Unrecognized glycometabolic disturbance as measured by hemoglobin A1c is associated with a poor outcome after acute myocardial infarction

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.