Glucometabolic responses during Glucose Tolerance Test: A comparison between known diabetes and newly detected diabetes after acute myocardial infarction

Background: Glucose Tolerance Test (GTT) newly detects diabetes (new diabetes) in a substantial number of patients without a history of diabetes (known diabetes) after acute myocardial infarction (AMI). Patients with new diabetes have poor outcomes, despite their lower HbA1c levels. Methods: This study consisted of 53 patients with new diabetes and 47 patients with known diabetes who underwent GTT 1 week after AMI. Sixty-eight patients with normal GTT and 78 patients with impaired glucose tolerance served as control. Plasma glucose and insulin were measured at fasting, 30 m, 60 m and 120 m after glucose load. Peak glucose-fasting glucose was used as a measure of glucose fluctuation. Homeostasis model assessment of insulin resistance and the Stumvoll's equations were used to assess insulin sensitivity and ß-cell function, respectively. Results: Fasting glucose (115 ± 20 mg/dl versus 129 ± 41 mg/dl, p = 0.02) and hemoglobin A1C (5.7 ± 0.5% versus 6.7 ± 1.4%, p < 0.001) in new diabetes were significantly lower than known diabetes. Insulin sensitivity was similarly impaired in both new diabetes and known diabetes (3.2 ± 2.2 versus 3.0 ± 1.9, p = 0.58). Impairment of insulin secretion was less severe in new diabetes than in known diabetes. Peak glucose-fasting glucose was significantly greater in diabetic patients than inpatients with normal GTT (75 ± 30 mg/dl, p < 0.001) and impaired glucose tolerance (95 ± 24 mg/dl, p < 0.001), with no difference between new diabetes and known diabetes (156 ± 36 mg/dl versus 165 ± 57 mg/dl, p = 0.36). Conclusions: These findings suggested that insulin resistance and exaggerated glucose fluctuation could be attributable to poor outcomes after AMI in patients with new diabetes.