Two weeks of low molecular weight heparin for isolated symptomatic distal vein thrombosis (TWISTER Study): Interim analysis of first 200 patients.

Abstract

Background : Most deep vein thrombosis (DVT) originate from distal (calf) vein thrombi, however 80- 90% of these lyse spontaneously. The management of isolated distal DVT (IDDVT) is controversial. Aims : Examine the efficacy and safety of two weeks of anticoagulation for a first symptomatic IDDVT. Methods : Multicentre prospective cohort study in Australia/New Zealand for patients with confirmed first symptomatic IDDVT. Exclusions included active malignancy, bleeding risk factors, pregnancy/ lactation, ongoing immobility, plaster casts or non- weightbearing. Patients received 2 weeks of therapeutic anticoagulation (enoxaparin or rivaroxaban) with repeat complete compression leg vein ultrasound (CUS) at the end of 2 weeks. If the patient was asymptomatic and there was no proximal DVT extension on CUS, treatment was stopped (group A). If the patient was still symptomatic, treatment was continued for a further 4 weeks(group B). The primary outcome is symptomatic recurrence of venous thromboembolism, VTE (DVT and pulmonary embolism, PE) within 3 months, in group A patients. Results : 200 patients were enrolled at eleven sites; one was withdrawn on day five due to clinically relevant non- major bleeding. Of the remaining 199, 140 (70%) received two weeks anticoagulation; 56 (28%) six weeks anticoagulation; and three patients (2%) had proximal extension on 2- week CUS. Nine patients in group A were lost to follow- up. Of the remaining 131 in the two- week anticoagulation arm, three had symptomatic distal DVT recurrence - VTE recurrence rate 3/131; 2.3%(95% CI 0.77- 5.07%). No patients, 0/131; 0%(95% CI 0.00- 2.78) had proximal DVT or PE recurrence. Conclusions : For patients with IDDVT, two weeks of anticoagulation is associated with a low risk of VTE recurrence (2.3%), if patients are symptom- free at two weeks and the repeat CUS at two weeks doesn ' t show thrombus extension into proximal veins. Based on this data, the previous standard of care, 6- 12 weeks anticoagulation, isn ' t required for the majority of IDDVT patients.