Cardiac arrhythmias and electrophysiologic responses during spontaneous hyperglycaemia in adults with type 1 diabetes mellitus.

ABSTRACT Aim We examined the effect of spontaneous hyperglycaemia in adults with type 1 diabetes mellitus (T1DM) and without history of cardiovascular disease on heart rate variability (HRV), cardiac repolarisation and incidence of cardiac arrhythmias. Methods Thirty-seven individuals with T1DM (age 17-50 years, 19 males, mean duration of diabetes 19.3 SD(9.6) years) underwent 96 hours of simultaneous ambulatory 12-lead Holter ECG and blinded continuous interstitial glucose (IG) monitoring (CGM). HRV, QT interval and cardiac repolarisation were assessed during hyperglycaemia (IG ≥ 15 mmol/l) and compared with matched euglycaemia (IG 5-10 mmol/l) on a different day, separately during the day and night. Rates of arrhythmias were assessed by calculating incidence rate differences. Results Simultaneous ECG and CGM data were recorded for 2395 hours, During daytime hyperglycaemia vs euglycaemia the mean QTc interval duration was 404 SD(21)ms vs 407 SD(20)ms, P = 0.263. T-peak to T-end interval duration corrected for heart rate (TpTendc) shortened (74.8 SD(16.1)ms vs 79.0 SD(14.8)ms, P = 0.033) and T-wave symmetry increased (1.62 SD(0.33) vs 1.50 SD(0.39), P = 0.02). During night-time hyperglycaemia vs euglycaemia, the mean QTc interval duration was 401 SD(26)ms vs 404 SD(27)ms, P = 0.13 and TpTend shortened (62.4 SD(12.0)ms vs 67.1 SD(11.8)ms, P = 0.003). The number of cardiac arrhythmias was low and confined to bradycardia and isolated ectopic beats. A considerable inter-subject and diurnal variability was observed. Conclusions Hyperglycaemia in individuals with T1DM without known cardiovascular disease was not associated with clinically important cardiac arrhythmias.