Serial echocardiographic and Doppler evaluation of left ventricular systolic performance and diastolic filling in premature infants

Evaluation of the Fetal Left Ventricular Myocardial Performance Index (MPI) by Using an Automated Measurement of Doppler Signals in Normal Pregnancies

The myocardial performance index is widely used as an indicator of the heart’s performance. However, due to the subjective nature of ultrasonic testing, there are differences in the measurements among inspectors, requiring a quantitative and objective assessment. In this study, an automated program was developed to quantitatively evaluate the myocardial performance index (MPI) and the cardiac time intervals in the left ventricle for each trimester. One hundred and thirty-three pregnant women who visited the hospital for prenatal examinations were studied, and skilled inspectors obtained left ventricular blood flow waveforms from 47 fetuses in the 12 weeks, 54 fetuses in the 22 weeks, and 32 fetuses in the 31 weeks of pregnancy using a pulse Doppler mode of ultrasound equipment. The acquired images automatically measured the isovolumetric contraction time (IVCT), isovolumetric relaxation time (IVRT,) ejection time (ET), and filling time (FT), and calculated the Tei index (TI) and the K-index (KI); each interval was manually measured during the actual inspection for comparison. In this study, the ultrasonic Doppler waveform was objectively analyzed and measured by the automated program, and it will help with the evaluation of fetal heart function.

Microarchitecture of the hearts in term and former-preterm lambs using diffusion tensor imaging

Diffusion tensor imaging (DTI) is an MRI technique that can be used to map cardiomyocyte tracts and estimate local cardiomyocyte and sheetlet orientation within the heart. DTI measures diffusion distances of water molecules within the myocardium, where water diffusion generally occurs more freely along the long axis of cardiomyocytes and within the extracellular matrix, but is restricted by cell membranes such that transverse diffusion is limited. DTI can be undertaken in fixed hearts and it allows the three-dimensional mapping of the cardiac microarchitecture, including cardiomyocyte organization, within the whole heart. The objective of this study was to use DTI to compare the cardiac microarchitecture and cardiomyocyte organization in archived fixed left ventricles of lambs that were born either preterm (n = 5) or at term (n = 7), at a postnatal timepoint equivalent to about 6 years of age in children. Although the findings support the feasibility of retrospective DTI scanning of fixed hearts, several hearts were excluded from DTI analysis because of poor scan quality, such as ghosting artifacts. The preliminary findings from viable DTI scans (n = 3/group) suggest that the extracellular compartment is altered and that there is an immature microstructural phenotype early in postnatal life in the LV of lambs born preterm. Our findings support a potential time-efficient imaging role for DTI in detecting abnormal changes in the microstructure of fixed hearts of former-preterm neonates, although further investigation into factors that affect scan quality is required.

Changes in the Preterm Heart From Birth to Young Adulthood: A Meta-analysis

CONTEXT

Preterm birth is associated with incident heart failure in children and young adults.

OBJECTIVE

To determine the effect size of preterm birth on cardiac remodeling from birth to young adulthood.

DATA SOURCES

Data sources include Medline, Embase, Scopus, Cochrane databases, and clinical trial registries (inception to March 25, 2020).

STUDY SELECTION

Studies in which cardiac phenotype was compared between preterm individuals born at <37 weeks' gestation and age-matched term controls were included.

DATA EXTRACTION

Random-effects models were used to calculate weighted mean differences with corresponding 95% confidence intervals.

RESULTS

Thirty-two observational studies were included (preterm = 1471; term = 1665). All measures of left ventricular (LV) and right ventricular (RV) systolic function were lower in preterm neonates, including LV ejection fraction (P = .01). Preterm LV ejection fraction was similar from infancy, although LV stroke volume index was lower in young adulthood. Preterm LV peak early diastolic tissue velocity was lower throughout development, although preterm diastolic function worsened with higher estimated filling pressures from infancy. RV longitudinal strain was lower in preterm-born individuals of all ages, proportional to the degree of prematurity (R ² = 0.64; P = .002). Preterm-born individuals had persistently smaller LV internal dimensions, lower indexed LV end-diastolic volume in young adulthood, and an increase in indexed LV mass, compared with controls, of 0.71 g/m² per year from childhood (P = .007).

