Left ventricular diastolic function and respiratory outcomes in preterm infants: a retrospective study

Changes in left ventricular diastolic flow dynamics in the neonatal transition period and beyond

Significant hemodynamic changes occur within the neonatal transition period including a sudden increase in pulmonary blood flow, disappearance of fetal shunts, and increase in systemic vascular resistance. How this affects left ventricular (LV) physiology and intraventricular flow dynamics is still poorly understood. Blood speckle tracking is a novel high frame rate echocardiographic technique that allows to visualize two-dimensional intraventricular flow dynamics. In this study, longitudinal changes in LV diastolic flow dynamics were explored in a prospective single-center design analyzing a total of 176 echocardiographic examinations in 36 healthy newborns from birth until 6 mo of age. Kinetic energy, energy loss, vorticity, and intraventricular pressure difference increased significantly from birth until 6-8 wk of age (P < 0.001 for all parameters). The increase in intraventricular pressure difference continued until 6 mo of age, whereas no further significant changes in the other quantitative LV flow parameters could be observed beyond 6-8 wk. Early after birth, diastolic vorticity was predominantly located at the anterior mitral valve leaflet whereas at 6 mo of age, vorticity was similar at the anterior compared with the posterior mitral valve leaflet. Overall, these results indicate that LV diastolic physiology and flow dynamics undergo substantial changes in early life. The observed changes in diastolic LV properties are likely associated with increased LV filling in the presence of increased pulmonary blood flow.NEW & NOTEWORTHY Assessment of left ventricular flow dynamics is highly feasible using high-frame rate echocardiography-based blood speckle tracking. In healthy newborns, left ventricular diastolic kinetic energy, energy loss, and vorticity significantly change during the first weeks, stabilizing after 6-8 wk, whereas intraventricular pressure difference continues to increase until 6 mo of age. These findings indicate that intraventricular flow dynamics can describe changes in cardiac physiology contributing to normal postnatal cardiovascular adaptation, maturation, and function.

Reference ranges of left ventricular diastolic multimodal ultrasound parameters in stable preterm infants in the early and late neonatal intensive care admission period

BACKGROUND

Diastolic dysfunction often precedes systolic dysfunction and provides opportunity for management strategies. We aim to present reference ranges for diastolic function parameters in stable preterm infants at 2 timepoints.

METHODS

Ultrasound scans of clinically stable preterm infants < 30 weeks gestation with no antenatal or postnatal complications were analysed for left heart size, mitral blood flows, myocardial velocities and shortening during the early (3 to 21 days) and late (corrected gestation 34 to 37 weeks) neonatal period.

RESULTS

92 early scans and 64 late scans were included. Mitral blood flow and myocardial velocities increased with augmented atrial function leading to higher EA and e'a' ratios and with relatively high Ee' ratio.

CONCLUSION

We present reference values for many left ventricular multimodal diastolic ultrasound parameters in preterm infants with uncomplicated fetal and neonatal development to guide prospective studies that explore diastolic function and diastolic heart failure in preterm infants.

Whole genome transcriptomics reveal distinct atrial versus ventricular responses to neonatal hyperoxia

Preterm infants exposed to supplemental oxygen (hyperoxia) are at risk for developing heart failure later in life. Exposing rodents in early postnatal life to hyperoxia causes heart failure that resembles cardiac disease seen in adult humans who were born preterm. Neonatal hyperoxia exposure affects the left atrium and left ventricle differently, inhibiting the proliferation and survival of atrial cardiomyocytes while enhancing cardiomyocyte differentiation in the ventricle. In this study, whole genome transcriptomics revealed the left atria of neonatal mice are more responsive to hyperoxia than the left ventricle, with the expression of 4,285 genes affected in the atrium and 1,743 in the ventricle. Although hyperoxia activated p53 target genes in both chambers, it caused greater DNA damage, phosphorylation of the DNA damage responsive ataxia-telangiectasia mutated (ATM) kinase, mitochondrial stress, and apoptosis in the atrium. In contrast, hyperoxia induced the expression of genes involved in DNA repair and stress granules in the ventricle. Atrial cells also showed a greater loss of extracellular matrix and superoxide dismutase 3 (SOD3) expression, possibly contributing to the enlargement of the left atrium and reduced velocity of blood flow across the mitral valve seen in mice exposed to hyperoxia. Diastolic dysfunction and heart failure in hyperoxia-exposed mice may thus stem from its effects on the left atrium, suggesting chamber-specific therapies may be needed to address diastolic dysfunction and heart failure in people who were born preterm.NEW & NOTEWORTHY Preterm infants often require oxygen (hyperoxia) at birth, but early exposure increases the risk of heart failure later in life. Previously, we showed neonatal mice exposed to hyperoxia develop adult diastolic dysfunction and heart failure like preterm-born humans. In this study, RNA-sequencing reveals hyperoxia induces broader transcriptional changes in the atrium than ventricle, including upregulation of stress pathways and loss of superoxide dismutase 3 and extracellular matrix genes, highlighting the atrium's heightened vulnerability to hyperoxia.

Left atrial strain assessment unveils left ventricular diastolic dysfunction in neonates with transient tachypnea of the newborn: A prospective observational study

INTRODUCTION

An inadequate clearance of lung fluid plays a key role in the pathogenesis of transient tachypnea of the newborn (TTN).

OBJECTIVES

To evaluate if left ventricular diastolic dysfunction contributes to reduced clearance of lung fluid in TTN.

MATERIALS AND METHODS

This was a prospective, observational study. Echocardiography and lung ultrasound were performed at 2, 24 and 48 h of life (HoL) to assess biventricular function and calculate lung ultrasound score (LUS). Left atrial strain reservoir (LASr) provided surrogate measurement of left ventricular diastolic function.

RESULTS

Twenty-seven neonates with TTN were compared with 27 controls with no difference in gestation (36.1 ± 2 vs. 36.9 ± 2 weeks) or birthweight (2508 ± 667 vs. 2718 ± 590 g). Biventricular systolic function was normal in both groups. LASr was significantly lower in cases at 2 (21.0 ± 2.7 vs. 38.1 ± 4.4; p < 0.01), 24 (25.2 ± 4.5 vs. 40.6 ± 4.0; p < 0.01) and 48 HoL (36.5 ± 5.8 and 41.6 ± 5.2; p < 0.01), resulting in a significant group by time interaction (p < 0.001), after adjusting for LUS and gestational diabetes. A logistic regression model including LUS, birth weight and gestational diabetes as covariates, showed that LASr at 2 HoL was a predictor of respiratory support at 24 HoL, with an adjusted odds ratio of 0.60 (CI 0.36-0.99).

CONCLUSIONS

LASr was reduced in neonates with TTN, suggesting diastolic dysfunction, that may contribute to the delay in lung fluid clearance.

Targeted Neonatal Echocardiography in the Management of Neonatal Pulmonary Hypertension

Pulmonary hypertension (PH) in neonates, originating from a range of disease states with heterogeneous underlying pathophysiology, is associated with significant morbidity and mortality. Although the final common pathway is a state of high right ventricular afterload leading to compromised cardiac output, multiple hemodynamic phenotypes exist in acute and chronic PH, for which cardiorespiratory treatment strategies differ. Comprehensive appraisal of pulmonary pressure, pulmonary vascular resistance, cardiac function, pulmonary and systemic blood flow, and extrapulmonary shunts facilitates delivery of individualized cardiovascular therapies in affected newborns.