Diagnostic accuracy of the 12-lead electrocardiogram in the first 48 hours of life for newborns of a parent with congenital long QT syndrome

Yalile Perez, Kathryn E. Tobert, Michaela J. Saunders, Katrina B. Sorensen, J. Martijn Bos, Michael J. Ackerman

Research output: Contribution to journalArticlepeer-review


Background: Long QT syndrome (LQTS) is an autosomal dominant disorder characterized by a prolonged QT interval. Electrocardiographic (ECG) screening in the first 48 hours of life may be misleading, even in newborns with a genotype-positive LQTS parent. Objective: The purpose of this study was to determine the ECG's diagnostic accuracy in the first 48 hours of life for neonates born to a parent with LQTS. Methods: We conducted a retrospective review of all neonates born at Mayo Clinic to a parent with ≥1 pathogenic variant in a LQTS-causative gene who had least 1 ECG in the first 48 hours and genetic test results were available. The sensitivity and specificity of the diagnostic ECG were calculated using Bazett's heart rate–corrected QT (QTc) thresholds of 440, 450, 460, and 470 ms. Results: Overall, 74 newborns (36 females [49%]) were included (mean QTc interval on the first ECG 489 ± 54 ms; 50 [68%] LQTS genotype-positive). The mean QTc interval in the first 48 hours for neonates that ultimately were genotype-positive was greater (506 ± 52 ms) than that for genotype-negative neonates (455 ± 41 ms) (P = .0004). When using a recommended threshold QTc interval of ≥440 ms, 6 of 50 genotype-positive neonates (12%) were missed (underdiagnosed) and 17 of 24 genotype-negative neonates (71%) were overdiagnosed (sensitivity 88%; specificity 29%). Conclusion: The newborn ECG should not be used in isolation to make the diagnosis of LQTS since it will result in many misclassifications. Genetic testing must be initiated before discharge, and proper anticipatory guidance is vital while awaiting test results.

Original languageEnglish (US)
Pages (from-to)969-974
Number of pages6
JournalHeart rhythm
Issue number6
StatePublished - Jun 2022


  • Bazett's heart rate–corrected QT (QTc) interval
  • Genetic testing
  • Long QT syndrome (LQTS)
  • Neonatal electrocardiogram
  • Sudden infant death syndrome (SIDS)

ASJC Scopus subject areas

  • Cardiology and Cardiovascular Medicine
  • Physiology (medical)


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