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Comparative Study
. 2015 Apr;166(4):960-4.e1-2.
doi: 10.1016/j.jpeds.2014.12.037. Epub 2015 Jan 31.

Comparison of formulas for calculation of the corrected QT interval in infants and young children

Derek Q Phan  1 , Michael J Silka  2 , Yueh-Tze Lan  3 , Ruey-Kang R Chang  4
Affiliations
Comparative Study

Comparison of formulas for calculation of the corrected QT interval in infants and young children

Derek Q Phan et al. J Pediatr. 2015 Apr.

Abstract

Objective: To compare 4 heart rate correction formulas for calculation of the rate corrected QT (QTc) interval among infants and young children.

Study design: R-R and QT intervals were measured from digital electrocardiograms. QTc were calculated with the Bazett, Fridericia, Hodges, and Framingham formulas. QTc vs R-R graphs were plotted, and slopes of the regression lines compared. Slopes of QTc-R-R regression lines close to zero indicate consistent QT corrections over the range of heart rates.

Results: We reviewed electrocardiograms from 702 children, with 233 (33%) <1 year of age and 567 (81%) <2 years. The average heart rate was 122 ± 20 bpm (median 121 bpm). The slopes of the QTc-R-R regression lines for the 4 correction formulas were -0.019 (Bazett); 0.1028 (Fridericia); -0.1241 (Hodges); and 0.2748 (Framingham). With the Bazett formula, a QTc >460 ms was 2 SDs above the mean, compared with "prolonged" QTc values of 414, 443, and 353 ms for the Fridericia, Hodges, and Framingham formulas, respectively.

Conclusions: The Bazett formula calculated the most consistent QTc; 460 ms is the best threshold for prolonged QTc. The study supports continued use of the Bazett formula for infants and children and differs from the use of the Fridericia correction during clinical trials of new medications.

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Conflict of interest statement

The authors declare no conflicts of interest.

Figures

Figure 1
Figure 1
Uncorrected QT-RR Scatter Plot of all subjects.
Figure 2
Figure 2
QTc-RR Scatter Plot of all subjects: (a) Bazett, (b) Fridericia, (c) Hodges, (d) Framingham formulas. A linear regression slope closer to zero indicates better QT correction across different heart rates (RR intervals).
Figure 3
Figure 3
Correlation coefficient between QTc and RR with various correction factor exponents. The correction factor exponent e in the formula QTc = QT/RRe is varied across the values of 0.3 – 0.6.
Figure 4
Figure 4
Two superimposed distribution curves comparing the QTc values computed by the Bazett vs Fridericia formulas. The X-axis denotes QTc values in msec. The vertical line represents the mean for each formula, and the shaded area under the curve represents values > 2SD, for each respective formula.
See this image and copyright information in PMC

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