Interobserver agreement and image quality of functional cardiac ultrasound measures used in a randomised trial of delayed cord clamping in preterm infants

Inter-observer variability of right ventricular output measurement in newborn infants: an observational study

Neonatologist Performed Echocardiography (NPE) is one of the emerging technologies used to evaluate Systemic Blood Flow (SBF) in term and preterm infants. Right Ventricular Output (RVO) can assess SBF correctly in the absence of significant interatrial or interventricular shunts, even in the presence of a large patent ductus arteriosus (PDA), but only few studies evaluated inter-observer variability in neonates. Furthermore, measuring pulmonary peak flow (PF) provides a simple screening tool for low SBF state, easier and faster to perform than RVO; no previous studies evaluated PF inter-observer variability. To describe inter-observer variability of RVO and PF measurement in neonates. We conducted a prospective observational study in term and preterm infants admitted to the Neonatal Intensive Care Unit (NICU). Echocardiographic examinations were performed by two expert neonatologists, blinded to each other. Recordings were analyzed off-line to assess RVO and PF variability between observers. We analyzed a cohort of 33 neonates, 17 of them born prematurely. Inter-observer mean difference for RVO was 22,1 mL/kg/min (p = 0.005); the biggest discrepancy was due to pulmonary valve diameter measurement (p = 0.0001). Inter-observer mean difference for PF measurement was not statistically significant. We found a statistically significant inter-observer variability for RVO measurement, consistent with previous reports; PF instead showed low inter-observer variability. For this reason, PF could be evaluated in future studies as a surrogate for RVO in both term and preterm infants, especially in emergency conditions or in presence of a poor echocardiographic window.

The Predictive Value of Lung Ultrasound Score on Hemodynamically Significant Patent Ductus Arteriosus among Neonates ≤25 Weeks

Lung ultrasound (LU) is increasingly used to diagnose and monitor neonatal pulmonary disorders; however, its role in hemodynamically significant patent ductus arteriosus (hsPDA) has not been elucidated. This prospective study investigated the predictive value of the LU score (LUS) for hsPDA in preterm infants with gestational age (GA) ≤ 25 weeks. Preterm infants with GA ≤ 25 weeks were enrolled in this study. LU was conducted on the fourth day of life (DOL). Six lung regions in every lung were scanned, with each region rated as 0-4 points. The performance of the LUS in predicting hsPDA among infants aged ≤25 weeks was analyzed by plotting the receiver operating characteristic (ROC) curve. A total of 81 infants were included in this study. GA, birth weight (BW), gender, Apgar score, delivery mode, antenatal steroids, meconium-stained amniotic fluid, premature rapture of membrane, and early-onset sepsis were not significantly different, but infants in the hsPDA group had increased LUS (38.2 ± 2.8 vs. 30.3 ± 4.3, p < 0.001) compared with non-hsPDA group. The area under the ROC curve (AUC) value of the LUS on the fourth DOL was 0.94 (95% CI: 0.93-0.99) in predicting hsPDA. The LUS threshold at 33 achieved 89% sensitivity and 83% specificity, with the positive and negative predictive values (PPV and NPV) being 87 and 86%, respectively. The LUS can predict hsPDA in extremely preterm infants at an early stage.

Impact of Aortic Diameter Measurements at Three Anatomical Landmarks on Left Ventricular Output Calculation in Neonates

OBJECTIVES

To assess reproducibility and accuracy of left ventricular output (LVO) quantifications in neonates, when left ventricular outflow tract diameter (LVOTD) was measured at the hinges of the aortic valve (AV), at the aortic sinus (AS), and at the sinotubular junction (STJ).

METHODS

This was an observational study. In the first cohort of very preterm neonates, we assessed intraobserver and interobserver repeatability of LVOTD measured at the AV, AS, and STJ and of the corresponding LVO. In the second cohort of older neonates, we compared paired LVO measurements by echo and magnetic resonance imaging (MRI).

