The secondary prevention trials. Lessons learned, questions raised.

In clinical trials to date, only two types of treatment have been shown to have a positive effect on survival in patients after acute myocardial infarction: beta blockers in acute-phase as well as long-term therapy and thrombolytic agents administered within three to four hours of the onset of symptoms. The favorable trial results from these interventions have raised new questions of scientific and clinical significance. What is the mechanism of the favorable action? Do all patients stand to benefit from treatment? What is the optimal time for initiation of treatment? How long is the treatment beneficial? What are the risks and costs? What is the public health impact of widespread use of these interventions?