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

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.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.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%, p0.001) 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, p0.001) and impaired glucose tolerance (95 ± 24 mg/dl, p0.001), with no difference between new diabetes and known diabetes (156 ± 36 mg/dl versus 165 ± 57 mg/dl, p=0.36).These findings suggested that insulin resistance and exaggerated glucose fluctuation could be attributable to poor outcomes after AMI in patients with new diabetes.