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Updated: Oct 5, 2025
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Published on: June 12, 2020
Physiological QT Interval Changes in Early Infancy Using Post-Menstrual and Post-Natal Age Calculation for
Wan-Ling Chih1,2, Eric C Lussier1, Jou-An Chen1
1Taiji Clinic.
Insights
QT intervals in infants peak around the third month and vary with sex. Bazett
Area of Science:
- Pediatrics
- Cardiology
- Neonatology
Background:
- Prolonged QT interval is linked to sudden infant death syndrome risk.
- QT interval varies with infant age, necessitating age-specific screening.
- Established screening protocols for Taiwanese infants are lacking.
Purpose of the Study:
- Establish reference QT interval values for early infancy.
- Assess QT interval changes based on different age calculation methods.
- Identify optimal QT correction methods and influencing infant factors.
Main Methods:
- Recorded electrocardiographic readings and QT intervals in 595 healthy infants.
- Calculated corrected QT intervals using Bazett's (QTc-B) and Fridericia's (QTc-F) formulas.
- Compared QTc values based on post-natal/post-menstrual age, sex, BMI, and heart rate.
Main Results:
- QTc-B and QTc-F peaked in the third month (61-90 days) of infancy.
- QTc-B showed similar lengths regardless of post-natal or post-menstrual age.
- QTc-F was associated with age, BMI, and heart rate; QTc-B was mainly associated with sex and heart rate.
- QTc-B was less sensitive to heart rate variations compared to QTc-F.
- Female infants exhibited slightly longer QTc intervals.
Conclusions:
- Infant QT intervals exhibit physiological changes, peaking around three months.
- Age correction methods did not significantly impact the rate of QT change.
- QTc-B is a more robust measure, less affected by age, BMI, and heart rate.
- Sex is a notable factor influencing QTc intervals in infants.
Background:
Prolongation of the QT interval is associated with the risk of sudden infant death syndrome. QT interval differs depending on age at the time of screening. Screening protocols have yet to be established for Taiwanese patients.
Objectives:
To construct QT interval reference values during early infancy, to investigate whether QT interval change differs according to age calculation methods, and to identify an optimal QT correction method and associated infant factors.
Methods:
Electrocardiographic readings and QT intervals were recorded cross-sectionally in 595 healthy infants and screened prospectively for long QT interval. Corrected QT intervals with Bazett's (QTc-B) and Fridericia's (QTc-F) formulas were compared by post-natal and post-menstrual screening age, sex, body mass index (BMI), heart rate (HR), birth and family history.
Results:
QTc-B and QTc-F decreased in the second month (31-60 days), and peaked in the third month (61-90 days). QT interval length was similar between post-menstrual and post-natal ages for QTc-B. Simple linear regression showed that post-menstrual age, post-natal age, HR and BMI were associated with QTc-F, while only sex and HR were associated with QTc-B. Although both QTc-B and QTc-F were significantly associated with HR, QTc-B was less affected by HR than QTc-F (β = -0.1, p < 0.05 for QTc-B vs. β = -0.3, p < 0.001 for QTc-F). Female infants tended to have slightly longer QTc intervals.
Conclusions:
QT interval in early infancy changed physiologically, peaking in the third month. The rate of QT change was not affected by different age correction methods. QTc-B was less affected by age, BMI and HR, although differences in sex should be noted.
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