Left ventricular preload reserve in preterm infants with patent ductus arteriosus

Biventricular function in preterm infants with patent ductus arteriosus ligation: A three-dimensional echocardiographic study

BACKGROUND

The detailed hemodynamics after patent ductus arteriosus (PDA) ligation in preterm infants remain unknown. We aimed to clarify the effect of surgical ligation on left ventricular (LV) and right ventricular (RV) volume and function.

METHODS

Echocardiography was performed in 41 preterm infants (median gestational age: 25 weeks) before and after PDA ligation. Global longitudinal strain was determined using three-dimensional speckle-tracking echocardiography. These values were compared with those in 36 preterm infants without PDA (non-PDA).

RESULTS

Preoperatively, the PDA group had greater end-diastolic volume (EDV) and cardiac output (CO) in both ventricles, a higher LV ejection fraction (LVEF) (53% vs 44%) and LV global longitudinal strain, and a lower RVEF (47% vs 52%) than the non-PDA group. At 4-8 h postoperatively, the two groups had a similar LVEDV and RVEDV. However, the PDA group had a lower EF and CO in both ventricles than the non-PDA group. At 24-48 h postoperatively, the RVEF was increased, but the LVEF remained decreased, and LVCO was increased.

CONCLUSIONS

PDA induces biventricular loading and functional abnormalities in preterm infants, and they dramatically change after surgery. Three-dimensional echocardiography may be beneficial to understand the status of both ventricles.

IMPACT

Preterm infants are at high risk of hemodynamic compromise following a sudden change in loading conditions after PDA ligation. Three-dimensional echocardiography enables quantitative and serial evaluation of ventricular function and volume in preterm infants with PDA. PDA induces biventricular loading and functional abnormalities in preterm infants, and they dramatically change after surgery.

Respiratory Variation in Aortic Blood Flow Velocity in Hemodynamically Unstable, Ventilated Neonates: A Pilot Study of Fluid Responsiveness

OBJECTIVES

To assess whether respiratory variation in aortic blood flow peak velocity can predict preload responsiveness in mechanically ventilated and hemodynamically unstable neonates.

DESIGN

Prospective observational diagnostic accuracy study.

SETTING

Third-level neonatal ICU.

PATIENTS

Hemodynamically unstable neonates under mechanical ventilation.

INTERVENTIONS

Fluid challenge with 10 mL/kg of normal saline over 20 minutes.

MEASUREMENTS AND MAIN RESULTS

Respiratory variation in aortic blood flow peak velocity and superior vena cava flow were measured at baseline (T0), immediately upon completion of the fluid infusion (T1), and at 1 hour after fluid administration (T2). Our main outcome was preload responsiveness which was defined as an increase in superior vena cava flow of at least 10% from T0 to T1. Forty-six infants with a median (interquartile range) gestational age of 30.5 weeks (28-36 wk) were included. Twenty-nine infants (63%) were fluid responders, and 17 (37%) were nonresponders Fluid responders had a higher baseline (T0) respiratory variation in aortic blood flow peak velocity than nonresponders (9% [8.2-10.8] vs 5.5% [3.7-6.6]; p < 0.001). Baseline respiratory variation in aortic blood flow peak velocity was correlated with the increase in superior vena cava flow from T0 to T1 (rho = 0.841; p < 0.001). The area under the receiver operating characteristic curve of respiratory variation in aortic blood flow peak velocity to predict preload responsiveness was 0.912 (95% CI, 0.82-1). A respiratory variation in aortic blood flow peak velocity cut-off point of 7.8% provided a 90% sensitivity (95% CI, 71-97), 88% specificity (95% CI, 62-98), 7.6 positive likelihood ratio (95% CI, 2-28), and 0.11 negative likelihood ratio (95% CI, 0.03-0.34) to predict preload responsiveness.

CONCLUSIONS

Respiratory variation in aortic blood flow velocity may be useful to predict the immediate response to a fluid challenge in hemodynamically unstable neonates under mechanical ventilation. If our results are confirmed, this measurement could be used to guide safe and individualized fluid resuscitation in critically ill neonates.

