title: Patients with a first symptomatic unprovoked deep vein thrombosis are at higher risk of recurrent venous thromboembolism than patients with a first unprovoked pulmonary embolism.
abstract: BACKGROUND
  Previous studies are mixed as to whether patients with unprovoked pulmonary embolism (PE) have a higher rate of venous thromboembolism (VTE) recurrence after anticoagulation is discontinued than patients with unprovoked deep vein thrombosis (DVT).
  
  
  OBJECTIVE
  To determine whether patients with unprovoked PE have a higher rate of VTE recurrence than patients with unprovoked DVT in a prospective multicenter cohort study.
  
  
  METHODS
  Six hundred and forty-six patients with a first episode of symptomatic unprovoked VTE were treated with heparin and subsequent oral anticoagulation for 5-7 months, and were followed every 6 months for recurrent VTE after their anticoagulant therapy was discontinued.
  
  
  RESULTS
  Of 646 patients, 194 had isolated PE, 339 had isolated DVT, and 113 had both DVT and PE. After a mean of 18 months of follow-up, there were 91 recurrent VTE events (9.5% annualized risk of recurrent VTE in the total population). The crude recurrent VTE rate for the isolated PE, isolated DVT and DVT and PE groups were 7.7%, 16.5% and 17.7%, respectively. The relative risk of recurrent VTE for isolated DVT vs. isolated PE was 2.1 (95% confidence interval 1.2-3.7).
  
  
  CONCLUSIONS
  This study has demonstrated that patients with a first episode of unprovoked isolated DVT are 2.1 times more likely to have a recurrent VTE episode than patients with a first episode of unprovoked isolated PE. These findings need to be considered when determining the optimal duration of anticoagulant therapy for patients with unprovoked VTE.
authors.affiliation: Department of Hematology, London Health Sciences Centre, Victoria Hospital, London, Ontario, Canada. Michael.Kovacs@lhsc.on.ca
authors.forename: M J
authors.initials: MJ
authors.lastname: Kovacs
authors.forename: S R
authors.initials: SR
authors.lastname: Kahn
authors.forename: P S
authors.initials: PS
authors.lastname: Wells
authors.forename: D A
authors.initials: DA
authors.lastname: Anderson
authors.forename: I
authors.initials: I
authors.lastname: Chagnon
authors.forename: G
authors.initials: G
authors.lastname: LE Gal
authors.forename: S
authors.initials: S
authors.lastname: Solymoss
authors.forename: M
authors.initials: M
authors.lastname: Crowther
authors.forename: A
authors.initials: A
authors.lastname: Perrier
authors.forename: T
authors.initials: T
authors.lastname: Ramsay
authors.forename: M T
authors.initials: MT
authors.lastname: Betancourt
authors.forename: R H
authors.initials: RH
authors.lastname: White
authors.forename: L
authors.initials: L
authors.lastname: Vickars
authors.forename: M A
authors.initials: MA
authors.lastname: Rodger
mesh_terms: D000284:Administration, Oral; D000368:Aged; D000925:Anticoagulants / Q000627:therapeutic use; D015331:Cohort Studies; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D011655:Pulmonary Embolism / Q000150:complications / Q000175:diagnosis*; D012008:Recurrence; D012306:Risk; D016896:Treatment Outcome; D054556:Venous Thromboembolism / Q000150:complications / Q000175:diagnosis*; D020246:Venous Thrombosis / Q000150:complications* / Q000628:therapy*
chemical_list: D000925:Anticoagulants