Heart‐rate Corrected QT Interval Prolongation in Impaired Fasting Glucose and Type 2 Diabetes: The Polish Norwegian Study (PONS)

Abstract

IntroductionProlonged QT interval is associated with cardiac arrhythmias and sudden death. Type 2 diabetes mellitus (DM) is associated with increased risk of arrhythmias. Repolarization abnormalities may play a role in increasing the arrhythmic risk in patients with DM.PurposeTo estimate QT interval across the entire spectrum of glucose abnormalities.MethodsCross‐sectional data from an ongoing cohort study, following a standardized protocol. The QT intervals were obtained from digital standard 12‐lead resting ECG. Heart rate correction (QTc) was performed with Bazett's formula. Plasma total, LDL, HDL cholesterol, triglycerides and glucose were measured in a fasting state. We classified glucose metabolism in three categories: normal (no DM and fasting glucose <100 mg/dL), impaired fasting glucose (IFG, no DM and fasting glucose between 100–125.9 mg/dL) and diabetes (history of diabetes or antidiabetic medication or fasting glucose >= 126 mg/dL). We considered as normal, QTc values < 430 ms for men and < 450 ms for women. After excluding medication known to influence the QT interval (antiarrhythmics, digoxin, antipsychotics), the analytic sample size was 11068 participants, ages 45 to 64 years. Multivariable linear and logistic models were used for analyses.ResultsMean (SD) QTc was 413.60 ms (27.37) for men and 421.40 (23.97) ms for women. The overall prevalence of IFG was 23.74% and of DM was 8.43%. The mean (95%CI) QTc was 417.72 ms (417.14–418.30) in the normal glycemic group, 419.88 ms (418.90–420.86) in the IFG group and 424.70 ms (423.06–426.34) in the DM group. After adjustment for age, sex, prevalent cardiovascular disease, hypertension, left ventricular hypertrophy and BMI, these QTc means were 418.06 ms (417.47–418.64), 419.38 ms (418.39–420.37) and 423.45 ms (421.77–425.13) respectively. The likelihood of a higher than normal sex‐specific, age‐adjusted QT interval was 79% higher in those with IFG (OR 1.79, 95% CI 1.50–2.14), compared to those with normal glucose metabolism. After additional adjustment for prevalent cardiovascular disease, hypertension, left ventricular hypertrophy and BMI, these figures remained statistically significant (IGF: OR 1.19, 95% CI 1.04–1.40), DM: OR 1.57, 95%CI 1.30–1.88). History of DM or current antidiabetic drug use was associated with a 46% increase in the odds of a higher than normal sex‐specific QTc interval (OR, 95% CI 1.46, 1.20–1.79), after multivariable adjustment. Among normal glucose and IFG groups, each one additional cardiovascular risk factor increased the likelihood of a higher than normal QTc by 15% (OR, 95% CI 1.11–1.23). However, this effect was not present among those with diabetes. Diabetes duration and/or glucose control in diabetics, was not associated with QTc.ConclusionWe found a progressively increasing QTc interval from normal glucose to IFG and diabetes. Our results suggest that abnormalities in glucose metabolism impact ventricular repolarization, independent of the presence of other cardiovascular risk factors accompanying the diabetic state.Support or Funding InformationThe data collection was supported by a grant from the Polish‐Norwegian Research Fund (PNRF‐228‐AI‐1/07)