LIMITATIONS

The influence of preterm-related complications on cardiac phenotype could not be fully explored.

CONCLUSIONS

Preterm-born individuals have morphologic and functional cardiac impairments across developmental stages. These changes may make the preterm heart more vulnerable to secondary insults, potentially underlying their increased risk of early heart failure.

Influence of maternal aerobic exercise during pregnancy on fetal cardiac function and outflow

BACKGROUND

Risk factors for cardiovascular disease, the leading cause of death, have been documented in children as young as 3 years of age. Maternal environment (eg, exercise) influences fetal development and long-term health. Thus, the development of the fetal cardiovascular system during pregnancy is likely a preliminary indicator of cardiac health at birth and a proxy for the future risk of cardiovascular disease throughout life.

OBJECTIVE

The purpose of this study was to assess the effects of supervised prenatal aerobic exercise at recommended levels on fetal cardiac function and outflow in the third trimester of pregnancy. We hypothesized that fetuses of aerobically trained women compared with fetuses of nonexercising women would exhibit increased cardiac function and greater cardiac output.

STUDY DESIGN

Secondary data analyses of a 20-week, randomized controlled exercise intervention trial in pregnant women between 2015 and 2018 in Eastern North Carolina were performed. Eligibility criteria included pregnant women <16 weeks gestation, singleton pregnancy, aged 18-40 years, body mass index of 18.5-34.99 kg/m², physician clearance letter for exercise participation, reliable transportation, and method of communication. Exclusion criteria included the presence of chronic conditions (eg, type 1 or 2 diabetes mellitus), current medications known to adversely affect fetal growth (eg, antidepressants), alcohol, smoking, or illicit drug use. The patient cohort consisted of 133 eligible pregnant women who were assigned randomly to either an aerobic exercise (n=66) group that participated in 150 minutes of supervised, moderate-intensity (40-59% VO_2peak; 12-14 on Borg Rating of Perceived Exertion) aerobic exercise per week or a nonexercising group (n=61) that consisted of 150 minutes per week of light (<40% VO_2peak) stretching and relaxation breathing techniques. Between 34 and 36 weeks gestation, a fetal echocardiogram was performed to assess fetal cardiac function, which included fetal heart rate, right- and left-ventricular stroke volume, stroke volume index, cardiac output, cardiac output index, and cardiac outflow that included pulmonary and aortic valve diameters, peak flow velocity, and peak flow velocity-time integral. Fetal activity state (quiet vs active) during the echocardiogram and maternal aerobic capacity served as covariates. Intention-to-treat and per-protocol (participants who attended ≥80% of exercise sessions) analysis of covariance regression models were performed.

RESULTS

Of the 127 randomly assigned participants, 66 and 50 participants were included in the intention-to-treat and per-protocol analyses, respectively. Prenatal aerobic exercise significantly increased fetal right-ventricular cardiac measures of right ventricular stroke volume (P=.001) and stroke index via velocity-time integral (P=.003), right ventricular cardiac output (P=.002), cardiac index via velocity-time integral (P=.006), pulmonary artery diameter (P=.02), and pulmonary valve velocity-time integral (P=.03). Only in the intention-to-treat analysis was a significant difference in fetal left ventricular cardiac outflow observed; there was a greater aortic valve peak velocity (P=.04) found among fetuses of aerobically trained pregnant women. No other statistically significant between-group differences were found.

CONCLUSION

The findings of this study demonstrate that participation in prenatal aerobic exercise at recommended levels may improve fetal cardiac function and outflow parameters. Follow-up cardiovascular measures in the postnatal period are needed to determine potential long-term effects on the offspring's cardiac function and outflow.

