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The hemodynamics in Fontan patients with single ventricles rely on favorable flow and energetics, especially in the absence of a subpulmonary ventricle. Age-related changes in energetics for extracardiac and lateral tunnel Fontan procedures are not well understood. Vorticity (VOR) and viscous dissipation rate (VDR) are two descriptors that can provide insights into flow dynamics and dissipative areas in Fontan pathways, potentially contributing to power loss. This study examined power loss and its correlation with spatio-temporal flow descriptors (vorticity and VDR). Data from 414 Fontan patients were used to establish a relationship between the superior vena cava (SVC) to inferior vena cava (IVC) flow ratio and age. Computational flow modeling was conducted for both extracardiac conduits (ECC, n = 16) and lateral tunnels (LT, n = 25) at different caval inflow ratios of 2, 1, and 0.5 that corresponded with ages 3, 8, and 15+. In both cohorts, vorticity and VDR correlated well with PL, but ECC cohort exhibited a slightly stronger correlation for PL-VOR (>0.83) and PL-VDR (>0.89) than that for LT cohort (>0.76 and > 0.77, respectively) at all ages. Our data also suggested that absolute and indexed PL increase (p < 0.02) non-linearly as caval inflow changes with age and are highly patient-specific. Comparison of indexed power loss between our ECC and LT cohort showed that while ECC had a slightly higher median PL for all 3 caval inflow ratio examined (3.3, 8.3, 15.3) as opposed to (2.7, 7.6, 14.8), these differences were statistically non-significant. Lastly, there was a consistent rise in pressure gradient across the TCPC with age-related increase in IVC flows for both ECC and LT Fontan patient cohort. Our study provided hemodynamic insights into Fontan energetics and how they are impacted by age-dependent change in caval inflow. This workflow may help assess the long-term sustainability of the Fontan circulation and inform the design of more efficient Fontan conduits., (© 2024. The Author(s) under exclusive licence to Biomedical Engineering Society.)

Background: Although the mechanism of action in newborns is unknown, sleep positioning is associated with many pathophysiological events. This study aimed to compare the effects of supine and prone sleeping positions on cardiac output (CO), systolic pulmonary arterial pressure (SPAP), and superior vena cava (SVC) flow in healthy newborns., Methods: In the first 24-72 h of life, 40 healthy term newborns born in the same hospital were included in this prospective, cross-sectional, observational study. CO, SVC flow, and SPAP values of newborns in the supine and prone sleeping positions were calculated using echocardiographic examination. The measurements were statistically compared., Results: In the supine sleeping position, CO, SVC flow, and SPAP were 235.00 (193.07-283.30) ml/kg/min, 92.80 (77.82-121.87) ml/kg/min, and 27.85 (24.70-30.48) mmHg. In the prone sleeping position, CO, SVC flow, and SPAP were measured as 195.35 (166.00-229.40) ml/kg/min, 67.25 (51.82-96.66) ml/kg/min, 31.60 (28.45-37.20) mmHg, respectively. Depending on sleeping position, these variables were significantly different between the groups., Conclusion: SVC flow and CO decreased in the prone sleeping position compared to the supine sleeping position in healthy newborns, whereas SPAP increased. The different hemodynamic effects of sleeping position on the cardiac, pulmonary, and nervous systems should be considered as flow and pressure changes are important in newborns., Competing Interests: Declaration of competing interest The authors have no conflicts of interest relevant to this article., (Copyright © 2023 Taiwan Pediatric Association. Published by Elsevier B.V. All rights reserved.)

Superior vena cava (SVC) flow has been considered a surrogate marker of systemic blood flow in neonates. We conducted a systematic review to evaluate the association between low SVC flow recorded during the early neonatal period and neonatal outcomes. We searched the following databases (until December 9, 2020; updated October 21, 2022): PROSPERO, OVID Medline, OVID EMBASE, Cochrane Library (CDSR and Central), Proquest Dissertations and Theses Global, and SCOPUS using controlled vocabulary and key words representing the concepts "superior vena cava" and "flow" and "neonate." Results were exported to COVIDENCE review management software. The search retrieved 593 records after the removal of duplicates, of which 11 studies (nine cohorts) met the inclusion criteria. The majority of the studies included infants born at <30 weeks of gestation. The included studies were assessed as high risk of bias in terms of the incomparability of the study groups, with infants in the low SVC flow group noted to be more immature than those in the normal SVC flow group or subjected to different cointerventions. We did not conduct meta-analyses in view of the significant clinical heterogeneity noted in the included studies. We found little evidence to suggest that SVC flow in the early neonatal period is an independent predictor for adverse clinical outcomes in preterm infants. Included studies were assessed at high risk of bias. We conclude that SVC flow interpretation for prognostication or for making treatment decisions should be restricted to the research setting for now. We highlight the need for strengthened methods in future research studies. KEY POINTS: · We studied whether low SVC flow in the early neonatal period is a marker for adverse outcomes in preterm infants.. · There is insufficient evidence to conclude that low SVC flow is a valid predictor of adverse outcomes.. · There is insufficient evidence to conclude that SVC flow-directed hemodynamic management improves clinical outcomes.., Competing Interests: None declared., (Thieme. All rights reserved.)

Background: The Fontan operation is a palliative technique for patients born with single ventricle heart disease. The superior vena cava (SVC), inferior vena cava (IVC), and hepatic veins are connected to the pulmonary arteries in a total cavopulmonary connection by an extracardiac conduit or a lateral tunnel connection. A balanced hepatic flow distribution (HFD) to both lungs is essential to prevent pulmonary arteriovenous malformations and cyanosis. HFD is highly dependent on the local hemodynamics. The effect of age-related changes in caval inflows on HFD was evaluated using cardiac magnetic resonance data and patient-specific computational fluid dynamics modeling., Methods: SVC and IVC flow from 414 patients with Fontan were collected to establish a relationship between SVC:IVC flow ratio and age. Computational fluid dynamics modeling was performed in 60 (30 extracardiac and 30 lateral tunnel) patient models to quantify the HFD that corresponded to patient ages of 3, 8, and 15 years, respectively., Results: SVC:IVC flow ratio inverted at ≈8 years of age, indicating a clear shift to lower body flow predominance. Our data showed that variation of HFD in response to age-related changes in caval inflows (SVC:IVC, 2, 1, and 0.5 corresponded to ages, 3, 8, and 15+, respectively) was not significant for extracardiac but statistically significant for lateral tunnel cohorts. For all 3 caval inflow ratios, a positive correlation existed between the IVC flow distribution to both the lungs and the HFD. However, as the SVC:IVC ratio changed from 2 to 0.5 (age, 3-15+) years, the correlation's strength decreased from 0.87 to 0.64, due to potential flow perturbation as IVC flow momentum increased., Conclusions: Our analysis provided quantitative insights into the impact of the changing caval inflows on Fontan's long-term HFD, highlighting the importance of SVC:IVC variations over time on Fontan's long-term hemodynamics. These findings broaden our understanding of Fontan hemodynamics and patient outcomes., Competing Interests: Disclosures Dr Govindarajan reports research funding from the American Heart Association (19TPA34860013), the National Heart, Lung, and Blood Institute (NHLBI)/National Institutes of Health (NIH; R01HL161507) and in-kind research support from National Science Foundation (high-performance computing resources from Texas Advanced Computing Center). A. Sahni, E. Eickhoff, and Drs Hoganson, Hammer, and Rathod report research funding from the NHLBI/NIH (R01HL161507). In addition, Dr Govindarajan reports collaborative research funding from Polyvascular Corp, Houston, TX.

Background: Cardiovascular support (CVS) treatment failure (TF) is associated with a poor prognosis in preterm infants., Methods: Medical charts of infants with a birth weight <1500 g who received either dopamine (Dp) or dobutamine (Db), were reviewed. Treatment response (TR) occurred if blood pressure increased >3rd centile for gestational age or superior vena cava flow was maintained >55 ml/kg/min, with decreased lactate or less negative base excess, without additional CVS. A predictive model of Dp and Db on TR was designed and the impact of TR on survival was analyzed., Results: Sixty-six infants (median gestational age 27.3 weeks, median birth weight 864 g) received Dp (n = 44) or Db (n = 22). TR occurred in 59% of the cases treated with Dp and 31% with Db, p = 0.04. Machine learning identified a model that correctly labeled Db response in 90% of the cases and Dp response in 61.4%. Sixteen infants died (9% of the TR group, 39% of the TF group; p = 0.004). Brain or gut morbidity-free survival was observed in 52% vs 30% in the TR and TF groups, respectively (p = 0.08)., Conclusions: New predictive models can anticipate Db but not Dp effectiveness in preterm infants. These algorithms may help the clinicians in the decision-making process., Impact: Failure of cardiovascular support treatment increases the risk of mortality in very low birth weight infants. A predictive model built with machine learning techniques can help anticipate treatment response to dobutamine with high accuracy. Predictive models based on artificial intelligence may guide the clinicians in the decision-making process., (© 2023. The Author(s), under exclusive licence to the International Pediatric Research Foundation, Inc.)