Ratio of arterial blood pressures at borders of window surrounding systolic peak indicates patent ductus arteriosus in preterm infants

OBJECTIVE

Presence of a patent ductus arteriosus (PDA) in neonates is assessed by echocardiography. Echocardiographic assessment has disadvantages, primarily its discontinuous nature. We hypothesize that the continuously measured ratio of arterial blood pressures (ABP) at the borders of a window surrounding the systolic peak ratio discriminates non-PDA from PDA patients.

APPROACH

Preterm infants (gestational age <32 weeks) with and without PDA were included. Patients were divided into controls (n = 8) and PDA patients (n = 22), the latter with a subset of patients with closed PDA after three doses Ibuprofen (n = 10). For each patient, a six-hour ABP segment from 12 AM to 6 AM on the day of echocardiographic assessment patency or closure of the DA was selected. The mean ratio of the ABP values a samples before and p samples after the systolic peak (R _ABP) was calculated for each segment. If R _ABP < 1, the patient was predicted to have a PDA. The a and p with the least misclassifications were selected (-64 and +104 ms).

MAIN RESULTS

R _ABP was significantly lower in PDA patients (median 0.95, IQR 0.06) compared to controls (median 1.05, IQR 0.10; p = 0.0024). R _ABP correctly predicted 19 out of 22 patients (86.4%) and six out of eight controls (75%). R _ABP increased after closure in nine out of 10 patients (median 1.01, IQR 0.04; p = 0. 0182).

SIGNIFICANCE

R _ABP may discriminate preterm PDA patients from non-PDA patients and can be calculated continuously from clinical data measured during standard of care.

Decreased Variability and Low Values of Perfusion Index on Day One Are Associated with Adverse Outcome in Extremely Preterm Infants

OBJECTIVE

To develop new quantitative features for the Perfusion Index signal recorded continuously over the first 24 hours of life in a cohort of extremely low gestational age newborns and to assess the association of these features with normal and adverse short-term outcome.

STUDY DESIGN

A cohort study of extremely low gestational age newborns. Adverse outcome was defined as early mortality before 72 hours of life, acquired severe periventricular-intraventricular hemorrhage, or severe cystic leukomalacia. Perfusion Index values were obtained from the plethysmographic signal of a pulse oximeter. Perfusion Index signals were separated into low-frequency (trend) and high-frequency (detrend) components. Three features were extracted during four 6-hour epochs: mean of the trend component (mean-trend), SD of the trend component (SD-trend), and SD of the detrend component (SD-detrend). The SD features represent long-term variability (SD-trend) and short-term variability (SD-detrend) of the Perfusion Index. A mixed-effects model was fitted to each feature.

RESULTS

Ninety-nine infants were included in the analysis. Quadratic-time mixed-effects models provided the best fit for all 3 features. The mean-trend component was lower for the adverse outcome compared with the normal outcome group with a difference of 0.142 Perfusion Index (P = .001). SD-detrend component was also lower for the adverse compared with the normal outcome group, although this difference of 0.031 Perfusion Index/days² was dependent on time (P < .001).

CONCLUSION

Low values and reduced short-term variability of Perfusion Index on day 1 are associated with adverse outcome.

Preoperative left ventricular internal dimension in end-diastole as earlier identification of early patent ductus arteriosus operation and postoperative intensive care in very low birth weight infants

Patent ductus arteriosus (PDA) is common in premature infants. In very low birth weight infants (VLBWI), PDA requires surgical therapy in many cases. It is unclear to know at-risk infants showing cardio-dysfunction after PDA surgery. The purpose of this study was to identify at-risk infants showing cardio-dysfunction after surgery for patent ductus arteriosus (PDA). We examined the relationship between left ventricular (LV) performance before and after PDA ligation in a retrospective observational cohort study. We studied 64 preterm neonates with symptomatic PDA before and after surgical ligation. Echocardiographic examinations were performed pre- and postoperatively. M-mode measurements included left ventricular internal dimension in end-diastole (LVIDd) and LV fractional shortening (FS). All cases showed decreased LVFS after PDA closure. Most cases (49/64, 77%) showed postoperative FS decreased to below normal (<28%). Preoperative relative LVIDd was significantly larger in abnormal FS infants (137 ± 18%) than in normal FS infants (118 ± 11%; p<0.01). A cut-off value of preoperative relative LVIDd (absolute LVIDd/normal value) for predicting postoperative cardio-dysfunction was 127.4% (sensitivity, 0.735; specificity, 0.933; area under curve, 0.817). Determination of preoperative LVIDd might facilitate earlier identification of infants needing early PDA surgery and postoperative intensive care.

