Predictors of the post-thrombotic syndrome during long-term treatment of proximal deep vein thrombosis.
BACKGROUND
The post-thrombotic syndrome is a chronic, poorly understood complication of deep venous thrombosis (DVT).


OBJECTIVE
To evaluate predictors of the post-thrombotic syndrome, including intensity of long-term anticoagulation, and to assess the impact of the post-thrombotic syndrome on quality of life.


METHODS
The setting was 13 Canadian hospitals and one US hospital. One hundred and forty-five patients with an unprovoked episode of proximal DVT who were initially treated with 3 months of conventional-intensity warfarin [target International Normalized Ratio (INR) of 2.5] then participated in a trial comparing two intensities of long-term warfarin therapy (target INR 2.5 vs. INR 1.7). Post-thrombotic syndrome was assessed at the end of the trial using a validated clinical scale. Generic and venous disease-specific quality of life was compared in patients with and without the post-thrombotic syndrome. Multivariable regression analyses were performed to identify predictors of the post-thrombotic syndrome and of its severity.


RESULTS
After an average follow-up of 2.2 years, the prevalence of post-thrombotic syndrome was 37% and of severe post-thrombotic syndrome was 4%. Quality of life was worse in patients with the post-thrombotic syndrome compared with patients who did not have it. The presence of factor (F)V Leiden or the prothrombin gene mutation was an independent predictor of both a lower risk (P = 0.006) and reduced severity (P = 0.045) of the post-thrombotic syndrome. Intensity of anticoagulation did not influence the risk of developing the post-thrombotic syndrome.


CONCLUSIONS
The post-thrombotic syndrome is a frequent and burdensome complication of proximal DVT, even among patients maintained on long-term oral anticoagulation. While the presence of FV Leiden or prothrombin gene mutation appears to be associated with a reduced risk of post-thrombotic syndrome, this finding requires further evaluation in prospective studies.
Kahn
S R
SR
McGill University, Montreal, Quebec, Canada. susan.kahn@mcgill.ca
Kearon
C
C
Julian
J A
JA
Mackinnon
B
B
Kovacs
M J
MJ
Wells
P
P
Crowther
M A
MA
Anderson
D R
DR
Van Nguyen
P
P
Demers
C
C
Solymoss
S
S
Kassis
J
J
Geerts
W
W
Rodger
M
M
Hambleton
J
J
Ginsberg
J S
JS
D000284:Administration, Oral; D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000925:Anticoagulants / Q000627:therapeutic use; D002170:Canada; D005165:Factor V / Q000235:genetics; D005260:Female; D006801:Humans; D019934:International Normalized Ratio; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D009154:Mutation; D011186:Postphlebitic Syndrome / Q000175:diagnosis*; D015995:Prevalence; D011516:Prothrombin / Q000235:genetics; D011788:Quality of Life; D012306:Risk; D013997:Time Factors; D014481:United States; D020246:Venous Thrombosis / Q000150:complications* / Q000628:therapy*; D014859:Warfarin / Q000627:therapeutic use
D000925:Anticoagulants; C095381:factor V Leiden; D014859:Warfarin; D005165:Factor V; D011516:Prothrombin