The significance of distal vein thrombosis and bilateral disease.

Abstract

The management of symptomatic distal venous thrombosis has been clearly defined by the American College of Chest Physician’s recommendations on antithrombotic therapy for venous thromboembolic disease. These recommendations apply equally to patients with proximal vein thrombosis, and to patients with symptomatic deep vein thrombosis (DVT) confined to the calf veins [1]. Patients with objectively confirmed DVT should have initial short-term treatment with SC low molecular weight heparin (LMWH) or IV UFH or SC UFH. For secondary prophylaxis, patients with acute proximal or distal calf DVT require long-term anticoagulant treatment to prevent a high frequency (15%–50%) of symptomatic extension of thrombosis and/or recurrent venous thromboembolic events [2–4]. The management of asymptomatic DVT is far from clear and is usually based on empirical therapy. None of us could ignore a proximal thrombosis diagnosed incidentally or following investigation in a clinical trial that involved screening. However a small asymptomatic distal DVT, how should that be managed? Do we need to follow these patients closely or offer treatment? Does the epidemiology of venous thromboembolism (VTE) allow us to make more informed decisions about empirical management? Epidemiological studies may be useful for determining prognosis and therefore help us plan therapeutic intervention studies in settings where they are most needed. Epidemiological studies cannot on their own guide the therapy. The distinction between the epidemiology and treatment of symptomatic and asymptomatic venous thromboembolic disease is important as the natural histories, although linked, are different. The relevant paper in this month’s journal looks at the epidemiology of DVT diagnosed by routine bilateral proximal and distal ultrasonography in patients at risk of VTE. The study then examines the prognostic impact of bilateral distal DVT over 2 years on thrombosis recurrence, cancer and death. The study finds that bilateral distal DVT has worse prognosis than unilateral distal DVT in all three areas [5]. The design of the study requires a number of comments. The cases of DVT presented both clinically (both bilateral and unilateral) and subclinically, only detected at routine screening for DVT, after presenting with unilateral symptoms of DVT or symptoms of pulmonary embolism (PE). Therefore this paper tells us about the outcomes of both symptomatic and asymptomatic DVT diagnosed following the practice of routinely screening all suspected pulmonary embolism (PE) and DVT patients with bilateral proximal and distal venous USS. As the three practices of bilateral screening, screening proximally and distally and the screening of asymptomatic PE are not routine, the results of this study and its generalizability need to be considered. The patients were not followed systematically and this paper linked the findings of different registries to achieve its results. The validity of this linking requires a number of assumptions to be satisfied as delineated by the authors. The therapeutic regimens used were different for proximal (3–12+ months) and distal (1.5–3 months) disease and this may have resulted in different recurrence rates. Finally, the cost of investigation and time consumption need to be considered. The authors have done much to recognize and defend these weaknesses of the study and the results should now be considered. The interesting findings of this study are that bilateral distal disease had a worse prognosis (for thrombosis recurrence, cancer and death) than unilateral distal disease, and that bilateral distal disease group had a similar poor prognosis to proximal disease. From a clinical perspective, this makes good sense. Bilateral disease makes a systemic etiology more likely, and both inherited and acquired thrombophilia may be associated with higher recurrence rates, cancer and underlying medical conditions, all of which are associated with increased mortality. In this study, cancer rates (26% vs. 17%), age and underlying medical disorders (11.6% vs. 6.1%), recent immobility (40% vs. 31%) were higher and more common in those with bilateral distal disease than those with unilateral distal disease. As the authors have stated, the association with cancer and bilateral thromboses has been described in other studies. The findings of increased mortality and recurrence rates make