The are used to treat, within 6 hours of onset, newly developed chest pain consistent with acute myocardial infarction, along with ST elevations 0.1 mV in at least two contiguous leads or the development of a new left bundle branch block. Administration between 6 and 12 hours after onset may show less benefit but is still deemed important. Time frames 12 hours but 24 hours yield diminishing benefits but may be useful in certain situations.
Thrombolytic agents may also be considered with ST-segment depression in leads V2 and V3; along with the development of an R wave in similar leads, that are thought to represent a posterior wall myocardial infarction and not unstable angina.
How are bleeding complications managed?
Bleeding is a major drawback to thrombolytic therapy. It is usually mild and easily treatable, but occasionally it can be devastating, especially intracerebral bleeding, which occurs in 0.2-0.6% of cases. Age, hypertension, prior stroke and prior use of tPA may predispose to bleeding.
Most bleeding occurs at vascular puncture sites, so the initial management is wound compression. If bleeding cannot be controlled or if it involves an intracranial site, all thrombolytic agents, heparin, and aspirin should be discontinued. Protamine can be given to reverse heparin’s effects. Because thrombolytic agents cause a depletion of clotting factors, cryoprecipitate infusion can replace fibrinogen and fresh frozen plasma can replace Factors V and VIII. Aspirin causes platelet dysfunction, and a platelet infusion may be considered. Additional antifibrinolytic agents, such as e-amino caproic acid, that prevent the binding of tPA and plasmin to fibrin may be useful. Even with this management, intracerebral bleeding still yields a poor prognosis.