In selected patients with acute PE who deteriorate after starting anticoagulant therapy but have yet to develop hypotension and who have a low bleeding risk, we suggest systemically administered thrombolytic therapy over no such therapy (Grade 2C). Remarks: Patients with PE and without hypotension who have severe symptoms or marked cardiopulmonary impairment should be monitored closely for deterioration. Development of hypotension suggests that thrombolytic therapy has become indicated. Cardiopulmonary deterioration (eg, symptoms, vital signs, tissue perfusion, gas exchange, cardiac biomarkers) that has not progressed to hypotension may also alter the risk-bene t assessment in favor of thrombolytic therapy in patients initially treated with anticoagulation alone. Catheter-Based Thrombus Removal for the Initial Treatment of PE Summary of the Evidence Interventional catheter-based treatments for acute PE include delivery of CDT if there is not a high risk of bleeding, or catheter-based treatment without thrombolytic therapy if there is a high risk of bleeding. CDT: The most important limitation of systemic thrombolytic therapy is that it increases bleeding, including intracranial bleeding. CDT, because it uses a lower dose of thrombolytic drug (eg, about one-third), is expected to cause less bleeding at remote sites (eg, intracranial, GI).138,150-153 CDT, however, may be as or more effective than systemic thrombolytic therapy for two reasons: (1) it achieves a high local concentration of thrombolytic drug by infusing drug directly into the PE and (2) thrombus fragmentation resulting from placement of the infusion catheter in the thrombus or additional maneuvers, or an increase in thrombus permeability from US delivered via the catheter, may enhance endogenous or pharmacologic thrombolysis. Thrombolytic therapy is usually infused over many hours or overnight. In emergent situations, systemic thrombolytic therapy can be given while CDT is being arranged, and active thrombus fragmentation and aspiration (see below) can be combined with CDT. 