Predictors of the Development of Post-Thrombotic Syndrome after Acute Symptomatic Deep Vein Thrombosis: Two-Year Results from a Canadian Multicenter Prospective Cohort Study (The VETO Study).

Background and Objectives: It is not understood why some patients develop post thrombotic syndrome (PTS) after DVT while others recover without sequelae. We performed a prospective, multicenter study of long-term outcomes after DVT (the Venous Thrombosis Outcomes [VETO] Study) whose principal aim was to identify predictors of PTS.

Methods: From 2001–2002, consecutive patients with objectively diagnosed DVT were recruited at 7 hospital centres. During study visits at Baseline, 1, 4, 8, 12 and 24 months, clinical data were collected, thrombophilia testing was performed and standardized assessments for PTS (using Villalta scale) were carried out by trained personnel. Patients were classified as having developed PTS if the ipsilateral Villalta score was ≥5 on at least 2 visits or at the final follow-up visit, and severe PTS if a score of >14 or a venous ulcer was documented on any one occasion. The influence of clinical, demographic, ergonomic and biological determinants on the risk of developing PTS was evaluated in bivariate and multivariate analyses.

Results: 359 patients were recruited; 49% were male, mean age was 56 years, 2/3 were outpatients and 55% had proximal DVT. The cumulative risk of PTS was 37%, of which 1 in 6 cases was severe. Patients who developed PTS, compared with those who did not, were more likely to be older (p=.005), have had previous episode(s) of DVT (p=.0003), have atherosclerosis risk factors [hypertension (p=.0002), high cholesterol (p=.02)], higher BMI (p=0.0007), longer duration of symptoms before DVT diagnosis (p=.049) and work in a job with high physical demands (p=.05), and they were less likely to have the Prothrombin gene mutation (p=0.03). Variables of interest that did not influence the risk of PTS included: sex, location of DVT (proximal vs. distal), side of DVT (left vs. right), type of DVT (cancer-related, temporary risk factors [e.g. surgery, trauma] or idiopathic), initial anticoagulation with LMWH vs. UFH, duration of warfarin, Factor V Leiden mutation or prior ipsilateral musculoskeletal condition. In adjusted multivariate analyses, BMI (odds ratio [OR] 2.1 for BMI >30 vs. < 30, 95% confidence interval [CI] 1.1, 4.2), previous DVT (OR 2.6, 95% CI 1.4, 4.9) and hypertension (OR 1.9, 95% CI 1.04, 3.6) were independently associated with PTS.

Conclusions: In our cohort, high BMI, previous history of DVT and hypertension were independent predictors of PTS, whereas presenting characteristics of the index DVT and its treatment did not influence the risk of developing PTS.