Comparison of Formulas for Calculation of the Corrected QT Interval inInfants and Young Children
Derek Q. Phan, Michael J. Silka, Yueh-Tze Lan, Ruey-Kang R. Chang
DOI:
http://dx.doi.org/10.1016/j.jpeds.2014.12.037 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%) prolonged QTc values of 414, 443, and 353ms for the Fridericia, Hodges, and Framingham formulas, respectively.
Conclusions
The Bazett formula calculated the most consistent QTc; 460ms 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.
