Previous well-publicised studies of thrombolysis in patients with suspected acute myocardial infarction have suggested that the sooner treatment is administered, the greater the benefit in terms of reduced mortality. Pre-hospital thrombolysis has been advocated as a way of treating more patients earlier EMIP (European Myocardial Infarction Project) is a large-scale randomised study which was set up and sponsored by the European Economic Community through its Medical Research Program to assess the risks and benefits of such an approach
To determine the theoretical risk/benefit ratio of prehospital thrombolytic treatment, the European Myocardial Infarction Project (EMIP) was established. In a double blind, randomised trial, prehospital thrombolysis was compared with in hospital treatment. Anistreplase was the chosen thrombolytic agent because, being administered as a bolus, it is suitable for a prehospital setting. The study involved 5469 patients who received either 30 units of anistreplase at home followed by placebo after hospital admission, or placebo at home followed by 30 units of anistreplase after hospital admission. In 92.4% of cases, the diagnosis of suspected myocardial infarction was confirmed by the hospital cardiologist. Minor adverse reactions were more frequent in the early treatment group but the incidence of severe adverse reactions such as cerebral bleeding, ischaemicstrokes and severe bleeding was similar in both groups. As severe bleeding was among the main concerns expressed about prehospital thrombolysis, it is important to note that there was no occurrence of severe bleeding before admission and only one after admission, prior to the second injection. The frequency of reinfarction, ventricular fibrillation, acute pulmonary oedema, shock and cardiac arrest was the same in both groups. A total of 569 deaths was observed at 30 days, mortality being 13% lower in the early treatment group. The risk ratio decreased with increasing time gained by early treatment (the interval between injections). Death from cardiac causes was 16% lower in the early treatment arm, the result being at the limit of statistical significance (p=0.049). EMIP has thus proved prehospital thrombolysis to be feasible and safe, with no more incorrect diagnosis of myocardial infarction than in hospital, provided that the teams are well equipped and staffed.
A pilot study, sponsored by the EEC showed that a gain of one to two hours could be expected from a pre-hospital strategy with pre-hospital administration of a thrombolytic agent, compared with the current hospital strategy.
The primary objective of this study was to evaluate the benefit/risk ratio of administering a thrombolytic agent to patients with suspected myocardial infarction as early as possible after the onset of symptoms in a pre-hospital setting. Anistreplase was chosen because it can be administered as a slow bolus. Patients were randomised to receive anistreplase either as a pre-hospital treatment or after hospital admission, but this comparison goes beyond that of a simple comparison of two treatments, it is a comparison of two treatment strategies involving different settings and staff with different backgrounds. The evaluation of all aspects of safety of the two strategies is, therefore, of utmost importance.