Acute changes in myocardial systolic function in preterm infants undergoing patent ductus arteriosus ligation: a tissue Doppler and myocardial deformation study

BACKGROUND

Ligation of a patent ductus arteriosus (PDA) in preterm infants causes profound hemodynamic changes that can result in low cardiac output syndrome and hypotension. The effect of PDA ligation on left ventricular myocardial function has not been studied using tissue Doppler and myocardial deformation imaging, mainly because of the limited validation of these methods in preterm infants. The primary objective of the present study was to determine the feasibility and reliability (intraobserver and interobserver variability) of tissue Doppler and myocardial deformation imaging for evaluating myocardial function in preterm infants undergoing surgical PDA ligation. Additionally, we sought to study the immediate effect of surgical ligation on the left ventricular tissue Doppler and strain measurements in the first 24 hours after surgery.

METHODS

Echocardiography was performed in 19 preterm infants before, 1 hour after, and 18 hours after PDA ligation born at 24-29 weeks of gestation. The tissue Doppler velocities of the lateral tricuspid and lateral and septal mitral valve annuli were obtained. The global and regional longitudinal peak systolic strain values were determined using two-dimensional speckle tracking echocardiography. The results of the three measurement points were compared using repeated measures analysis of variance. The intra- and interobserver variability was assessed using the intraclass correlation coefficient and Bland-Altman analysis.

RESULTS

The median gestational age was 25.0 weeks (interquartile range 24.9-25.9) and the birth weight was 750 g (interquartile range 600-810). For the global longitudinal strain, the intraobserver intraclass correlation coefficient was 0.92 (95% CI, 0.78-0.97, P < .001), and the interobserver intraclass correlation coefficient was 0.93 (95% CI, 0.66-0.98, P < .001). Bland-Altman analysis showed no significant bias between the two observers, with good agreement. The systolic and diastolic tissue Doppler velocities of the mitral valve decreased significantly immediately after ligation and remained significantly lower than the preoperative levels at 18 hours. Also, the global longitudinal strain values significantly decreased 1 hour after the procedure (global longitudinal strain before -19.7% ± -3.8% vs -11.5% ± -3.5%; P = .001) but had significantly improved 18 hours after the procedure (-15.1% ± -2.9%, P = .01).

CONCLUSIONS

The present study has shown the feasibility and reliability of using tissue Doppler and strain imaging in premature infants with a hemodynamically significant PDA. Significant changes in myocardial function were observed immediately after PDA ligation, suggesting important changes in myocardial performance immediately after ductal ligation.

Evaluation of the Neonatal Resuscitation Program's recommended chest compression depth using computerized tomography imaging

BACKGROUND

Neonatal Resuscitation Program (NRP) guidelines recommend chest compression depths of 1/3 the anterior-posterior (AP) chest depth. Appropriateness of this recommendation has not been rigorously assessed.

OBJECTIVE

To compare the efficacy and safety of neonatal chest compression depths of 1/4, 1/3, and 1/2 AP chest depth during cardiopulmonary resuscitation.

DESIGN/METHODS

Anterior-posterior internal and external chest depth, heart dimensions, and non-cardiac thoracic tissue depth were measured from neonatal chest CTs. Using these measurements, residual internal chest depth, the remaining depth of the chest between the sternum and spine after external compression, was calculated for compression depths of 1/4, 1/3 and 1/2 anterior-posterior chest depth. Compression sufficient to compress the chest to <10mm of residual internal chest depth was defined as over-compression. Using a mathematic model, an estimated ejection fraction (EF) was calculated for each chest compression depth. Compression inadequate to obtain a predicted 50% EF was defined as under-compression. Descriptive statistics, Fisher's exact test and Student's t-test were used to analyze data, where appropriate.

