Glucose metabolism in patients with acute myocardial infarction and no previous diagnosis of diabetes mellitus:: a prospective study

Background Glycometabolic state at hospital admission is an important risk marker for long-term mortality in patients with acute myocardial infarction, whether or not they have known diabetes mellitus. Our aim was to ascertain the prevalence of impaired glucose metabolism in patients without diagnosed diabetes but with myocardial infarction, and to assess whether such abnormalities can be identified in the early course of a myocardial infarction. Methods We did a prospective study, in which we enrolled 181 consecutive patients admitted to the coronary care units of two hospitals in Sweden with acute myocardial infarction, no diagnosis of diabetes, and a blood glucose concentration of less than 11.1 mmol/L. We recorded glucose concentrations during the hospital stay, and did standardised oral glucose tolerance tests with 75 g of glucose at discharge and again 3 months later. Findings The mean age of our cohort was 63.5 years (SD 9) and the mean blood glucose concentration at admission was 6.5 mmol/L (1.4). The mean 2-h postload blood glucose concentration was 9.2 mmol/L (2.9) at hospital discharge, and 9.0 mmol/L (3.0) 3 months later. 58 of 164 (35%, 95% CI 28-43) and 58 of 144 (40%, 32-48) individuals had impaired glucose tolerance at discharge and after 3 months, respectively, and 51 of 164 (31%, 24-38) and 36 of 144 (25%, 18-32) had previously undiagnosed diabetes mellitus. Independent predictors of abnormal glucose tolerance at 3 months were concentrations of HbA(1c) at admission (p=0.024) and fasting blood glucose concentrations on day 4 (p=0.044). Interpretation Previously undiagnosed diabetes and impaired glucose tolerance are common in patients with an acute myocardial infarction. These abnormalities can be detected early in the postinfarction period. Our results suggest that fasting and postchallenge hyperglycaemia in the early phase of an acute myocardial infarction could be used as early markers of high-risk individuals.