The Neonatal QRS Complex and Its Association with Left Ventricular Mass.

To evaluate QRS complex features during the first month of life and the association with echocardiographic measurements of left ventricular mass in neonates. Prospective cohort study of neonates with electrocardiography (ECG) and echocardiography performed during the first month of life. Left ventricular mass index (LVMI) was determined by echocardiography and the correlation with electrocardiographic markers of LVMI outliers (≥ 98th percentile) were analyzed. We included 17,450 neonates (52% boys; median age at examination 11 days) and found an increase in median QRS duration and LVMI during the first month of life (54 vs. 56 ms and 24.7 vs. 28.6 g/m2 at days 0-4 and 25-30, respectively; both p < 0.001). All investigated ECG features (QRS duration, QRS area in V1/V6, maximum amplitudes of S-V1/R-V6, and the Sokolow-Lyon voltage product) showed no to low correlation with LVMI, resulting in low sensitivities (0-9.0%), but high specificities (97.2-98.1%), and area under the curve values close to the identity line (0.49-0.61) for identifying LVMI outliers. Adjustment of outlier definition for LVMI and threshold for QRS features had no significant effect on sensitivity. We present reference values for QRS complex features and their association with LVMI in neonates from a large, unselected, population-based cohort. The QRS complex gradually evolved during the first month of life but had a low correlation with LVMI. Our results indicate a poor diagnostic value of using ECG features to identify LVMI outliers in neonates.Trial Registry Copenhagen Baby Heart, NCT02753348, https://clinicaltri-als.gov/ct2/show/NCT02753348?cond=Copenhagen+Baby+Heart&draw=2&rank=1 , deidentified individual participant data will not be made available.

Cardiac findings in newborn twins.

AIMS: To evaluate cardiac findings in newborn twins from the general population and investigate if newborn twins may require systematic evaluation of cardiac parameters. METHODS: Prospective cohort study of newborns with cardiac evaluation performed during the first month of life. Cardiac findings were compared 1:3 with matched singletons. RESULTS: We included 412 newborn twins (16% monochorionic; 50% boys) and 1236 singletons. Comparing cardiac findings showed twins had an increased prevalence of non-severe structural heart disease (most common: ventricular septal defects in both groups), thinner left ventricular posterior wall in diastole (LVPWd; 1.82 vs. 1.87 mm, p = 0.02), smaller diameter of the left atrium (10.6 vs. 11.1 mm, p = 0.04), higher heart rate (148 vs. 144 bpm, p = 0.04), more left-shifted QRS axis (106 vs. 111°, p < 0.001), and lower maximum R-wave amplitude in V1 (927 vs. 1015 µV, p = 0.02) compared to singletons. After multifactorial adjustment for potential confounders, the effect of twinning on cardiac parameters persisted only for LVPWd (p < 0.05). CONCLUSION: Despite contemporary surveillance, we found an increased prevalence of non-severe structural heart disease in a population-based cohort of newborn twins. However, the effect of twinning on cardiac parameters was modest and generally did not persist after correction for likely confounding factors.

The Impact of Maternal and Perinatal Factors on the Neonatal Electrocardiogram.

INTRODUCTION: Myocardial development is still transitioning by the time of birth making the cardiomyocyte vulnerable to maternal and perinatal factors. We aimed at investigating the impact of maternal and perinatal factors on the neonatal electrocardiogram. METHODS: In a prospective cohort study, neonates underwent cardiac evaluation with electrocardiograms and echocardiograms (age 0-30 days). Associations between medical and demographic data, pregnancy, and birth-related factors, and electrocardiographic parameters were assessed. RESULTS: A total of 15,928 singletons with normal echocardiograms were included (52% boys). Neonates were divided into groups by accumulated number of maternal/perinatal factors: 0, 1, 2, 3, 4, and ≥5, and between-group differences in electrocardiographic parameters were analysed. We observed an additive effect with a leftward shift of the QRS axis and QT prolongation (all p < 0.01). Comparing extreme groups (0 vs. ≥5 maternal/perinatal factors), we found a 4.3% more left-shifted QRS axis (117 vs. 112°, p < 0.001) and a 0.8% prolonged QTcFridericia (QTcF; 363 vs. 366 ms, p < 0.001); the effect on QTcF was most pronounced in neonates examined in the first week of life (360 vs. 368 ms, p < 0.0001). CONCLUSION: We observed a cumulative effect of maternal and perinatal factors on neonatal electrocardiographic parameters, including a more left-shifted QRS axis and increased QT duration, although the variation was within normal reference ranges. Our findings add to the knowledge on the neonatal cardiac transition and the cardiac effect of maternal/perinatal factors.