Isolated distal deep vein thrombosis (IDDVT) is a common clinical manifestation of venous thromboembolism (VTE). However, there are only scant and heterogeneous data available on the long-term risk of recurrent VTE after IDDVT, and the optimal therapeutic management remains uncertain. We carried out a retrospective cohort study of consecutive patients diagnosed with symptomatic IDDVT between 2004 and 2011, according to a predefined short-term treatment protocol (low molecular weight heparin (LMWH) for 4-6 weeks). The primary outcome was the occurrence of recurrent VTE. A total of 321 patients were enrolled. IDDVT was associated with a transient risk factor or cancer in 165 (51.4%) and 56 (17.4%) patients, respectively. LMWH was administered for 4-6 weeks to 280 patients (87.2%), who were included in the primary analysis. Overall, during a mean follow-up of 42.3 months, 42 patients (15%) developed recurrent VTE, which occurred as proximal DVT or PE in 21 cases. The recurrence rate of VTE per 100 patient-years was 3.5 in patients with transient risk factors, 7.2 in patients with unprovoked IDDVT, and 5.9 in patients with cancer ( p=0.018). At multivariable analysis, unprovoked IDDVT and previous VTE were significantly associated with recurrent VTE (HR 2.16, 95% CI 1.12-4.16 and HR 1.97, 95% CI 1.01-3.86, respectively). In conclusion, the long-term risk of recurrent VTE after IDDVT treated for 4-6 weeks is not negligible, in particular in patients with unprovoked IDDVT or cancer. Further studies are needed to clarify whether a longer, but definite treatment duration effectively prevents these recurrences.
Keywords: calf DVT; distal deep vein thrombosis (DVT); low molecular weight heparin; recurrence; venous thromboembolism (VTE).