Factor VII and heparin in thrombosis.

Factor VII is the term used by Koller, Loeliger, and Duckert (1951) for the accelerator complex of prothrombin conversion present in both plasma and serum which is markedly reduced by treatment with drugs of the dicoumarin group. It has been shown by Poller (1954 and 1956a) that there is a significant reduction in the anticoagulant action of heparin on the plasma clotting times of patients with recent thrombo-embolic disease. It has also been shown by Poller (1957) that there was a significant increase in plasma factor VII activity in such patients at the same stage of their illness. The aim of the present investigation was to determine whether there was any association between the increase in factor VII activity and the " heparin resistance " of these cases. The problem is of particular interest because both factor VII and heparin are of established importance in maintaining the normal balance of coagulation.