Objective: To assess the hemodynamic safety and efficacy of umbilical cord milking (UCM) compared with early cord clamping (ECC) in nonvigorous newborn infants enrolled in a large multicenter randomized cluster-crossover trial., Study Design: Two hundred twenty-seven nonvigorous term or near-term infants who were enrolled in the parent UCM vs ECC trial consented for this substudy. An echocardiogram was performed at 12 ± 6 hours of age by ultrasound technicians blinded to randomization. The primary outcome was left ventricular output (LVO). Prespecified secondary outcomes included measured superior vena cava (SVC) flow, right ventricular output (RVO), peak systolic strain, and peak systolic velocity by tissue Doppler examination of the RV lateral wall and the interventricular septum., Results: Nonvigorous infants receiving UCM had increased hemodynamic echocardiographic parameters as measured by higher LVO (225 ± 64 vs 187 ± 52 mL/kg/min; P < .001), RVO (284 ± 88 vs 222 ± 96 mL/kg/min; P < .001), and SVC flow (100 ± 36 vs 86 ± 40 mL/kg/min; P < .001) compared with the ECC group. Peak systolic strain was lower (-17 ± 3 vs -22 ± 3%; P < .001), but there was no difference in peak tissue Doppler flow (0.06 m/s [IQR, 0.05-0.07 m/s] vs 0.06 m/s [IQR, 0.05-0.08 m/s])., Conclusions: UCM increased cardiac output (as measured by LVO) compared with ECC in nonvigorous newborns. Overall increases in measures of cerebral and pulmonary blood flow (as measured by SVC and RVO flow, respectively) may explain improved outcomes associated with UCM (less cardiorespiratory support at birth and fewer cases of moderate-to-severe hypoxic ischemic encephalopathy) among nonvigorous newborn infants., (Copyright © 2023 Elsevier Inc. All rights reserved.)

Greater interest in imaging the superior vena cava (SVC) in recent years has arisen because of increased focus on disorders of the right heart; the growing use of transvenous access lines, dialysis catheters, and device leads; and the emergence of right ventricular mechanical circulatory support systems via the transcatheter approach. As a low-pressure venous conduit in the right upper mediastinum, the SVC is prone to compression by various pathologic processes, to invasion by malignancies originating in nearby structures, and to complications arising from intraluminal device leads and indwelling catheters. Computed tomography and magnetic resonance venography are the modalities of choice for structural imaging of the SVC. Ultrasound allows a reasonable, yet less detailed anatomic assessment of this venous conduit. Spectral and color Doppler imaging by ultrasound are the most valuable noninvasive tools for the interrogation of SVC blood flow, a marker of the filling pattern of the right heart. Analysis of the velocity, duration, and direction of the Doppler waveforms and their phasic response to respiration makes it possible to distinguish normal from abnormal flow patterns and offers diagnostic insights into disorders that affect right heart function. The aims of this review are to demonstrate the added value SVC imaging provides during transthoracic and transesophageal echocardiographic studies, to outline its usefulness for the detection and evaluation of structural abnormalities, and to detail the role of spectral Doppler imaging in aiding the diagnosis of various disorders that affect the right heart., (Copyright © 2023 American Society of Echocardiography. Published by Elsevier Inc. All rights reserved.)

To evaluate feasibility, reproducibility, and prognostic value of a new echocardiographic method to assess systemic arterial blood flow directed to the upper part of the body (UBAF, upper body arterial flow) alternative to superior vena cava flow (SVCF) measurement. We performed echocardiographic evaluations in 106 infants in the first 2 days of life to obtain SVCF, left ventricle output (LVO), UBAF, and standard parameters of patent ductus arteriosus (PDA) significance. UBAF was calculated by subtracting from LVO the aortic arch blood flow measured immediately distally to the origin of the left subclavian artery. Main outcome measures: UBAF and SVCF agreement was assessed by Bland-Altman analysis in terms of bias, limits of agreement and repeatability index. The Intraclass Correlation Coefficient was used to measure the strength of inter-rater agreement. The agreement between UBAF and SVCF was high. The Concordance Correlation Coefficient (CCC) was 0.7434. (CCC 0.7434, 95% C.I. [0.656, 0.8111]). There was a good absolute agreement between the two raters ICC = 0.747; p value < 0.0001; 95%CI [0.601; 0.845]. Adjusting for confounding factors (BW, GA, PDA) included in the model, there was a statistically significant relationship between UBAF and SVCF., Conclusion: UBAF showed a strong agreement with the SCVF with a better reproducibility. Our data support UBAF as a potentially useful marker of cerebral perfusion in the evaluation of preterm infants., What Is Known: • Low SVC (superior vena cava) flow in the neonatal period has been associated with periventricular haemorrhage and unfavourable long-term neurodevelopmental outcome. • Ultrasound measurement of flow in SVC shows relatively high inter-operator variability., What Is New: • Our study highlights how much overlap there is between upper-body arterial flow (UBAF) measurement and SCV flow measurement. UBAF is easier to perform and has a strong correlation with better reproducibility. • UBAF may replace measurement of cava flow as a method for haemodynamic monitoring of unstable preterm and asphyxiated infants., (© 2023. The Author(s).)

Despite of growing evidence of the beneficial effects of placental transfusion techniques, there is no available sufficient data about their effects on vulnerable hemodynamics and myocardium of premature infants. The purpose of this work is to study ventricular functions and hemodynamics after applying different placental transfusion techniques, delayed cord clamping (DCC), cut cord milking (C-UCM), and intact cord milking (I-UCM). Sixty-four infants delivered whether by C-section or vaginal delivery were randomly assigned to undergo C-UCM (20-30 cm), I-UCM (3-4 strippings), and DCC (30-60 s). Functional echocardiography was done on day 1 and day 3 of life for 57 infants. Primary outcome variable was superior vena cava flow measurement in infants having placental transfusion in the first 24 h of life and between 64 and 72 h. Secondary outcomes were other echocardiographic and clinical hemodynamic parameters, and biventricular functions in those infants. Of a total 196 preterm infants ≤ 32 weeks delivered in the study period, from January 2021 to August 2021, 57 infants were eligible and survived till the second examination. They were randomly assigned to the three groups. Neonates randomly assigned to DCC had significantly higher superior vena cava flow and lower right ventricular systolic function in the first 24 h of life. This finding vanished at day 3. Neonates undergone different methods of placental transfusions had similar hemoglobin, admission temperature, and mean blood pressure in the first 24 h of life., Conclusion: Despite their potential benefits, placental transfusions have shown to alter the hemodynamics and adversely affect myocardial function of premature neonates., Trial Registration: This trial was registered in the clinical trial gov NCT04811872., What Is Known: • Placental transfusion techniques might have benefits regarding prematurity- related morbidities and mortality., What Is New: • Placental transfusion might adversely affect the myocardium and alter hemodynamics in premature infants., (© 2022. The Author(s).)

Unstable hemodynamics and prematurity are the main players in intraventricular hemorrhage (IVH) development. Our objective was to study 8 the use of superior vena cava flow (SVCF), left ventricular output (LVO), and right ventricular output (RVO), and anterior cerebral artery (ACA) Doppler measures in prediction of IVH in the first week of life in preterm infant ≤ 32 weeks and birth weight ≤ 1500 g. This prospective cohort study was conducted in 55NICU of Alexandria University maternity hospital. Of 147 enrolled patients, 132 infants born ≤ 32 weeks GA and birth weight ≤ 1500 g were eligible for- the study. One hundred twenty-seven infants completed the study. Infants were scanned for ACA-RI using transfontanellar ultrasound, and SVCF, LVO, and RVO using functional echocardiography in the first 24 h after birth. Patients had another two scans on DOL3 and 7 to detect IVH development. Low SVCF and high ACA-RI significantly increased the risk of IVH using logistic regression models with OR, 3.16; 95%CI, 1.19-8.39; P = 0.02 and OR, 1.64; 95%Cl, 1.10-2.44; P = 0.02, respectively. Low SVCF and high ACA-RI significantly increased risk of catastrophic IVH P = 0.025 and 0.023, respectively. Combined use of low SVCF < 55 ml/kg/min and ACA-RI > 0.75 is predictor of IVH with sensitivity 40.8% and 82.1% specificity., Conclusions: There are strong relations between both low SVCF and high ACA-RI, and IVH development in premature neonates ≤ 32 weeks and birth weight ≤ 1500 g, with more significance towards catastrophic IVH. Admission RSS and LVO are the strongest factors affecting SVCF. Maternal anemia, patent ductus arteriosus size (mm/kg), and capillary refill time were significantly associated with high ACA-RI. These findings help in more understanding of pathophysiological factors affecting central perfusion that might affect the longer term neurodeveopmental outcome., Trial Registration: This work was registered in clinical trial.gv no NCT05050032., What Is Known: •Whether SVCF and RI-ACA can predict IVH in preterm neonates is still debatable., What Is New: •Low SVC flow and high ACA-RI significantly increased risk of IVH, confirming the role of hypoperfusion-reperfusion cycle in IVH development. The most striking result that combined metrics using the cut-off value of < 41 ml/kg/min for SVCF and > 0.85 for ACA-RI "in the first day of life" can correctly reject the presence of IVH in 98% of patients "during the first week of life.", (© 2022. The Author(s).)