RESULTS

Fifty-four neonatal chest CT scans were evaluated. Estimated chest compression induced EF increased incrementally with increasing chest compression depth (EF was 51+/-3% with 1/4 AP chest depth vs 69+/-3% with 1/3 AP chest depth, and 106% with 1/2 AP chest depth, p<0.001). Under-compression was predicted in 29/54 patients with 1/4 AP compression depth, but none of the patients with 1/3 or 1/2 AP compression depth, p<0.001. Over-compression, or lack of adequate residual chest depth, was predicted in 49/54 patients with 1/2 AP compression depth, but none of the patients with 1/4 or 1/3 AP compression depth, p<0.001.

CONCLUSIONS

Mathematical modeling based upon neonatal chest CT scan dimensions suggests that current NRP chest compression recommendations of 1/3 AP chest depth should be more effective than 1/4 compression depth, and safer than 1/2 AP compression depth.

Acute hemodynamic decompensation following patent ductus arteriosus ligation in premature infants

INTRODUCTION

Patent ductus arteriosus (PDA) ligation can lead to postoperative hemodynamic instability requiring inotropic support, termed hemodynamic decompensation. The purpose of this study was to prospectively determine the incidence, predictors, and clinical impact of hemodynamic decompensation after PDA ligation in preterm infants.

METHODS

All infants undergoing PDA ligation were eligible for this prospective cohort study. After undergoing ligation, patients were followed until 30 days after successful extubation, discharge from the NICU, or death. Data collection included perinatal and preoperative clinical information, operative details, postoperative course, and outcome.

RESULTS

Ninety-six preterm infants were enrolled and underwent PDA ligation. Hemodynamic decompensation occurred in 27 patients (28%). Overall in-hospital mortality rate was 18%. Mortality was significantly higher among infants that developed hemodynamic decompensation (33% vs 11%, p = .012). Hemodynamic decompensation was associated with an adjusted odds ratio (OR) for death of 3.1 (95% confidence interval: 1.0-9.5, p = .05). Lower estimated gestational age, lower corrected age, and higher rate of preoperative mechanical ventilation were significant predictors of hemodynamic decompensation.

CONCLUSION

Hemodynamic decompensation occurred in 28% of patients after PDA ligation, resulting in a significantly higher mortality. Younger patients requiring higher ventilator support are most likely to develop hemodynamic decompensation.

Myocardial contractility in premature neonates with and without patent ductus arteriosus

Controversy exists as to whether a hemodynamically significant left-to-right shunt due to a patent ductus arteriosus (PDA) affects ventricular contractility. Load-dependent indices such as ejection fraction and shortening fraction have traditionally been used to assess contractility, but the relationship between the rate-corrected velocity of fiber shortening (MVCFc) and wall stress may be more suitable, as it is a preload-independent, afterload-adjusted method of assessing ventricular contractility. Age-related differences have been established for these variables in normal adults and children and it has been recommended for use in the premature neonate. The study was performed to assess left ventricular contractility in premature neonates with a significant left-to-right shunt due to a PDA. Using echocardiography, we measured the relationship of MVCFc to stress at peak systole (SPS) in two groups of premature infants. Group 1 consisted of 15 controls (680-1495 g, 25-32 weeks' gestation), and Group 2 of 15 neonates with hemodynamically significant PDA (840-1635 g, 26-33 weeks' gestation). In both groups, MVCFc was linearly and inversely related to SPS ( p < 0.001). The regression equations were as follows: Group 1, MVCFc = -0.0153SPS + 1.70 ( R(2) = 0.68); and Group 2, MVCF = - 0.019SPS + 1.89 ( R(2) = 0.76). There was no significant difference in the relationship between the two groups, but their slopes were significantly steeper and had a higher Y-intercept than the relationship we previously reported for older children. This preliminary study establishes the normal MVCFc/SPS relationship in the premature neonate (25-33 weeks' gestation) and suggests that premature infants function at a higher resting contractile state than older children. A hemodynamically significant PDA has no effect on contractility. These data will be useful in assessing left ventricular contractility in premature neonates with other types of ventricular loading and noncardiac stress.

