For neonatal ECG screening there is no reason to relinquish old Bazett’s correction

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.