Heparin Neutralizing Activity (HNA) and Antithrombin III in Coronary Artery Disease

Evaluation of some coagulation parameters in cerebral ischemia

In order to investigate some aspects of blood coagulation and of platelet function in cerebral ischemia, 18 healthy subjects, 24 patients with previous cerebral infarction and 12 patients with transient ischemic attacks were studied. All patients were in a non-active state of the illness. In all subjects, platelet count, prothrombin time, activated partial thromboplastin time and determination of the fibrinogen concentration were performed as routine. All subjects were tested for platelet adhesiveness, circulating platelet aggregates, factor VIII coagulant (VIII C), factor VIII-related von Willebrand factor (VII RWF), factor VIII-related antigen (VII RAg), antithrombin III (AT III) concentration and activity and euglobulin clot lysis time. No significant difference between patients and controls was found in routine tests, platelet function, AT III concentration or activity. Plasma levels of VIII C, VIII RWF, VIII RAg were significantly increased in both patient groups. The VIII RAg/VIII C ratio was significantly increased only in patients with previous cerebral infarction. Euglobulin clot lysis time was significantly increased in both patient groups.

Substitution therapy with an antithrombin III concentrate in shock and DIC

In 15 patients admitted to the Intensive Care Unit for shock and with signs of DIC, Antithrombin III (AT III) was substituted. Immediately after the first blood sampling, 1,000 units of AT III was given. This was followed by 500 units AT III after 24 h and after 48 h. A continuous dose of heparin of between 250 and 500 I.U./h was simultaneously given. The following results were obtained: The activity of AT III on admission of 63 +/- 19% increased to 83 +/- 17% 30 min after the initial substitution. There was a clear difference between the recovery of the substituted AT III in acute DIC and in patients in a steady state. AT III recovered in circulation was 47 +/- 15% in the former group but 83 +/- 16% in the latter cases. One unit of AT III per kg body weight increased AT III activity in circulation by 1% in acute DIC but by 1.8% in a steady state. The average half life of the substituted AT III was 4.4 +/- 1.6 h in acute DIC and was 20.2 +/- 4.1 h when the patients were in a steady state.

Further observations on the effects of dietary fatty acid composition on platelet reactivity and blood coagulation in man and the influence of methodology on findings

Eight human subjects were fed diets enriched in saturated fat (SF), or polyunsaturated fat (PUF) and after each dietary regimen the plasma heparinthrombin clotting time (HTCT) was determined. The HTCT of citrated plasma indicated reduced heparin-neutralizing activity (HNA) after PUF feeding compared with SF feeding. Platelet factor 4 (PF4) levels in the citrated plasma samples demonstrated an inverse correlation with the HTCT (r = 0.62). Experiments with purified PF4 indicated that the PF4 present in citrated plasma could only account for approximately 10% of the HNA. Plasma prepared in a manner which minimized in vitro release of platelet constituents contained significantly less PF4 after PUF feeding and indicated that most of the PF4 found in citrated plasma resulted from in vitro release. The factor Xa inhibitory activity of citrated plasma was not significantly altered by either of the dietary regimens.

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.