Background: Delayed cord clamping (DCC) is practiced worldwide, as standard care in both term and preterm babies. Our aim was to determine the hemodynamic effects of DCC on transitional circulation., Material and Methods: This prospective observational study was carried out in a tertiary care hospital, at Pune, India, from May 2018 to October 2019.Term neonates born during the study period were included. The primary outcome variables of the study were right ventricular output (RVO), left ventricular output (LVO), superior vena cava (SVC) flow (ml/kg/min) and heart rate(HR) at 12 ± 6 and 48 ± 6 h of life measured by point of care functional echocardiography. Inter-observer and intra-observer variability was calculated for these parameters., Results: Out of a total of 2744 deliveries during the study period, 620 babies were included. Mean gestational age of the enrolled babies was 38.96 ± 1.08 weeks and mean birth weight was 2.9 ± 0.39 kg. Mean heart rate of babies recorded at 12 ± 6 h of life was 127 beats per minute (bpm) whereas it was 128 bpm at 48 ± 6 h of life. RVO {mean (SD)} was 209.55(44.89) and 205.85(46.35) ml/kg/min, LVO {mean (SD)} was 133.68(31.15) and 134.78(29.84) ml/kg/min whereas SVC flow {mean (SD)} was 106.85(26.21) and 109.29(25.11) ml/kg/min at 12 ± 6 and 48 ± 6 h of life respectively. There was good intra-observer agreement in all the variables. SGA babies had a significantly higher heart rate at 12 ± 6 h of life as compared to AGA babies, although this difference in heart rate could not be appreciated at 48 ± 6 h of life. However SGA babies had a higher LVO, RVO and SVC flow than AGA babies at both the time points of observation., Conclusion: After DCC there is less fluctuation in the hemodynamic parameters (heart rate, cardiac output) at the two time points of observation.. As compared to AGA babies, SGA babies had a significantly higher baseline heart rate, LVO, RVO and SVC flow. LVO of SGA babies after delayed cord clamping is found to be significantly lower than LVO seen in other studies, favoring the cardio-stabilizing effect of DCC., Brief Rationale: This is the first study with a large sample size evaluating the hemodynamic effects of DCC in term neonates by functional echocardiography. The normative data of heart rate and cardiac output of term, stable babies with small for gestational age(SGA) as a special subgroup undergoing DCC requires further evaluation., (© 2022. The Author(s).)

The performance of each veno-venous extracorporeal membrane oxygenation (vv-ECMO) configuration is determined by the anatomic context and cannula position. A mathematical model was built considering bicaval specificities to simulate femoro-jugular configuration. The main parameters to define were cardiac output (Q C ), blood flow in the superior vena cava (Q SVC ), extracorporeal pump flow (Q EC ), and pulmonary shunt (k S-PULM ). The obtained variables were extracorporeal flow ratio in the superior vena cava (EFR SVC  = Q EC /[Q EC  + Q SVC ]), recirculation coefficient (R), effective extracorporeal pump flow (Q eff-EC  = [1 - R] × Q EC ), Q eff-EC /Q C ratio, and arterial blood oxygen saturation (SaO 2 ). EFR SVC increased logarithmically when Q EC increased. High Q C or high Q SVC /Q C decreased EFR SVC (range, 68%-85% for Q EC of 5 L/min). R also increased following a logarithmic shape when Q EC increased. The R rise was earlier and higher for low Q C and high Q SVC /Q C (range, 12%-49% for Q EC of 5 L/min). The Q eff-EC /Q C ratio (between 0 and 1) was equal to EFR SVC for moderate and high Q EC . The Q eff-EC /Q C ratio presented the same logarithmic profile when Q EC increased, reaching a plateau (range, 0.67-0.91 for Q EC /Q C  = 1; range, 0.75-0.94 for Q EC /Q C  = 1.5). The Q eff-EC /Q C ratio was linearly associated with SaO 2 for a given pulmonary shunt. SaO 2  < 90% was observed when the pulmonary shunt was high (Q eff-EC /Q C  ≤ 0.7 with k S-PULM  = 0.7 or Q eff-EC /Q C  ≤ 0.8 with k S-PULM  = 0.8). Femoro-jugular vv-ECMO generates a systematic structural recirculation that gradually increases with Q EC . EFR SVC determines the Q eff-EC /Q C ratio, and thereby oxygen delivery and the superior cava shunt. EFR SVC cannot exceed a limit value, explaining refractory hypoxemia in extreme situations., (© 2021 International Center for Artificial Organs and Transplantation and Wiley Periodicals LLC.)

Background: Phasic venous flow variation with respiration is surrounded by controversy and not well understood. The current concept assigns a major role to the "abdominal pump." According to this model, inspiratory increases in abdominal pressure compress the vena cava, increasing its internal venous pressure and propelling blood upstream. Some have assigned a secondary role to the "thoracic pump," with the negative intrapleural pressure aiding blood flow toward the heart. The aim of the present study was to examine the phasic changes in flow, pressure, and volume in the central veins and named tributaries., Methods: Caliber area changes were measured using intravascular ultrasonography in 37 patients undergoing iliac vein stenting. The pressure was measured in 48 patients using transducer tip catheters with electronic zero calibration. Duplex ultrasound flow in the head and neck and truncal and limb veins during inspiration and expiration was measured in 15 normal volunteers., Results: The caliber of the abdominal inferior vena cava had increased by 32% and its lateral pressure had decreased significantly during inspiration. Intravenous pressure in the central veins of the chest and right atrium was positive at 6 to 14 mm Hg. Negative pressures were rarely seen and then only transiently. The internal jugular vein displayed little phasic variation. The upper limb veins displayed weak inspiratory phasicity. Phase polarity was reversed in the lower limbs, with near flow stoppage during inspiration., Conclusions: These observations conflict with the current notions of venous flow phasicity, which are based on push-pull pressure changes in the abdominal and thoracic veins. The paradoxical inspiratory inferior vena cava caliber increase probably explains the concurrent pressure decrease. Sustained negative pressures in the thoracic central veins and right atrium did not occur. We have proposed an alternate hypothesis for venous flow phasicity based on alternate stretching and relaxation of the mobile section of the great veins with respiratory movement., (Copyright © 2020 Society for Vascular Surgery. Published by Elsevier Inc. All rights reserved.)

Background: Fetal superior vena cava (SVC) is essentially the single vessel returning blood from the upper body to the heart. With approximately 80-85% of SVC blood flow representing cerebral venous return, its interrogation may provide clinically relevant information about fetal brain circulation. However, normal reference values for fetal SVC Doppler velocities and pulsatility index are lacking. Our aim was to establish longitudinal reference intervals for blood flow velocities and pulsatility index of the SVC during the second half of pregnancy., Methods: This was a prospective study of low-risk singleton pregnancies. Serial Doppler examinations were performed approximately every 4 weeks to obtain fetal SVC blood velocity waveforms during 20-41 weeks. Peak systolic (S) velocity, diastolic (D) velocity, time-averaged maximum velocity (TAMxV), time-averaged intensity-weighted mean velocity (TAMeanV), and end-diastolic velocity during atrial contraction (A-velocity) were measured. Pulsatility index for vein (PIV) was calculated., Results: SVC blood flow velocities were successfully recorded in the 134 fetuses yielding 510 sets of observations. The velocities increased significantly with advancing gestation: mean S-velocity increased from 24.0 to 39.8 cm/s, D-velocity from 13.0 to 19.0 cm/s, and A-velocity from 4.8 to 7.1 cm/s. Mean TAMxV increased from 12.7 to 23.1 cm/s, and TAMeanV from 6.9 to 11.2 cm/s. The PIV remained stable at 1.5 throughout the second half of pregnancy., Conclusions: Longitudinal reference intervals of SVC blood flow velocities and PIV were established for the second half of pregnancy. The SVC velocities increased with advancing gestation, while the PIV remained stable from 20 weeks to term.

Background: Cytokeratin-positive interstitial reticulum cells (CIRCs), which are a subgroup of fibroblastic reticular cells (FRCs), are known to be present in the lymph nodes. There have been only a few cases of tumors derived from CIRCs., Case Presentation: We have reported a new case involving a CIRC tumor in a 75-year-old man and reviewed the literature. The resected mediastinal lymph nodes showed epithelial-like proliferation of large atypical round and polygonal epithelioid cells. The tumor cells expressed CK8, CK18, CAM5.2, AE1/AE3, epithelial membrane antigen, vimentin, fascin, and some FRC markers, which is consistent with the diagnosis of a CIRC tumor. Following chemotherapy, the CIRC tumor was observed to have responded very well and became difficult to confirm on imaging, but a small cell lung carcinoma developed 12 months later. Chemoradiotherapy was performed, but the patient passed away 29 months after the initial diagnosis. The autopsy revealed the recurrence of the CIRC tumor, residual small cell lung carcinoma, and a very small latent carcinoma of the prostate. The relapsed CIRC tumor cells had a spindle shape; they were highly pleomorphic and had invaded the superior vena cava., Conclusion: We first reported autopsy findings of CIRC tumors and demonstrated the transformation of the tumor from the epithelioid cell type to the spindle cell type.

