Serial changes in myocardial function in preterm infants over a four week period: the effect of gestational age at birth

Cardiac Development and Related Clinical Considerations

The anatomy, physiology, and hemodynamics of the premature heart vary along the range of gestational ages cared for in neonatal intensive care units, from 22 weeks to term gestation. Clinical management of the preterm neonate should account for this heterogenous development. This requires an understanding of the impact of ex utero stressors on immature and disorganized cardiac tissue, the different state of hemodynamics across intracardiac shunts impacting the natural transition from fetal to neonatal life, and the effects of intensive pharmacologic and non-pharmacologic interventions that have systemic consequences influencing cardiac function. This article provides a review of the increasing but still limited body of literature on the anatomy, hemodynamics, and electrophysiology of the preterm heart with relevant clinical considerations.

Cardiac biomarkers and left ventricular systolic function in former very preterm infants and term controls at preschool age

Introduction

Due to improvements in perinatal care, survival rates of preterm infants have improved during the last decades. However, these infants remain at risk of developing cardiovascular sequelae later in life. This study aimed to investigate the cardiac biomarkers and left ventricular systolic function in former preterm infants in comparison with term controls at preschool age.

Methods

The study included children aged 5-7 years old born below 32 weeks of gestational age. The control group consisted of same-age children born at term. Basic data of study participants were collected using questionnaires and follow-up databases. During the study visit, we recorded anthropometric data and blood pressure readings, determined high-sensitive cardiac troponin T (hs-cTnT) and N-terminal pro-B-type natriuretic peptide (NT-pro-BNP) concentrations, and calculated fractional shortening (FS) and left ventricular mass (LVM).

Results

Term-born (n = 25; median gestational age, 40.1 weeks) compared with preterm-born infants (n = 80; median gestational age 29.6 weeks) showed no significant differences in the median concentration of hs-cTnT [median, 3.5 (IQR 3.5; 3.5) vs. 3.5 (3.5; 3.5) ng/L, p = 0.328] and the median concentration of NT-pro-BNP [median, 91.0 (IQR 40.8; 150.3) vs. 87.5 (50.1; 189.5) ng/L, p = 0.087]. FS and LVM/LVMI were not significantly different between the two groups.

Conclusion

At preschool age, we observed no significant differences in cardiac biomarkers and left ventricular systolic function in preterm infants. Further studies are warranted to explore the potential of cardiac biomarkers as a prognostic tool for subclinical cardiac alterations after preterm birth.

Hemodynamic considerations in preterm infants born at less than 25 weeks gestation

As survival rates continue to improve for infants born at less than 25 weeks gestation, delineating normal cardiovascular physiology from pathophysiology becomes much more challenging. With a paucity of 'normative' data for such infants, an over-reliance on studies at older gestations can result in a 'best guess' approach. Here we offer a pragmatic approach to these diagnostic challenges from a cardiovascular viewpoint. An appreciation of the unique physiology, from the immature myocardium and altered vascular tone to an innately large patent ductus arteriosus is essential, as is a thorough history for case specific contributing factors. We explore the additional difficulties in achieving a balance between minimal handling at the bedside and delineating important objective markers of perfusion. Finally, we discuss treatment approaches including inotrope therapy and patent ductus treatment, acknowledging the limited data available to guide these decisions.

Effect of Preterm Birth on Cardiac and Cardiomyocyte Growth and the Consequences of Antenatal and Postnatal Glucocorticoid Treatment

Preterm birth coincides with a key developmental window of cardiac growth and maturation, and thus has the potential to influence long-term cardiac function. Individuals born preterm have structural cardiac remodelling and altered cardiac growth and function by early adulthood. The evidence linking preterm birth and cardiovascular disease in later life is mounting. Advances in the perinatal care of preterm infants, such as glucocorticoid therapy, have improved survival rates, but at what cost? This review highlights the short-term and long-term impact of preterm birth on the structure and function of the heart and focuses on the impact of antenatal and postnatal glucocorticoid treatment on the immature preterm heart.

Cardiovascular and cerebrovascular responses to cardio-respiratory events in preterm infants during the transitional period

KEY POINTS

Non-invasive simultaneous multiparametric monitoring allows the in vivo evaluation of cerebral and cardiovascular haemodynamic responses to different types of recurrent episodes of intermittent hypoxia and/or bradycardia, also defined as cardio-respiratory events (CRE), in preterm neonates during postnatal transition. By decreasing left cardiac output, bradycardia further contributes to cerebral hypoxia during CRE. The presence of a haemodynamically significant patent ductus arteriosus results in a deeper impairment of cerebral oxygen status in response to CRE, whereas the brain-sparing remodelling of the fetal circulation resulting from placental insufficiency is associated with more favourable haemodynamic responses to intermittent hypoxia. During transition, the haemodynamic impact of CRE is influenced not only by the event type, but also by specific clinical features; this highlights the importance of developing individualized approaches to reduce the hypoxic burden in this delicate phase.

