| Objective The electrocardiographic QT interval reflects the total time taken for ventricular myocardial depolarization and repolarization.Prolonged heart rate-corrected QT(QTc)interval is related to ventricular arrhythmia and cardiovascular mortality,with considerably high prevalence of type 2 diabetes.Additionally,long-term glycaemic variability could be a significant risk factor for diabetic complications in addition to chronic hyperglycaemia.We compared the associations of long-term glycaemic variability versus sustained chronic hyperglycaemia with the QTc interval among type 2 diabetic patients.Methods1.In this cross-sectional study,2904 type 2 diabetic patients were recruited who had undergone at least four fasting plasma glucose(FPG)and 2-hour postprandial plasma glucose(PPG2h)measurements(at least once for every 3 months,respectively)during the preceding year.2.Long-term glycaemic variabilities of FPG and PPG2 h were assessed by their standard deviations(SD-FPG and SD-PPG2 h,respectively).3.Chronic fasting and postprandial hyperglycaemia were assessed by their means(M-FPG and M-PPG2 h,respectively).4.QTc interval was estimated from resting 12-lead electrocardiograms,and more than 440 ms was considered abnormally prolonged.5.Hb A1 c was determined upon enrolment to assess current overall glycaemic control.Other metabolic risks,such as age,diabetic duration,body mass index,blood press and lipid profiles,were aslo collected.And regimens for diabetic treatments were also documented.Results1.Patients with abnormally prolonged QTc interval(>440 ms)had greater M-FPG,M-PPG2 h,SD-PPG2 h and Hb A1 c than those with normal QTc interval but comparable SD-FPG.2.QTc interval was correlated with M-FPG,M-PPG2 h,SD-PPG2 h and Hb A1c(r=0.133,0.153,0.245 and 0.207,respectively,p<0.001)but not with SD-FPG(r=0.024,p=0.189).3.After adjusting for metabolic risk factors via multiple linear regression analysis,SD-PPG2 h,M-PPG2 h and Hb A1c(t=12.16,2.69 and 10.16,respectively,p<0.001)were the major independent contributors to the increased QTc interval.4.The proportion of abnormally prolonged QTc interval increased significantly from 10.9% to 14.1% to 26.5% for the first(T1)to second(T2)to third(T3)tertiles of SD-PPG2 h.After adjusting via multiple logistic regression analysis,the odd ratios of abnormally prolonged QTc interval of the T2 and T3 versus the T1 of SD-PPG2 h were 1.15(95% CI,0.82–1.60)and 2.62(1.92–3.57),respectively.Conclusions1.Increased long-term variability of PPG2h(SD-PPG2h)is a strong independent risk factor for prolonged QTc interval in patients with type 2 diabetes.2.Additionally,long-term postprandial hyperglycaemia and current Hb A1 c are independently associated with prolonged QTc interval in these patients.3.The association of prolonged QTc interval with SD-PPG2 h is stronger than the associations with M-PPG2 h and current Hb A1 c.4.M-FPG is not an independent risk factor for prolonged QTc intervals,although it is correlated with QTc intervals in the univariate analysis.5.The study does not reveal a relationship between SD-FPG and the QTc interval. |
