Arrhythmogenic effects of hypoglycemia in children and adolescents with type 1 diabetes mellitus

Aim. To determine the effects of hypoglycemia on the duration of QT interval, heart rate variability (HRV) and frequency of arrhythmic events, as well as to closer investigate the factors associated with the development of various heart rhythm disorders in children and adolescents with type 1 diabetes mellitus (T1DM). Materials and methods. The study included 150 children and adolescents with T1DM at the age of 6-18 years. All participants underwent Holter monitoring and continuous glucose monitoring (CGM) for 24 hours. QTc and HRV parameters (SDNN, RMSSD, SVVR) were calculated automatically. Data was averaged for 5'-interval and juxtaposed with CGM. Patients identified with hypoglycemic events (blood glucose <3.5 mmol/L) during the day (7:00-23:00) and nighttime (23:00-7:00) were selected for further study. In these patients length of QTc and RR intervals, HRV parameters and arrhythmic events were analyzed and collated with CGM data. Results. We observed 39 episodes of nocturnal hypoglycaemia in 32 patients (21.3%) and 89 episodes of daytime hypoglycaemia in 46 patients (30.7%). Marked prolongation of QTc (hypo-vs. normoglycemia, respectively: 431 vs. 420 ms; p<0.05) and reduced HRV (hypo-vs. normoglycemia, respectively: SDNN 68 and 90 ms; RMSSD 56 and 61 ms; p <0.05) occurred during episodes of nocturnal hypoglycemia. The same pattern was observed during the day (hypo-vs. normoglycemia, respectively: SDNN 58 and 63 ms; RMSSD 32 and 36 ms; p<0.05). Eleven subjects with nocturnal hypoglycemia demonstrated either ventricular or supraventricular premature complexes. Thirty of subjects with diurnal hypoglycemia also had either ventricular or supraventricular premature complexes. Hypoglycemic episodes vs. normoglycemia were characterized by an increase in ventricular and supraventricular ectopic beats, ST segment and T-wave amplitude depression. Various rhythm abnormalities were associated with cardiovascular autonomic and peripheral neuropathy. Conclusion. During episodes of hypoglycemia, HRV parameters decrease, QT elongates and episodes of arrhythmia occur more frequently. History of autonomic and peripheral neuropathy contributes to the development of arrhythmias.