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.

Electrocardiographic Characteristics in 438 Neonates with Atrial Septal Defects.

Arrhythmias and electrocardiographic (ECG) abnormalities are common among patients with atrial septal defects (ASDs). We studied a large cohort of neonates with ASDs to investigate whether ECG abnormalities are present at this early stage or develop later, secondary to hemodynamic changes. We analyzed the echocardiograms and ECGs from the Copenhagen Baby Heart Study, a population-based cohort study. We compared ECG characteristics of 438 neonates with secundum ASDs to 1314 matched controls. In subgroup analyses, we investigated whether electrocardiographic characteristics were associated with age at examination. Neonates with ASDs (median age, 11 days; males, 51%) had longer P-wave durations (58 vs. 56 ms, p < 0.001), PR intervals (100 vs. 96 ms, p < 0.001), and a more rightward-shifted QRS axis (116 vs. 114 degrees, p = 0.032) compared to controls (median age, 10 days; males, 51%). There were no differences between cases and controls in the P-wave area, amplitude, or axis. Subgroup analyses showed that the differences in P-wave duration and PR interval were present in neonates examined in the first week after birth. The difference in the QRS axis was not found in neonates examined this early but was found in neonates examined at age two to four weeks. In conclusion, ASDs are associated with ECG changes from the neonatal phase. The P-wave duration and PR interval are longer in neonates with ASDs when compared to controls as early as the first week after birth, indicating that these changes are not purely secondary, but that neonates with an ASD have altered cardiac electrical activity.ClinicalTrials.gov Identifier NCT02753348 (April 27, 2016).

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.

Electrocardiographic characteristics of newborns with ventricular septal defects: a Copenhagen Baby Heart Study.

Ventricular septal defects (VSD) represent the most common congenital heart defect in newborns. We assessed the electrocardiographic characteristics of newborns with VSDs in a general population sample. The Copenhagen Baby Heart Study is a prospective population-based cohort study offering cardiac evaluation of newborns. Echocardiograms and electrocardiograms were obtained within 30 days after birth and systematically analysed. A VSD was identified in 530 newborns (mean age 11 ± 7 days, 42% boys). Newborns with VSDs had a more left-shifted QRS axis (116 ± 34 vs. 120 ± 3°, p = 0.02), and a higher S-wave amplitude in V1 (721 ± 584 vs. 636 ± 549 µV, p = 0.001) than controls. The largest differences were found in newborns with large or perimembraneous VSDs with a higher frequency of left axis deviation, higher S-wave amplitudes in V1, and higher R- and S-wave amplitudes in V6 compared with controls. R-waves in V1 and V6 were significantly associated to left ventricular mass, whereas S-waves in V1 and V6 were dependent on left ventricular end-diastolic diameter on echocardiography.  Conclusion: Newborns with VSDs showed significant differences in QRS axis, and R- and S-wave precordial amplitudes compared to matched controls. Perimembranous and large VSDs had the greatest effect on the neonatal ECG. What is Known: • Ventricular septal defects in newborns are prevalent and may affect cardiac function and structure. What is New: • The Copenhagen Baby Heart Study is the largest study including a cohort of unselected newborns undergoing postnatal cardiac examination. • We found that newborns with VSD showed significant electrocardiographic differences depending on size and type of VSD compared with healthy newborns.

The Wolff-Parkinson-White pattern in neonates: results from a large population-based cohort study.

AIMS: Wolff-Parkinson-White (WPW) syndrome is a conduction disorder characterized by an accessory electrical pathway between the atria and ventricles, which may predispose to supraventricular tachycardia (SVT) and sudden cardiac death. It can be seen as an isolated finding or associated with structural heart disease. Our aims were to determine the prevalence of a WPW pattern in a large and unselected cohort of neonates and to describe the electro- and echocardiographic characteristics as well as the natural history during early childhood. METHODS AND RESULTS: Electrocardiograms and echocardiograms of neonates (aged 0-30 days) from a large, prospective, population-based cohort study were included. Neonates with a WPW pattern were identified and matched 1:4 to controls. Localization of the accessory pathway was assessed by different algorithms. Among 17 489 neonates, we identified 17 (76% boys) with a WPW pattern consistent with a prevalence of 0.1%. One neonate had moderate mitral regurgitation while other echocardiographic parameters were similar between cases and controls (all P > 0.05). The accessory pathways were primarily predicted to be left-sided. At follow-up (available in 14/17 children; mean age 3.2 years) the pre-excitation pattern persisted in only four of the children and none of the children had experienced any episodes of SVT. CONCLUSION: The prevalence of a WPW pattern in our cohort of unselected neonates was 0.1%. The WPW pattern was more frequent in boys and generally not associated with structural heart disease, and the accessory pathways were primarily left-sided. At follow-up, the WPW pattern had disappeared in most of the children suggesting either an intermittent nature or that normalization occurs. CLINICAL TRIAL REGISTRATION: Copenhagen Baby Heart, NCT02753348.

