Idiopathic versus secondary venous thromboembolism. Findings of the RIETE registry

Background and objectives: The Computerized Registry of Patients with Venous Thromboembolism (RIETE) is a prospective registry that consecutively includes patients diagnosed with venous thromboembolism. We compared the clinical presentation and response to anticoagulant treatment in patients with idiopathic venous thromboembolism (IVT) versus secondary venous thromboembolism (SVT, associated with a risk factor).

Patients and methods: We analyzed the differences in clinical characteristics, comorbidity, treatment and events during the first 3months after the diagnosis of venous thromboembolism in patients with IVT or SVT and according to their initial clinical presentation.

Results: A total of 39,921 patients with IVT (n=18,029; 45.1%) or SVT (n=21,892; 54.9%) were enrolled. The patients with IVT had a greater history of venous thromboembolism than those diagnosed with SVT (p<.001). The initial treatment was similar for the 2 groups, but more inferior vena cava filters were placed in the SVT group (p<.001). In the long term, low-molecular-weight heparin was used more often in the SVT group than in the IVT group. At 90days, bleeding, death and the recurrence of venous thromboembolism were significantly more frequent in the SVT group. The multivariate analysis confirmed that IVT was associated with fewer major (OR, 0.60; 95%CI, 0.50-0.61; p<.001) and fatal (OR, 0.41; 95%CI, 0.29-0.62; p<.001) bleedings, fewer relapses (OR, 0.58; 95%CI, 0.39-0.78; p<.001) and fewer fatal pulmonary embolisms (OR, 0.29; 95%CI, 0.12-0.52; p<.001). These differences were maintained in patients whose venous thromboembolism started with a pulmonary embolism or with deep vein thrombosis.

Conclusions: IVT has a better prognosis than SVT at 90days of the diagnosis.