Serum myoglobin levels in patients with ischemic myocardial insult.

Serum myoglobin levels were studied in 178 consecutive patients admitted for chest pain due to ischemic cardiac injury. Serum myoglobin level was compared with the clinical condition, electrocardiographic changes, and serum creatine kinase levels. Elevated serum myoglobin concentration was present in all patients with acute myocardial infarction, as defined by World Health Organization, Geneva, criteria, and, in addition, in about 50% of patients with so-called acute coronary insufficiency. On this basis we could define two different groups of patients with acute coronary insufficiency: cases exhibiting elevated serum myoglobin levels (group 1) and those with normal levels (group 2). In group 1 although creatine kinase levels were in the normal range, they were significantly higher than in group 2. Four patients from group 1 developed heart failure and another a typical acute myocardial infarction during hospitalization, whereas no patients of group 2 had such complications. In patients with acute myocardial infarction, the elevation of serum myoglobin preceded that of creatine kinase in most cases. Myoglobin release appears to be related to infarct size, the highest levels were found in extensive myocardial infarction and less marked elevations in cases of subendocardial infarction and in half of the cases with acute coronary insufficiency. It is proposed that serum myoglobin is a reliable measure of myocardial necrosis and serves to detect a hitherto undefined population of small-size acute myocardial infarction, with its attendant clinical and prognostic implications.