Heparin and atherosclerosis. A review of old and recent findings.

This article reviews the experimental and clinical evidence regarding heparin therapy in the prophylaxis of coronary heart disease. The actions of heparin take place at the vascular endothelium where injected heparin concentrates, and within the bloodstream. At the endothelium heparin acts to prevent endothelial injury, prevent thrombin generation, prevent platelet adhesion to endothelium, and to decrease uptake of serum lipoproteins. Within the bloodstream heparin increases lipoprotein lipase activity and reduces the concentration of atherogenic very low-density lipoproteins. The reduction in lipemia enhances oxygen transfer from blood to the tissues, and decreases thrombin or ADP-induced platelet aggregation. Heparin increases the concentration of high-density lipoproteins. It decreases hypercoagulability and inhibits overactivation of serum complement. Heparin reduced atherosclerosis in most studies in cholesterol-fed animals. In human subjects who had a myocardial infarct at least one year before the onset of treatment, long-term intermittent heparin therapy significantly decreased cardiovascular deaths as compared to control groups.