Two weeks of low molecular weight heparin for isolated symptomatic distal vein thrombosis (Twister Study): Final analysis of 242 patients.

Abstract

Background: Most deep vein thromboses (DVT) originate from distal (calf) vein thrombi, however 80-90% of these lyse spontaneously. The management of isolated distal DVT(IDDVT) is controversial. Aim(s): Examine the efficacy/safety of two weeks of anticoagulation for a first symptomatic IDDVT. Method(s): Multicentre prospective cohort study in Australia/New Zealand for patients with confirmed first symptomatic IDDVT. Exclusions included active malignancy, bleeding risk factors, pregnancy/ lactation, immobility, plaster casts or non-weight-bearing. Patients received therapeutic anticoagulation (enoxaparin or rivaroxaban) with repeat complete compression leg vein ultrasound (CUS) at the end of 2 weeks. Those with extension into proximal veins on two-week CUS were treated off study (group A). For those with ongoing symptoms, treatment was continued for a further 4 weeks (group B). If the patient was asymptomatic and there was no proximal DVT extension on CUS, treatment was stopped (group C). The primary outcome was the symptomatic recurrence of venous thromboembolism, VTE (DVT and pulmonary embolism, PE) within 3 months, in group C patients. Result(s): 242 patients were enrolled at twelve sites; one was withdrawn on day five due to clinically relevant non-major bleeding. Of the remaining 241, 167(69%) received two weeks anticoagulation; 71(30%) six weeks anticoagulation; and three patients(1%) had proximal extension on 2-week CUS. Eleven patients in group C were lost to follow-up. Of the remaining 156 in the two-week anticoagulation arm, two had symptomatic distal DVT recurrence; VTE recurrence rate 2/156; 1.3%(95% CI 0.19-5.41%). No patients, 0/156; 0%(95% CI 0.00-2.34) had proximal DVT or PE recurrence. Conclusion(s): For IDDVT patients, two weeks of anticoagulation is associated with a low risk of VTE recurrence (1.3%), if patients are symptom-free at two weeks and repeat CUS at two weeks does not show thrombus extension into proximal veins. Based on this data, the previous standard of care, 6-12 weeks anticoagulation, is not required for most IDDVT patients.