Thrombosis and Factor Vii Activity

The tests for the coagulation time of the blood which are in general use have contributed little to the understanding of abnormal tendencies to thrombosis, as they are extremely insensitive to all but gross changes in the coagulation mechanism. A variety of techniques have been evolved to meet this defect. One group of these methods depends on the addition of an inhibitor, e.g., heparin, to the routine clotting time method (Waugh and Ruddick, 1944; Silverman, 1948). It has been shown, using a heparin sensitized method (Poller, 1956), that statistically the coagulation time is significantly shortened 48 hours after a thrombo-embolic episode. The drawbacks to the use of such methods as simple prediction tests have been discussed (Poller, 1955). As thromboplastin and heparin are to a large extent mutually antagonistic in action, and shortened heparin plasma clotting times have been found in the first few days after operation when tissue damage and other factors may cause an increase in thromboplastin activity, it may be supposed that increased resistance to heparin may be related to the ability to produce thromboplastin in the plasma of such patients. An investigation of various aspects of thromboplastin production was therefore performed in a group of patients and parallel controls. Prothrombin activity, factor V and VII activity, and the production of thromboplastin in the thromboplastin generation test were studied in both groups, together with heparin plasma clotting times. In view of the recently established effect of chylomicra on the coagulation time (Poole, 1955), serum cholesterol values were determined in both groups as a feature of secondary interest.