Abstract
BackgroundQT interval as an indicator of ventricular repolarization is a clinically important parameter on an electrocardiogram (ECG). QT prolongation predisposes individuals to different ventricular arrhythmias and sudden cardiac death. The current study aimed to identify the best heart rate corrected QT interval for a non-hospitalized Iranian population based on cardiovascular mortality.MethodsUsing Fasa PERSIAN cohort study data, this study enrolled 7071 subjects aged 35–70 years. Corrected QT intervals (QTc) were calculated by the QT interval measured by Cardiax® software from ECGs and 6 different correction formulas (Bazett, Fridericia, Dmitrienko, Framingham, Hodges, and Rautaharju). Mortality status was checked using an annual telephone-based follow-up and a minimum 3-year follow-up for each participant. Bland–Altman, QTc/RR regression, sensitivity analysis, and Cox regression were performed in IBM SPSS Statistics v23 to find the best QT. Also, for calculating the upper and lower limits of normal of different QT correction formulas, 3952 healthy subjects were selected.ResultsIn this study, 56.4% of participants were female, and the mean age was 48.60 ± 9.35 years. Age, heart rate in females, and QT interval in males were significantly higher. The smallest slopes of QTc/RR analysis were related to Fridericia in males and Rautaharju followed by Fridericia in females. Thus, Fridericia’s formula was identified as the best mathematical formula and Bazett’s as the worst in males. In the sensitivity analysis, however, Bazett’s formula had the highest sensitivity (23.07%) among all others in cardiac mortality. Also, in the Cox regression analysis, Bazett’s formula was better than Fridericia’s and was identified as the best significant cardiac mortality predictor (Hazard ratio: 4.31, 95% CI 1.73–10.74, p value = 0.002).ConclusionFridericia was the best correction formula based on mathematical methods. Bazett’s formula despite its poorest performance in mathematical methods, was the best one for cardiac mortality prediction. Practically, it is suggested that physicians use QTcB for a better evaluation of cardiac mortality risk. However, in population-based studies, QTcFri might be the one to be used by researchers.
Highlights
QT interval as an indicator of ventricular repolarization is a clinically important parameter on an electrocardiogram (ECG)
Corrected QT interval (QTc) corrected QT interval, RR RR interval, 95% CI 95% confidence interval, ms milliseconds, Bazett’s correction formula (QTcB), Fridericia’s correction formula (QTcFri), Dmitrienko’s correction formula (QTcD), Framingham’s correction formula (QTcFra), Hodges’s correction formula (QTcH), Rautaharju’s correction formula (QTcR)
QTc corrected QT interval, Lower limits of normal (LLN) lower limit of normal, Upper limits of normal (ULN) upper limit of normal, 95% CI 95% confidence interval, ms milliseconds, Bazett’s correction formula (QTcB), Fridericia’s correction formula (QTcFri), Dmitrienko’s correction formula (QTcD), Framingham’s correction formula (QTcFra), Hodges’s correction formula (QTcH), Rautaharju’s correction formula (QTcR)
Summary
QT interval as an indicator of ventricular repolarization is a clinically important parameter on an electrocardiogram (ECG). The current study aimed to identify the best heart rate corrected QT interval for a non-hospitalized Iranian population based on cardiovascular mortality. The QT interval on an electrocardiogram (ECG) indicates ventricular repolarization which is measured from the beginning of the QRS wave to the end of the T wave. It is an important parameter on ECG due to its prolongation. The first is a congenital or familial form of QT prolongation, known as long QT syndrome (LQTS). There are at least 14 genes responsible for LQTS [2], and the prevalence of LQTS is reported as approximately one in 2500 people [3] which makes this etiology an important one. The effects of age [13] and the female gender [14] on the QT interval should not be ignored
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