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 Age on the Neonatal Electrocardiogram.

BACKGROUND: Previous studies have suggested an increased prevalence of congenital heart disease among children born to women aged ≥35 years. In recent decades, the mother's age at childbirth has increased dramatically in industrialized countries. It has not been investigated if increasing maternal age affects the neonatal cardiac electrical system. METHODS: The Copenhagen Baby Heart Study is a prospective general population study that performed cardiac evaluation in newborns. Electrocardiograms were analyzed with a computerized algorithm. RESULTS: We included 16,518 newborns with normal echocardiograms (median age 11 days; range 0-30 days; 52% boys). Median maternal age at delivery was 31 years; 790 newborns were born to mothers aged between 16 and 24 years, 11,403 between 25 and 34 years, 4,279 between 35 and 44 years, and 46 newborns had mothers aged between 45 and 54 years. The QRS axis and maximum R-wave amplitude in V1 (R-V1) differed across the four maternal age groups (both p < 0.01), with absolute differences of 3.5% (114 vs. 110°) and 12% (1,152 vs. 1,015 µV), respectively, between newborns with the youngest and oldest mothers. Associations between maternal age and the QRS axis and R-V1 remained significant after multifactorial adjustment. Heart rate, PR interval, QRS duration, uncorrected QT interval, QTcBazett, and maximum amplitudes of S-V1, R-V6, and S-V6 were not associated with maternal age (all p > 0.05). CONCLUSION: We observed a significant association between maternal age and the neonatal QRS axis and R-V1. However, the absolute differences were relatively small and maternal age is unlikely to have a clinically significant effect on the neonatal cardiac electrical system.

Gestational Age and Neonatal Electrocardiograms.

OBJECTIVES: Interpretation of the neonatal electrocardiogram (ECG) is challenging due to the profound changes of the cardiovascular system in this period. We aimed to investigate the impact of gestational age (GA) on the neonatal ECG and create GA-specific reference values. METHODS: The Copenhagen Baby Heart Study is a prospective general population study that offered cardiac evaluation of neonates. ECGs and echocardiograms were obtained and systematically analyzed. GA, weight, height, and other baseline variables were registered. RESULTS: We included 16 462 neonates (52% boys) with normal echocardiograms. The median postnatal age was 11 days (range 0 to 30), and the median GA was 281 days (range 238 to 301). Analyzing the ECG parameters as a function of GA, we found an effect of GA on almost all investigated ECG parameters. The largest percentual effect of GA was on heart rate (HR; 147 vs 139 beats per minute), the QRS axis (103° vs 116°), and maximum R-wave amplitude in V1 (R-V1; 0.97 vs 1.19 mV) for GA ≤35 vs ≥42 weeks, respectively. Boys had longer PR and QRS intervals and a more right-shifted QRS axis within multiple GA intervals (all P < .01). The effect of GA generally persisted after multifactorial adjustment. CONCLUSIONS: GA was associated with significant differences in multiple neonatal ECG parameters. The association generally persisted after multifactorial adjustment, indicating a direct effect of GA on the developing neonatal cardiac conduction system. For HR, the QRS axis, and R-V1, the use of GA-specific reference values may optimize clinical handling of neonates.

The Evolution of the Neonatal QRS Axis during the First Four Weeks of Life.

