Electrocardiograpic responses during spontaneous hypoglycaemia in people with type 1 diabetes and impaired awareness of hypoglycaemia.

Aims: Hypoglycaemia causes abnormal cardiac repolarisation, which has been related to sympathoadrenal activation. We examined whether individuals with type 1 diabetes (T1D) and impaired awareness of hypoglycaemia (IAH) were protected against proarrhythmogenic alterations on their electrocardiogram during clinical episodes of hypoglycaemia.

Methods: Adults with T1D and IAH underwent 96 h of simultaneous ambulatory electrocardiogram and blinded continuous interstitial glucose (IG) monitoring. Measures of cardiac repolarisation and heart rate variability (HRV) were compared during hypoglycaemia versus time and person-matched euglycaemia. We compared these data to a historical control group of individuals with T1D and no IAH.

Results: Fourteen individuals (10/14 female) with a mean (SD) age of 39 (10) years and T1D duration of 24 (9) years were examined. Fourteen daytime and 12 nocturnal hypoglycaemic episodes were analysed. During daytime hypoglycaemia versus euglycaemia, the mean (SD) QT_c interval was prolonged to 443 (38) versus 422 (27) ms, p = 0.027; the Tpeak-to-Tend interval was prolonged to 93 (18) versus 77 (9) ms, p = 0.002; and the T wave area symmetry decreased to 1.19 (0.37) versus 1.39 (0.23), p = 0.014. High-frequency power decreased during daytime hypoglycaemia versus euglycaemia to 1.66 (0.41) versus 1.92 (0.52), p = 0.038. At daytime, the Tpeak-to-Tend interval decreased significantly more (hypoglycaemia vs. euglycaemia) in the IAH group in comparison to the decrease observed in the historical control group of T1D individuals without IAH (p for interaction 0.005). Cardiac arrhythmias were infrequent and of no clinical significance.

Conclusions: Hypoglycaemia can still lead to proarrhythmogenic electrocardiographic changes in individuals with T1D and IAH. We observed diurnal, inter- and intraindividual variability in responses to hypoglycaemia.