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

Echocardiographic Reference Ranges of Non-Invasive Myocardial Work Indices in Newborns

Background: Myocardial work (MCW), estimated using non-invasive pressure-strain loops, is a novel approach for assessing left ventricular function. MCW offers potential advantages over left ventricular ejection fraction and global longitudinal strain (GLS). This study aimed to establish a reference range for MCW in newborns.

Methods and Results: Overall, 113 healthy newborns (mean [±SD] birth weight 3,120±378 g) were included in the study. After entering peripheral systolic and diastolic blood pressure (BP) values, global constructive work (GCW), global work index (GWI), global work efficiency (GWE), and global wasted work (GWW) were calculated using EchoPAC software (version 204). Considering a mean [±SD] GLS of −16.3±2.8%, the mean [±SD] GWI, GCW, GWW, and GWE was 698.7±147.9 mmHg%, 1,008.5±200.1 mmHg%, 58.1±28.1 mmHg%, and 93.1±2.9%, respectively. All MCW parameters in newborns were lower than those previously reported in children and adults. However, GWI and GCW were more closely correlated with BP and GLS, as in adulthood and children. Estimation of the correlation between MCW and the frame rate index revealed no significant correlations among MCW parameters.

Conclusions: Cardiac function in newborns was evaluated by assessing MCW. With the establishment of reference ranges and normative MCW data for newborns, routine clinical use and rotational mechanics are likely to become increasingly common. Future studies are needed to determine whether MCW is useful in screening for cardiac illness among newborns.

Does chest wall conformation influence myocardial strain parameters in infants with pectus excavatum?

PURPOSE

To investigate the possible influence of chest wall conformation on myocardial strain parameters in a consecutive population of infants with pectus excavatum (PE), noninvasively assessed by modified Haller index (MHI).

METHODS

Sixteen consecutive PE infants (MHI >2.5) and 44 infants with normal chest shape (MHI ≤2.5) entered in this prospective case-control study. All infants underwent evaluation by neonatologist, transthoracic echocardiography implemented with two-dimensional speckle tracking echocardiography (2D-STE) analysis of both ventricles and MHI assessment (ratio of chest transverse diameter over the distance between sternum and spine), at two time points: within 3 days and at about 40 days of life.

RESULTS

At 2.1 ± 1 days of life, compared to controls (MHI = 2.01 ± 0.2), PE infants (MHI = 2.76 ± 0.2) were diagnosed with significantly smaller cardiac chambers dimensions. Biventricular contractile function and hemodynamics were similar in both groups of infants. Left ventricular (LV) global longitudinal strain (GLS) (-16.0 ± 2.8 vs. -21.7 ± 2.2%), LV-global circumferential strain (GCS) (-16.3 ± 2.7 vs. -24.0 ± 5.2%), LV-global radial strain (GRS) (24.2 ± 3.0 vs. 31.5 ± 6.3%), and right ventricular free wall longitudinal strain (RVFWLS) (-16.0 ± 3.2 vs. -22.3 ± 4.4%) were significantly reduced in PE infants versus controls (all p < 0.001). A strong inverse correlation between MHI and the following parameters: LV-GLS (r = -0.92), LV-GCS (r = -0.88), LV-GRS (r = -0.87), and RVFWLS (r = -0.88), was demonstrated in PE infants, but not in controls, in perinatal period (all p < 0.001). Analogous results were obtained at 36.8 ± 5.2 days after birth.

CONCLUSIONS

Abnormal chest anatomy progressively impairs myocardial strain parameters in PE infants. This impairment might reflect intraventricular dyssynchrony due to compressive phenomena rather than intrinsic myocardial dysfunction.

The impact preload on left ventricular three-plane deformation measurements in extremely premature infants

BACKGROUND

Left Ventricular (LV) deformation analysis using two-dimensional speckle tracking echocardiography (STE) is an emerging modality in premature infants.