BACKGROUND: The QRS axis represents the sum and orientation of the ventricular depolarization. Accurate interpretation of abnormalities in the QRS axis may facilitate early diagnosis of heart disease in newborns. We aimed at describing the evolution of the QRS axis during the first 4 weeks of life and provide reference values from healthy newborns. METHODS: The Copenhagen Baby Heart Study is a prospective general population study that offered cardiac evaluation during the first month of life to all newborns delivered in the Copenhagen area. RESULTS: Electrocardiograms from 12,317 newborns (52% boys; mean age 12 days) with normal echocardiograms were included. The median QRS axis was 119° at the ages 0-7 days and shifted leftward to 102° at the ages 22-28 days (p < 0.001). We found that girls had a significantly less pronounced right-shifted axis than boys (p < 0.001) and that increasing gestational age (GA) was associated with a more pronounced right-shifted axis (p < 0.05). Infant size did not affect the axis (p > 0.05). Only 0.5% had an axis within the interval 0 to -90° and 1.1% in the interval +240 to +30°. CONCLUSIONS: The QRS axis showed a gradual leftward-shift during the first 4 weeks of life and was affected by sex and GA but unaffected by infant size. Less than 1% of the newborns had a QRS axis between 0 and -90°. This study represents updated reference values, which may facilitate the clinical handling of newborns.

Precordial ECG Amplitudes in the Days After Birth: Electrocardiographic Changes During Transition from Fetal to Neonatal Circulation.

During the first month of life, the relation between right and left ventricular function is markedly altered. We aimed at describing the electrocardiographic transition from fetal to neonatal circulation by investigating changes in R- and S-wave amplitudes in V1 and V6 during the first 4 weeks of life. This study is part of the prospective, population-based Copenhagen Baby Heart Study offering cardiac evaluation to newborns within 28 days from birth. ECGs were obtained and analyzed using a computerized algorithm. A total of 14,577 newborns (52% boys), median age of 11.0 days, were included. All had normal echocardiograms. Within 28 days from birth, the amplitudes in V1 decreased: R-V1 (1262 µV day0; 947 µV day28, p < 0.001) and S-V1 (1240 µV day0; 473 µV day28, p < 0.001). An increase was observed for R-V6 (825 µV day0; 1196 µV day28, p = 0.002), while S-V6 decreased (830 µV day0; 634 µV day28, p = 0.003). For all amplitudes, interindividual variation was large (up to 20 times). The amplitudes were not affected by sex (p > 0.05), but R-V1, R-V6, and S-V6 positively correlated with newborn weight (p < 0.01). R-V1 and S-V6 showed positive correlation with gestational age (p < 0.05). In conclusion, systematic analyses of ECGs from healthy newborns showed significant decreases in R-V1, S-V1, and S-V6 amplitudes, while R-V6 increased. Interindividual variation was large, making ECGs unlikely as a sensitive tool for diagnosing congenital heart diseases. Our data may serve as updated, digitalized reference values in newborns.

Defining the normal QT interval in newborns: the natural history and reference values for the first 4 weeks of life.

AIMS: Evaluation of the neonatal QT interval is important to diagnose arrhythmia syndromes and evaluate side effects of drugs. We aimed at describing the natural history of the QT interval duration during the first 4 weeks of life and to provide reference values from a large general population sample. METHODS AND RESULTS: The Copenhagen Baby Heart Study is a prospective general population study that offered cardiac evaluation of newborns. Eight-lead electrocardiograms were obtained and analysed with a computerized algorithm with manual validation. We included 14 164 newborns (52% boys), aged 0-28 days, with normal echocardiograms. The median values (ms, 2-98%ile) for the corrected intervals QTc (Bazett), QTc (Hodges), QTc (Fridericia), and QTc (Framingham) were 419 (373-474), 419 (373-472), 364 (320-414), and 363 (327-405). During the 4 weeks, we observed a small decrease of QTcFramingham, and an increase of QTcHodges (both P < 0.01), while QTcBazett and QTcFridericia did not change (P > 0.05). Applying published QT interval cut-off values resulted in 5-25% of the newborns having QT prolongation. Uncorrected QT intervals decreased linearly with increasing heart rate (HR). Sex and infant size did not affect the QT interval and the gestational age (GA) only showed an effect when comparing the extreme low- vs. high GA groups (≤34 vs. ≥42 weeks, P = 0.021). CONCLUSION: During the 4 weeks QTcFramingham and QTcHodges showed minor changes, whereas QTcBazett and QTcFridericia were stable. The QT interval was unaffected by sex and infant size and GA only showed an effect in very premature newborns. Reference values for HR-specific uncorrected QT intervals may facilitate a more accurate diagnosis of newborns with abnormal QT intervals.