Stockings to prevent post-thrombotic syndrome

Until recently, the effectiveness of elastic compression stockings for the prevention of post-thrombotic syndrome following deep venous thrombosis (DVT) was considered irrefutable. Compression stockings had been embedded in daily practice and in guidelines,1 2 at least in Europe, since two randomised clinical trials showed that compression reduced the incidence of post-thrombotic syndrome by more than 20%.1 2 The results of the SOX trial, published in 2014, challenged this dogma, suggesting that elastic compression did not prevent post-thrombotic syndrome.3 Although the trial was hampered by a lack of adherence to treatment, treating clinicians readily accepted the negative outcome. Since then, guidelines have been updated and compression stockings devalued and even discouraged.4

In a linked paper (doi:10.1136/bmj.i2691), Mol and colleagues report the results of the OCTAVIA trial, a non-inferiority study comparing two years of elastic compression therapy with one year of elastic compression for the prevention of post-thrombotic syndrome in adults with a proximal DVT.5 The findings suggest that compression might still be an important preventive strategy, even one year after their DVT, in selected patients with no evidence of post-thrombotic syndrome (based on low Villalta scores).

The rationale for evaluating a shorter duration of treatment is derived from previous studies showing that most cases of post-thrombotic syndrome occurred within the first year after an acute DVT.1 2 6 Although most therapeutic benefit is expected in the first year, the costs of treatment and its effect on quality of life are similar for both the first and the second year. The expected incidence of post-thrombotic syndrome in the second year is not very high (2-3%),1 2 6 but it is not zero. So the expected trade-off for patients forgoing a second year of therapy (the convenience and lower cost of not wearing stockings compared with a possible increase in post-thrombotic syndrome) should be clearly weighed up.7

The OCTAVIA trial did not evaluate the efficacy of elastic compression beyond one year of treatment for all patients with proximal DVT. The authors chose to select participants who were highly compliant with therapy (had a proven track record) and had not developed post-thrombotic syndrome in the first year after a DVT . In these patients, the trial shows that stopping treatment after one year is clearly not non-inferior to continuing treatment for two. Selection of patients has probably reduced the generalisability of these findings. It might be more appropriate to tailor treatment for unselected patients by using the Villalta score instead, and we hope that findings from the ongoing IDEAL study (NCT01429714, due in 2017) will provide this information.8

The prevalence of post-thrombotic syndrome in the patient population considered for inclusion in OCTAVIA is not entirely clear. Among potential participants, only 93 had post-thrombotic syndrome in the first year after their DVT and were excluded from the trial; this is a rather low number. Conversely, the proportion of patients that developed post-thrombotic syndrome in the second year was 20% (51/518) in the group that stopped compression treatment and 13% (34/518) in the group that continued. This substantially exceeds the expected incidence (2-3%) in both treatment groups.

Although the incidence of post-thrombotic syndrome in the second year was high, the severity was very mild in most patients (84% of affected patients who stopped and 91% of those who continued had mild post-thrombotic syndrome). This might explain why the class of compression stocking made no difference to study outcomes among the 28% of patients erroneously given class II stockings (20-30 mm Hg) instead of the higher pressure class III (30-40 mm Hg).

What are the implications of the findings from the OCTAVIA trial? The authors estimate that 14 patients would have to continue compression treatment for an extra year to prevent one case of post-thrombotic syndrome. Although questions concerning the optimal selection of patients for extended treatment remain, this study clearly shows that compression stockings have the potential to prevent post-thrombotic syndrome in a selected group. Adherence to therapy is once again identified as a major determinant of treatment success.