To define the optimal diagnostic strategy for acute myocardial infarction, 225 patients with suspected myocardial infarction were studied by serial (3 hour intervals) sampling for CK and CK-MB enzyme activity. In 12 patients the diagnosis of myocardial infarction was rejected. In the remaining 213 the myocardial infarction was transmural in 183 (anterior in 79, postero-inferior in 95, anterior and inferior in 9), non transmural in 30. In these patients the mean increase of enzyme activity, the time to pick activity and the infarct size (Sobel method) were measured. The best diagnostic sensitivity in the early phases of myocardial infarction was obtained by the combined use of CK and CK-MB determinations (95.9% of the diagnosis at 9 hours after the acute event). However the percent of positivity of CK & CK-MB values occurred significantly (p less than 0.01) later in non transmural (4.3% at 3, 34.7% at 6 and 86.9% at 9 hours after the onset of the chest pain) than in transmural myocardial infarction (25.2% at 3, 54.4% at 6 and 97.6% at 9 hours) and among these in inferior as compared to anterior (18.7% vs 32.2% at 3 hours, 46.8% vs 62.7% at 6 hours and 96.8% vs 98.3% at 9 hours). The CK/CK-MB ratio was of limited diagnostic value because it was increased (greater than 8) in most of the patients, either with normal or abnormal enzymes activities. Early kinetics differed in the different anatomo-clinical types of infarction. In all locations of myocardial infarction the mean enzyme activity increase was significantly correlated with the calculated enzymatic infarct size.(ABSTRACT TRUNCATED AT 250 WORDS)
Clinical Enzyme Tests Creatine Kinase