Asymptomatic "breakthrough" thrombosis and anticoagulant "failure": Keep calm and carry on

Despite therapeutic anticoagulation, patients with venous thromboembolism (VTE) not uncommonly present with findings of progressive thrombosis, sometimes within the first several weeks of treatment. While the prevailing strategy in these scenarios is to assume the current anticoagulant is ineffective and to switch to a different drug class, this practice may be unnecessary. Numerous trials of heparins and vitamin K antagonists for VTE have demonstrated that asymptomatic thrombus propagation despite therapeutic anticoagulation is common. While similar, serial imaging studies after initial VTE have not been replicated in trials of the direct oral anticoagulants, we reason that asymptomatic thrombus propagation detected within the first month of VTE diagnosis can be managed with continuation of the current anticoagulant strategy and close follow-up for worsening or recurrent symptoms.