Activase is a tissue plasminogen activator (tpa) indications and usage:*acute ischemic strokeexclude intracranial hemorrhage as the primary cause of stroke signs and symptoms prior to initiation of treatment . initiate treatment as soon as possible but within 3 hours after symptom onset.*acute myocardial infarctionit is indicated for use in acute myocardial infarction (ami) for the reduction of mortality and reduction of the incidence of heart failure.limitation of use: the risk of stroke may outweigh the benefit produced by thrombolytic therapy in patients whose ami puts them at low risk for death or heart failure.*pulmonary embolismit is indicated for the lysis of acute massive pulmonary embolism, defined as:acute pulmonary emboli obstructing blood flow to a lobe or multiple lung segments.acute pulmonary emboli accompanied by unstable hemodynamics, e.g., failure to maintain blood pressure without supportive measures.