Usefulness of serial determinations of myoglobin and creatine kinase in serum compared for assessment of acute myocardial infarction.

Twenty-one patients with their first myocardial infarction underwent serial blood sampling every 2 h for determination of serum creatine kinase (CK) and myoglobin during the first 48-72 h after onset of pain. The first blood sample, obtained at a mean time of 4.4 h after infarct onset, invariably showed increased myoglobin (mean, 8.3-fold normal), whereas CK was often normal (mean, 1.6-fold normal). Peak myoglobin values occurred earlier than peak CK values (9.9 h vs 21.6 h, p less than 0.0005), but there was a significant correlation of peak values (myoglobin = 0.384CK - 0.264, r = 0.794, p less than 0.0005). The mean exponential disappearance rate (Kd) of CK was 0.00106 min-1 and of myoglobin was 0.00265 min-1 (p less than 0.0005). The disappearance of myoglobin was well described by a mono-exponential expression except in two patients. The total duration of the increase in myoglobin was significantly less than that of CK (34.7 h vs 74.4 h, p less than 0.0005).