Abstract
ObjectivesProlonged 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 diabetes patients.MethodsIn this cross-sectional study, 2904 type 2 diabetes patients were recruited who had undergone at least four fasting plasma glucose (FPG) and 2-hour postprandial plasma glucose (PPG) measurements (at least once for every 3 months, respectively) during the preceding year. Long-term glycaemic variabilities of FPG and 2-hour PPG were assessed by their standard deviations (SD-FPG and SD-PPG, respectively), and chronic fasting and postprandial hyperglycaemia were assessed by their means (M-FPG and M-PPG, respectively). HbA1c was also determined upon enrolment to assess current overall glycaemic control. QTc interval was estimated from resting 12-lead electrocardiograms, and more than 440 ms was considered abnormally prolonged.ResultsPatients with prolonged QTc interval (≥440 ms) had greater M-FPG, M-PPG, SD-PPG and HbA1c than those with normal QTc interval but comparable SD-FPG. QTc interval was correlated with M-FPG, M-PPG, SD-PPG and HbA1c (r = 0.133, 0.153, 0.245 and 0.207, respectively, p = 0.000) but not with SD-FPG (r = 0.024, p = 0.189). After adjusting for metabolic risk factors via multiple linear regression analysis, SD-PPG, M-PPG and HbA1c (t = 12.16, 2.69 and 10.16, respectively, p = 0.000) were the major independent contributors to the increased QTc interval. The proportion of prolonged QTc interval increased significantly from 10.9% to 14.2% to 26.6% for the first (T1) to second (T2) to third (T3) tertiles of SD-PPG. After adjusting via multiple logistic regression analysis, the odd ratios of prolonged QTc interval of the T2 and T3 versus the T1 of SD-PPG were 1.15 (95% CI, 0.82–1.60) and 2.62 (1.92–3.57), respectively.ConclusionsIncreased long-term variability of PPG is a strong independent risk factor for prolonged QTc interval in type 2 diabetes patients, in addition to long-term postprandial hyperglycaemia and current HbA1c.
Highlights
The electrocardiographic QT interval reflects the total time taken for ventricular myocardial depolarization (QRS complex) and repolarization (T wave) [1]
QTc interval was correlated with M-fasting plasma glucose (FPG), M-postprandial plasma glucose (PPG), SD-PPG and HbA1c (r = 0.133, 0.153, 0.245 and 0.207, respectively, p = 0.000) but not with SD-FPG (r = 0.024, p = 0.189)
The distribution of QTc interval and glycaemic parameters are shown in S1 Fig. The average QTc interval of the total participants was 420±31 ms, that of the group with normal QTc interval was 402±24 ms, and that of the group with prolonged QTc interval was 458±20 ms
Summary
The electrocardiographic QT interval reflects the total time taken for ventricular myocardial depolarization (QRS complex) and repolarization (T wave) [1]. The prolonged QTc interval may be mainly or partly dependent on glycaemic disorders in type 2 diabetes. In addition to sustained hyperglycaemia, glycaemic variability could be an significant risk factor for vascular complications in diabetes [11]. The roles of the various glycaemic parameters that participate in the development of diabetic complications may differ [12,13,14]. We hypothesized that long-term glycaemic variability may play an essential role in the development of diabetic complications, such as a prolonged QTc interval. Long-term glycaemic variability parameters can be assessed based on the annual variability of FPG and PPG. Few studies far have evaluated the relationship between the time-dependent variation in PPG and cardiovascular complications among diabetic patients, such as prolonged QTc interval
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