Comparison of 1 month with 3 months of anticoagulation for a first episode of venous thromboembolism associated with a transient risk factor.
BACKGROUND
The risk of recurrence is lower after treatment of an episode of venous thromboembolism associated with a transient risk factor, such as recent surgery, than after an episode associated with a permanent, or no, risk factor. Retrospective analyses suggest that 1 month of anticoagulation is adequate for patients whose venous thromboembolic event was provoked by a transient risk factor.


METHODS
In this double-blind study, patients who had completed 1 month of anticoagulant therapy for a first episode of venous thromboembolism provoked by a transient risk factor were randomly assigned to continue warfarin or to placebo for an additional 2 months. Our goal was to determine if the duration of treatment could be reduced without increasing the rate of recurrent venous thromboembolism during 11 months of follow-up.


RESULTS
Of 84 patients assigned to placebo, five (6.0%) had recurrent venous thromboembolism, compared with three of 81 (3.7%) assigned to warfarin, resulting in an absolute risk difference of 2.3%[95% confidence interval (CI) - 5.2, 10.0]. The incidence of recurrent venous thromboembolism after discontinuation of warfarin was 6.8% per patient-year in those who received warfarin for 1 month and 3.2% per patient-year in those who received warfarin for 3 months (rate difference of 3.6% per patient-year; 95% CI - 3.8, 11.0). There were no major bleeds in either group.


CONCLUSIONS
Duration of anticoagulant therapy for venous thromboembolism provoked by a transient risk factor should not be reduced from 3 months to 1 month as this is likely to increase recurrent venous thromboembolism without achieving a clinically important decrease in bleeding.
Kearon
C
C
McMaster University, Hamilton, Ontario, Canada. kearonc@mcmaster.ca
Ginsberg
J S
JS
Anderson
D R
DR
Kovacs
M J
MJ
Wells
P
P
Julian
J A
JA
Mackinnon
B
B
Demers
C
C
Douketis
J
J
Turpie
A G
AG
Van Nguyen
P
P
Green
D
D
Kassis
J
J
Kahn
S R
SR
Solymoss
S
S
Desjardins
L
L
Geerts
W
W
Johnston
M
M
Weitz
J I
JI
Hirsh
J
J
Gent
M
M
D000328:Adult; D000368:Aged; D017152:Antibodies, Antiphospholipid / Q000097:blood; D000925:Anticoagulants / Q000008:administration & dosage*; D004311:Double-Blind Method; D004334:Drug Administration Schedule; D005260:Female; D006470:Hemorrhage / Q000209:etiology; D006801:Humans; D008297:Male; D008875:Middle Aged; D017354:Point Mutation; D011516:Prothrombin / Q000235:genetics; D011956:Receptors, Cell Surface; D012307:Risk Factors; D055502:Secondary Prevention; D013923:Thromboembolism; D013997:Time Factors; D020246:Venous Thrombosis; D014859:Warfarin / Q000008:administration & dosage*
D017152:Antibodies, Antiphospholipid; D000925:Anticoagulants; D011956:Receptors, Cell Surface; C083864:factor V receptor, human; D014859:Warfarin; D011516:Prothrombin