Effect of coronary care on myocardial infarct mortality.

Abstract

To study the effect of coronary care on the hospital mortality rate of acute myocardial infarction, patients treated in a coronary care unit (CCU) were compared with patients treated in general wards. To assess the comparability of cases, the coronary prognostic index of Chapman and Gray was modified. The modified index was based on serum aspartic aminotransferase (AST) level and cardiogenic shock. Modification was necessary because oliguria, the 3rd variable on which the original index was based, could not always be determined for general ward cases. This modified index assessed very accurately the prognosis of myocardial infarct patients treated in the hospital. Patients treated in the CCU had a significantly higher mean modified prognostic index than control patients treated in the general wards, before or after the introduction of coronary care. They also had a significantly shorter mean delay in admission than either group of general ward cases. These differences would be expected to worsen the results of coronary care. The 2 groups of general ward patients were very similar as shown by mean modified prognostic index, mean admission delay and results of correlation and regression analysis. In spite of their higher mean modified prognostic index and shorter mean admission delay, the CCU patients had a significant reduction in their mortality rate, which dated from the opening of the unit, to little more than half that for the general ward patients. For general ward patients treated after the introduction of coronary care, the mortality rate was not significantly different from that for ones treated before. The reduction in mortality for CCU cases was approximately the same over the whole range of infarct severity, and did not vary significantly from 15% as the modified index rose from minimum to maximum values. Apparently severity of infarction should no longer be a reason for excluding any patients from coronary care.