Influence of exercise mode on pregnancy outcomes: ENHANCED by Mom project

Background

The extent of the benefits of exercise training during pregnancy on maternal, fetal, and neonatal health outcomes has not been sufficiently addressed. While aerobic exercise training has been determined as safe and efficacious throughout pregnancy, the effects of other training modes on fetal health and development as well as any continued benefits for the neonate, especially with regards to cardiovascular development and function, is largely unknown. In the ENHANCED by Mom study we aim to determine the effects of different modes of exercise training (aerobic, circuit, and resistance) throughout pregnancy on childhood health by controlling individual exercise programs and assessing the effects of each on fetal and neonatal health adaptations.

Methods/Design

ENHANCED by mom is a cross sectional comparison study utilizing 3 intervention groups in comparison to a control group. Participants will complete three 5 min warmup + 45 min sessions weekly from 16 weeks to 36 weeks gestation of aerobic, resistance, or circuit training, in comparison to non-exercising controls. Maternal physical measurements will occur every 4 weeks throughout the intervention period. Fetal morphometric and heart measurements will occur at 34 weeks gestation. Neonatal measurements will be acquired at birth and at 1 month, 6 months, and 12 months.

Discussion

A better understanding on the effects of exercise training during pregnancy on fetal and neonatal health could have a profound impact on the prevention and development of chronic diseases such as obesity, hypertension, and diabetes.

Evolution of left ventricular function in the preterm infant

BACKGROUND

The aim of this study was to evaluate left ventricular function in preterm infants from 28 days to near term using echocardiography.

METHODS

Thirty clinically stable preterm infants delivered at <30 weeks' gestational age were prospectively enrolled. At 28 days, conventional, tissue Doppler, and speckle-tracking echocardiography evaluations of left ventricular function were performed, with comparison made to findings in 30 healthy term infants of similar postnatal age. Sixteen preterm infants underwent repeat examinations near term.

RESULTS

Compared with controls, preterm infants at 28 days had decreased peak mitral valve (MV) E-wave velocities (P < .01), E/A ratios (P < .0001), annular e' velocities (P < .0001), and e'/a' ratios (P < .0001); increased MV E/e' ratios (P < .01); and lower basal circumferential early diastolic and higher late diastolic strain rates. No significant differences were found in fractional shortening, ejection fraction, and longitudinal or circumferential strain and strain rate between preterm infants and controls. Although preterm infants at 28 days had higher heart rates compared with controls (161 ± 15 vs 142 ± 16 beats/min), no significant correlations existed between heart rate and MV E, E/A ratio, e', e'/a' ratio, and E/e' ratio. Near term, the differences in diastolic function persisted, including decreased MV e'/a' ratio (P < .05), increased E/e' ratio (P < .01), and increased late diastolic strain rate.

CONCLUSIONS

Clinically stable preterm infants have normal left ventricular systolic function but altered diastolic function, with greater dependence on atrial contraction, the latter of which persists despite nearing term. These findings may be relevant to the management of preterm infants and may relate to the longer term myocardial dysfunction observed in affected adults.

Glucocorticoids and foetal heart maturation; implications for prematurity and foetal programming

Glucocorticoids are steroid hormones, essential in mammals to prepare for life after birth. Blood levels of glucocorticoids (cortisol in most mammals including humans; corticosterone in rats and mice) rise dramatically shortly before birth. This is mimicked clinically in the routine administration of synthetic glucocorticoids to pregnant women threatened by a preterm birth or to preterm infants to improve neonatal survival. Whilst effects on lung are well documented and essential for postnatal survival, those on heart are less well known. In this study, we review recent evidence for a crucial role of glucocorticoids in late gestational heart maturation. Either insufficient or excessive glucocorticoid exposure before birth may alter the normal glucocorticoid-regulated trajectory of heart maturation with potential life-long consequences.

Left and right ventricular myocardial performance index (Tei index) in very-low-birth-weight infants

This study presents a report of serial assessment of ventricular myocardial performance index (Tei index) in very-low-birth-weight (VLBW) infants. One hundred ninety-five VLBW infants, weighing <1,500 g, who were admitted to the neonatal intensive care units at Kakogawa Municipal Hospital between September 2000 and August 2004. Left ventricular (LV) and right ventricular (RV) Tei indexes were assessed consecutively from birth to day 28 in all VLBW infants using pulsed-Doppler echocardiography. The mean values of the LV Tei index rose rapidly from 3 to 12 h after birth and then fell significantly after 24 h. Those of the RV Tei index increased slightly from 3 to 12 h, then decreased drastically after 24 h. The LV Tei index was found to correlate inversely with LV output and LV ejection fraction in the early neonatal period, while the relationship between the LV Tei index and the LV E/A velocity ratio was not significant. The RV Tei index was inversely correlated with RV output. In conclusion, both of the ventricular Tei indexes in VLBW infants showed drastic and significant changes on the first to second day after birth.