Left ventricular systolic and diastolic function during early neonatal period using transthoracic echocardiography

To examine the effects of ductal closure on left ventricular (LV) systolic and diastolic function during the early neonatal periods, 45 normal term neonates delivered after uncomplicated pregnancies (mean 39 weeks) were studied using two-dimensional and Doppler echocardiography. We measured ductus arteriosus size, arterial blood pressures, ascending aortic size, LV dimensions, and transmitral flow velocity patterns and calculated LV output and rate-corrected fiber shortening fraction (mVcfc) at 2, 12, 24, and 120 hours after birth. The inner diameter of the ductus arteriosus was 4.3 +/- 0.7mm at 2 hours, 2.1 +/- 0.6 mm at 12 hours, and had closed in 42 of 45 neonates at 24 hours. LV output and LV end-diastolic dimension showed the highest level at 2 hours of age. However, the mVcfc did not change from 2 to 120 hours of age. The peak velocity during early diastole (peak E) was significantly greater at 2 hours than at 12 hours. The peak velocity during atrial contraction (peak A) remained unchanged during this period. The normalized peak filling rate at isovolumic relaxation time did not change over 120 hours. The present study demonstrated changes in LV systolic function and LV diastolic filling during the early neonatal period. LV systolic and diastolic function was preserved under the hemodynamic changes associated with the early neonatal period.

Cerebral blood flow velocity wave form as an indicator of neonatal left ventricular heart function

OBJECTIVE

To investigate the relationship between cerebral blood flow velocity wave form (CBFV-WF) parameters and myocardial contractility indices in healthy and sick preterm and term newborns.

METHODS

Total group of 82 babies was divided into four subgroups: prematures with gestational age <34 weeks with (n=20) and without (n=14) respiratory distress syndrome (RDS) and infants with gestational age of >33 weeks with (n=18) and without (n=30) asphyxia. On day 1, 2, 3, 6 and 14, the acceleration time, Q(ECG)-peak(flow) time and preejection period of CBFV-WF (internal carotid artery) were measured through the anterior fontanel by Doppler ultrasonography. Simultaneously cardiac output, fractional shortening, systolic time intervals and their ratio were determined echocardiographically.

RESULTS

RDS-babies had higher cardiac output and better myocardial performance then non-RDS-babies. Asphyxiated babies had lower cardiac output as compared to healthy babies, improving over time. Correlations were found between CBFV-WF parameters and several myocardial function indicators, but preejection period of cerebral blood flow velocity correlated closest with the same period measured echocardiographically (r=0.67, P<0.0001). Multiple linear regression revealed no influence of gestational age or clinical condition on this relationship. Assessment of agreement indicated that only substantial changes in myocardial performance could be monitored using preejection period of CBFV.

CONCLUSION

Although a relationship was detected between the preejection period of CBFV and left ventricular systolic time interval (used as indicator of changes in left ventricular function), only rather large changes in left ventricular performance can be reliably detected using the preejection period of CBFV.

Abnormal left ventricular diastolic filling patterns in small-for-gestational-age infants

