Hypoglycaemia and QT interval prolongation in type 1 diabetes--bridging the gap between clamp studies and spontaneous episodes

AIMS

We propose a study design with controlled hypoglycaemia induced by subcutaneous injection of insulin and matched control episodes to bridge the gap between clamp studies and studies of spontaneous hypoglycaemia. The observed prolongation of the heart rate corrected QT interval (QTc) during hypoglycaemia varies greatly between studies.

METHODS

We studied ten adults with type 1 diabetes (age 41±15years) without cardiovascular disease or neuropathy. Single-blinded hypoglycaemia was induced by a subcutaneous insulin bolus followed by a control episode on two occasions separated by 4weeks. QT intervals were measured using the semi-automatic tangent approach, and QTc was derived by Bazett's (QTcB) and Fridericia's (QTcF) formulas.

RESULTS

QTcB increased from baseline to hypoglycaemia (403±20 vs. 433±39ms, p<0.001). On the euglycaemia day, QTcB also increased (398±20 vs. 410±27ms, p<0.01), but the increase was less than during hypoglycaemia (p<0.001). The same pattern was seen for QTcF. Plasma adrenaline levels increased significantly during hypoglycaemia compared to euglycaemia (p<0.01). Serum potassium levels decreased similarly after insulin injection during both hypoglycaemia and euglycaemia.

CONCLUSIONS

Hypoglycaemia as experienced after a subcutaneous injection of insulin may cause QTc prolongation in type 1 diabetes. However, the magnitude of prolongation is less than typically reported during glucose clamp studies, possible because of the study design with focus on minimizing unwanted study effects.

Objective measurements of activity patterns in people with newly diagnosed Type 2 diabetes demonstrate a sedentary lifestyle

AIMS

To evaluate physical activity in people with newly diagnosed Type 2 diabetes using objective measures.

METHODS

We analysed data from a study aimed at assessing carotid femoral pulse wave velocity in which a piezoelectric accelerometer was worn by 100 people with newly diagnosed Type 2 diabetes and by 100 age- and sex-matched control subjects. Differences in physical activity patterns were investigated.

RESULTS

Compared with the control group, the people with Type 2 diabetes spent significantly more time engaged in sedentary or lower level activities during the day, with a mean (sd) time of 926 (44) vs 898 (70) min, P < 0.001). This difference remained significant after correction for differences in BMI between the two groups.

CONCLUSIONS

Using objective measurements, our findings demonstrate that people with newly diagnosed Type 2 diabetes have a more sedentary lifestyle compared with well-matched controls.