The antithrombotic effect of heparin in deep venous thrombosis: relation to four heparin assays.

In a prospective study, 280 patients with phlebographically proven deep venous thrombosis received intravenous heparin infusion; 224 of the patients were subjected to control phlebography after 5-8 days of treatment. Females above 70 years showed least phlebographic improvement despite similar heparin dosage and heparin activity. Heparin activity in daily drawn blood samples was determined by four different assays. Chromogenic substrate (CS) assay (Coatest heparin), activated partial thromboplastin time (Cephotest), and thrombin time with recalcified plasma (CaTT) showed weak but significant correlations with thrombus resolution judged by phlebography (p = 0.004, 0.003 and 0.018, respectively). A linear prediction equation showed that the phlebographic result was about equally influenced by the mean dose and by the result of any of the three heparin assays. Thrombin time with citrated plasma showed no correlation. CS assay and CaTT showed significantly lower mean heparin activity in patients with (n = 13) than without clinically diagnosed pulmonary embolism (p = 0.012 and 0.001, respectively).