ABSTRACT

The present observational prospective study aimed to investigate cerebral and cardiovascular haemodynamic responses to different types of cardio-respiratory events (CRE) in preterm infants during postnatal transition, as well as evaluate the impact of relevant clinical characteristics. Infants with gestational age (GA) <32 weeks and/or birth weight <1500 g were enrolled after birth. Cerebral oxygenation index (cTOI), fractional oxygen extraction (cFTOE), cardiac output (CO), cardiac contractility (iCON) and systemic vascular resistances (sVR) were simultaneously monitored over the first 72 h by near-infrared spectroscopy and electrical velocimetry. CRE were clustered into isolated bradycardia (IB), isolated desaturation (ID) and combined desaturation/bradycardia (DB). For each parameter, percentage changes from baseline (%Δ) were calculated. The impact of different CRE types and clinical variables on %Δ was evaluated with generalized estimating equations. In total, 1426 events were analysed. %ΔcTOI significantly differed among ID, IB and DB (P < 0.001), with the latter showing the greatest drop. %ΔcFTOE decreased significantly during DB (P < 0.001) and ID (P < 0.001) compared to IB. DB and IB were associated with more negative %ΔCO (P < 0.001) and more positive %ΔsVR (P < 0.001) compared to ID. A slight iCON reduction was observed during DB compared to ID (P = 0.043). Antenatal umbilical Doppler impairment, GA and the presence of a haemodynamically significant patent ductus arteriosus had a significant independent impact on %ΔcTOI, %ΔcFTOE and %ΔCO. During the transitional period, the haemodynamic responses to CRE are influenced by the event type and by specific neonatal characteristics, suggesting the importance of targeted individualized approaches for minimizing the risk of cerebral injury in the preterm population.

Risk factors for adverse events within one year after atrial septal closure in children: a retrospective follow-up study

INTRODUCTION

Secundum atrial septal defect is one of the most common congenital heart defects. Previous paediatric studies have mainly addressed echocardiographic and few clinical factors among children associated with adverse events. The aim of this study was to identify neonatal and other clinical risk factors associated with adverse events up to one year after closure of atrial septal defect.

METHODS

This retrospective case-control study includes children born in Sweden between 2000 and 2014 that were treated surgically or percutaneously for an atrial septal defect. Conditional logistic regression was used to evaluate the association between major and minor adverse events and potential risk factors, adjusting for confounding factors including prematurity, neonatal sepsis, neonatal general ventilatory support, symptomatic atrial septal defects, and pulmonary hypertension.

RESULTS

Overall, 396 children with 400 atrial septal defect closures were included. The median body weight at closure was 14.5 (3.5-110) kg, and the median age was 3.0 (0.1-17.8) years. Overall, 110 minor adverse events and 68 major events were recorded in 87 and 49 children, respectively. Only symptomatic atrial septal defects were associated with both minor (odds ratio (OR) = 2.18, confidence interval (CI) 95% 1.05-8.06) and major (OR = 2.80 CI 95% 1.23-6.37) adverse events.

CONCLUSION

There was no association between the investigated neonatal comorbidities and major or minor events after atrial septal defect closure. Patients with symptomatic atrial septal defects had a two to four times increased risk of having a major event, suggesting careful management and follow-up of these children prior to and after closure.

Reproducibility of the assessment of myocardial function through tissue Doppler imaging in very low birth weight infants

OBJECTIVES

This study aims to analyze the variability between two trained neonatologists when performing consecutive echocardiograms using tissue Doppler imaging (TDI) and conventional methods in very low birth weight infant (VLBWI).

METHODS

Two serial echocardiograms were performed in 30 VLBWI infants. The echocardiographic parameters analyzed were tricuspid annular plane systolic excursion (TAPSE), A', E', and S' waves, and myocardial performance index acquired by TDI (MPI-TDI) of both ventricles and shortening fraction (SF). The intra-observer and inter-observer agreements and the intra-operator agreement were analyzed using quantitative and qualitative statistical methods.

