The importance of timing of thrombolytic therapy as shown in clinical trials.

With the onset of acute coronary artery occlusion, which occurs as a result of thrombus, the development of myocardial ischemia and reversible ischemic injury leads to a wavefront of necrosis if reperfusion does not occur within 30 to 40 min. Thus, the magnitude and extent of myocardial damage, occurring during acute myocardial infarction are time-dependent. It follows that the sooner reperfusion intervention is instituted after the onset of occlusion, the greater the magnitude of recovery of injured, but not irreversibly damaged, left ventricular myocardium. Thus, earlier treatment should have an important effect on outcome. Data are available from several large, controlled trials to support this concept. These trials include the Gruppo Italiano per lo Studio della Streptochinasi nell'Infarto Miocardico (GISSI-1), the Thrombolysis in Myocardial Infarction (TIMI-I), and the European Cooperative Study Group (ECSG) studies. Strong evidence suggests that the shorter the time between onset of symptoms and institution of thrombolytic therapy, the greater the amount of myocardium preserved.