Clinical question: Is therapeutic anticoagulation superior to placebo in patients with symptomatic acute calf deep venous thrombosis (DVT)?
Background: Medical evidence supporting the usage of therapeutic anticoagulation in symptomatic acute isolated calf DVT is lacking. This type of DVT has a low embolic potential. The bleeding risk of anticoagulation might therefore be higher than its benefit.
Study design: Double-blind, placebo-controlled trial.
Setting: Twenty-three centers in Canada, France and Switzerland.
Synopsis: A total of 259 outpatients with a first acute symptomatic objectively confirmed isolated calf DVT were enrolled to receive either a therapeutic dose of the low-molecular weight heparin nadroparin (122 patients), or a placebo (130 patients).
The primary efficacy outcome (a composite endpoint of extension of calf DVT to proximal veins, contralateral proximal DVT and symptomatic pulmonary embolism) was not statistically significant between the two groups (3% in the nadroparin group and 5% in the placebo group, P = .54). The primary safety outcome (the number of patients with major or clinically relevant non-major bleeding) was significantly higher in the nadroparin group (4% in nadroparin group, 0 patients in the placebo group, P = .0255).
The study was limited by the relative low number of patients (goal was 286 patients). The results of the study do not apply to inpatients and to cancer patients as patients with high risk for extension or recurrence of their DVT were excluded.
Bottom line: Therapeutic anticoagulation in low-risk outpatients with isolated calf DVT will likely cause more harm from bleeding than benefit.
Citation: Righini M, Galanaud J, Guenneguez H, et al. Anticoagulant therapy for symptomatic calf deep vein thrombosis (CACTUS): A randomised, double-blind, placebo-controlled trial. The Lancet Haematology. 2016;3(12):e556-e562. doi:
Dr. Badr is a hospitalist at Cooper University Hospital in Camden, N.J., and an assistant professor of clinical medicine at the Cooper Medical School of Rowan University.