Effects of glucose-insulin-potassium infusion on QT dispersion in patients with acute myocardial infarction

Background: Increased QT dispersion during acute myocardial infarction (AMI) has been associated with the occurrence of ventricular arrhythmias. Also, serum potassium levels have been shown to be relevant to the arrhythmic risk in this group of patients. The aim of the present study was to assess changes in QT dispersion during infusion of glucose-insulin-potassium (GIK) during AMI. Methods: Patients from the Pol-GIK study were analyzed retrospectively. The patients were selected from the placebo (1000 mL of 0.89% NaCl) and the GIK (1000 mL of 10% dextrose, 20-32 units of insulin, 80 mEq K+) groups (18 and 24 patients, respectively). QT interval duration and dispersion (the difference between the longest and shortest QT intervals) were measured at baseline, 18-24 hours into placebo/GIK infusion and 24 hours after the end of infusion. Results: In the placebo group, plasma potassium levels changed from 4.1 +/- 0.5 mmol/L at baseline to 4.6 +/- 0.8 mmol/L during infusion (P < 0.05) and 4.6 +/- 0.4 mmol/L after infusion, whereas in the GIK group the respective values were 4.0 +/- 0.4, 4.6 +/- 0.3 (P < 0.0001), and 4.5 +/- 0.5 mmol/L. QT interval duration was stable throughout the study and there was no difference between the groups. The two groups did not differ in respect to QT dispersion at any time point, the respective values were 79 +/- 28, 65 +/- 25, and 77 +/- 27 ms in the placebo group, and 61 +/- 35, 60 +/- 26, and 76 +/- 43 ms in the GIK group. The incidence of arrhythmias was also similar in both groups. Conclusions: GIK, at the dose used, is unlikely to affect heterogeneity of ventricular repolarization during AMI.