Left Ventricular Diastolic Performance in Neonates

BACKGROUND

The left ventricular (LV) diastolic performance of infants who were in a stable post-treatment condition in the neonatal intensive care unit was evaluated using echocardiography.

METHODS AND RESULTS

The study group comprised 55 infants (Stable infant group, SI) and the parameters of LV performance were: LV propagation velocity (Vp) by color M-mode Doppler echocardiography (CMD), peak E wave, peak A wave, and the E/A ratio of transmitral flow. In a second set of measurements, a subset of 10 infants (patent ductus arteriosus (PDA) infant group, PI) were evaluated for LV diastolic performance during closure of PDA. The mean Vp in the SI was 27.2+/-7.3 cm/s and a positive correlation was observed between Vp and gestational age (r = 0.477, p = 0.0002). In the PI, Vp did not change significantly during closure of the PDA (from 23.3+/-8.2 cm/s to 27.5+/-8.4 cm/s); however, the E/Vp ratio decreased significantly with closure (from 3.14+/-0.83 to 2.12+/-0.68, p = 0.0051).

CONCLUSION

The measurement of Vp by CMD can be considered a parameter for the evaluation of LV diastolic performance, even in the neonatal period. The LV diastolic performance of the infant is maintained from immediately after birth to spontaneous closure of the PDA.

Doppler flow parameters of left ventricular filling in infants: how long does it take for the maturation of the diastolic function in a normal left ventricle to occur?

OBJECTIVE

To study the impact of the maturational process of diastolic left ventricular function on trans-mitral Doppler flow parameters.

METHODS AND PARTICIPANTS

In a survey we examined pulsed-wave Doppler signals and diastolic time intervals from 238 healthy neonates and infants. Using multiple linear regression analysis, we evaluated the impact of physiological determinants on parameter expression.

RESULTS

Early-filling and atrial-filling peak velocities, early-filling acceleration and deceleration rates, and the atrial-filling time velocity integral reached a climax within 2 months after birth, while early-filling time velocity integral followed increasing throughout the study period. The isovolumic relaxation time was found to be significantly longer for neonates than for infants older than 2 months. The observed parameter movements could be attributed to changes of stroke volume and mitral valve area for early filling-time velocity integral (R2 = 0.93), and of heart rate, stroke volume, and mitral valve area for early filling peak velocity (R2 = 0.84), and atrial-filling time velocity integral (R2 = 0.65). Isovolumic relaxation time and atrial-filling peak velocity became heart rate dependent not before 3 months after birth.

CONCLUSIONS

The observed parameter changes are powerful indicators for the maturational process in diastolic function. This process is mainly completed by 3 months of age.

Doppler-derived parameters of diastolic left ventricular function in preterm infants with a birth weight <1500 g: reference values and differences to term infants

Transmitral flow parameters in preterm and term infants were compared in order to study differences in signal expression and temporal dynamics of left ventricular diastolic function. In 63 preterm infants between 26 and 33 weeks of gestation and 102 term infants, a Doppler survey was performed during 6 months after birth. Early and atrial filling-time velocity integrals and peak velocities were significantly lower in the preterm neonates. Atrial filling parameters reached the level observed in term infants by 2 months of age. Peak early filling velocity was still lower for 2-month-old preterms and attained the term infants' level by 3 months of age. Preterm infants continued having high atrial filling fraction (AFF) (0.51+/-0.07) during 2 months after birth, while in term infants the fraction decreased continuously from 0.41+/-0.06 to 0.37+/-0.05. Isovolumic relaxation time (IVRT) was the only parameter without differences between preterm and term infants, and it decreased from 54+/-7 ms in neonates to 41+/-4 ms over 3 months. Stroke volume passing the mitral valve doubled in preterm (4+/-1 to 7.9+/-1.5 ml/cm2), but increased by only 37% (6.9+/-1.6 to 9.5+/-2.2 ml/cm2) in term infants. Our observations show that the maturational period of diastolic function appears prolonged in preterm infants. As preterm infants have to cope with a higher physiologic preload augmentation during growth, part of the delay in parameter changes might be caused by preload stress rather than by persistence of functional impairment. Although doing well under physiological conditions, preterm neonates may be at higher risk for diastolic dysfunction than term infants when an additional preload challenge is encountered.

