Influence of acute myocardial infarct size on acute and one-year mortality.

In order to determine the prognostic effect of the size of an acute myocardial infarction (AMI), we prospectively studied a consecutive series of patients below 70 years of age, who had been admitted to the coronary care unit because of clinical suspicion of AMI. In 218 patients the diagnosis AMI was confirmed and the size of their infarcts was estimated from serum CK-MB measurements. In 102 patients the suspicion of fresh AMI was disproven, and they served as a control group. Both groups of patients were similar with regard to distribution of age, sex and coronary risk factors. During one year after discharge, all patients were observed with regard to death. The follow-up was 100% for the one-year observation period. The one-year survival was found to be much better in the patients without AMI on admission than among those with AMI (P less than 0.01). The infarct size was larger among those who died than in those who survived (P less than 0.01); mortality in hospital and within one year was closely associated with the estimated infarct size (P less than 0.01). However, the influence of infarct size on survival decreased with time. After six months there was no difference in the survival rate.