G.S. Wagner

Patients currently experiencing acute myocardial infarcts are the beneficiaries of information gathered during the 80 years since this clinical phenomenon was described and the 20 years since treatment in coronary care units was introduced. Physicians have gained the ability to minimize inhospital mortality from rhythm disturbances and have gained insight into the importance of optimizing both left ventricular fIlling pressure and outflow resistance in the management of myocar dial failure. Understanding of the pathophysiology of acute myocardial infarcts has matured sufficiently so that now it is possible to consider whether an infarct must evolve to a predetermined size or whether the size could be limited by implementing one or more clinically feasible strategies. Concurrently, it has become evident that patients with acute infarcts are not as 'fragile' as previously supposed, and that they may undergo procedures such as coronary angiography and coronary bypass surgery with acceptable risks. Clinical trials are currently in progress to assess the possible benefit of various interventions for limiting myocardial infarct size. The outcome of these studies may be used to formulate strategies for clinical care of future patients. If the results are positive, community hospitals may undergo changes even more exten sive than those required when they established coronary care units. If the inter ventions are not proven to provide significant advantages over the course of nature, the current concepts of coronary care may be retained. However, such conclusions will be only as valid as the techniques used to measure infarct size.

Measurement and Intervention

Myocardial Infarction

Robert M. Califf

During the 25 years since acute coronary care was focused into Coronary Care Units there have been three major Phases: I. prevention of death caused by arrhythmias; II. prevention of death due to myocardial failure; and III. limitation of infarct size. In the latter two Phases, there has been infringement upon the time honored concept of a prolonged period of rest for the patient in general and the heart in particular to minimize myocardial metabolic demands. During the second Phase of coronary care, patients with myocardial failure received aggressive measures to increase cardiac work via increase in preload, decrease in afterload, and direct increase in inotropy. It was believed that true cardiogenic shock was so irreversible that it should be prevented by vigorous efforts to improve the cardiac output despite the risk of extending the area of ischemic myocardium. However, Phase II produced minimal overall reduction in mortality. In the initial part of Phase III, myocardial infarct (MI) size limitation was attempted by reducing myocardial metabolic demands via either beta adrenergic or calcium channel blocking agents. We are currently several years into the second part of Phase III of coronary care where the principle means of limiting MI size is restoration of coronary blood flow.

G.S. Wagner

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