primary prevention need to be evaluated as thoroughly as lipid-lowering regimens. If thrombosis is seen as the final arterial event in virtually all major episodes of IHD, the indications for antithrombotic agents in primary prevention may be wider than those for lipid-lowering regimens. It is therefore necessary to establish as quickly as possible not only the preventive effectiveness of antithrombotic measures, including low-dose aspirin and low-intensity oral anticoagulation, but also the relative effectiveness and safety of antithrombotic and lipid-modifying regimens.