Activated partial thromboplastin time monitoring in patients receiving unfractionated heparin for venous thromboembolism in relation to clinical outcomes

Venous thromboembolism (VTE) is a prevalent and serious condition, which requires anticoagulation treatment for prolonged time duration. The use of unfractionated heparin administered intravenously or subcutaneously for acute management of VTE has been studied with favourable clinical results. Most physicians use activated partial thromboplastin time to monitor the treatment effect, in an effort to obtain better efficacy with less bleeding complications. Recent data however does not support this practice. We set to explore the medical literature for the correlation between the level of anticoagulation and the clinical outcomes. Randomised controlled trials comparing subcutaneous unfractionated heparin to any other treatment modality in patients with venous thromboembolism were obtained and a meta-analysis was performed. Seventeen reports from 15 randomised controlled trials were included. Of these, eleven included anticoagulation measurements. Seven and six trials were included in our analysis for subcutaneous and intravenous modes of administration, respectively. No correlation between the anticoagulation level and the major clinical outcomes were found, except for the initial anticoagulation measurement and the total mortality at three months, but not to death related to treatment or disease progression. In conclusion, weight-adjusted subcutaneous unfractionated heparin without anticoagulation monitoring may be feasible for patients with acute venous thromboembolism. No differences exist between intravenous and subcutaneous modes of administration with regards to the correlation between anticoagulant measures and the clinical outcomes. More research is needed to substantiate this observation.