Detection of early myocardial infarction by radioimmunoassay of myoglobin.

A newly devised radioimmunoassay for the measurement of myocardial myoglobin has been modified by us to measure circulating myoglobin levels in rats subjected to isoproterenol-induced myocardial infarction of various degrees of severity. The method has been found to be very effective. Myoglobinemia proved to be a sensitive index of early myocardial damage in rats, perhaps superseding the enzyme CPK in detecting early myocardial damage. Both myoglobin and CPK were equally effective in providing an index of the extent of histopathologic myocardial infarction. The changes in myoglobin and CPK did not correlate well with the changes in plasma SGOT, SGPT, and LDH, which are more diagnostic of the later stages of acute myocardial infarction. Myoglobinemia offers excellent promise as a diagnostic aid in detecting early myocardial infarction in rats, and perhaps ultimately in humans, since there are only small differences between the immunologic specificity of human versus rat myoglobin.