AIMS

To assess the impact of increased preload on LV deformation in three planes: longitudinal, circumferential and radial in premature infants.

STUDY DESIGN AND SUBJECTS

Infants recruited to the PDA RCT (ISRCTN 13281214) and survived to discharge were included with the cohort divided into infants who closed their patent ductus arteriosus (PDA) by Day 8 (Low preload, PDA Closed) and those who maintained ductal patency (high preload, PDA Open).

OUTCOME MEASURES

Longitudinal, circumferential and radial strain and systolic strain rate (SRs) were measured at 36 h, Days 4 & 8 and 36 weeks.

RESULTS

61 infants were included. The PDA open Group had a lower gestation (26.4 vs. 27.4 weeks, p < 0.01) with a median PDA exposure of 30 days (vs. 2 days, p < 0.01), and demonstrated echocardiography evidence of pulmonary overcirculation. There was higher LV longitudinal strain and SRs over the first 3 scans in the PDA Open Group. Circumferential strain was higher over the first 2 scans while circumferential SRs was higher at 36 h. Radial Strain and SRs were only higher on Day 4.

CONCLUSION

Increased preload is associated with higher strain and systolic strain rate values in the premature population indicating that preload has a significant effect on deformation measurements in this population across all three planes.

Maturational patterns of left ventricular rotational mechanics in pre-term infants through 1 year of age

BACKGROUND

Pre-mature birth impacts left ventricular development, predisposing this population to long-term cardiovascular risk. The aims of this study were to investigate maturational changes in rotational properties from the neonatal period through 1 year of age and to discern the impact of cardiopulmonary complications of pre-maturity on these measures.

METHODS

Pre-term infants (<29 weeks at birth, n = 117) were prospectively enrolled and followed to 1-year corrected age. Left ventricular basal and apical rotation, twist, and torsion were measured by two-dimensional speckle-tracking echocardiography and analysed at 32 and 36 weeks post-menstrual age and 1-year corrected age. A mixed random effects model with repeated measures analysis was used to compare rotational mechanics over time. Torsion was compared in infants with and without complications of cardiopulmonary diseases of pre-maturity, specifically bronchopulmonary dysplasia, pulmonary hypertension, and patent ductus arteriosus.

RESULTS

Torsion decreased from 32 weeks post-menstrual age to 1-year corrected age in all pre-term infants (p < 0.001). The decline from 32 to 36 weeks post-menstrual age was more pronounced in infants with cardiopulmonary complications, but was similar to healthy pre-term infants from 36 weeks post-menstrual age to 1-year corrected age. The decline was due to directional and magnitude changes in apical rotation over time (p < 0.05).

CONCLUSION

This study tracks maturational patterns of rotational mechanics in pre-term infants and reveals torsion declines from the neonatal period through 1 year. Cardiopulmonary diseases of pre-maturity may negatively impact rotational mechanics during the neonatal period, but the myocardium recovers by 1-year corrected age.

Left ventricular ejection fraction using manual and semi-automated biplane method of discs in very preterm infants

BACKGROUND

Biplane left ventricular ejection fraction (LVEF) is a valuable echocardiographic parameter for assessment of LV systolic pump efficiency in adults and children, but not often reported in preterm infants. The primary aim of this study was to longitudinally measure biplane LVEF in very preterm infants during the neonatal intensive care period. Secondary aim was to compare manual and semi-automatic determination of LVEF for agreement and variability.

METHODS

Stable preterm infants less than 30 weeks gestation were scanned on day 3, day 28, and at 36 weeks postmenstrual age. The LV endocardium was traced manually and semi-automatically using integrated speckle tracking software in apical 4-chamber and apical 3-chamber images to obtain end-diastolic volume and end-systolic volume, and calculate LVEF. Agreement between methods and variability within and between observers was determined using an interclass correlation coefficient (ICC) and Bland-Altman analysis.