Diastolic left ventricular function in preterm infants with a patent ductus arteriosus: a serial Doppler echocardiography study

In very low birth weight neonates, a left-to-right shunt via persistent ductus arteriosus (PDA) may interact with diastolic left ventricular function, but specific changes of Doppler parameters have yet to be reported. In a serial transmitral Doppler study, we investigated the impact of a PDA on diastolic function parameters. Twenty-two patients with and without PDA were examined on day 3.8+/-1 and day 14+/-2 after birth. By the first examination, 13 out of 22 patients had a PDA; by the second examination, the number was still 8 out of 22. Peak early and atrial flow velocities (44.8+/-15 and 50.1+/-13 cm/s, respectively) were higher (p<0.05) for neonates with PDA compared to those with closed duct (30.9+/-6 and 34.2 cm/s, respectively). Isovolumic relaxation time (IVRT) was shorter in neonates with PDA (45+/-7 ms, N=21) compared to those with a closed duct (55.3+/-5 ms, N=23) (p<0.01). IVRT correlated inversely with cardiac index (R=-0.79, p<0.01). All observed changes reversed to the normal range after closure of the PDA. When premature infants with a PDA experience a preload challenge, early and atrial peak velocities increase and IVRT shortens significantly. This coincidence of elevated transvalvular pressure differences and decreased IVRT in neonates with immature diastolic function can best be explained as a result of left atrial pressure elevation. Consequently, pulmonary venous pressure must be elevated, with its inherent effect on pulmonary capillary physiology. Thus, the monitoring of left ventricular diastolic function adds significant information to the care of preterm infants with a PDA.

Development of left ventricular systolic and diastolic function in preterm infants during the first month of life: a prospective follow-up study

OBJECTIVES

We studied the left ventricular systolic and diastolic function in preterm infants during the first month of life in comparison with the respective patterns in term neonates.

STUDY DESIGN

Serial 2-dimensional/M-mode and Doppler transmitral flow velocity measurements were performed in 20 preterm (gestational age, 32 to 36 weeks) and 25 term infants between days 2 and 5 after birth and at age 1 month.

RESULTS

After birth, the early velocity, early integral, early filling fraction, early and atrial velocity ratios, and early and atrial integral ratios were lower in the preterm than in the term infants (P <.01). During the first 4 weeks of life, these values, the atrial velocity, and the atrial integral increased gradually, whereas the atrial filling fraction, diastolic filling time, and deceleration time of early diastolic filling decreased slightly with postnatal age (P <.01) in the preterm infants. At age 1 month their diastolic function reached the level of term infants with the exception of early and atrial integral ratios and atrial filling fraction. The measures of systolic performance were within normal range, but midwall fractional shortening at 2 to 5 days (P <.05), and fractional shortening area (P <.05), as well as midwall fractional shortening (P <.01) at 1 month of age, were slightly inferior in the preterm than in the term infants. During the first month the left ventricular mass and left ventricular mass/body surface area ratio increased more markedly in the preterm than term infants, significantly in both groups (P <.05).

CONCLUSIONS

The preterm diastolic patterns represent a transition between the patterns of the fetus and those of term neonates. These changes reflect an improvement in the left ventricular diastolic function, more markedly in relaxation than in compliance. The postnatal increase in the transmitral measures and left ventricular mass suggest marked myocardial adaptation to the extrauterine environment in the preterm infant already during the first month.