Myocardial infarction and the evolution of the intensive coronary care unit.

From the start of the 1960s it became increasingly evident that sudden death with acute myocardial infarction was owing to reversible derangement in heart rhythm rather than to gross myocardial damage. Patients at risk were placed in specialised areas, intensive coronary care units (ICCUs), and their heart rhythms were continuously monitored. Initially, the prime function of the ICCU was to resuscitate a patient who had suffered cardiac arrest. Since the survival rate after resuscitation was low, no obvious reduction in mortality was noted in the early ICCU. As intensive care evolved, better resuscitation techniques became available, understanding of the terminal arrhythmic mechanism improved, and the prevention of cardiac arrest by aggressive and prompt treatment of the minor warning arrhythmias became feasible. With these developments, the ICCU appeared to show a reduction in the mortality of acute myocardial infarction. It is argued that the 'supposed' decrease represents a 'real' decrease. This is on the basis of the consistency and similarity of all ICCU results throughout the world over a period of 7 years, coupled with the fact that cardiac arrests (which were initially reported to occur in 10%-20% of patients) had been eliminated. The principles of modern intensive coronary care have been equally well utilised in small community hospitals and in large academic hospitals. Thus, the extension of soundly-based management can have application in situations which, by force of circumstances, are far from ideal. An outstanding feature which emerged early on, was the high incidence of arrhythmias recorded by continuous monitoring. The percentage frequently quoted was 80% and above. Emphasis was placed on the dangerous ventricular arrhythmias, including the ventricular premature systole. The atrial arrhythmias were considered to be of lesser clinical significance.