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Enhanced Demographically Adaptive QT Correction Improves Pediatric Screening for Congenital Long QT Syndrome
Kazi T Haq1, Charles I Berul2,3, Nikki Gillum Posnack1,3,4
1Sheikh Zayed Institute for Pediatric Surgical Innovation, Children's National Hospital, Washington, DC.
Insights
A new adaptive QTc (QTcAd) formula improves congenital long QT syndrome (LQTS) detection in children. This optimized formula enhances diagnostic accuracy and reduces unnecessary repeat ECGs, aiding in earlier and more reliable LQTS screening.
Area of Science:
- Pediatric Cardiology
- Electrocardiography
- Genetics
Background:
- Traditional heart rate (HR)-corrected QT interval (QTc) formulas struggle with the inverse HR-QT relationship in pediatric patients.
- Previous adaptive QTc (QTcAd) formulas require optimization for broader pediatric age ranges and demographic variables.
- Congenital long QT syndrome (LQTS) diagnosis in children is challenging due to limitations in existing QTc correction methods.
Purpose of the Study:
- To optimize the adaptive QTc (QTcAd) formula by incorporating additional demographic data and expanding the pediatric age range.
- To test the hypothesis that the enhanced QTcAd formula improves congenital LQTS detection and reduces misclassifications in pediatric cohorts.
- To develop age-adjusted dynamic thresholds for QTcAd to aid in congenital LQTS screening.
Main Methods:
- Retrospective analysis of 8,306 ECGs from 4,556 cardiovascular disease-free pediatric patients.
- Derivation of daily QTcAd parameters for neonates and development of regression models for older children.
- Validation of QTcAd diagnostic performance in confirmed LQTS, Pediatric Heart Network, and Emergency Department cohorts.
Main Results:
- QTcAd demonstrated significantly higher sensitivity (92%) compared to QTcB (46.7%) in confirmed LQTS cases.
- QTcAd maintained high specificity (96.9%) and a superior Youden index (0.889 vs 0.456).
- QTcAd reduced borderline/prolonged QTc classifications in the Emergency Department cohort, leading to 270 fewer repeat-testing triggers than QTcB.
Conclusions:
- The developed and validated QTcAd formula offers enhanced performance for pediatric congenital LQTS screening.
- Age-adjusted dynamic thresholding with QTcAd improves diagnostic accuracy while maintaining high specificity.
- QTcAd reduces false-positive LQTS classifications and repeat ECGs, minimizing unnecessary clinical evaluations.
Background:
Traditional heart rate (HR) adjusted QT correction (QTc) formulae often fail to eliminate the inverse HR-QT interval relationship, particularly in pediatric patients. In this study, we optimized our previously published adaptive QTc (QTcAd) formula by including additional demographic variables and broadening the pediatric age range. We tested the hypothesis that QTcAd improves congenital long QT syndrome (congenital LQTS) detection performance and reduces erroneous classifications across pediatric cohorts.
Methods:
We retrospectively analyzed 8,306 ECGs from 4,556 cardiovascular disease (CVD)-free pediatric patients. For neonatal patients (1-30 days old), we derived daily QTcAd parameter values. For older patients, we developed regression models to estimate QTcAd parameters (mean Heart Rate (HR) = -15.9ln(days) + 219; , where HR-QT regression slope). To support LQTS screening, we constructed dynamic QTcAd thresholds by estimating age-specific reference limits. Diagnostic performance was tested in a clinically confirmed LQTS cohort (n=137), and further evaluated in the Pediatric Heart Network (PHN; n=2,394) and Emergency Department (ED; n=2,002) cohorts.
Results:
Using the confirmed LQTS cohort as the event population and the CVD-free cohort as the non-event population, QTcAd demonstrated higher sensitivity than QTcB (92% vs 46.7%). QTcAd maintained high specificity (96.9% vs 98.9%), which resulted in a higher Youden index (0.889 vs 0.456). In the PHN healthy cohort, both QTc formulae classified the majority of individuals as normal (QTcAd 95%; QTcB 98.2%) indicating few false-positives. In the ED cohort, QTcAd reduced borderline/prolonged QTc classifications requiring follow-up, yielding 270 fewer repeat-testing triggers than QTcB. We developed a publicly accessible calculator to compute QTcAd and classify congenital LQTS risk.
Conclusion:
We developed and validated an enhanced QTcAd formula for pediatric patients. QTcAd-based-age-adjusted dynamic thresholding improved performance for congenital LQTS screening, while maintaining high specificity. This reduces false-positive LQTS classifications and repeat ECGs, thereby decreasing unnecessary downstream clinical evaluation.