RESULTS

Sixty-six preterm infants with a mean birth weight of 1100 (239) g were analyzed. The average manual biplane LVEF was 58 (3)%, 59 (3)%, and 55 (4)% at the three respective time points. Manual LVEF showed good agreement with semi-automatic LVEF (ICC 0.76) with a small bias of -1.5 (3.0)%. Interobserver variability of LVEF improved with semi-automatic tracing of the LV endocardial border (ICC manual 0.68 vs semi-automatic 0.80).

CONCLUSION

Left ventricular systolic pump efficiency in preterm infants remains stable during the neonatal intensive care period. Semi-automatic biplane LVEF has less interobserver variability and can be used interchangeably with manual biplane LVEF.

Dilated hypertrophy: a distinct pattern of cardiac remodeling in preterm infants

BACKGROUND

Young adults born preterm have remodeled hearts, i.e., altered cardiac shape and size with impaired cardiac function. At present, the natural history and pattern of prematurity related cardiac remodeling are not clearly established. The aim of this study was to compare the left ventricle (LV) geometry and function of preterm infants at 36 weeks postmenstrual age (PMA) with gestation matched newborn infants.

METHODS

LV end diastolic volume index (LV EDVI), LV mass index (LVMI), relative wall thickness (RWT), and sphericity index (SI) were prospectively obtained with echocardiography. LV geometry was classified according to the Gaasch method. LV function was assessed by determining ejection fraction (EF), longitudinal strain (LS), mitral annulus systolic motion (s'), and estimated LV filling pressure (E/e').

RESULTS

Eighty-three preterm infants between 23 and 29 weeks gestation, and 40 infants of 36 weeks gestation at birth were analysed. LV EDVI, LVMI, SI, LS, s', and E/e' were higher in preterm group while RWT and EF were comparable between groups. LV showed normal geometry in 55.4%, physiological enlargement in 23% and dilated hypertrophy in 21.6% preterm infants.

CONCLUSION

At 36 week, preterm infants have significantly dilated, hypertrophied, and more spherical LV with impaired diastolic function compared with PMA matched newborn infants.

Left Ventricular Diastolic Dysfunction and Diastolic Heart Failure in Preterm Infants

Diastolic dysfunction is primarily an echocardiographic diagnosis. Its clinical counterpart is diastolic heart failure, where the heart has difficulty to fill at normal pressure and the patient develops signs of pulmonary edema. Although diastolic dysfunction is common in adults, limited information is available in preterm infants. The aim of this study is to explore left ventricular diastolic dysfunction and diastolic heart failure in preterm infants and describe clinical manifestations in this population. This is a retrospective observational study in preterm infants < 30 weeks' gestation who received an echocardiography in the first 4 weeks after birth. Diastolic dysfunction was graded using a population-specific adapted version of the adult recommendations for the evaluation of left ventricular diastolic function by echocardiography. Left ventricular diastolic dysfunction was absent, indeterminate, and definite in 82%, 14%, and 4% of the 168 echocardiograms analyzed, and is associated with increased respiratory signs and respiratory deterioration at 48 h before echocardiogram. In seven infants, diastolic heart failure was diagnosed with both ultrasound and clinical signs. The cumulative risk of diastolic dysfunction increased with the increasing postnatal age and a patent ductus arteriosus. Evidence of left ventricular diastolic dysfunction on echocardiography is relatively common in preterm infants, while the left ventricular diastolic heart failure is less frequent. Prolonged exposure to volume load was the most common cause.

Maturational patterns in right ventricular strain mechanics from the fetus to the young infant

AIM

To test the hypothesis that right ventricular (RV) function has age-specific patterns of development, we tracked the evolution of RV strain mechanics by 2D-speckle tracking echocardiography (2DSTE) in healthy subjects from mid-gestation through one year of age.

