Post mortem detection of early myocardial infarction by determination of the tissue K+/Na+ ratio.

The K+/Na+ ratio was determined in myocardial specimens obtained post mortem from a total of 90 patients. The ratio was 1.0 or higher 25 cases in which there was firm evidence against myocardial infarction, and 0.7, or less in 30 cases with grossly visible signs of myocardial narcosis. The remaining 35 cases were suspect of myocardial infarction on the grounds of either clinical observation or sudden death, without gross change. Out of these the K+/Na+ ratio was above 0.7 histological evidence of myocardial infarction was absent, but other changes accounting for death were present in 17 cases. In another 16 cases a K+/Na+ ratio of 0.7 or less was the sole indication of myocardial infarction, and any other change likely to be responsible for death was absent. In two further cases a false negative result was obtained for the K+/Na+ ratio, owing in all probability to some technical error. The findings suggest that determination of the myocardial K+/Na+ ratio is a great aid in detecting early myocardial infarction. The technique is not affected by post mortem autolysis, and is simple enough for routine use.