RESULTS

The intra-observer agreement was very good, TAPSE, and TDI-derived parameters had an intra-class correlation (ICC) > 0.8. TDI-derived velocities had a coefficient of variation (COV) < 11%, while MPI-TDI had a COV between 20%-28%. The inter-observer agreement was excellent. There was greater variability when analyzing intra-operator agreement, with the least variable parameter being TAPSE. According to PABAK, the variability presented moderately substantial agreement.

CONCLUSIONS

Tricuspid annular plane systolic excursion is very reproducible between observers and operators. Measurements of TDI wave velocities are more reproducible than MPI-TDI. TDI is sufficiently reproducible in the VLBWI if adequate training is performed, and guidelines are followed to obtain standardized echocardiographic images.

Myocardial Function Maturation in Very-Low-Birth-Weight Infants and Development of Bronchopulmonary Dysplasia

Background: Myocardial function in very-low-birth-weight infants (VLBWIs) develops during early postnatal life, but different patterns of temporal evolution that might be related to the development of bronchopulmonary dysplasia (BPD) are not completely understood. Methods: A prospective cohort study including VLBWIs admitted to our NICU from January 2015 to 2017 was conducted. Plasma N-terminal pro B type natriuretic peptide (NTproBNP) levels were measured, and echocardiograms were performed at 24 and 72 h of life and weekly thereafter until 36 weeks of postmenstrual age (PMA). We measured the tricuspid annular plane systolic excursion (TAPSE) by M-mode; the lateral tricuspid E', A', and S' waves; and the myocardial performance index (MPI) by tissue doppler imaging (TDI). The subjects were divided into non-BPD and BPD groups. Results: We included 101 VLBWIs. The TAPSE and E', A', and S' waves increased while MPI-TDI decreased over time. Birth gestational age (GA) and postnatal PMA impacted these parameters, which evolved differently in those who developed BPD compared to those in the non-BPD group. The NTproBNP levels at 14 days of life and different echocardiographic parameters were associated with the development of BPD in different multivariate models. Conclusion: TAPSE and TDI values depend on GA and PMA and follow a different temporal evolution that is related to the later development of BPD. Combined biochemical and echocardiographic biomarkers can help identify which VLBWIs are at higher risk of developing BDP.

Left atrium function and deformation in very preterm infants with and without volume load

BACKGROUND

Left atrium (LA) function can be assessed by volumetric measurements, conventional and tissue Doppler, and more recently, deformation imaging using two-dimensional speckle tracking echocardiography (2DSTE). 2DSTE allows for measurement of volume and deformation and can quantify the contribution of the reservoir, conduit, and contraction phase. A common cause for LA dysfunction in very preterm infants is volume overload with a patent ductus arteriosus (PDA). The aim of this study was to explore the feasibility and reliability of LA 2DSTE in preterm infants, and describe LA function with and without PDA volume load.

METHODS

We prospectively recruited preterm infants <30 weeks of gestation referred for assessment of a possible PDA. A cardiac ultrasound was performed at day 3 and in week 4 of life and analyzed using conventional techniques and 2DSTE.

RESULTS

Forty-eight infants (32 with PDA) were included. LA 2DSTE analysis was feasible in 96% of measurements with good reliability of strain and volume parameters. Strain rate was less reliable. Poorer LA contraction and reservoir function was associated with larger LA volume index, higher inflow over the mitral valve at early diastole, higher EA ratio, and higher Ee' ratio. Poorer conduit function was associated with higher Ee' ratio. A larger PDA diameter was found to be an independent contributor to deteriorating LA contraction and reservoir function.

CONCLUSION

LA 2DSTE analysis is feasible in preterm infants and provides detailed information on atrium mechanics. Further studies are needed to explore the clinical value of these new parameters in this population.

The Preterm Heart in Childhood: Left Ventricular Structure, Geometry, and Function Assessed by Echocardiography in 6-Year-Old Survivors of Periviable Births

BACKGROUND

Preterm birth has been associated with increased risk of cardiovascular morbidity in adult life. We evaluated whether preterm birth is associated with deviating cardiac structure and function before school start.

