Effects of Glucose Fluctuations on Electrocardiogram Readings and the Development of Ventricular Arrhythmia in Diabetic Rats

Objective:Many studies have shown that blood glucose fluctuations(GFs)are more harmful to patients with diabetes mellitus(DM)than sustained hyperglycemia.However,the effect of GF on electrocardiogram(ECG)parameters and vulnerability to ventricular tachycardia/fibrillation(VT/VF)remains poorly characterized.This study aimed to assess the effect of GF on ECG parameters and induction of VT/VF in streptozotocin(STZ)-induced diabetic Sprague-Dawley rats.Methods:Male Sprague-Dawley rats were injected with STZ and randomly divided into 3 treatment groups:controlled STZ-induced diabetic rats(C-STZ)(n=10);uncontrolled STZ-induced diabetic rats(U-STZ)(n=10);and STZ-induced diabetic rats with glucose fluctuations(GF-STZ)(n=10).After 12 weeks,baseline ECG recordings were taken and a VT/VF test was performed with the administration of caffeine and dobutamine.Hematoxylin&eosin and masson staining were used to evaluate pathological cardiac changes after intervention.Results:No significant difference in heart rate,RR interval,P wave(duration and height),PR segment,PR interval,QRS wave duration,and T wave height was observed among the 3 groups(P>0.05).Compared with the C-STZ group,the U-STZ and GF-STZ groups both had a longer T wave duration((62.41±2.38)ms vs.(78.37±4.64)ms and(96.06±4.60)ms,P<0.05),QT interval((83.66±2.31)ms vs.(101.75±4.56)ms and(119.14±4.88)ms,P<0.05),and QTc interval((77.45±1.36)ms vs.(91.36±3.49)ms and(104.55±3.01)ms,P<0.05),all of which were longest in the GF-STZ group(P<0.05).Additionally,the GF-STZ group had the highest VT/VF occurrence and duration and the highest arrhythmia score.Conclusion:This study revealed GF can significantly prolong the QT interval,QTc interval,and T wave duration,as well as increase vulnerability to VT/VF in rats,which may be an important electrophysiological mechanism of GF-related ventricular arrhythmia.