The relation between the activated partial thromboplastin time response and recurrence in patients with venous thrombosis treated with continuous intravenous heparin

Background: It is unknown whether the true risk of recurrent venous thromboembolism (VTE) is increased in patients with proximal deep vein thrombosis who are treated with continuous intravenous heparin and fail to reach a therapeutic activated partial thromboplastin time (APTT) within 24 to 48 hours of initiation of treatment. Methods: To compare the risk of recurrent VTE in patients with early subtherapeutic APTT results and those with APTT results above the lower limit of the therapeutic range, we performed a formal review of the literature. We examined all available studies that provided information on the relation between the risk of recurrent VTE and the APTT response to heparin when initiated as a bolus followed by a continuous intravenous infusion of at least 30 000 U/24 h. Results: Five studies were included in the final analysis. The overall recurrence rate was 6.3% in patients whose APTT results were subtherapeutic for the first 24 to 48 hours and 7% in patients whose APTT results were above the lower limit of the therapeutic range, providing a pooled odds ratio of 0.89 with a 95% confidence interval of 0.2 to 4.0. Conclusions: In patients with VTE who are treated with a bolus of heparin followed by a continuous intravenous infusion of at least 30 000 U/24 h, no convincing evidence shows that the risk of recurrent VTE is critically dependent on achieving a therapeutic APTT result at 24 to 48 hours.