ABSENCE OF RESIDUAL VEIN THROMBOSIS AFTER AN EPISODE OF IDIOPATHIC DEEP VEIN THROMBOSIS: SHORT-TERM ANTICOAGULA-TION IS SAFE. THE'EXTENDED DACUS STUDY'

BACKGROUND: The optimal duration of Oral Anticoagulant Therapy (OAT) for Deep Vein Thrombosis (DVT) can be tailored by Residual Vein Thrombosis (RVT) (Siragusa S et al. Blood 2003;102(11):OC183), a marker able to assess the individual risk for recurrent thrombosis. However, in patients with idiopathic DVT the safety of early interruption of OAT, because of absence of RVT, is still debated. Objective of the study. In the present study, we evaluated the safety of withholding OAT, in patients with idiopathic DVT and without RVT, three months after the index thrombotic episode. STUDY DESIGN: Prospective controlled study with two groups: patients without RVT stopped OAT after 3 months while those with RVT continued for additional 3 months. MATERIAL AND METHODS: Consecutive patients with a first episode of idiopathic DVT of the lower limbs. Patients with cancer or known thrombophilia were excluded. At the third months of OAT, RVT was assessed as previously described; briefly, RVT was considered absent when a clot occupying less than 40% of the vein lumen was detected by compression ultrasonography. Events, classified as recurrent DVT and/or Pulmonary Embolism and/or major and minor bleeding were evaluated; all patients were followed-up for at least 12 months after OAT discontinuation. RESULTS: During the period 1999-2006, 518 patients were included in the study. In 206 (39.7%) RVT was considered absent (RVT negative group) and they stopped OAT; the remaining 312 patients continued anticoagulants for additional 3 months (RVT positive group). Total duration of follow-up (FU) was 184.7 years for RVT negative group (with a mean FU of 3.0+0.83 years) and 191.3 years for RVT positive group (with a mean FU of 3.1+0.89 years). The recurrent events [n/100 person-year (%)] between patients with and without RVT were 63/191.3 (32.9%) and 2/184.7 (1.08%), respectively. This difference was statistically significant (p<0.0005). Major bleeding occurred in 3/312 (0.9%) of patients Who continued OAT for 1 year; no events were Recorded in those who stopped anticoagulation after 3 months. In Figure 1 is reported the Kaplan-Mayer curve of recurrent events between RVT positive and negative group. CONCLUSIONS: This investigation shows that in patients without RVT, three months of OAT Are safe even after an episode of idiopathic DVT. This hold for at least 30% of the entire DVT population and has an important clinical impact; in fact, it is possible to select a group of patients with a very low risk for recurrency over a period of 3 years. This approach carries also a negligible risk for bleeding.