ABC | Volume 114, Nº2, February 2020

Original Article Evaluation of Electrocardiographic Ventricular Depolarization and Repolarization Variables in Type 1 Diabetes Mellitus Mehmet Inanır, 1 Yilmaz Gunes, 1 Isa Sincer, 1 Emrah Erdal 1 Abant Izzet Baysal University Hospital, 1 Bolu – Turkey Mailing Address: Mehmet Inanır • Abant Izzet Baysal University Hospital – Cardiology. Bolu 14000 – Turkey E-mail: mdmehmetinanir@yahoo.com Manuscript received November 12, 2018, revised manuscript February 11, 2019, accepted March 10, 2019 DOI: https://doi.org/10.36660/abc.20180343 Abstract Background: The risk of cardiovascular events and sudden death increases with type 1 diabetes mellitus (T1DM). Objective: To evaluate electrocardiographic markers of arrhythmias in T1DM patients. Methods: Electrocardiographic parameters reflecting ventricular depolarization and repolarization, namely, QT, QTc, QTd, QTdc, Tp-e, JT, and JTc intervals and Tp-e/QT and Tp-e/QTc ratios, of 46 patients diagnosed with T1DM were retrospectively analyzed and compared with 46 healthy age-, sex-, and body mass-matched controls. Correlations between T1DM duration, hemoglobin A1c (HbA1c), and ventricular repolarization variables were analyzed. P values lower than 0.05 were considered statistically significant. Results: Diabetes duration was 16.6 ± 7.1 years, and HbA1c was 10.81%± 3.27% in the T1DM group. In comparison with the control group, heart rate, QTc, QTd, QTdc, Tp-e and JTc intervals, Tp-e/QT ratio (p < 0.001), and Tp-e/QTc ratio (p = 0.007) were significantly higher in T1DM patients. T1DM duration and HbA1c levels were significantly correlated with QTc, QTd, QTdc, Tp-e, and JTc intervals and Tp-e/QT and Tp-e/QTc ratios. Conclusions: In T1DM patients, potential electrocardiographic repolarization predictors were significantly increased in correlation with disease duration and HbA1c levels. These findings may contribute to the understanding of sudden cardiac death in patients with T1DM. (Arq Bras Cardiol. 2020; 114(2):275-280) Keywords: Diabetes Complications; Risk Factors; Prevention and Control; Arrhythmias, Cardiac; Electrocardiography/methods. Introduction Diabetes is a major health problem that is associated with various comorbidities such as hypertension, cardiovascular diseases, metabolic syndrome, and cardiopulmonary diseases. Over long periods of time, it is also a major underlying risk factor for coronary heart disease, heart failure, peripheral artery disease, atrial fibrillation, chronic renal failure, and stroke. It is also associated with an increased mortality risk. 1-4 The interval between the beginning of the QRS complex and the end of the T wave in the surface electrocardiogram (ECG) reflects ventricular depolarization and repolarization. Cardiac electrical changes during ventricular repolarization may lead to lethal arrhythmias. 5 Sudden death risk is also increased in type 1 diabetes mellitus (T1DM) subjects. 6 Accordingly, prolonged repolarization has been speculated to play a role in sudden death among T1DM patients. 6 In this study, we aimed to evaluate potential ventricular arrhythmia predictors of surface ECG, namely, QT and corrected QT (QTc) intervals, QT dispersion (QTd), corrected QTd (QTdc), Tp-e, JT and JTc intervals, and Tp-e/QT and Tp-e/QTc ratios, in patients with T1DM. Methods Study population ECG records of 46 patients with T1DM, who were followed in the endocrinology and metabolism diseases outpatient clinic of our hospital between January 2017 and May 2018, were retrospectively analyzed and compared with the ECG results of 46 age-, sex-, and body mass-matched controls. T1DM was defined according to the AmericanDiabetes Association criteria. 7 Patients over the age of 45 were not included due to increased probability of unknown atherosclerosis and comorbidities that may affect ECG. Subjects who had history of coronary artery disease, peripheral artery disease, heart failure, structural heart disease, chronic lung disease, liver or renal failure, thyroid disorders, malignancies, electrolyte imbalances, or any other systemic disease and subjects who were using any drug (e.g. betablockers, calcium channel blockers, antidepressant drugs, etc.) other than insulin were excluded. Subjects who had history of ventricular arrhythmias or atrial fibrillation and subjects who had low QRS voltage, increased QRS duration, left-axis deviation, hypertrophic findings, nonspecific flattening of the T waves, left atrial abnormalities, or ST segment depression on ECG were also excluded due to the probable effects of these ECG changes on the measured ECG parameters. 275