RESULTS

In the first cohort of 48 neonates, mean (standard deviation) weight and age at scan were 1046 (302) g and 28.1 (2.7) weeks. Interobserver bias (95% limits of agreement [LOA]) for LVOTD at the AV, AS, and STJ was 0 (-0.3 to 0.3) mm, 0 (-0.7 to 0.7) mm, and 0 (-0.8 to 0.7) mm, respectively. Interobserver bias (95% LOA) for the corresponding LVO was -1.3 (-31 to 33) ml/kg/min, -0.5 (-88 to 87) ml/kg/min, and -7.2 (-83 to 69) ml/kg/min, respectively. In the second cohort of 10 neonates, median (range) weight and age at scan were 1942 (970-3640) g and 37.2 (31.7-39.8) weeks. LVO measured at the AV showed stronger agreement with MRI: bias (LOA) -10.6 (-74 to 52) ml/kg/min, compared to LVO measured at AS and STJ: 194 (-0.5 to 388) ml/kg/min and 43 (-72 to 159) ml/kg/min respectively.

CONCLUSIONS

Reproducibility and accuracy of LVO quantification by echo were better when aortic diameter was measured at AV.

Mitral valve Doppler for cardiac output assessment in preterm neonates

INTRODUCTION

Cardiac output (CO) assessment in neonates is commonly done by echocardiography. It is unclear which is the best site to measure the left ventricular (LV) outflow tract for CO assessment (the aortic valve [AV] aortic sinus [AS] or the sinotubular junction [STJ]). In the normal heart, the blood flow entering the LV equals the blood ejected from it. Therefore, measuring the blood flow into the LV through the mitral valve (MV) is an alternative way to measure CO.

METHODS

In stable preterm infants the MV CO was compared with the right ventricular (RV) CO and the three ways to measure LV CO, in 30 stable preterm neonates. Interobserver variability for MV CO was established.

RESULTS

In the 30 neonates studied, MV CO was best correlated and had a minimal bias to the RV CO and LV CO measured at the STJ. Left ventricular CO measured at the AV and AS had significant bias relative to RV CO and MV CO. MV CO inter-observer variability was similar to other echocardiographic CO assessment methods.

CONCLUSION

MV CO may be used as an alternative way to assess CO. The STJ may be the optimal site to measure LV outflow tract.

Assessing patent ductus arteriosus in preterm infants from standard neonatal intensive care monitoring

Monitoring patent ductus arteriosus (PDA) in premature infants is currently performed intermittently using echocardiography which requires considerable expertise. The aim of this pilot study was to investigate whether PDA status could be assessed from standard neonatal intensive care monitoring. Electrocardiography (ECG) and blood pressure (BP) waveforms were acquired from extremely preterm infants using standard neonatal monitors. We developed software using MATLAB to analyse ECG and BP waveforms and their interrelationships in terms of pulse transit time (PTT) and pulse wave velocity (PWV). The times from peak systolic BP to diastolic trough (BPFt) and from the diastolic trough to peak systolic BP (BPRt) were also calculated. PTT, BPFt and BPRt were normalised for heart rate (HR) termed NPTT, NBPFt and NBPRt, respectively. ECG, invasive aortic BP monitoring and echocardiography were performed in 14 preterm infants < 29 weeks' gestation in the first 3 days after birth. The median (range) birth weight of the infants was 0.90 (0.48-1.31) kg, gestation 26.6 (24.0-28.7) weeks, PDA diameter 1.6 (0.8-3.6) mm and mean BP 32 (16-40) mmHg. We found a significant positive correlation between PDA diameter and NPTT (r = 0.69, P = 0.007) as well as NBPFt (r = 0.65, P = 0.012) and NBPRt (r = 0.71, P = 0.005). No relationship was found between PDA diameter and pulse pressure.Conclusions: Interrelationships between ECG and BP traces as well as BP waveform time analysis are straightforward to measure and associated with PDA diameter. The results of this pilot study suggest that this approach may help provide biomarkers for continuous monitoring PDA diameter and function. What is Known: • Patent ductus arteriosus (PDA) in premature infants is associated with increased risk of developing chronic lung disease, necrotising enterocolitis and cerebral injury. • Currently PDA is assessed intermittently using echocardiography which requires considerable expertise and sometimes is not well tolerated by critically ill preterm infants. What is New: • Blood pressure (BP) and ECG waveform interrelation and BP trace time analysis, taking account of heart rate, relate to PDA diameter. • ECG and BP waveform phase difference as well as BP waveform time analysis may be useful in the continuous assessment of PDA function.

