Heart-Rate-Corrected QT Interval Evolution in Premature Infants During the First Week of Life

Abstract

Automated monitoring of the QT interval is increasingly common in a variety of clinical settings. A better understanding of how the heart-rate-corrected QT interval (QTc) evolves in early postnatal life is needed before its clinical utility in neonates can be determined. This study aimed to use real-time bedside monitoring as a tool to describe the QTc evolution of premature neonates during the first week of life. All neonates born at a gestation age (GA) of 31 weeks or later and admitted to the level 2 intensive care nursery of the authors' institution between December 2012 and March 2013 were included in this study. The authors prospectively collected QTc values at 15-min intervals during the first week of life, then used two-way analysis of variance (ANOVA) to compare these data among three GA cohorts: 31 to <34 weeks (cohort A), 34 to <37 weeks (cohort B), and ≥37 weeks (cohort C). All the cohorts demonstrated a statistically significant decline in the 24-h average QTc during the first 3-4 days of life before reaching a stable baseline. No diurnal variation in the QTc was identified in any of the study patients. Marked variability and a progressive decline in the QTc of premature neonates occur during the first 3-4 days of life. Understanding this phenomenon is imperative when screening programs for the early detection of QT prolongation are considered.

Evaluation of the autonomic nervous system by analysis of heart rate variability in the preterm infants

“…A study enrolling newborn preterm infants found that HRV is progressively present in the first 3 to 4 days of life and forms a stable base after this period; the study further demonstrated that there is a reduction in ANS modulation at the onset of preterm infant life [18]. With the inadequate functioning of the SNA, the organism tends towards linearity, with the expected changes and adaptations not occurring.…”

Universal Electrocardiographic Screening for Long QT Syndrome in Hospitalized Neonates

“…We previously studied the same QTc "data sniffer" and patient population and found that neonatal QTc is highly variable during the first 3 to 4 days of life and undergoes a gradual decline toward lower and more stable values among all age groups. 16 Using standard means and SDs from that study, we determined a cutoff (>475 ms after day of life three) that would capture those infants most at a risk of QTc prolongation on 12-lead ECG and selected those infants for more "traditional" ECG screening.…”

“…A threshold of 475 ms was chosen as this represented >2 standard deviation (SD) during a previous population-based pilot study performed in the same unit. 16 When QTc prolongation was detected, the DS triggered an automated page and e-mail to the on-call neonatologist covering the level II NICU.…”

“…As bedside monitors now allow for the continuous measurement of the QTc at bedside, 13,14 we have previously used this technology to demonstrate alterations in the QTc interval with changes in positioning and to model QTc maturation in premature infants. 15,16 While others have shown in adults that continuous electronic QTc measurement has an acceptable correlation with manual measurement from a single 12-lead ECG, 17 the efficacy of continuous QTc monitoring to screen for QTc interval prolongation in hospitalized neonates is unknown.…”

Use and safety of azithromycin in neonates: a systematic review

“… 43 Prolonged QT c interval can be normal in the first few days of life in premature neonates, hence it is difficult to identify drug-induced aetiology during this period. 44 …”