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QT interval in normal infants during sleep with concurrent evaluation of QT correction formulae
Avram Benatar1, Jose Ramet, Tine Decraene
1Department of Pediatric Cardiology, Academic Hospital, Free University of Brussels, Brussels, Belgium. Abraham.Benatar@az.vub.ac.be
Insights
Investigating the QT-RR relationship in infants during sleep revealed that common QT correction formulas have varying accuracy. The Hodges formula showed the best correlation with the RR interval in this population.
Area of Science:
- Pediatric Cardiology
- Sleep Physiology
- Electrocardiography
Background:
- Physiological QT interval changes during sleep are crucial for normal QT interval assessment.
- Bazett's formula is traditionally used for heart rate correction in pediatric QT intervals.
- Understanding the QT-RR relationship in infants during sleep is essential for accurate interpretation.
Purpose of the Study:
- To establish the QT-RR relationship in infants during sleep.
- To evaluate the performance and comparability of four QT correction formulas.
- To determine the clinical utility of different QT correction methods in infants.
Main Methods:
- 130 healthy term infants underwent polysomnography with continuous EKG monitoring.
- QT intervals and heart rate were measured manually at hourly intervals.
- QTc was calculated using Bazett, Hodges, Fridericia, and Framingham formulas; analysis included ANOVA and regression.
Main Results:
- The QT-RR relationship during sleep is curvilinear and slightly shifted.
- Bazett and Hodges formulas overcorrected QTc in infants with higher heart rates and younger age.
- Fridericia and Framingham formulas undercorrected QTc; Hodges formula showed the best RR interval correlation.
Conclusions:
- QT correction formulas exhibit significant heart rate dependency.
- Hodges formula may serve as a useful adjunct for borderline QTc Bazett prolongation.
- Normal infants may exhibit a slightly prolonged QTc Bazett during sleep.
Background:
Physiological changes in the QT interval caused by sleep are important in the evaluation of the normal QT interval. Traditionally, Bazett's formula is used for correcting the QT interval for heart rate in childhood. We set out to establish the QT-RR relationship in infants during sleep and concurrently test the performance of four QT correction formulae to determine their comparability and clinical utility.
Material/Methods:
130 healthy term born infants undergoing routine 8-hour polysomnography were enrolled. Continuous EKG limb lead II recording, saturation monitoring, and electroencephalography were conducted. QT intervals and heart rate were measured manually digitally on-screen at hourly intervals. The QT-RR relationship was plotted and QTc calculated using the Bazett, Hodges, Fridericia and Framingham formulae. QTc values for each formula were plotted against age and RR interval. Analysis of variance and regression analysis were used to compare the four formulae and the QT-RR relationship.
Results:
Mean age was 17.7 weeks (range 4-72) and mean weight 6.3 kg (range 2.68-12.7). The QT-RR relationship during sleep is curvilinear and appears to be slightly shifted. With increasing heart rate and younger age the Bazett and Hodges formulae overcorrect the QTc whereas the Fridericia and Framingham formulae undercorrect. The Hodges formula correlated best with the RR interval.
Conclusions:
These formulae are strongly dependent on heart rate. In the setting of a borderline QTc Bazett prolongation, Hodges formula may be a useful adjunct. Normal infants may have a slightly longer QTc Bazett during sleep.