Value of glycosylated hemoglobin measurements after acute myocardial infarction.

All nondiabetic patients admitted to a coronary care unit with suspected myocardial infarction (MI) had glycosylated hemoglobin (Hb A1) determinations to aid in the interpretation of hyperglycemia. Hyperglycemia was frequent among patients with a confirmed MI, whereas an elevated Hb A1 level was less common and affected patients with and without MI equally. With the use of a fasting plasma glucose level of 140 mg/dL and an Hb A1 level of more than 8.5% as combined diagnostic criteria, 9% of patients (8/93) with MI and 12% of patients (8/68) without MI had previously unrecognized diabetes. Follow-up studies three months after the acute episode supported these results. The Hb A1 measurements provide a practical method to separate hyperglycemia due to stress from that due to diabetes mellitus. Marked hyperglycemia with a normal Hb A1 level indicates a severe MI.