The link between hypoglycaemia, cardiac arrythmia, and dead in bed syndrome

Arrhythmia incidents differ in nocturnal and diurnal hypoglycemic patients.

In young adults with type 1 diabetes (T1D), severe hypoglycemia may increase the risk of all-cause mortality and cardiovascular diseases.

According to Peter Novodvorsky, from the University of Sheffield in the United Kingdom, and his colleagues, there are differences in arrhythmic risk and cardiac repolarization during nocturnal versus daytime hypoglycemia. Hypoglycemia may exert proarrhythmogenic effects on the heart by sympathoadrenal stimulation and hypokalemia. The dysrhythmias induced by hypoglycemia have been associated with the “dead-in-bed syndrome,” a devastating condition that is rarely heard of. In this study, the effects of nocturnal and daytime clinical hypoglycemia are examined through electrocardiogram (ECG) in young people with T1D.

In an observational study, 37 participants were recruited from Sheffield Teaching Hospitals outpatient clinics with a median age of 34 years with T1D for at least four years. The purpose of this study was to examine the effect of clinical hypoglycemia in T1D patients age 50 or less and compare it with matched euglycemia on the frequency of cardiac arrhythmias, HRV, and cardiac repolarization.

Participants were told to avoid vigorous exercise, caffeine, and smoking 12 h prior to monitoring. Hypoglycemia awareness was assessed using a visual analog scale of 1 to 7. All subjects underwent 96 h of simultaneous  ECG and blinded continuous interstitial glucose monitoring (CGM) while continuing daily activities and symptomatic hypoglycemia were recorded.

The researchers obtained 2,395 hours of simultaneous ECG and CGM recordings with 159 and 1,355 hours designated hypoglycemia and euglycemia respectively. The median duration of hypoglycemia was longer during the night (60 min) than daytime (44 min) [P =0.020]. Overall, there were 24.1% of nocturnal and 51% of daytime symptomatic episodes respectively.

Bradycardia (low heart rate ) was more frequent during nocturnal hypoglycemia in comparison to matched euglycemia with an incidence rate ratio [IRR] 6.44 [95% CI, 6.26-6.66; P <0.001].

During daytime hypoglycemia, bradycardia was less frequent with an IRR 0.023 [95% CI, 0.002-0.26; P =0.002], while atrial ectopic was more frequent (IRR: 2.29; 95% CI, 1.19-4.39; P =.013). Moreover, during nocturnal and daytime hypoglycemia there was decreased T-wave symmetry, but prolonged QTc and T-peak to T-end interval duration.

The study confirmed that asymptomatic hypoglycemia commonly occurs in T1D. This causes abnormal heart rhythms and these are more abnormal at night, more frequent  and last longer.

Practice Pearls:

• Hypoglycemia is pro-arrhythmogenic.
• The study confirmed that there is high frequency of hypoglycemia, particularly of nocturnal asymptomatic episodes among young people with type 1 diabetes.
• Hypoglycemia-induced mechanism is independent of the type of diabetes, age, or cardiovascular risk profile.

References:

1. American Diabetes Association. 5. Glycemic targets. Diabetes Care. 2016;39 (Suppl. 1):S39–S46
2. Nordin C. The case for hypoglycaemia as a proarrhythmic event: basic and clinical evidence. Diabetologia. 2010;53:1552–1561
3. Novodvorsky P, bernjak A, Chow E, Iqbal A, Sellors L, Williams S, et al. Diurnal differences in risk of cardiac arrhythmias during spontaneous hypoglycemia in young people with type 1 diabetes. Diabetes Care. 2017, Feb 17.

From Diabetes in Control  18th March 2017