Alteration in Serum Myoglobin Level as Diagnostic Significance in Myocardial Infarction

Abstract

A new method of radioimmunoassay for canine myoglobin was devised. Chan- ges in myoglobin levels in serum and myocardium of dogs were followed with this technique after acute myocardial infarction was produced by ligation of left anterior descending branch of the coronary artery at a proximal site. The amount of in farction was determined by the method of Hackel after autopsy and the myocardium was devided into 3 parts: intact, border, and infarction zones.
Serum myoglobin levels in normal dogs ranged from 18 to 97 ng/ml (mean 48.6±35.1 ng/ml). The serum level elevated in 15 minutes, reached a peak 5 to 8 hours after ligation and then started to decrease gradually. The maximum levels of serum myoglobin determined in 8 dogs showed a good correlation to the weights of infarction (r=0.731). The myoglobin conentration in the infarction zone (2.74±0.58mg/g wet weight) was significantly (p<0.01) lower than that in the intact zone (3.63±0.75mg/g wet weight). The myoglobin content in the border zone was also reduced, though not so significantly.
It was concluded that serum myoglobin level appears to be a useful indicator in deter- mining the severity of acute myocardial infarction.