The electrophysiological properties of the superior vena cava (SVC) myocardium, which is considered a minor source of atrial arrhythmias, were studied in this study during postnatal development. Conduction properties were investigated in spontaneously active and electrically paced SVC preparations obtained from 7-60-day-old male Wistar rats using optical mapping and microelectrode techniques. The presence of high-conductance connexin 43 (Cx43) was evaluated in SVC cross-sections using immunofluorescence. It was found that SVC myocardium is excitable, electrically coupled with the atrial tissue, and conducts excitation waves at all stages of postnatal development. However, the conduction velocity (CV) of excitation and action potential (AP) upstroke velocity in SVC were significantly lower in neonatal than in adult animals and increased with postnatal maturation. Connexins Cx43 were identified in both neonatal and adult rat SVC myocardium; however, the abundance of Cx43 was significantly less in neonates. The gap junction uncoupler octanol affected conduction more profound in the neonatal than in adult SVC. We demonstrated for the first time that the conduction characteristics of SVC myocardium change from a slow-conduction (nodal) to a high-conduction (working) phenotype during postnatal ontogenesis. An age-related CV increase may occur due to changes of AP characteristics, electrical coupling, and Cx43 presence in SVC cardiomyocyte membranes. Observed changes may contribute to the low proarrhythmicity of adult caval vein cardiac tissue, while pre- or postnatal developmental abnormalities that delay the establishment of the working conduction phenotype may facilitate SVC proarrhythmia.

Objective: To determine associations of low superior vena cava (SVC) flow (≤55 ml/kg/min) and low right ventricular output (RVO) (≤150 ml/kg/min) in preterm infants., Design/methods: An observational study in infants <30 weeks gestation randomized to receive immediate (<10 s) or delayed cord clamping (DCC) (≥60 s)., Results: The study enrolled 265 infants with a mean (SD) gestation 28 (2) weeks. Eighty-six (33%) infants had low SVC flow and 81 (31%) infants had low RVO. In multivariate analysis, low SVC flow was associated with gestation; low RVO was associated with DCC, gender and 5-minute Apgar; whereas mean RVO was negatively associated with both FiO 2 and mean airway pressure (MAP) at 9 h and 24 h. Low SVC flow was associated with ductus arteriosus (DA) treatment. Infants with low RVO had higher mortality on univariate analysis, but this was not significant after adjusting for gestation., Conclusions: SVC flow was associated with gestation, whilst RVO was associated with placental transfusion, gender, condition at birth, and early respiratory adaptation. Compared to infants with normal values, more infants with low SVC flow were treated for DA, but infants with low RVO had no significant difference in mortality or morbidity.

Objective: To investigate whether umbilical cord milking (UCM) at birth improves systemic blood flow and short-term outcomes, as compared with immediate cord clamping (ICC)., Design: Randomised clinical trial., Setting: Single tertiary care centre., Patients: Infants born to eligible women presenting in preterm labour between 24 and 31 weeks' gestation., Interventions: UCM three times at birth or ICC., Outcome Measures: Primary outcome included systemic blood flow as represented by echo-derived superior vena cava(SVC) flow at 4-6 hours after birth. The echocardiographer and interpreter were blinded to the randomisation. Secondary outcomes included cardiac output, neonatal morbidities and mortality. Analysis was by intention to treat., Results: A total of 73 infants were randomised (37 to UCM and 36 to ICC). Mean (SD) gestational age was 27 (2) weeks and mean (SD) birth weight was 1040 (283) g. Haemoglobin on admission was higher in the UCM than in the ICC group (16.1 vs 15.0 g/L), p=0.049 (mean difference 1.1, 95% CI 0.003 to 2.2). No statistically significant differences were found between groups in SVC flow at 4-6 hours (88.9±37.8 and 107.3±60.1 mL/kg/min), p=0.13 (mean difference -18.4, 95% CI -41.7 to 5.0 mL/kg/min) or at 10-12 hours of age (102.5±41.8 and 90.6±28.4 mL/kg/min), p=0.17 (mean difference 12.0, 95% CI -4.7 to 28.7 mL/kg/min), cardiac output or neonatal morbidities., Conclusions: Cord milking was not shown to improve functional cardiac outcomes, neonatal morbidity or mortality. More research is needed before routine cord milking can be recommended for very preterm infants., Trial Registration: NCT01487187., Competing Interests: Competing interests: None declared., (© Article author(s) (or their employer(s) unless otherwise stated in the text of the article) 2019. All rights reserved. No commercial use is permitted unless otherwise expressly granted.)

Background: In preterm infants, caffeine citrate is used to stimulate breathing before they are weaned from mechanical ventilation and to reduce the frequency of apnea. In recent studies, effects of caffeine on the cardiovascular system have been emphasized in preterm infants with patent ductus arteriosus (PDA)., Methods: This study aimed to assess the short-term hemodynamic effects on systemic blood flow and ductal shunting flow after loading standard doses of intravenous caffeine in preterm infants. Echocardiographic studies were performed by a single investigator, before and at 1 hour and 4 hours after an intravenous infusion of a loading dose as 20 mg/kg caffeine citrate for 30 minutes., Results: In 25 preterm infants with PDA, left ventricular output decreased progressively during 4 hours after caffeine loading. Superior vena cava (SVC) flow decreased and ductal shunting flow increased at 1 hour and then recovered at 4-hour to baseline values. A diameter of PDA significantly decreased only at 4-hour after caffeine loading. There were no significant changes of these hemodynamic parameters in 29 preterm infants without PDA., Conclusion: In preterm infants with PDA, a standard intravenous loading dose of 20 mg/kg caffeine citrate was associated with increasing ductal shunting flow and decreasing SVC flow (as a surrogate for systemic blood flow) 1 hour after caffeine loading, however, these hemodynamic parameters recovered at 4 hours according to partial constriction of the ductus arteriosus. Close monitoring of hemodynamic changes would be needed to observe the risk for pulmonary over-circulation or systemic hypo-perfusion due to transient increasing ductal shunting flow during caffeine loading in preterm infants with PDA., Competing Interests: The authors have no potential conflicts of interest to disclose., (© 2018 The Korean Academy of Medical Sciences.)

Fluid-induced shear stresses are involved in the development of cardiovascular tissues. In a tissue engineering framework, this stimulus has also been considered as a mechanical regulator of stem cell differentiation. We recently demonstrated that the fluid-oscillating effect in combination with a physiologically-relevant shear stress magnitude contributes to the formation of stem cell-derived de novo heart valve tissues. However, the range of oscillations necessary to induce favorable gene expression and engineered tissue formation is unknown. In this study, we took a computational approach to establish a range of oscillatory shear stresses that may optimize in vitro valvular tissue growth. Taking a biomimetic approach, three physiologically-relevant flow waveforms from the human: (i) aorta, (ii) pulmonary artery and (iii) superior vena cava were utilized to simulate pulsatile flow conditions within a bioreactor that housed 3 tissue specimens. Results were compared to non-physiological pulsatile flow (NPPF) and cyclic flexure-steady flow (Flex-Flow) conditions. The oscillatory shear index (OSI) was used to quantify the fluid-induced oscillations occurring on the specimen surfaces. The range of mean OSI under the physiological conditions investigated was found to be 0.18 ≤ OSI ≤ 0.23. On the other hand, NPPF and Flex-Flow environments yielded a mean OSI of 0.37 and 0.11 respectively, which were 46% higher and 45% lower than physiological conditions. Moreover, we subsequently conducted OSI-based human bone marrow stem cell (HBMSC) culture experiments which resulted in preferential valvular gene expression and phenotype (significant upregulation of BMP, KLF2A, CD31 and α-SMA using an OSI of 0.23 in comparison to a lower OSI of 0.10 or a higher OSI of 0.38; p < .05). These findings suggest that a distinct range or a "sweet-spot" for physiological OSI exists in the mechanical conditioning of tissue engineered heart valves grown from stem cell sources. We conclude that in vitro heart valve matrix development could be further enhanced by simultaneous exposure of the engineered tissues to physiologically-relevant magnitudes of both fluid-induced oscillations and shear stresses., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

Objectives: This study sought to determine if anatomic atrial ganglionated plexus (GP) ablation leads to long-term sinus rate (SR) increase and improves quality of life in patients with symptomatic sinus bradycardia (SB)., Background: Atrial GP ablation has been demonstrated to increase SR in our previous study. Atrial GP ablation may also be effective in treating patients with symptomatic SB., Methods: Sixty-two patients with symptomatic SB were recruited: Group A included patients <50 years of age (n = 40); Group B included patients ≥50 years of age (n = 22). All patients underwent anatomic ablation of the main atrial GP, and 24-h Holter monitoring and quality-of-life assessment were performed during 1 year of follow-up. Quality of life was accessed by the Medical Outcomes Study Short-Form 36 Health Survey., Results: Although SR markedly increased in all patients after GP ablation, the increase was significantly greater in patients <50 years of age than in patients ≥50 years of age (19.3 ± 9.9 beats/min vs. 10.8 ± 5.4 beats/min; p = 0.001). The right anterior GP and the GP at the junction of the aorta and superior vena cava made the greatest contributions to SR increase among all GP. The mean and minimal SR increased significantly after ablation and remained elevated for 12 months only in Group A patients. Although symptoms and quality of life improved in all patients, 5 of the 8 domains of the Medical Outcomes Study Short-Form 36 Health Survey did not show obvious improvements in patients of Group B at 12 months., Conclusions: Anatomic atrial GP ablation effectively increased SR and improved quality of life in patients <50 years of age with symptomatic SB., (Copyright © 2017 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.)