METHODS AND RESULTS

In total, 176 children aged 6 years and born extremely preterm (EXPT; gestational age of 22-26 weeks) and 134 children born at term (control [CTRL]) were studied. We used echocardiography to assess left heart dimensions, geometry, and functions. Recording and off-line analyses of echocardiographic images were performed by operators blinded to group belonging. Body size, blood pressure, and heart rate were also measured. Rates of family history of cardiovascular disease and sex distribution were similar in the EXPT and CTRL groups. Heart rate and systolic blood pressure did not differ, whereas diastolic blood pressure was slightly higher in EXPT than CTRL participants. After adjusting for body surface area, left ventricular length, width, and aortic valve annulus diameter were 3% to 5% smaller in EXPT than CTRL participants. Left ventricular longitudinal shortening and systolic tissue velocity were 7% to 11% lower, and transversal shortening fraction was 6% higher in EXPT than CTRL participants. The EXPT group also exhibited lower atrial emptying velocities than the CTRL group. Sex, fetal growth restriction, or a patent ductus arteriosus in the neonatal period did not contribute to cardiac dimensions or performance.

CONCLUSIONS

Six-year-old children born extremely preterm exhibit a unique cardiac phenotype characterized by smaller left ventricles with altered systolic and diastolic functions than same-aged children born at term.

Tissue Doppler velocity imaging and event timings in neonates: a guide to image acquisition, measurement, interpretation, and reference values

Neonatologists can use echocardiography for real-time assessment of the hemodynamic state of neonates to support clinical decision-making. There is a large body of evidence showing the shortcomings of conventional echocardiographic indices in neonates. Newer imaging modalities have evolved. Tissue Doppler imaging is a new technique that can provide measurements of myocardial movement and timing of myocardial events and may overcome some of the shortcomings of conventional techniques. The high time resolution and its ability to assess left and right cardiac function make tissue Doppler a favorable technique for assessing heart function in neonates. The aim of this review is to provide an up-to-date overview of tissue Doppler techniques for the assessment of cardiac function in the neonatal context, with focus on measurements from the atrioventricular (AV) plane. We discuss basic concepts, protocol for assessment, feasibility, and limitations, and we report reference values and give examples of its use in neonates.

Post-transitional adaptation of the left heart in uncomplicated, very preterm infants

BACKGROUND

The postnatal period in preterm infants involves multiple physiological changes occurring immediately after birth and continuing for days or weeks. To recognise and treat compromise, it is important to measure cardiovascular function. The aim of this study was to describe longitudinal left ventricular function using conventional and novel echocardiography techniques in preterm infants who did not experience significant antenatal or postnatal complications and treatments.

METHODS

We prospectively obtained cardiac ultrasound images at days 3, 7, 14, 21, and 28 in 25 uncomplicated, preterm infants <30 weeks of gestation. Speckle tracking analysis of the four chambers and short-axis images provided parameters of left ventricular volume, deformation, and basal myocardial velocities. The patent ductus arteriosus, cardiac dimensions, and atrial volume were also measured.

RESULTS

Stroke volume increased by 24% during the study period (1.05-1.30 ml/kg, p<0.05). Cardiac length, diameter, and systolic basal myocardial velocity increased with unchanged wall stress and deformation parameters. Diastolic function parameters resembled that of the fetus with predominance of atrial contraction compared with early diastolic velocities. Blood pressure and estimates of left ventricular filing pressure increased, suggesting that left ventricular compliance did not change in this period.

CONCLUSION

Stroke volume increased in the first 28 days after preterm birth. The preterm heart adapted by increasing its size, while maintaining systolic and atrial function, independent of early diastolic maturation. Longitudinal deformation of the left ventricle remained unchanged, suggesting relatively preserved function with maturation.

Serial measures of cardiac performance using tissue Doppler imaging velocity in preterm infants <29weeks gestations

INTRODUCTION

Tissue Doppler imaging (TDI) is a useful marker of myocardial performance in preterm infants. We aimed to demonstrate serial changes in TDI velocity in preterm infants <29weeks gestation, to assess the impact of inotropes and a haemodynamically significant patent ductus arteriosus (hsPDA).

METHODS

This was a prospective observational study of preterm infants <29weeks gestation. Echocardiography was performed at days 1, 2, 5-7 and at 36weeks, or before hospital discharge. Infants with hsPDA's on day 5-7 and those who received inotropes in the first week of life were not included in the Reference Cohort. Systolic (s`) and diastolic (e` and a`) velocity waves were assessed at the mitral and tricuspid annulus and basal septum.

