The natural history of acute myocardial infarction

The majority of readers of this article are likely to be hospital based clinicians whose experience of acute myocardial infarction is necessarily limited to examination of the survivors of a storm which has already taken its major toll. As has always been the case, most deaths from heart attack occur outside hospital and are medically unattended, as are about one quarter of non-fatal infarctions which are “silent” with no or atypical symptoms. For out-of-hospital deaths, even if a necropsy is carried out, it is in the majority of cases impossible to determine whether death had been caused by a developing infarction or by re-entrant ventricular fibrillation starting at the borders of a myocardial scar. Finally, it is impossible strictly speaking nowadays to speak about “natural” history. The history is inevitably “unnatural” in that it has in many cases been modified by treatment. In the most recent study performed in the UK,1, 74% of 1589 deaths from acute coronary heart attacks in people under 75 years of age occurred outside hospital; the proportion of out-of-hospital to total deaths varied inversely with age from 91% at age < 55 years to 67% at age 70–74 years (fig 1). Had the lives of 5% of potential victims of out-of-hospital sudden death not been saved by advanced life support given by ambulance staff, the proportion of out-of-hospital deaths to total deaths would have been even higher. The finding of three quarters rather than the previously quoted two thirds of deaths outside hospital may reflect a declining hospital fatality rate owing to better treatment, with no or a lesser reduction in the numbers of early sudden deaths. Figure 1 Total case fatality in the UK heart attack study and case fatality outside hospital by age group. Reproduced from Norris1 with permission of BMJ Publishing Group. …