BACKGROUND: Glycated hemoglobin A1c (HbA1c) is a measure of the average blood glucose levels over 2 months and is minimally affected by acute hyperglycemia often observed in myocardial infarction (MI). In a large population of high-risk patients with MI, we examined the prognostic impact of HbA1c in patients with and without a history of diabetes.

METHODS: In the OPTIMAAL trial, patients with MI complicated with heart failure were randomized to losartan or captopril. Of the 2841 patients who had HbA1c measured at randomization, 495 (17%) reported a history of diabetes. The remaining patients without diabetes history were stratified into 3 categories according to HbA1c level: HbA1c, <4.9% (n = 1642); HbA1c, 4.9% to 5.1% (n = 432); and HbA1c, >5.1% (n = 272). Mean follow-up time was 2.5 years.

RESULTS: Mortality rate during follow-up was 18% in patients with a history of diabetes. Increasing HbA1c levels were associated with higher mortality rate among patients without diabetes history (13% in patients with HbA1c <4.9%, 17% in patients with HbA1c 4.9%-5.1%, 22% in patients with HbA1c >5.1%). Among patients with no prior history of diabetes, a 1% absolute increase in HbA1c level at baseline resulted in a 24% increase in mortality, whereas the level of HbA1c had no impact on mortality among the patients with well-known diabetes (multivariate analyses).

CONCLUSIONS: In this high-risk MI population, HbA1c level was a potent predictor of mortality in patients without previously known diabetes.