Antenatal and perinatal factors influencing neonatal blood pressure: a systematic review

OBJECTIVE

A comprehensive understanding of the factors contributing to perinatal blood pressure is vital to ensure optimal postnatal hemodynamic support. The objective of this study was to review existing literature on maternal and perinatal factors influencing blood pressure in neonates up to 3 months corrected age.

METHODS

A systematic search of published literature in OVID Medline, OVID Embase and the COCHRANE library identified publications relating to maternal factors affecting blood pressure of neonates up to corrected age of 3 months. Summary data were extracted and compared (PROSPERO CRD42018092886).

RESULTS

Of the 3683 non-duplicate publications identified, 44 were eligible for inclusion in this review. Topics elicited were sociodemographic factors, maternal health status, medications, smoking during pregnancy, and cord management at birth. Limited data were available for each factor. Results regarding the impact of these factors on neonatal blood pressure were inconsistent across studies.

CONCLUSIONS

There is insufficient evidence to draw definitive conclusions regarding the impact of various maternal and perinatal factors on neonatal blood pressure. Future investigations of neonatal cardiovascular therapies should account for these factors in their study design. Similarly, studies on maternal diseases and perinatal interventions should include neonatal blood pressure as part of their primary or secondary analyses.

Assessment of superior vena cava flow and cardiac output in different patterns of patent ductus arteriosus shunt

BACKGROUND

Despite the widespread use of superior vena cava (SVC) flow as a marker of systemic blood flow from the upper body, no previous studies have systematically evaluated the correlation between SVC flow and other echocardiography measures of systemic blood flow in the context of different patterns of patent ductus arteriosus (PDA) shunt direction METHODS: A retrospective cohort study of preterm infants (< 30 weeks, < 21 days of life) who underwent comprehensive targeted neonatal echocardiography (TnECHO) was performed. Patients were categorized as follows: (i) Hemodynamically significant left-to-right shunt; (ii): Bidirectional shunt; (iii) No PDA or insignificant shunt. SVC flow, as measured by two distinct methods, was compared to left and right ventricular outputs (LVO and RVO). Intra- and inter-observer reliability testing was performed RESULTS: In total, 45 patients were included (15 in each group) with a median [IQR] weight of 720 [539, 917] grams at the time of assessment. SVC dimensions and flow measurements were not different between the groups, although patients with left-to-right shunt had higher LVO/RVO ratio. SVC flow, as estimated using the modified method, had a strong correlation with LVO (r = .63, p = 0.012) and RVO (r = .635, p = 0.011) in patients with no PDA. Inter- and intra-observer reliability were both stronger for LVO and RVO when compared to SVC flow measurements CONCLUSION: SVC flow was comparable across all three groups irrespective of higher LVO and LVO/RVO ratio in patients with left-to-right shunts. This may reflect poor measurement reliability or compensation for left-to-right ductal shunt by increased LVO to maintain systemic perfusion.

Comparison of Two Techniques of Superior Vena Cava Flow Measurement in Preterm Infants With Birth Weight <1,250 g in the Transitional Period-Prospective Observational Cohort Study

Objectives: Superior Vena Cava (SVC) flow in neonates measured by the standard approach has been validated by different groups around the world. The modified SVC flow measurement technique was recently suggested. The aim of our study was to evaluate standard and modified technique of echocardiography SVC flow measurement in a cohort of extremely preterm neonates in the immediate postnatal period. Methods: Prospective, observational cohort study in a level III neonatal center. Infants with birth weight <1,250 g were eligible for enrolment. SVC flow was measured by echocardiography using standard and modified methods at 6, 18 and 36 h of age. Our primary outcome was equivalency (using raw bounds of -20 to +20 mL/kg/min difference between the paired measurements), agreement and correlation between standard and modified methods of the SVC flow measurements. Results: Thirty-nine infants were enrolled. The mean gestational age of the cohort was 27.4 (SD 2.1) weeks of postmenstrual age, the mean birth weight was 0.95 kg (SD 0.2). The measurements at 6 and 36 h of age were equivalent as defined in the design of the study (p = 0.003 and p = 0.004 respectively; raw bounds -20 to +20 mL/kg/min). At 6 h of age the mean difference (bias) between the measurements was -0.8 mL/kg/min with 95% limits of agreement -65.0 to 63.4 mL/kg/min. At 18 h of age, the mean difference (bias) between the measurements was +9.5 mL/kg/min, with 95% limits of agreement -79.6 to 98.7 mL/kg/min. At 36 h of age the mean difference (bias) between the measurements was -2.2 mL/kg/min with 95% limits of agreement -73.4 to 69.1 mL/kg/min. There was a weak, but statistically significant correlation between the standard and modified method at 6 h of age (r = 0.39, p = 0.04). Conclusion: Both SVC flow echocardiography measurement techniques yielded clinically equivalent results, however due to wide limits of agreement and poor correlation they do not seem to be interchangeable.