RESULTS

One hundred and thirty nine infants with a mean (SD) gestation and birthweight of 26.7 (1.5) weeks and 946 (247) grams were enrolled. The 66 infants (47%) in the Reference Cohort demonstrated an increase in functional parameters with increasing age [LV s`, Septal s`, and RV s`, Day 1-36weeks: 2.8 (0.6) to 4.7 (1.0), 2.4 (0.6) to 4.6 (0.8), 3.6 (0.6) to 6.9 (1.0) cm/s respectively; all p<0.05). The 24 infants who received inotropes had lower LV e` [2.9 vs. 3.6cm/s], Septal e` [2.3 vs. 2.8cm/s] and a` [3.2 vs. 3.9cm/s], and lower RV a` [3.3 vs. 3.9cm/s] on Day 1 (all p<0.05). Fifty five infants had a hsPDA on Day 5-7, demonstrating higher LV [4.7 vs. 4.0cm/s] and Septal e` [3.9 vs. 3.3cm/s], and a higher LV E/e` [13 vs. 10] (all p<0.05).

CONCLUSION

Extremely preterm infants display a gradual increase in tissue Doppler velocities from birth until 36weeks corrected age. The presence of a hsPDA increases diastolic TDI velocities. Infants requiring inotropes have lower diastolic myocardial velocities on Day 1.

The effects of preterm birth and its antecedents on the cardiovascular system

INTRODUCTION

Preterm birth occurs in approximately 10% of all births worldwide. It prematurely exposes the developing cardiovascular system to the hemodynamic transition that occurs at birth and to the subsequent functional demands of life ex utero. This review describes the current knowledge of the effects of preterm birth, and some of its common antecedents (chorioamnionitis, intra-uterine growth restriction, and maternal antenatal corticosteroid administration), on the structure of the myocardium.

MATERIAL AND METHODS

A thorough literature search was conducted for articles relating to how preterm birth, and its antecedents, affect development of the heart. Given that sheep are an excellent model for the studies of cardiac development, this review has focused on experimental studies in sheep as well as clinical findings.

RESULTS

Our review of the literature demonstrates that individuals born preterm are at an increased risk of cardiovascular disease later in life, including increased mean arterial pressure, abnormally shaped and sub-optimally performing hearts and changes in the vasculature. The review highlights how antenatal corticosteroids, intra-uterine growth restriction, and exposure to chorioamnionitis also have the potential to impact cardiac growth in the preterm newborn.

CONCLUSIONS

Preterm birth and its common antecedents (antenatal corticosteroids, intra-uterine growth restriction, and chorioamnionitis) have the potential to adversely impact cardiac structure immediately following birth and in later life.

Cardiac Function After the Immediate Transitional Period in Very Preterm Infants Using Speckle Tracking Analysis

BACKGROUND

The postnatal period in preterm infants involves multiple physiologic changes starting directly after birth and continuing for days or weeks. To recognize and treat compromise, it is important to measure cardiovascular function. We used a novel technique (speckle tracking echocardiography, STE) to measure cardiac function in this period.

METHODS

We obtained cardiac ultrasound images at day 3, 7, 14, 21 and 28 in preterm infants <30-week gestation. Conventional measures included cardiac size, left ventricular stroke volume, atrial volume and the patent ductus arteriosus (PDA). Four chamber images were analyzed with STE, which provided parameters of left ventricular volume, longitudinal deformation and myocardial velocities.

RESULTS

Images of 54 infants (gestational age 23-29 weeks) were analyzed. STE-derived stroke volume correlated well with conventional echocardiography-derived stroke volume, but agreement was suboptimal. Most STE parameters showed good reliability. All volume parameters and systolic and atrial velocities increased over time. Cardiac deformation and early diastolic velocity did not change. A PDA was associated with 33 % increased stroke volume at day 3 up to 98 % at day 28 with a spherically enlarged heart and increased filling pressure.

CONCLUSION

Speckle tracking echocardiography analysis is a feasible and reliable technique that can simultaneously obtain systolic and diastolic volumes, longitudinal deformation and myocardial velocities from one ultrasound window. Preterm hearts maintain cardiac function well during the first weeks of life, even with increased preload as a consequence of a PDA.

Novel Echocardiography Methods in the Functional Assessment of the Newborn Heart

Echocardiography in the neonatal intensive care unit has led to improvements in our ability to assess the neonatal heart in health and disease. Advances in neonatal cardiac imaging have provided the capability to obtain quantitative information that often supersedes the qualitative information provided by conventional methods. Novel quantitative measures of function include the assessment of the velocity of muscle tissue movement during systole and diastole using tissue Doppler velocity imaging, and evaluation of deformation and rotational characteristics of the myocardium utilizing speckle tracking echocardiography or tissue Doppler-derived strain imaging. A comprehensive understanding of these novel functional modalities, their predictive value, and limitations can greatly assist in managing both the normal and maladaptive responses in the newborn period. This article discusses the novel and emerging methods for assessment of left and right heart function in the neonatal population.