Objective: To analyse the incidence of long and short corrected QT (QTc) in a healthy sample of the population of Changsha in China.
Methods: Standard 12-lead electrocardiograms (ECGs) were performed on 4025 subjects in Changsha of China, whose age ranged from 6 minutes after birth to 83 years, between January 1993 and December 2012. Heart rate and QT interval were measured and recorded. Corrected QT was calculated with Bazett´s formula (QTc = QT/RR0.5). All recruited individuals had taken healthy examination, ruling out general health issue, in The Second Xiangya Hospital of Central South University. Statistical analyses were performed using the SPSS 16.0 software (IBM Corp, Armonk, NY, USA).
Results: The incidence of short QTc was 7.13% (287/4025 cases). The peak values of the incidence were in the 30–40 years group (15.71%). The low values were in the 1–3 months group and 3–6 months group (0%, 0.76%), respectively. The incidence of long QTc was 3.16% (127/4025 cases). The values diminished significantly after adulthood. The low values were in the age groups of 18–30 years (0.86%) and 30–40 years (0.71%), respectively. After the age of 50 years, the incidence of long QTc increased with age 50–60 years and 60–70 years and 70–83 years (7.89%, 9.06%, 14.06%), respectively. There was no statistically significant difference between the genders (p > 0.05).
Conclusion: The peak incidences of long and short QTc existed in two separate age groups in the healthy sample. The peak incidence of short QTc was in the age group of 18–40 years, and the peak incidence of long QTc was in the age group beyond the 50 years. For these two age groups, it was recommended to pay close attention to the changes in their QTc in order to prevent cardiovascular events.