The relevance of right atrial pressure (RAP) as the backpressure for venous return (Q VR ) and mean systemic filling pressure as upstream pressure is controversial during dynamic changes of circulation. To examine the immediate response of Q VR (sum of caval vein flows) to changes in RAP and pump function, we used a closed-chest, central cannulation, heart bypass porcine preparation ( n = 10) with venoarterial extracorporeal membrane oxygenation. Mean systemic filling pressure was determined by clamping extracorporeal membrane oxygenation tubing with open or closed arteriovenous shunt at euvolemia, volume expansion (9.75 ml/kg hydroxyethyl starch), and hypovolemia (bleeding 19.5 ml/kg after volume expansion). The responses of RAP and Q VR were studied using variable pump speed at constant airway pressure (P AW ) and constant pump speed at variable P AW Within each volume state, the immediate changes in Q VR and RAP could be described with a single linear regression, regardless of whether RAP was altered by pump speed or P AW ( r 2 = 0.586-0.984). RAP was inversely proportional to pump speed from zero to maximum flow ( r 2 = 0.859-0.999). Changing P AW caused immediate, transient, directionally opposite changes in RAP and Q VR (RAP: P ≤ 0.002 and Q VR : P ≤ 0.001), where the initial response was proportional to the change in Q VR driving pressure. Changes in P AW generated volume shifts into and out of the right atrium, but their effect on upstream pressure was negligible. Our findings support the concept that RAP acts as backpressure to Q VR and that Guyton's model of circulatory equilibrium qualitatively predicts the dynamic response from changing RAP. NEW & NOTEWORTHY Venous return responds immediately to changes in right atrial pressure. Concomitant volume shifts within the systemic circulation due to an imbalance between cardiac output and venous return have negligible effects on mean systemic filling pressure. Guyton's model of circulatory equilibrium can qualitatively predict the resulting changes in dynamic conditions with right atrial pressure as backpressure to venous return., (Copyright © 2017 the American Physiological Society.)

Echocardiographic assessment of right atrial (RA) volume, inferior vena cava (IVC) diameter, and hepatic vein flow velocity independently correlate with the RA pressure by direct catheter measurement in adults. We prospectively collected invasive RA pressure measurements and echocardiographic data in infants and young children with the goal of developing a predictive model to noninvasively determine normal RA pressure. All subjects had a central venous catheter through which RA pressure could be transduced. Specific inclusion criteria consisted of (1) biventricular heart, (2) absence of inotropes, (3) sinus rhythm, and (4) at least 24 hours from surgery. Two-dimensional echocardiography (2DE)-Doppler and 3DE-Doppler were used to measure RA volume, systemic venous diameters, and flow velocity. Regression equations of RA pressure with RA volume, systemic venous size, and flow velocity were explored. Of 46 studies, 43 (93%) had echocardiograms adequate for analysis. RA pressure did not correlate with body surface area or age (p = 0.69, p = 0.87). The mean indexed RA volume by 3DE-Doppler was significantly higher than by 2DE (p <0.005). On multivariable analysis, only IVC systolic flow velocity and systolic 2D Simpson's derived indexed RA volume demonstrated significant independent correlation with RA pressure, resulting in the equation: RA pressure (mm Hg) = 7.35 - 0.0025 × IVC systolic flow velocity (cm/s) + 0.119 × indexed RA volume by systolic 2D Simpson's (ml/m 2 ). RA pressure did not show correlation with systemic venous diameters or systolic and diastolic flow velocities in the SVC and hepatic veins. In conclusion, regression incorporating 2DE-derived RA volume and IVC systolic flow velocity provided the best noninvasive estimate of normal RA pressure in infants and children. The model derived requires validation in an independent sample., (Copyright © 2017 Elsevier Inc. All rights reserved.)

Objective: To determine whether delayed cord clamping improves systemic blood flow compared with immediate cord clamping in very preterm infants in the first 24 hours., Study Design: Women delivering at <30 weeks' gestation at 5 tertiary centers were randomized to receive immediate cord clamping (<10 seconds) or delayed cord clamping (≥60 seconds). Echocardiography and cardiorespiratory data were collected at 3, 9, and 24 hours after birth. The primary outcome was mean lowest superior vena cava (SVC) flow., Results: Of 266 infants enrolled, 133 were randomized to immediate cord clamping and 133 to delayed cord clamping. The 2 groups were similar at baseline, including mean gestation (immediate cord clamping 28 weeks vs delayed cord clamping 28 weeks) and birth weight (immediate cord clamping 1003 g vs delayed cord clamping 1044 g). There was no significant difference between groups in the primary outcome of mean lowest SVC flow (immediate cord clamping 71.4 mL/kg/min [SD 28.1] vs delayed cord clamping 70.2 mL/kg/min [SD 26.9]; P = .7). For secondary outcomes, hemoglobin increased by 0.9 g/dL at 6 hours in the group with delayed cord clamping (95% CI 3.9, 14.4; P = .0005, adjusted for baseline). The group with delayed cord clamping had lower right ventricular output (-21.9 mL/kg/min, 95% CI -39.0, -4.7; P = .01). Rates of treated hypotension, ductus arteriosus size and shunt direction, and treatment of the ductus arteriosus were similar., Conclusions: Delayed cord clamping had no effect on systemic blood flow measured as mean lowest SVC flow in the first 24 hours in infants <30 weeks' gestation., Trial Registration: Australia New Zealand Clinical Trials Registry: ACTRN12610000633088., (Copyright © 2016 Elsevier Inc. All rights reserved.)

Objective: Fontan completion, resulting in a total cavopulmonary connection, is accomplished using a lateral tunnel, extracardiac conduit, or bifurcated Y-graft. The use of Y-grafts is hypothesized to provide symmetric hepatic blood flow distribution to the lungs, a factor related to pulmonary arteriovenous malformations. The present study evaluates the hemodynamic performance of the largest commercially available Y-graft cohort to date, highlights 6 representative cases, and compares commercially available Y-graft performance with lateral tunnel/extracardiac conduit connections., Methods: A total of 30 patients with commercially available Y-grafts and 30 patients with lateral tunnel/extracardiac conduits were analyzed. Total cavopulmonary connection anatomies and flow waveforms were reconstructed using cardiac magnetic resonance images and phase-contrast cardiac magnetic resonance. Computational fluid dynamic simulations were performed to quantify total cavopulmonary connection power loss, resistance, and hepatic flow distribution. Comparisons between graft types were investigated., Results: Total cavopulmonary connection resistance was significantly higher for Y-grafts. Hepatic flow distribution was similar overall but showed discrepancies at extreme values with more unbalanced flow in the Y-graft cohort. Power loss was more sensitive to left pulmonary artery stenosis in the Y-graft cohort. Prediction of Y-graft hepatic flow distribution is multifactorial., Conclusions: Commercially available Y-grafts do not inherently provide more balanced hepatic flow distribution than lateral tunnel/extracardiac conduit connections, which are more energetically favorable and less sensitive to pulmonary artery stenosis. Graft type should be considered on an individual basis because hemodynamic performance is based on a combination of factors, including pulmonary flow distribution, pulmonary artery stenosis, and superior vena cava positioning., (Copyright © 2016 The American Association for Thoracic Surgery. Published by Elsevier Inc. All rights reserved.)

Background: Impaired autoregulation capacity implies that changes in cerebral perfusion follow changes in blood pressure; however, no analytical method has explored such a signal causality relationship in infants. We sought to develop a method to assess cerebral autoregulation from a mechanistic point of view and explored the predictive capacity of the method to classify infants at risk for adverse outcomes., Methods: The partial directed coherence (PDC) method, which considers synchronicity and directionality of signal dependence across frequencies, was used to analyze the relationship between spontaneous changes in mean arterial pressure (MAP) and the cerebral tissue oxygenation index (TOI). PDCMAP>>TOI indicated that changes in TOI were induced by MAP changes, and PDCTOI>>MAP indicated the opposite., Results: The PDCMAP>>TOI and PDCTOI>>MAP values differed. PDCMAP>>TOI adjusted by gestational age predicted low superior vena cava flow (≤41 ml/kg per min), with an area under the receiver operating characteristic curve of 0.72 (95% CI: 0.63-0.81; P < 0.001), whereas PDCTOI>>MAP did not. The adjusted pPDCMAP>>TOI (the average value per patient) predicted severe intracranial hemorrhage and mortality., Conclusion: PDCMAP>>TOI allows for a noninvasive physiological interpretation of the pressure autoregulation process in neonates. PDCMAP>>TOI is a good classifier for infants at risk of brain hypoperfusion and adverse outcomes.

