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For neonatal ECG screening there is no reason to relinquish old Bazett's correction
Marco Stramba-Badiale1, Dilip R Karnad2, Karine M Goulene1
1Pediatric Arrhythmias Center, IRCCS Istituto Auxologico Italiano, Via Ariosto 9, 20145 Milan, Italy.
Insights
The Bazett
Area of Science:
- Cardiology
- Neonatal Medicine
- Medical Diagnostics
Background:
- Screening for Long QT Syndrome (LQTS) in neonates involves controversial QT correction formulas.
- Accurate heart rate (HR) independent QT interval correction is crucial for reliable LQTS screening in newborns.
Purpose of the Study:
- To compare the performance of four common QT correction formulas and a novel neonate-specific formula for LQTS screening.
- To evaluate the heart rate independence and diagnostic accuracy of different QT correction methods in neonates.
Main Methods:
- Analyzed 5000 electrocardiograms (ECGs) from healthy neonates, including 17 with LQTS mutations.
- Compared Bazett's (QTcB), Fridericia's (QTcF), Framingham (QTcL), and Hodges (QTcH) formulas.
- Developed and validated a neonate-specific exponential correction (QTcNeo) using regression analysis for HR independence and ROC curves for diagnostic accuracy.
Main Results:
- QTcB demonstrated the most heart rate independent correction (slope +0.086 ms/b.p.m.), similar to QTcNeo.
- QTcB, QTcF, and QTcNeo showed comparable accuracy in identifying neonates with LQTS (sensitivity 100%).
- Recommended cut-off values were 460 ms for QTcB, 394 ms for QTcF, and 446 ms for QTcNeo.
Conclusions:
- Bazett's correction (QTcB) is effective for heart rate independent QT correction in neonates.
- QTcB accurately identifies neonates with LQTS and can be confidently used for screening.
- While QTcB is recommended, other formulas like QTcF and QTcNeo may also be used with specific cut-off values.
Aims:
There is an almost endless controversy regarding the choice of the QT correction formula to be used in electrocardiograms (ECG) in neonates for screening for long QT syndrome (LQTS). We compared the performance of four commonly used formulae and a new formula derived from neonates.
Methods And Results:
From a cohort of 44 596 healthy neonates prospectively studied in Italy between 2001 and 2006, 5000 ECGs including 17 with LQTS-causing mutation identified by genotyping were studied using four QT correction formulae [Bazett's (QTcB), Fridericia's (QTcF), Framingham (QTcL), and Hodges (QTcH)]. A neonate-specific exponential correction (QTcNeo) was derived using 2500 randomly selected ECGs and validated for accuracy in the remaining 2500 ECGs. Digital ECGs were recorded between the 15th and 25th day of life; QT interval was measured manually in leads II, V5, and V6. To assess the ability to provide heart rate (HR) independent QT correction, regression analysis of the QTc-HR plots for all 5000 ECGs with each correction formula was done. QTcB provided the most HR independent correction with a slope closest to zero (slope +0.086 ms/b.p.m.) followed by QTcF (slope -0.308 ms/b.p.m.), QTcL (slope -0.364 ms/b.p.m.), and QTcH (slope +0.962 ms/b.p.m.). The QTc-HR slope of QTcNeo (QT/RR0.467) was similar to QTcB. The ability to correctly identify neonates with LQTS was best with QTcB, QTcF, and QTcNeo (comparable areas under the receiver operating characteristic curves) with positive predictive value of 39-40% and sensitivity of 100%. Cut-off values were 460 ms for QTcB, 394 ms for QTcF, and 446 ms for QTcNeo.
Conclusions:
The Bazett's correction provides an effective HR independent QT correction and also accurately identifies the neonates affected by LQTS. It can be used with confidence in neonates, although other methods could also be used with appropriate cut-offs.
