<prompt> True statement about pulmonary embolismPrompt heparin therapy will dissolve thrombiKnown risk factors include gastric cancer, AIDSMost patients manifest dyspnea, pain, hemoptysisFree floating iliofemoral thrombi are an indication for a caval filter  <response>: Unfractionated Heparin UFH anticoagulates by binding to and accelerating the activity of antithrombin, thus preventing additional thrombus formation. UFH is dosed to achieve a target activated paial thromboplastin time aPTT of 60-80 s. The two principal indications for inseion of an IVC filter are 1 active bleeding that precludes anticoagulation and 2 recurrent venous thrombosis despite intensive anticoagulation. Ref Davidson edition23rd pg 620 