MIDAS: Myocardial Infarct Diagnosis by Assessment of Slope

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We describe a simple nomogram for the interpretation of plasma creatine kinase activity (CK) changes in patients with acute chest pain and the demonstration of excessive rate of increase (slope of the CK versus time graph). Taken together with other patient data, it serves as a useful decision aid for the very early diagnosis of acute myocardial infarction. We have previously shown that measurement of the rate of increase ('slope') of creatine kinase (CK) and creatine kinase MB isoenzyme (CK-MB) in plasma on serial samples obtained on admission and 4 h, 8 h or 12h thereafter allows rapid and efficient diagnosis of acute myocardial infarction (AMI) in patients presenting with acute chest pain (less than 12 h duration).? A change in log CK activity per hour exceeding 0'015 over the first 12h (equivalent to a 51070 increment) differentiated between AMI and non-infarction with a diagnostic sensitivity of 97070 and specificity of 91% (efficiency 94%). This slope discriminant (equivalent to a 4 h increment of 15% or an 8 h increment of 32%) similarly had high diagnostic efficiency (88% at 4 h, 93% at 8 h) when applied to CK change from admission to 4 h or to 8 h post-admission. Calculation of the rate of change of the logarithm of the percentage increment of CK activity is inconvenient for emergency situations. In order to circumvent this problem we have devised a simple nomogram ('MIDAS'; Myocardial Infarct Diagnosis by Assessment of Slope) to indicate whether the slope discriminant has been exceeded. We recommend that the nomogram be used by clinicians for all cases where confirmation of the diagnosis or exclusion of acute myocardial infarction is required.