METHODS

We conducted a prospective longitudinal echocardiography study in 50 healthy subjects at five time periods across gestation (16-20 weeks, 21-25 weeks, 26-30 weeks, 31-35 weeks, and 36-40 weeks) and four time periods following delivery (1 week, 1 month, 6 months, and 1 year of age). We characterized RV function by measuring RV global and free wall longitudinal strain and systolic strain rate, and segmental longitudinal strain at the apical-, mid-, and basal- ventricular levels of the free wall. Possible associations of gestational age, postnatal age, estimated fetal weight, body surface area, gender, and heart rate on strain were investigated.

RESULTS

The magnitudes of RV global and free wall longitudinal strain and global strain rate were decreased throughout gestation (p < 0.05 for all). Following birth, the magnitudes of all measures increased from one week through one year (p < 0.001 for all). RV segmental longitudinal strain maintained a base-to-apex gradient (highest-to-lowest) from mid-gestation through one year (p < 0.001). There was no significant difference in strain patterns based on gender or hear rate.

CONCLUSION

The maturational patterns of RV strain are gestational- and postnatal age- specific. With accepted physiological maturation patterns in healthy subjects, these myocardial deformation parameters can provide a valid basis that allows comparison between health and disease.

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.

Early diastolic dysfunction and respiratory morbidity in premature infants: an observational study

OBJECTIVE

To test if diastolic dysfunction measured on day one of age is associated with the need for invasive ventilation in preterm infants.

STUDY DESIGN

We conducted a retrospective observational tissue Doppler echocardiographic study over the first 12 h of age for infants born <32 weeks who were invasively ventilated, and infants on continuous positive pressure ventilation (CPAP).

RESULTS

One hundred and eighty-three infants were included (27 ± 2 weeks and 999 ± 296 g). Invasively ventilated infants [(n = 96 (53%)] had lower left ventricular (LV) e' (3.4 ± 1.0 vs. 4.1 ± 1.5 cm/s, p < 0.01) and lower LV ea' ratio (0.8 ± 0.2 vs. 1.0 ± 0.4, p < 0.01), even after adjusting for common neonatal confounders (LV e' adjusted OR 0.62, 95% CI 0.45 - 0.87, p < 0.01; LV ea' adjusted OR 0.14, 95% CI 0.03-0.68, p = 0.01).

CONCLUSION

LV diastolic dysfunction is independently associated with a higher risk for invasive ventilation on day one of age.

Early modifications of cardiac function in preterm neonates using speckle tracking echocardiography

BACKGROUND AND AIMS

Preterm newborns undergo hemodynamic challenges in the postnatal period. The aim of this study was to investigate myocardial mechanics changes in the postnatal period in preterm infants using speckle tracking echocardiography (STE).

MATERIAL AND METHODS

Thirty-nine preterm infants ≤34 weeks' gestation underwent cardiac ultrasound evaluation during the first 96 hours of life. A repeated echocardiogram at 3 weeks of age was performed. Echocardiographic assessment involved left ventricular ejection fraction, mitral E/A ratio, S' and E' velocities, E/E' ratio, tricuspid annular plane systolic excursion (TAPSE), left atrium-to-aorta ratio, ductal diameter and ductal shunt pattern. Left ventricular longitudinal, circumferential and radial strain, apex-basal rotation and twist were measured from the apical 4-chamber and short-axis views using STE.

RESULTS

The mean gestational age was 30 ± 2.7 weeks with a mean birth weight of 1318 ± 485 g. Apical segments demonstrated higher longitudinal strain than basal and mid-ones. In all gestational ages, endocardial longitudinal strain was higher than the epicardial. Epicardial longitudinal strain significantly increased during the first 3 weeks, resulting in the change in basal rotation from counterclockwise to clockwise and thus in the acquisition of twist. Deformation parameters were higher in infants with a hemodynamic significant patents ductus arteriosus.

CONCLUSIONS

Echocardiographic assessment of myocardial deformation parameters is feasible in preterm infants. Our data suggest that the maturational process of the myocardium is due to the development of the epicardial layer after birth, which allows the acquisition of the twist.

