Effect of insulin infusion on electrocardiographic findings following acute myocardial infarction : importance of glycaemic control

Aims To determine the effects of insulin infusion and blood glucose levels during acute myocardial infarction (AMI) on electrocardiographic (ECG) features of myocardial electrical activity. Methods ECGs at admission and 24 h were examined in a randomized study of insulin infusion vs. routine care for AMI patients with diabetes or hyperglycaemia. Results were analysed according to treatment allocation and also according to average blood glucose level. Results ECG characteristics were similar at admission in both groups. Patients allocated to conventional treatment had prolongation of the QT interval (QTc) after 24 h but those receiving infused insulin did not. In patients with a mean blood glucose in the first 24 h > 8.0 mmol/l, new ECG conduction abnormalities were significantly more common than in patients with mean blood glucose ≤ 8.0 mmol/l (15.0% vs. 6.0%, P < 0.05). Conclusions Prevention of QTc prolongation by administration of insulin may reflect a protective effect on metabolic and electrical activity in threatened myocardial tissue. Abnormalities of cardiac electrical conduction may also be influenced by blood glucose.