[Myoglobin and CPK-MM isoforms during the acute phase of myocardial infarction]

The biological diagnosis is usually late with respect to clinical and electrocardiographic signs of acute myocardial infarction. Recent laboratory methods have stimulated renewed interest in very early marker of infarction: myoglobin and CPK isoforms. The authors undertook a prospective study of the diagnostic sensitivity of myoglobin (MG), CPK and CPK-MM isoforms in 30 consecutive patients undergoing intravenous thrombolytic therapy in the acute phase of myocardial infarction. Blood samples were obtained on admission and every 30 minutes for 1 h 30. The Mb contributed to diagnosis of infarction on admission in 89% of patients. This percentage fell to 44% for the ratio MM3/MM1 > 0.5 to 27% for the CPK and to 24% for the ratio MM3/MM1 > 1. The sensitivity of all tests increased in the later blood samples but it remained low in the CPK and MM3/MM1 > 1 criteria. The diagnostic sensitivity of the first sample was also better in patients admitted after the 3rd hour (Mb = 100%; MM3/MM1 > 0.5: 58%; CPK: 41%) compared with those admitted before the 3rd hour (Mb = 82%; MM3/MM1 > 0.5: 35%; CPK: 17%). These results show that the diagnostic sensitivity of biological markers of myocardial infarction is very different. The serum myoglobin is an earlier and more sensitive marker than the CPK or CPK-MM isoforms.