Deformation imaging and rotational mechanics in neonates: a guide to image acquisition, measurement, interpretation, and reference values

Advances in neonatal cardiac imaging permit a more comprehensive assessment of myocardial performance in neonates that could not be previously obtained with conventional imaging. Myocardial deformation analysis is an emerging quantitative echocardiographic technique to characterize global and regional ventricular function in neonates. Cardiac strain is a measure of tissue deformation and strain rate is the rate at which deformation occurs. These measurements are obtained in neonates using tissue Doppler imaging (TDI) or two-dimensional speckle tracking echocardiography (STE). There is an expanding body of literature describing longitudinal reference ranges and maturational patterns of strain values in term and preterm infants. A thorough understanding of deformation principles, the technical aspects, and clinical applicability is a prerequisite for its routine clinical use in neonates. This review explains the fundamental concepts of deformation imaging in the term and preterm population, describes in a comparative manner the two major deformation imaging methods, provides a practical guide to the acquisition and interpretation of data, and discusses their recognized and developing clinical applications in neonates.

A comparison between Philips and Tomtec for left ventricular deformation and volume measurements in neonatal intensive care patients

BACKGROUND

Two-dimensional speckle tracking echocardiography is an emerging technique for analyzing cardiac function in newborns. Strain is a highly reliable and reproducible parameter, and reference values have been established for term and preterm newborns. Its implementation into clinical practice has been slow, partly due to lack of inter-vendor consistency. Our aim was to compare recent versions of Philips and Tomtec speckle tracking software for deformation and semiautomated volume and area measurements in neonatal intensive care patients.

METHODS AND RESULTS

Longitudinal and circumferential deformation and cavity dimensions (volume, area) were determined off line from apical and short-axis images in 50 consecutive newborns with a median birthweight of 760 g (range 460-3200 g). Absolute mean endocardial global longitudinal strain measurements were similar between vendors, but with wide limits of agreement (Philips -18.9 [2.1]%, Tomtec -18.6 [2.5]%, bias -0.3 [1.7]%, and limits of agreement -3.6%-3.1%). Longitudinal strain rate and circumferential measurements showed poor correlation. All volume and area measurements correlated well between the vendors, but with significant bias.

CONCLUSION

Global longitudinal strain measurements compared well between vendors but wide limits of agreement, suggesting that longitudinal measurements are preferred using similar hardware and software.

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.

Maturational Patterns of Systolic Ventricular Deformation Mechanics by Two-Dimensional Speckle-Tracking Echocardiography in Preterm Infants over the First Year of Age

BACKGROUND

The aim of this study was to determine the maturational changes in systolic ventricular strain mechanics by two-dimensional speckle-tracking echocardiography in extremely preterm neonates from birth to 1 year of age and discern the impact of common cardiopulmonary abnormalities on the deformation measures.

METHODS

In a prospective multicenter study of 239 extremely preterm infants (<29 weeks gestation at birth), left ventricular (LV) global longitudinal strain (GLS) and global longitudinal systolic strain rate (GLSRs), interventricular septal wall (IVS) GLS and GLSRs, right ventricular (RV) free wall longitudinal strain and strain rate, and segmental longitudinal strain in the RV free wall, LV free wall, and IVS were serially measured on days 1, 2, and 5 to 7, at 32 and 36 weeks postmenstrual age, and at 1 year corrected age (CA). Premature infants who developed bronchopulmonary dysplasia or had echocardiographic findings of pulmonary hypertension were analyzed separately.

RESULTS

In uncomplicated preterm infants (n = 103 [48%]), LV GLS and GLSRs remained unchanged from days 5 to 7 to 1 year CA (P = .60 and P = .59). RV free wall longitudinal strain, RV free wall longitudinal strain rate, and IVS GLS and GLSRs significantly increased over the same time period (P < .01 for all measures). A significant base-to-apex (highest to lowest) segmental longitudinal strain gradient (P < .01) was seen in the RV free wall and a reverse apex-to-base gradient (P < .01) in the LV free wall. In infants with bronchopulmonary dysplasia and/or pulmonary hypertension (n = 119 [51%]), RV free wall longitudinal strain and IVS GLS were significantly lower (P < .01), LV GLS and GLSRs were similar (P = .56), and IVS segmental longitudinal strain persisted as an RV-dominant base-to-apex gradient from 32 weeks postmenstrual age to 1 year CA.

