Newly diagnosed diabetes based on an oral glucose tolerance test predicts cardiovascular outcomes in patients with coronary artery disease: An observational study

Diabetes is prevalent in patients with coronary artery disease (CAD). Using the oral glucose tolerance test (OGTT), abnormal glucose regulation can be detected early in CAD patients without known diabetes. In the present study, we assessed the impact of abnormal glucose regulation on the long-term cardiovascular outcomes of patients with established CAD. Patients hospitalized for a scheduled angiography due to angina were enrolled in Taichung Veterans General Hospital. Fasting plasma glucose (FPG) and 2-hour postload glucose (2hPG) were assessed using the OGTT. Hemoglobin A1c (HbA1c) and other biochemical analyses were assessed using fasting blood samples. During a median follow-up period of 4.6 years, a composite of all-cause mortality, nonfatal myocardial infarction, and nonfatal stroke was recorded as the primary endpoint. In 682 enrolled patients who completed the follow-up, there were 16 myocardial infarction events, 12 stroke events, and 58 deaths as composite endpoints. According to FPG and 2hPG, patients with newly diagnosed diabetes had a 2-fold higher risk for the composite endpoint than those in the normal glucose group (hazard ratio [HR], 2.011; 95% confidence interval (CI), 1.101-3.673; P = .023); however, prediabetes was not significantly associated with the composite endpoint (HR, 1.452; 95% CI, 0.788-2.675; P = .232). On the other hand, patients with diabetes diagnosed by FPG and HbA1c did not have a significantly higher risk for the composite endpoint than those in the normal glucose group (HR, 1.321; 95% CI, 0.686-2.545; P = .405). A 2hPG >= 7.8 mmol/L was a significant predictor for the composite endpoint (odds ratio, 1.743; 95% CI, 1.060-2.863; P = .028) after adjusting for age, sex, and estimated glomerular filtration rate. Diabetes, but not prediabetes, detected via OGTT is associated with a significantly increased risk for the composite endpoint in patients with established CAD. The 2hPG provided a greater predictive power for the composite endpoint than fasting glucose and HbA1c.