Journal of the Bahrain Medical Society
Year 2014, Volume 25, Issue 1, Pages 24-28
https://doi.org/10.26715/jbms.p25_6Yasir M. Khaleel,* Baybeen K. Al-Selevany,* Muzahim F. Mahmood**
*Department of Medical Physiology, College of Medicine, University of Mosul, Mosul, Iraq
**Department of Medicine, College of Medicine, University of Mosul, Mosul, Iraq
Correspondence to: ymk6889@gmail.com
Abstract
Background: In spite of the clinical importance of accurate measurement of QT and corrected QT intervals during electrocardiographic interpretation, there appears to be some considerable difficulty in its precise measurement and in the determining of the upper accepted value for each gender. In addition to gender, QT intervals can also be affected by age and racial factors.
Objectives: To evaluate the impact of age on corrected QT interval in healthy adults according to gender.
Methods: Electrocardiograms from 563 apparently healthy adults (386 male and 177 female) aged 18-40 years were obtained using Cardios PC based ECG machine; 12-lead ECGs were recorded and corrected QT interval was measured by computer and reviewed manually in leads II, V2, V3, V5 and V6. The correction of QT interval was based on Bazett’s formula. The mean QTc was calculated for the whole study sample and then for each gender separately; the mean QTc was compared between genders and in different age groups. Linear regression lines of QTc versus age were drawn in each gender separately.
Results: The mean ±SD of QTc (414.95 ±24.94) in the study sample was within normal range although close to upper limits. Subjects with prolonged QTc (>430 ms) represented about 24% of the total. The mean QTc in females was significantly longer than males (p=0.001), prolonged QTc was also significantly more frequent in females (p=0.001). There was a significant increase in the mean QTc with increasing age in the study sample (p=0.001), and a significant increase in the frequency of reported prolonged QTc with the older age group (p=0.018). Linear regression lines of QTc versus age in each gender separately have shown that females have longer QTc than males; the difference was more noticeable in younger females and decreased with increasing age.
Conclusions: QTc interval is both age and gender dependent, so it is worth using linear regression lines drawn according to age and gender in the determination of its normal value.
Keywords: corrected QT interval; healthy adults; age; gender