Glucometrics in patients hospitalized with acute myocardial infarction: defining the optimal outcomes-based measure of risk

Abstract

Background: Hyperglycemia on admission is associated with an increased mortality rate in patients with acute myocardial infarction. Whether metrics that incorporate multiple glucose assessments during acute myocardial infarction hospitalization are better predictors of mortality than admission glucose alone is not well defined.

Methods and results: We evaluated 16,871 acute myocardial infarction patients hospitalized from January 2000 to December 2005. Using logistic regression models and C indexes, 3 metrics of glucose control (mean glucose, time-averaged glucose, hyperglycemic index), each evaluated over 3 time windows (first 24 hours, 48 hours, entire hospitalization), were compared with admission glucose for their ability to discriminate hospitalization survivors from nonsurvivors. Models were then used to evaluate the relationship between mean glucose and in-hospital mortality. All average glucose metrics performed better than admission glucose. The ability of models to predict mortality improved as the time window increased (C indexes for admission, mean 24 hours, 48 hours, and hospitalization glucose were 0.62, 0.64, 0.66, 0.70; P<0.0001). Statistically significant but small differences in C indexes of mean glucose, time-averaged glucose, and hyperglycemic index were seen. Mortality rates increased with each 10-mg/dL rise in mean glucose > or = 120 mg/dL (odds ratio, 1.8; P=0.003 for glucose 120 to < 130 mg/dL) and with incremental decline < 70 mg/dL (odds ratio, 6.4; P=0.01 versus glucose 100 to < 110 mg/dL). The slope of these relationships was steeper in patients without diabetes.

Conclusions: Measures of persistent hyperglycemia during acute myocardial infarction are better predictors of mortality than admission glucose. Mean hospitalization glucose appears to be the most practical metric of hyperglycemia-associated risk. A J-shaped relationship exists between average glucose and mortality, with both persistent hyperglycemia and hypoglycemia associated with adverse prognosis.