Background: Late-onset intrauterine growth restriction (IUGR) results from a failure of the placenta to supply adequate nutrients and oxygen to the rapidly growing late-gestation fetus. Limitations in current monitoring methods present the need for additional techniques for more accurate diagnosis of IUGR in utero. New magnetic resonance imaging (MRI) technology now provides a noninvasive technique for fetal hemodynamic assessment, which could provide additional information over conventional Doppler methods., Objective: The objective of the study was to use new MRI techniques to measure hemodynamic parameters and brain growth in late-onset IUGR fetuses., Study Design: This was a prospective observational case control study to compare the flow and T2 of blood in the major fetal vessels and brain imaging findings using MRI. Indexed fetal oxygen delivery and consumption were calculated. Middle cerebral artery and umbilical artery pulsatility indexes and cerebroplacental ratio were acquired using ultrasound. A score of ≥ 2 of the 4 following parameters defined IUGR: (1) birthweight the third centile or less or 20% or greater drop in the centile in estimated fetal weight; (2) lowest cerebroplacental ratio after 30 weeks less than the fifth centile; (3) ponderal index < 2.2; and (4) placental histology meets predefined criteria for placental underperfusion. Measurements were compared between the 2 groups (Student t test) and correlations between parameters were analyzed (Pearson's correlation). MRI measurements were compared with Doppler parameters for identifying IUGR defined by postnatal criteria (birthweight, placental histology, ponderal index) using receiver-operating characteristic curves., Results: We studied 14 IUGR and 26 non-IUGR fetuses at 35 weeks' gestation. IUGR fetuses had lower umbilical vein (P = .004) and pulmonary blood flow (P = .01) and higher superior vena caval flow (P < .0001) by MRI. IUGR fetuses had asymmetric growth but smaller brains than normal fetuses (P < .0001). Newborns with IUGR also had smaller brains with otherwise essentially normal findings on MRI. Vessel T2s, oxygen delivery, oxygen consumption, middle cerebral artery pulsatility index, and cerebroplacental ratio were all significantly lower in IUGR fetuses, whereas there was no significant difference in umbilical artery pulsatility index. IUGR score correlated positively with superior vena caval flow and inversely with oxygen delivery, oxygen consumption, umbilical vein T2, and cerebroplacental ratio. Receiver-operating characteristic curves revealed equivalent performance of MRI and Doppler techniques in identifying IUGR that was defined based on postnatal parameters with superior vena caval flow area under the curve of 0.94 (95% confidence interval, 0.87-1.00) vs a cerebroplacental ratio area under the curve of 0.80 (95% confidence interval, 0.64-0.97)., Conclusion: MRI revealed the expected circulatory redistribution in response to hypoxia in IUGR fetuses. The reduced oxygen delivery in IUGR fetuses indicated impaired placental oxygen transport, whereas reduced oxygen consumption presumably reflected metabolic adaptation to diminished substrate delivery, resulting in slower fetal growth. Despite brain sparing, placental insufficiency limits fetal brain growth. Superior vena caval flow and umbilical vein T2 by MRI may be useful new markers of late-onset IUGR., (Copyright © 2016 Elsevier Inc. All rights reserved.)

Objective: Positive external pressure is said to decrease transmural pressure; negative pressure in the pleural cavity is widely believed to result in negative pressure in systemic chest veins. The discrepancy between erect column height and foot venous pressure has been explained on this basis., Methods: These core concepts rest on static closed models that may not be appropriate. This study examined the effects of external pressures in a dynamic open model that may better reflect in vivo conditions. Flow in a Penrose drain enclosed in a chamber that could be positively or negatively pressurized was used. Input and output reservoirs with pressures in the physiological range provided flow. Flow and pressure were monitored in horizontal and erect models with modifications to suit particular experiments., Results: The discrepancy between foot venous pressure and erect venous column height was shown in this experimental model to be a result of two flows in opposite directions (superior and inferior vena cavae) meeting at the zero reference level at the heart; the upper column pressure therefore does not register at the foot. Positive external pressure results in slowing of velocity with conversion to pressure. Internal and transmural pressures therefore do not decrease. Negative external pressure has only a marginal effect on flow; importantly, internal pressure does not become negative. In an experimental set-up it was shown that negative pressure in chest veins was not necessary for air embolism to occur., Conclusion: Persistent negative pressure in systemic chest veins probably does not occur. The reason for the discrepant foot venous pressure is likely to be a result of dynamic flow and not negative pressure in chest veins. External positive pressure results in slowing of velocity but the transmural pressure remains largely unchanged., (Copyright © 2015 European Society for Vascular Surgery. Published by Elsevier Ltd. All rights reserved.)

Objective: To evaluate the relationship between superior vena cava flow (SVCF) measurements within the first 24 h of life, and development of intraventricular haemorrhage (IVH) in extremely preterm infants., Study Design: Single centre retrospective cohort study of 108 preterm infants born less than 28 weeks' gestation. Main outcome measure was degree of IVH at day 7 postnatal age., Results: The mean GA of the study group was 25.4 weeks. Mean SVCF was lower (75 ml/kg/min) in infants later diagnosed with IVH (n = 46) compared to infants, who did not develop IVH (87.7 ml/kg/min, p = 0.055). PDA diameter was inversely associated with SVCF (p = 0.024) and reversal of flow in the descending aorta (p = 0.001). Sensitivity analysis did not confirm an independent association of SVCF with development of IVH [OR 0.990 (0.978-1.002), p = 0.115]., Conclusion: Our study describes early SVCF in extremely preterm infants is associated with the extent of ductal shunting, but insensitive in predicting IVH.

Central venous catheters (CVCs), placed in the superior vena cava (SVC) for hemodialysis or chemotherapy, are routinely filled while not in use with heparin, an anticoagulant, to maintain patency and prevent thrombus formation at the catheter tip. The heparin-locking procedure, however, places the patient at risk for systemic bleeding, as heparin is known to leak from the catheter into the blood stream. We provide evidence from detailed in vitro experiments that shows the driving mechanism behind heparin leakage to be convective-diffusive transport due to the pulsatile flow surrounding the catheter. This novel mechanism is supported by experimental planar laser-induced fluorescence (PLIF) and particle image velocimetry (PIV) measurements of flow velocity and heparin transport from a CVC placed inside a model SVC inside a pulsatile flow loop. The results predict an initial, fast (<10 s), convection-dominated phase that rapidly depletes the concentration of heparin in the near-tip region, the region of the catheter with side holes. This is followed by a slow, diffusion-limited phase inside the catheter lumen, where the concentration is still high, that is insufficient at replenishing the lost heparin concentration in the near-tip region. The results presented here, which are consistent with previous in vivo estimates of 24 hour leakage rates, predict that the concentration of heparin in the near-tip region is essentially zero for the majority of the interdialytic phase, rendering the heparin locking procedure ineffective.

Objective: To gather information for a future confirmatory trial of dobutamine (DB) for circulatory impairment (ie, low superior vena cava [SVC] flow)., Study Design: A total of 127 infants born at < 31 weeks gestational age were serially scanned from birth to 96 hours after birth. The infants were randomly assigned to 2 groups and were treated with DB (stepwise dose increase, 5-10-15-20 μg/kg/min) or placebo if they had an SVC flow < 41 mL/kg/min within the first 24 hours after birth. The primary outcome measures were the achievement and maintenance of an SVC flow ≥ 41 mL/kg/min. Secondary outcome measures were the short-term evolution of clinical and biochemical variables, near-infrared spectroscopy, cranial Doppler ultrasound, and clinical outcomes., Results: SVC flow increased throughout the first 96 hours for the entire cohort. All of the randomized infants (n = 28) except 2 achieved and maintained an SVC flow ≥ 41 mL/kg/min after intervention; however, the infants treated with DB (n = 16) showed a higher heart rate and improved base excess compared with those treated with placebo (n = 12). Low SVC flow was associated with low gestational age (P = .02) and poor condition at birth (P = .02). Low SVC flow significantly increased the risk of severe ischemic events (OR, 13; 95% CI, 2.4-69.2; P < .01)., Conclusion: This exploratory trial demonstrates a tendency toward improved short-term clinical and biochemical perfusion variable outcomes in infants with low SVC flow treated with DB., Trial Registration: ClinicalTrials.gov (NCT01605279) and the European Clinical Trials Database (EurodraCT 2009-010901-35)., (Copyright © 2015 Elsevier Inc. All rights reserved.)

Introduction: Differential hypoxia is a pivotal problem in patients with femoral veno-arterial (VA) extracorporeal membrane oxygenation (ECMO) support. Despite recognition of differential hypoxia and attempts to deliver more oxygenated blood to the upper body, the mechanism of differential hypoxia as well as prevention strategies have not been well investigated., Methods: We used a sheep model of acute respiratory failure that was supported with femoral VA ECMO from the inferior vena cava to the femoral artery (IVC-FA), ECMO from the superior vena cava to the FA (SVC-FA), ECMO from the IVC to the carotid artery (IVC-CA) and ECMO with an additional return cannula to the internal jugular vein based on the femoral VA ECMO (FA-IJV). Angiography and blood gas analyses were performed., Results: With IVC-FA, blood oxygen saturation (SO₂) of the IVC (83.6 ± 0.8%) was higher than that of the SVC (40.3 ± 1.0%). Oxygen-rich blood was drained back to the ECMO circuit and poorly oxygenated blood in the SVC entered the right atrium (RA). SVC-FA achieved oxygen-rich blood return from the IVC to the RA without shifting the arterial cannulation. Subsequently, SO₂ of the SVC and the pulmonary artery increased (70.4 ± 1.0% and 73.4 ± 1.1%, respectively). Compared with IVC-FA, a lesser difference in venous oxygen return and attenuated differential hypoxia were observed with IVC-CA and FA-IJV., Conclusions: Differential venous oxygen return is a key factor in the etiology of differential hypoxia in VA ECMO. With knowledge of this mechanism, we can apply better cannula configurations in clinical practice.