Superior vena cava flow: Role, assessment and controversies in the management of perinatal perfusion

The superior vena cava (SVC) is a large vein responsible for the venous return of blood from structures located superior to the diaphragm. The flow in the SVC can be assessed with Doppler ultrasound and can be used as a proxy for cerebral perfusion. Early clinical research studies showed that low SVC flow, particularly if for a prolonged period, was associated with short term morbidity such as intraventricular hemorrhage, mortality, and poorer neurodevelopmental outcomes. However, these findings have not been consistently reported in more recent studies, and the role of SVC flow in early management and as a predictor of poor long-term neurodevelopment has been questioned. This paper provides an overview of SVC assessment, the expected range of findings, and reviews the role of SVC flow as a diagnostic and monitoring tool for the assessment of perinatal perfusion.

The Future of Cardiac Ultrasound in the Neonatal Intensive Care Unit

Cardiac ultrasound is increasingly used to guide hemodynamic decision making in the neonatal intensive care unit (NICU). This article focuses on likely future progress in training, accreditation, digital connectivity, miniaturization, and modality development. Many documents have been published internationally to guide cardiac ultrasound training, accreditation, and implementation in the NICU, but challenges remain in providing assessments of hemodynamic status without risking missed structural diagnoses. Advances in simulation training and digital connectivity provide an opportunity to standardize approaches across institutions and continents. Development of machine learning and ultrasound modalities in turn provide huge scope for improving robustness and completeness of assessment.

Delayed cord clamping in Rh-alloimmunised infants: a randomised controlled trial

Despite advancement in medical care, Rh alloimmunisation remains a major cause of neonatal hyperbilirubinaemia, neuro-morbidity, and late-onset anaemia. Delayed cord clamping (DCC), a standard care now-a-days, is yet not performed in Rh-alloimmunised infants due to paucity of evidence. Hence, we randomised these infants of 28- to 41-week gestation to delayed cord clamping (N = 36) or early cord clamping (N = 34) groups. The primary outcome variable was venous packed cell volume (PCV) at 2 h of birth. The secondary outcomes were incidence of double volume exchange transfusion (DVET) and partial exchange transfusion (PET), duration of phototherapy (PT), functional echocardiography (parameters measured: superior vena cava flow, M-mode fractional shortening, left ventricular output, myocardial perfusion index, and inferior vena cava collapsibility) during hospital stay, and blood transfusion (BT) until 14 weeks of life. Neonates were managed as per unit protocol. The baseline characteristics of enrolled infants were comparable between the groups. The median (IQR) gestation and mean (SD) birth weight of enrolled infants were 35 (33-37) weeks and 2440 (542) g, respectively. The DCC group had a higher mean PCV at 2 h of life (48.4 ± 9.2 vs. 43.5 ± 8.7, mean difference 4.9% (95% CI 0.6-9.1), p = 0.03). However, incidence of DVET and PET, duration of PT, echocardiography parameters, and BT until 14 weeks of postnatal age were similar between the groups.Conclusion: DCC in Rh-alloimmunised infants improved PCV at 2 h of age without significant adverse effects.Trial registration: Clinical Trial Registry of India (CTRI), Ref/2016/11/012572 http://ctri.nic.in/Clinicaltrials, date of trial registration 19.12.2016, date of first patient enrolment 1 January 2017.What is Known:•Delayed cord clamping improves haematocrit, results in better haemodynamic stability, and decreases the need of transfusion in early infancy.•However, due to lack of evidence, potential risk of hyperbilirubinaemia, and exacerbation of anaemia (following delayed cord clamping), early cord clamping is the usual norm in Rh-alloimmunised infantsinfants.What is New:•Delayed cord clamping in Rh-alloimmunised infants improves haematocrit at 2 h of life without any increase in incidence of serious adverse effects.