Doppler transmitral flow velocity patterns in assessing left ventricular diastolic function in small-for-gestational-age infants have been poorly understood. The purpose of this study is to examine Doppler filling patterns in small-for-gestational-age infants (n = 13) and to compare them with those in age-matched appropriate-for-gestational-age infants (n = 29). We measured peak flow velocities of early diastole (peak E wave) and atrial contraction (peak A wave), ratio of peak E wave to peak A wave (peak E/A wave), velocity time integrals of E wave (VTIE wave) and A wave (VTIA wave), ratio of VTIE wave to VTIA wave (VTIE/A wave), first third filling fraction, peak filling rate normalized to stroke volume, and deceleration time. Mean gestational age and heart rate did not show a significant difference between the appropriate- and the small-for-gestational-age infants. The mean birth weight in the small-for-gestational-age infants was significantly lower than that in the appropriate-for-gestational-age infants (802+/-220 vs. 1184+/-260 g, P<0.01). In the small-for-gestational-age infants, the peak E wave, peak A wave, peak E/A wave,VTIE wave, first third filling fraction, and peak filling rate normalized to stroke volume were significantly lower than those in the age-matched appropriate-for-gestational-age infants (21.9+/-6.7 vs. 32.2+/-6.9 cm/s, 26.5+/-6.2 vs. 34.5+/-6.2 cm/s, 0.82+/-0.15 vs. 0.93+/-0.14, 1.88+/-0.45 vs. 2.39+/-0.51 cm, 0.36+/-0.04 vs. 0.41+/-0.04, 5.86+/-0.75 vs. 7.11+/-0.63/s, P<0.05, respectively). In the small and appropriate for gestational age infants, peak E wave, VTIE wave, and peak E/A increased significantly with increasing body weight. In the small-for-gestational-age infants, the slopes of regression lines between body weights and peak E wave and VTIE wave were significantly lower than those in the appropriate for gestational age infants, suggesting a significant reduction in E wave even when considering a difference in their body weight. This study suggests that the significant decreases in the early diastolic filling in the small-for-gestational-age infants may be related to the reduced left ventricular diastolic function.

Changes in left ventricular diastolic filling patterns before and after the closure of the ductus arteriosus in very-low-birth weight infants

To evaluate serial changes in left ventricular diastolic filling patterns in preterm infants, we performed echocardiographic examinations in 18 very-low-birth weight infants and 20 fullterm infants before and after the closure of the ductus arteriosus. In the fullterm infants, the ductal closure induced significant decreases in the peak velocity and flow velocity integral of early diastole, first third filling fraction, and mitral stroke volume. In the preterm infants, by contrast, there were significant increases in the flow velocity integral of early diastole, first third filling fraction, and mitral stroke volume after the ductal closure. No differences following the ductal closure were found in the atrial phase of filling and peak filling rate normalized to stroke volume in either group. When the ductus arteriosus was open, essentially the same left-to-right shunting of the ductus arteriosus was detected in both preterm and fullterm infants, but the Doppler flow patterns of the patent foramen ovale were different: the fullterm infants had a single flow peak mainly during ventricular late systole and early diastole, but the preterm infants had two or three flow peaks with nearly equal amplitudes lasting from ventricular systole to diastole, which resembled the Doppler flow pattern of atrial septal defect. Only a faint Doppler flow signal of the foramen ovale was observed after the ductus arteriosus closed. Our results obtained from the preterms suggest that the left-to-right shunt through the foramen ovale may be one important factor to alter the Doppler transmitral filling patterns during the fetal to neonatal cardiovascular changes.

Changes in left ventricular volume and systolic function before and after the closure of ductus arteriosus in full-term infants

Using echocardiographic techniques, the change in left ventricular (LV) volume and its effect on systolic function were studied before and after the closure of ductus arteriosus in 18 full-term infants. Examinations were performed twice in each infant, within 6 h after birth and on day 5, and the patency of the ductus with left-to-right shunt was confirmed at the first examination by Doppler echocardiography. A biplane Simpson's rule method was used for volume measurements. The LV end-diastolic volume, stroke volume, and cardiac output were more than 1.3-fold before the ductal closure, and the ejection fraction showed the similar change. However, the mean normalized systolic ejection rate, an index of contractility, and heart rate showed no significant difference. The Frank-Starling curve was obtained from the relationship between the LV end-diastolic and stroke volumes, and the LV performance was operated at a higher level on that curve when the ductus was open. Our data indicated that LV cardiac output was significantly higher during the patency of the ductus arteriosus and that this high cardiac performance might depend more on the Frank-Starling response to the volume load through the ductus arteriosus than on the increase of LV contractility and heart rate.