Purpose: Symmetric-tip dialysis catheters have become alternative devices because of low access recirculation and ease of tip positioning. Flow characteristics of three symmetric catheters were compared based on computational fluid dynamics (CFD) as they relate to catheter function., Materials and Methods: In Palindrome, GlidePath, and VectorFlow catheters, a computational fluid dynamics-based approach was used to assess (i) regions of flow separation, which are prone to thrombus development; (ii) shear-induced platelet activation potency; (iii) recirculation; and (iv) venous outflow deflection. A steady-state, laminar flow model simulated catheter tip position within the superior vena cava. Catheter performance was investigated at high hemodialysis flow rate (400 mL/min). Blood was assumed as a Newtonian fluid., Results: Wide regions of flow separation downstream of the Palindrome side slot and close to the distal tip were observed in forward and reversed line configurations. Geometric asymmetry of the distal guide wire aperture of the GlidePath catheter produced the highest levels of inverted velocity flow when run in reversed configuration. The lowest mean shear-induced platelet activation was exhibited by GlidePath and VectorFlow catheters; the Palindrome catheter exhibited 152% higher overall platelet activation potency. All catheters were associated with a recirculation close to zero; the helically contoured lumens of the VectorFlow catheter produced the greatest amount of deflection of venous flow away from the arterial lumen., Conclusions: The VectorFlow catheter produced less shear-induced platelet activation than the Palindrome catheter and less flow separation than the Palindrome and GlidePath catheters irrespective of line configuration. These findings have potential implications for differences in thrombogenic risk during clinical performance of these catheters., (Copyright © 2015 SIR. Published by Elsevier Inc. All rights reserved.)

Aim: Few studies have focused on cardiac ventricular diastolic function in preterm neonates in the immediate post-natal period. This study evaluated Doppler-derived parameters of diastolic ventricular function in infants with birth weights of <1250 g during the transitional period., Methods: This was a prospective observational study conducted in the Coombe Women and Infants University Hospital in Dublin, Ireland. Flow patterns on the mitral and tricuspid valve, isovolumic relaxation time (IVRT), left and right ventricular output and superior vena cava flow were measured in 22 infants with a birth weight of below 1250 g at six, 12, 24 and 48 h of age., Results: Early filling peak velocity of the left and right ventricle increased significantly from 30.3 to 39.5 cm/sec and 26.6 to 32.1 cm/sec, respectively. IVRT of the right ventricle decreased from 70 to 57 ms, and there was a nonsignificant decrease in IVRT of the left ventricle from 61.6 to 54 ms over the first 48 h., Conclusion: We have demonstrated that parameters of diastolic ventricular function change significantly over the first 48 h of life in preterm infants <1250 g and that these changes may represent early diastolic dysfunction during the transitional period., (©2014 Foundation Acta Paediatrica. Published by John Wiley & Sons Ltd.)

Background: As patients with a single-ventricle physiology age, long-term complications inherent to this population become more evident. Previous studies have focused on correlating anatomic and hemodynamic performance, but there is little information of how these variables change with time. Vessel growth and flow rate changes were quantified using cardiac magnetic resonance and their effects on hemodynamics were assessed, which could affect the long-term outcome., Methods: Forty-eight patients with a lateral tunnel or extracardiac conduit Fontan who underwent two cardiac magnetic resonance scans (average interval, 5.1 ± 2.3 years) were studied. Total cavopulmonary connection anatomic and flow variables were reconstructed and normalized to body surface area(1/2). Total cavopulmonary connection hemodynamic efficiency (indexed power loss) was obtained through computational fluid dynamic modeling., Results: Absolute vessel diameters increased with time, normalized diameters decreased, and vessel mean flow rates remained unchanged. Indexed power loss changed significantly in the cohort, as well as in patients in whom the minimum normalized left pulmonary artery decreased. Age at first scan and connection type (lateral tunnel or extracardiac conduit) were not associated with changes in indexed power loss., Conclusions: We present the largest serial cardiac magnetic resonance Fontan cohort to date. Although flow rates increased proportionally to body surface area, vessel diameters did not match somatic growth. As a result, energy losses increased significantly with time in the cohort analyzed., (Copyright © 2015 The Society of Thoracic Surgeons. Published by Elsevier Inc. All rights reserved.)

Early detection and rapid treatment of tissue hypoxia are important goals. Venous oxygen saturation is an indirect index of global oxygen supply-to-demand ratio. Central venous oxygen saturation (ScvO2) measurement has become a surrogate for mixed venous oxygen saturation (SvO2). ScvO2 is measured by a catheter placed in the superior vena cava. After results from a single-center study suggested that maintaining ScvO2 values >70% might improve survival rates in septic patients, international practice guidelines included this target in a bundle strategy to treat early sepsis. However, a recent multicenter study with >1500 patients found that the use of central hemodynamic and ScvO2 monitoring did not improve long-term survival when compared to the clinical assessment of the adequacy of circulation. It seems that if sepsis is recognized early, a rapid initiation of antibiotics and adequate fluid resuscitation are more important than measuring venous oxygen saturation., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

Objectives: Optimal contrast within the pulmonary artery is achieved by the maximum amount of contrast-enhanced blood flowing through the superior vena cava (SVC), while minimum amounts of non-contrasted blood should originate from the inferior vena cava (IVC). This study aims to clarify whether "suction against resistance" might optimise this ratio., Methods: Phase-contrast pulse sequences on a 1.5T MRI magnet were used for flow quantification (mean flow (mL/s), stroke volume (Vol) in the SVC and IVC in volunteers. Different breathing manoeuvers were analysed repeatedly: free breathing; inspiration; expiration; suction against resistance, and Valsalva. To standardise breathing commands, volunteers performed suction and Valsalva manoeuvers with an MR-compatible manometer., Results: Suction against resistance was associated with a significant drop of the IVC/SVC flow quotient (1.63 [range 1.3-2.0] p < 0.05 at -10 mmHg and 1.48 [1.1-1.9] p < 0.01 at -20 mmHg) corresponding to increased blood flow from SVC and diminished flow originating from the IVC. The remaining breathing commands (free breathing 2.2; inspiration 2.4; expiration 2.4; Valsalva 10 mmHg 2.3; Valsalva 20 mmHg 2.6; and Valsalva 30 mmHg 2.2) showed no differences (p > 0.05)., Conclusions: Suction against resistance caused a significant drop in the IVC/SVC quotient. Theoretically, this breathing manoeuver might significantly improve the enhancement characteristics of CT angiography., Key Points: Suction provokes reduction in blood flow in the inferior vena cava. Ratio between the inferior and superior vena cava blood flow diminished during suction. Manometer used during breathing standardises MR phase-contrast blood flow measurements.

Objective: To describe an alternative analysis in the frequency-domain of the temporal relationship between 2 biological signals and evaluate the method's predictive capacity for classifying infants at risk for an adverse outcome., Study Design: We studied 54 infants (mean gestational age 27 weeks) with invasive mean arterial blood pressure monitoring. The bivariate autoregressive spectral coherence (BiAR-COH) method and the spectral coherence methods were used to analyze the relationship between spontaneous changes in mean arterial blood pressure and the near-infrared tissue oxygenation index., Results: The mean postnatal age at the beginning and end of the autoregulation study was 6.0 (3.0) and 29.0 (7.5) hours, respectively. The BiAR-COH was superior to the spectral coherence in predicting low superior vena cava (SVC) flow (≤ 41 mL/kg per minute), with an area under the receiver operating characteristic curve of 0.84 (95% CI, 0.77-0.90; P < .001). The BiAR-COH threshold for identifying low SVC flow was 0.577, with 0.8 sensitivity and 0.76 specificity. After adjusting for the repeated measures effect (multiple epochs) in a given patient, the averaged BiAR-COH per patient and averaged COH per patient were calculated as the average value per patient. The pBiAR-COH (but not the pCOH) was associated with intraventricular hemorrhage grades 3 and 4 and predicted mortality., Conclusions: The BiAR-COH classifier identifies low SVC flow infants who are at risk for brain hypoperfusion. The BiAR-COH is superior to frequency domain methods in predicting adverse outcomes in infants., (Copyright © 2014 Elsevier Inc. All rights reserved.)

