Potential use of thrombolytic therapy before hospitalization

Three trials of thrombolytic therapy in myocardial infarction (MI) up to 12 hours after symptom onset were conducted to measure the mean time from onset of chest pain to hospital arrival, and mean time to therapy. The trials, using intracoronary streptokinase, intravenous streptokinase and tissue plasminogen activator (t-PA), indicated a progressive shortening of time between symptom onset and hospital arrival. The Seattle Myocardial Infarction, Triage and Intervention (MITI) trial is evaluating the safety and efficacy of thrombolytic therapy initiated by paramedics in the prehospital setting. Phase I of the trial indicates that one-half of the patients would receive prehospital therapy in the field within the first hour of symptoms, substantially sooner than what can be achieved in the hospital. Phase II of MITI, in a nonrandomized trial, will compare the use of intravenous t-PA in the field with t-PA administered in the emergency department.