Myoglobin and creatine kinase rates of release during acute myocardial infarction

The release of cardiac enzymes as an index of infarct size (IS) development was studied in patients with acute myocardial infarction (AMI) treated at a coronary care unit. Serial determinations of serum myoglobin (MG) and creatine kinase (CK) were made on 34 consecutive patients with duration of symptoms less than 6 h at admission and with initial CK values below the upper reference limit. Computer-calculated CK-IS was determined on the basis of the log-normal algorithm. This was compared to discretely calculated CK and MG release. The correlation between computer- and discretely calculated cumulated CK release was 0.995 with a regression close to the line of equivalence. Computer-calculated CK rates of release showed a one-peak development, while, when discretely calculated, mostly three or four peaks were observed, as found also for MG rates of release. The occurrence of MG and CK peaks was related as indicated by a correlation coefficient of 0.75. The initial CK rate of release was slower when computer-calculated. In the group studied, CK release began about 3 h post onset of symptoms, at which time 56% had an MG value above the upper reference limit. The CK and MG releases were finished about 31 and 36 h post onset of symptoms, respectively, with MG peaks at 6, 11, 19, and 22 h with corresponding CK peaks delayed 2, 3, 3, and 9 h. The first MG and CK peaks represented between 30 and 40% of the total release while the following three peaks represented between 20 and 30% each. Cumulative MG release was correlated to the time of AMI development. No such correlation was found for CK. The results indicate that the development of AMI is a wavelike process not sufficiently described by the log-normal algorithm, on the basis of which, however, an index of total release might be obtained.