Copyright © 1990 by the European Society of Cardiology.
© 1990 The European Society of Cardiology
Time as a factor in thrombolytic therapy
British Heart Foundation London, U.K.
Address for correspondence: Professor D. G. Julian, Consultant Medical Director, British Heart Foundation, 14 Fitzhardinge St, London W1H 4DH, U.K.
There is abundant evidence from angiographic studies that reperfusion and/or patency rates are greater when thrombolysis is initiated earlier. Evidence of a reduction in infarct size has been provided by a number of studies, which have also suggested that earlier therapy preserves left ventricular function.
The major intravenous thrombolytic mortality trials appear to confirm the importance of delivering therapy soon after the onset of symptons e.g. GISSI and ISIS-2. However, the benefit reported in the first hour in GISSI may be questioned. Furthermore, it seems probable that those coming in late to trials are patients who did not have a sudden onset of symptoms, but whose symptoms persisted, perhaps with recurrent pain, or with heart failure symptoms. This may account for the fact that the benefit seen relatively late, particularly in ISIS-2, does not seem to accord with reperfusion, infarct size and LVEF findings.
The true benefits of earlier therapy will be established only when patients are randomized to active therapy or placebo at one point in time and then switched to alternative therapy at a specified later time. This has been done in a small trial with alteplase in Belfast. The findings were suggestive but not conclusive of an improvement in LVEF in those treated earlier. The European Myocardial Infarction Project (EMIP) should go far towards answering the question.
In most European cities the time between onset of symptoms and the initiation of skilled treatment for myocardial infarction is of the order of 5–6 h. This delay is composed of several elements. Efforts to educate the public in responding to a heart attack more quickly have been disappointing. Substantial savings in time can be obtained by ensuring that whether a physician is called or not, an ambulance is sent immediately. The role of physicians and paramedics in the pre-hospital use of thrombolytic therapy has yet to be clarified. It would seem that out-of-hospital administration might advance treatment by 1 h, but other improvements in the organization of the treatment of myocardial infarction, may have a greater impact.
Key Words: Time • thrombolysis