Ulrich, Timothy J.

Objective Long QT syndrome (LQTS) is a known cause of unexpected death, leading some to recommend routine neonatal electrocardiographic (ECG) screening. We used continuous electronic heart rate corrected QT interval (QTc) monitoring to screen for interval prolongation in a cohort of hospitalized neonates to identify those at a risk of having LQTS. We hypothesized that this screening method would yield an acceptable positive predictive value (PPV). Study Design A cohort of 589 infants hospitalized in a level II neonatal intensive care unit were screened through continuous electronic QTc monitoring linked to an investigator-designed, computerized data sniffer. Screening was conducted from days-of-life 3 through 7 or until hospital discharge. The data sniffer alerted investigators for a 24-hour average QTc of ≥475 ms. Positively screened patients were further evaluated with 12-lead ECG. Results Positive screens were obtained in 5.6% of patients, all of whom had negative follow-up ECG testing (PPV = 0%). Furthermore, one-quarter of positively screened neonates underwent echocardiography based on ECG findings, none of which identified clinically relevant pathology. Conclusion Electronic monitoring of QTc in hospitalized neonates during the first week of life was not an efficient way to identify those at a risk of having LQTS. Conversely, screening triggered unnecessary testing.

For more than a decade there has been considerable interest in the role of QT interval prolongation in the pathogenesis of sudden infant death syndrome. It has been proposed that the QT interval is a surrogate marker for autonomic instability and can be used to identify infants at risk for significant morbidity and mortality, including sudden infant death syndrome. We present the case of an infant that experienced a significant increase in his QTc, as detected by continuous QTc monitoring in the NICU after repositioning from a supine to prone position. This increase from a 413 ± 6 millisecond baseline average to 500 milliseconds was sustained for 2 hours and associated with clinically relevant apnea that ultimately required repositioning of the infant back to the supine position. Repositioning resulted in an immediate decrease of the QTc back to the previous baseline and termination of the apneic events. This case demonstrates an example of how the use of continuous QTc monitoring in the NICU setting may be used to detect QTc-accentuating factors in real time and identify situations that cause perturbations in an infant’s autonomic nervous system.