QT interval prolongation during rapid fall in blood glucose in type I diabetes

Prolongation of QT interval on the ECG has been shown to be possibly associated with hypoglycaemia. In this study we investigated QT prolongation in episodes of single bolus induced hypoglycaemia in ten subjects with known type 1 diabetes mellitus. A mean QTc prolongation from baseline of 27(SD 19) ms (p<0.001) was measured 15 minutes after the injection of insulin. At this point the mean blood glucose was 7.2(SD 3.1) mmol/L. At the nadir of blood glucose the mean QTc prolongation from baseline was 25 (SD 22) ms (p<0.001). The study suggests that changes in the QTc in diabetics may occur not only as a result of low blood glucose per se but maybe also during rapid fall in blood glucose. The finding could be explained by pathophysiological changes in diabetes.