Evaluation of infants born to a parent with gene-positive long QT syndrome: a retrospective single-centre review.

Objective: To describe early management of infants born to a parent with gene-positive long QT syndrome (LQTS) referred for specialist review. Review the diagnostic utility of the early neonatal and first clinic ECG.

Design: Retrospective cohort study, including a review of the first neonatal and first clinic ECG.

Setting: Quaternary paediatric-only referral hospital with specialised unit for the management of paediatric inherited cardiovascular diseases.

Patients: Infants born 2015-2022 referred in the setting of parental LQTS who subsequently underwent predictive genetic testing for a parental LQTS-causative genetic variant.

Main outcome measures: Age (at first early neonatal ECG, referral, first clinic attendance), genetic testing data, clinical course, exposure to QT-prolonging medications, neonatal hypoxia-ischaemia and cardiac events (cardiac arrest or death) in the infant's first year.The first neonatal and first clinic ECGs were evaluated for QTc and T-wave morphology, by two observers.

Results: Twenty-six infants met inclusion criteria. Eighteen (69%) were referred in the first month of life. Twelve (46%) inherited the familial LQTS variant. Fourteen (54%) commenced beta-blocker therapy to treat suspected or genetically confirmed LQTS, two subsequently ceased treatment due to a negative genetic result. There were no cardiac events. For the ECG analysis, 40 ECGs from 26 infants were reviewed (early neonatal n=14 (54%)). The first clinic ECG allowed more accurate determination of genetic status with better interobserver variability. Inclusion of T-wave morphology assessment improved its sensitivity.

Conclusions: Streamlined pathways to manage families with LQTS across institutions need to be firmly established to permit a timely diagnosis. Incorporation of formalised T-wave morphology assessment adds value.