title: The incidence of recurrent venous thromboembolism after treatment with vitamin K antagonists in relation to time since first event: a meta-analysis.
abstract: BACKGROUND
  After a first episode of venous thromboembolism, patients are treated with vitamin K (phytonadione) antagonists. There are indications that the risk of recurrence after treatment with vitamin K antagonists decreases relative to the time since the first event. The aim of the present meta-analysis is to describe the risk of recurrent venous thromboembolism after treatment with vitamin K antagonist in relation to the time since the index event.
  
  
  METHODS
  Computerized searches in MEDLINE and EMBASE databases; reference checks of pertinent articles; personal communication with colleagues to find randomized clinical trials and cohort studies in which patients with venous thromboembolism were treated with vitamin K antagonists. Per treatment arm, 2 reviewers independently extracted data on the number of recurrent events and the duration of follow-up per time period of 3 months.
  
  
  RESULTS
  A total of 135 potentially eligible studies were identified. Of these, 18 studies could be included, comprising 25 treatment arms that could be analyzed. Treatment arms were divided into 3 groups based on treatment duration (short, medium, and long). For all 3 groups, the monthly incidence immediately after discontinuation of treatment was high and declined rapidly thereafter. The monthly incidence after 9 months seemed independent of the treatment duration.
  
  
  CONCLUSIONS
  There is a diminishing risk of recurrent venous thromboembolism over time and a stabilization after 9 months independent of the duration of the initial treatment with vitamin K antagonists. These findings have important implications for decision making about the optimal duration of treatment with vitamin K antagonists.
authors.affiliation: Department of Clinical Epidemiology, Academic Medical Center, Amsterdam, The Netherlands. c.j.vandongen@amc.uva.nl
authors.forename: Carlo J J
authors.initials: CJ
authors.lastname: van Dongen
authors.forename: Roel
authors.initials: R
authors.lastname: Vink
authors.forename: Barbara A
authors.initials: BA
authors.lastname: Hutten
authors.forename: Harry R
authors.initials: HR
authors.lastname: Büller
authors.forename: Martin H
authors.initials: MH
authors.lastname: Prins
mesh_terms: D000925:Anticoagulants / Q000008:administration & dosage* / Q000009:adverse effects; D006801:Humans; D011655:Pulmonary Embolism / Q000517:prevention & control; D012008:Recurrence; D012307:Risk Factors; D013997:Time Factors; D020246:Venous Thrombosis / Q000517:prevention & control*; D014812:Vitamin K / Q000037:antagonists & inhibitors*
chemical_list: D000925:Anticoagulants; D014812:Vitamin K