CONCLUSIONS

This study tracks the maturational patterns of global and regional deformation by two-dimensional speckle-tracking echocardiography in extremely preterm infants from birth to 1 year CA. The maturational patterns are ventricular specific. Bronchopulmonary dysplasia and pulmonary hypertension leave a negative impact on RV and IVS strain, while LV strain remains stable.

Right ventricular performance using myocardial deformation imaging in infants with bronchopulmonary dysplasia

OBJECTIVE

Right ventricular (RV) performance among infants with bronchopulmonary dysplasia (BPD) remains poorly understood. We tested the hypothesis that myocardial deformation imaging (MDI) strain and strain rate would allow for differentiation between infants with severe and milder forms of BPD, independent of tissue Doppler imaging (TDI) and superior to conventional echocardiographic measurements.

STUDY DESIGN

Infants with various severities of BPD (11 with none or mild, 13 with moderate and 10 with severe) underwent conventional echocardiography, TDI and MDI assessments at >36 weeks of corrected gestational age. BPD severity grading was determined according to the National Institutes of Child Health and Disease workshop rating scale by physicians blinded to the echocardiogram results. Group data were compared with one-way analysis of variance or Kruskal-Wallis tests, with post hoc multiple comparisons.

RESULTS

No differences in traditional echocardiographic parameters or TDI among the three BPD severity groups were observed; none of the infants had evidence of pulmonary hypertension. Using MDI, infants with severe BPD had lower peak global systolic strain than did infants with moderate BPD (P<0.01) or mild/none BPD (P<0.01). Early and late diastolic strain rate measurements were similar across the three groups.

CONCLUSIONS

Among infants with severe forms of BPD, evidence of abnormal RV systolic function was detected with MDI, but not traditional echocardiographic or TDI measurements. Infants with severe forms of BPD may represent a particularly high-risk subgroup for decreased RV performance warranting cardiac surveillance. MDI should be considered as a method to quantitate RV function in this population.

Myocardial function during bradycardia events in preterm infants

BACKGROUND

Transient bradycardia episodes are common in preterm infants and often secondary to apnea. Decreased ventilation with resultant hypoxemia is believed to be the predominant mechanism. Sudden bradycardias without apnea are also reported, possibly due to vagal stimulation. Point of care ultrasound is used to diagnose and follow cardiovascular complications in preterm infants. Inadvertently, the operator would sometimes capture bradycardia events. This study reports on left ventricular function during such events.

METHODS

We retrospectively reviewed our cardiac ultrasound database for bradycardia events. Apical four or three chamber images before, during and after a bradycardia event were analysed with speckle tracking software which provides systolic and diastolic parameters of myocardial motion, deformation and volume.

RESULTS

Over a 2year period, 15 bradycardia events were noted in 14 patients with a median gestational age of 26weeks (range 23 to 29). Heart rate decreased by an average of 43% (171/min to 98/min). Myocardial velocity and longitudinal strain rate during the atrial component of diastole were reduced during bradycardia. Longitudinal strain during systole was increased and radial deformation was unchanged. Ventricular volumes and ejection fraction did not change. Most parameters returned to baseline values after the event. Longitudinal systolic strain rate remained lower and stroke volume was 12% higher compared to baseline.

CONCLUSION

Parameters of systolic contractility and stroke volume were maintained and parameters of atrial contractility were reduced during mild to moderate bradycardia in preterm infants. Bradycardia reduces total cardiac output with a compensatory increase detected following the event.

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.