Associations of measures of systemic blood flow used in a randomized trial of delayed cord clamping in preterm infants

OBJECTIVE

To determine associations of low superior vena cava (SVC) flow (≤55 ml/kg/min) and low right ventricular output (RVO) (≤150 ml/kg/min) in preterm infants.

DESIGN/METHODS

An observational study in infants <30 weeks gestation randomized to receive immediate (<10 s) or delayed cord clamping (DCC) (≥60 s).

RESULTS

The study enrolled 265 infants with a mean (SD) gestation 28 (2) weeks. Eighty-six (33%) infants had low SVC flow and 81 (31%) infants had low RVO. In multivariate analysis, low SVC flow was associated with gestation; low RVO was associated with DCC, gender and 5-minute Apgar; whereas mean RVO was negatively associated with both FiO₂ and mean airway pressure (MAP) at 9 h and 24 h. Low SVC flow was associated with ductus arteriosus (DA) treatment. Infants with low RVO had higher mortality on univariate analysis, but this was not significant after adjusting for gestation.

CONCLUSIONS

SVC flow was associated with gestation, whilst RVO was associated with placental transfusion, gender, condition at birth, and early respiratory adaptation. Compared to infants with normal values, more infants with low SVC flow were treated for DA, but infants with low RVO had no significant difference in mortality or morbidity.

Cord milking versus immediate clamping in preterm infants: a randomised controlled trial

OBJECTIVE

To investigate whether umbilical cord milking (UCM) at birth improves systemic blood flow and short-term outcomes, as compared with immediate cord clamping (ICC).

DESIGN

Randomised clinical trial.

SETTING

Single tertiary care centre.

PATIENTS

Infants born to eligible women presenting in preterm labour between 24 and 31 weeks' gestation.

INTERVENTIONS

UCM three times at birth or ICC.

OUTCOME MEASURES

Primary outcome included systemic blood flow as represented by echo-derived superior vena cava(SVC) flow at 4-6 hours after birth. The echocardiographer and interpreter were blinded to the randomisation. Secondary outcomes included cardiac output, neonatal morbidities and mortality. Analysis was by intention to treat.

RESULTS

A total of 73 infants were randomised (37 to UCM and 36 to ICC). Mean (SD) gestational age was 27 (2) weeks and mean (SD) birth weight was 1040 (283) g. Haemoglobin on admission was higher in the UCM than in the ICC group (16.1 vs 15.0 g/L), p=0.049 (mean difference 1.1, 95% CI 0.003 to 2.2). No statistically significant differences were found between groups in SVC flow at 4-6 hours (88.9±37.8 and 107.3±60.1 mL/kg/min), p=0.13 (mean difference -18.4, 95% CI -41.7 to 5.0 mL/kg/min) or at 10-12 hours of age (102.5±41.8 and 90.6±28.4 mL/kg/min), p=0.17 (mean difference 12.0, 95% CI -4.7 to 28.7 mL/kg/min), cardiac output or neonatal morbidities.

CONCLUSIONS

Cord milking was not shown to improve functional cardiac outcomes, neonatal morbidity or mortality. More research is needed before routine cord milking can be recommended for very preterm infants.

TRIAL REGISTRATION

NCT01487187.

Cardiac Output Monitoring in Preterm Infants

Maintaining optimal circulatory status is a key component of preterm neonatal care. Low-cardiac output (CO) in the preterm neonate leads to inadequate perfusion of vital organs and has been linked to a variety of adverse outcomes with heightened acute morbidity and mortality and adverse neurodevelopmental outcomes. Having technology available to monitor CO allows us to detect low-output states and potentially intervene to mitigate the unwanted effects of reduced organ perfusion. There are many technologies available for the monitoring of CO in the preterm neonatal population and while many act as useful adjuncts to aid clinical decision-making no technique is perfect. In this review, we discuss the relative merits and limitations of various common methodologies available for monitoring CO in the preterm neonatal population. We will discuss the ongoing challenges in monitoring CO in the preterm neonate along with current gaps in our knowledge. We conclude by discussing emerging technologies and areas that warrant further study.