Objective: Real-time phase-contrast flow MRI at high spatiotemporal resolution was applied to simultaneously evaluate haemodynamic functions in the ascending aorta (AA) and superior vena cava (SVC) during elevated intrathoracic pressure (Valsalva manoeuvre)., Methods: Real-time phase-contrast flow MRI at 3 T was based on highly undersampled radial gradient-echo acquisitions and phase-sensitive image reconstructions by regularized non-linear inversion. Dynamic alterations of flow parameters were obtained for 19 subjects at 40-ms temporal resolution, 1.33-mm in-plane resolution and 6-mm section thickness. Real-time measurements were performed during normal breathing (10 s), increased intrathoracic pressure (10 s) and recovery (20 s)., Results: Real-time measurements were technically successful in all volunteers. During the Valsalva manoeuvre (late strain) and relative to values during normal breathing, the mean peak flow velocity and flow volume decreased significantly in both vessels (p < 0.001) followed by a return to normal parameters within the first 10 s of recovery in the AA. By contrast, flow in the SVC presented with a brief (1-2 heartbeats) but strong overshoot of both the peak velocity and blood volume immediately after pressure release followed by rapid normalization., Conclusion: Real-time phase-contrast flow MRI may assess cardiac haemodynamics non-invasively, in multiple vessels, across the entire luminal area and at high temporal and spatial resolution., Advances in Knowledge: Future clinical applications of this technique promise new insights into haemodynamic alterations associated with pre-clinical congestive heart failure or diastolic dysfunction, especially in cases where echocardiography is technically compromised.

Aim: To evaluate the potential of real-time phase-contrast flow magnetic resonance imaging (MRI) at 40 ms resolution for the simultaneous determination of blood flow in the ascending aorta (AA) and superior vena cava (SVC) in response to reduced intrathoracic pressure (Mueller manoeuvre)., Materials and Methods: Through-plane flow was assessed in 20 healthy young subjects using real-time phase-contrast MRI based on highly undersampled radial fast low-angle shot (FLASH) with image reconstruction by regularized non-linear inversion. Haemodynamic alterations (three repetitions per subject = 60 events) were evaluated during normal breathing (10 s), inhalation with nearly closed epiglottis (10 s), and recovery (20 s)., Results: Relative to normal breathing and despite interindividual differences, reduced intrathoracic pressure by at least 30 mmHg significantly decreased the initial peak mean velocity (averaged across the lumen) in the AA by -24 ± 9% and increased the velocity in the SVC by +28 ± 25% (p < 0.0001, n = 23 successful events). Respective changes in flow volume per heartbeat were -25 ± 9% in the AA and +49 ± 44% in the SVC (p < 0.0001, n = 23). Flow parameters returned to baseline during sustained pressure reduction, while the heart rate was elevated by 10% (p < 0.0001) after the start (n = 24) and end (n = 17) of the manoeuvre., Conclusions: Real-time flow MRI during low intrathoracic pressure non-invasively revealed quantitative haemodynamic adjustments in both the AA and SVC., (Copyright © 2014 The Royal College of Radiologists. Published by Elsevier Ltd. All rights reserved.)

Background: Current literature provides limited data on the hemodynamic changes that may occur during bi-level continuous positive airway pressure (CPAP) support in preterm infants. However, the application of a positive end-expiratory pressure may be transmitted to the heart and the great vessels resulting in changes of central blood flow., Objective: To assess changes in central blood flow in infants with respiratory distress syndrome (RDS) during bi-level CPAP support., Design: A prospective study was performed in a cohort of 18 Very-Low-Birth-Weight Infants who were put on nasal CPAP support (4-5 cmH2O) because they developed RDS within the first 24-72 hours of life. Each subject was switched to bi-level CPAP support (Phigh 8 cmH2O, Plow 4-5 cmH2O, Thigh 0.5-0.6 seconds, 20 breaths/min) for an hour. An echocardiographic study and a capillary gas analysis were performed before and after the change of respiratory support., Results: No differences between n-CPAP and bi-level CPAP in left ventricular output (LVO, 222.17 ± 81.4 vs 211.4 ± 75.3 ml/kg/min), right ventricular output (RVO, 287.8 ± 96 vs 283.4 ± 87.4 ml/kg/min) and superior vena cava flow (SVC, 135.38 ± 47.8 vs 137.48 ± 46.6 ml/kg/min) were observed. The hemodynamic characteristics of the ductus arteriosus were similar. A significant decrease in pCO2 levels after bi-level CPAP ventilation was observed; pCO2 variations did not correlate with modifications of central blood flow (LVO: ρ=0.11, p=0,657; RVO: ρ=-0.307, p=0.216; SVC: ρ=-0.13, p=0.197)., Conclusions: Central blood flow doesn't change during bi-level CPAP support, which could become a hemodinamically safe tool for the treatment of RDS in preterm infants.

Objective: To determine whether umbilical cord milking (UCM) improves systemic blood flow and reduces neonatal morbidities compared with immediate cord clamping (ICC)., Study Design: Women admitted to a tertiary care center and delivering before 32 weeks' gestation were randomized to receive UCM or ICC. Three blinded serial echocardiograms were performed in the first 2 days of the infant's life. The primary outcome was measured systemic blood flow (superior vena cava flow) at each time point., Results: Of the 60 neonates who were enrolled and randomized, 30 were assigned to cord milking and 30 to ICC. Neonates randomized to cord milking had greater measures of superior vena cava flow and right ventricular output in the first 6 hours and 30 hours of life. Neonates receiving UCM also had greater serum hemoglobin, received fewer blood transfusions, fewer days on oxygen therapy, and less frequent use of oxygen at 36 weeks' corrected postmenstrual age., Conclusions: We demonstrate greater systemic blood flow with UCM in preterm neonates compared with ICC. Future large prospective trials are needed to determine whether UCM reduces intraventricular hemorrhage and other long-term morbidities., (Copyright © 2014 Elsevier Inc. All rights reserved.)

Objective: Preterm infants are at risk of circulatory compromise following birth. Functional neonatal echocardiography including superior vena cava (SVC) flow is increasingly used in neonatal medicine, and low SVC flow has been associated with adverse outcome. However, echocardiography is not readily available in many neonatal units and B-type natriuretic peptides (BNPs) may be useful in guiding further cardiovascular assessment. This study investigated the relationship between BNP, N-terminal pro-BNP (NTproBNP) and echocardiographic measurements of systemic blood flow in very preterm infants., Study Design: This is a prospective observational study. Sixty preterm infants <32 weeks gestational age were included after the treating neonatologist had requested an echocardiogram for suspected cardiovascular compromise. BNP and NTproBNP were sampled just before the echocardiogram. Echocardiographic examination included fractional shortening (FS), SVC flow, left and right ventricular output (LVO and RVO). Statistical analysis included simple linear regression of BNP and NTproBNP with echocardiographic measures and multiple regression including potential confounding variables., Result: Mean (s.d.) gestational age at birth was 27(5) (2(1)) weeks, median (interquartile range, IQR) birth weight was 995 (845 to 1175) grams. Neither BNP nor NTproBNP correlated with SVC flow (BNP 95% confidence interval (CI) -0.0014 to 0.013, P=0.12; NTproBNP 95% CI -0.00069 to 0.01, P=0.085); LVO (BNP 95% CI -0.00078 to 0.0072, P=0.11; NTproBNP 95% CI -0.0034 to 0.0034, P=0.99); RVO (BNP 95% CI -0.00066 to 0.0058, P=0.12; NTproBNP 95% CI -0.0012 to 0.0044, P=0.25); or FS (BNP 95% CI -0.053 to 0.051, P=0.96; NTproBNP 95% CI -0.061 to 0.019, P=0.3). Multivariate linear regression did not significantly alter results., Conclusion: In this cohort of very preterm infants, BNP and NTproBNP did not correlate with echocardiographic measurements of systemic blood flow within the first 72 h of life.

Background: Left to right (L-R) shunting through a patent ductus arteriosus (PDA) can reduce systemic and cerebral blood flow in preterm infants. To minimize this, the positive end-expiratory pressure (PEEP) is often raised to increase pulmonary vascular resistance and reduce L-R shunting. The effects of this maneuver on systemic and cerebral hemodynamics and oxygenation are not well documented., Objective: To compare the effects of different PEEP on the left ventricular output (LVO), superior vena cava (SVC) flow, LVO/SVC flow ratio, cerebral oxygenation (CrSO2) and gas exchange in mechanically ventilated preterm infants with PDA., Methods: Sixteen mechanically ventilated infants of 23-30 weeks' gestational age with L-R shunting through the PDA were studied. Ultrasound measurements of LVO and SVC flow, CrSO2, arterial oxygen saturation and transcutaneous CO2 tension (TcPCO2) obtained at PEEP of 2 and 8 cm H2O were compared with baseline values at 5 cm H2O., Results: There was a small but significant reduction in LVO and the LVO/SVC flow ratio at PEEP of 8 compared to 5 cm H2O. SVC flow and CrSO2 did not differ significantly., Conclusions: Increasing PEEP to 8 cm H2O in ventilated preterm infants with a PDA produced a modest decrease in L-R ductal shunting as indicated by a lower LVO/SVC flow ratio. The higher PEEP did not have a significant effect on cerebral perfusion or oxygenation., (© 2013 S. Karger AG, Basel.)

Background:  Right atrial pressure (RAP) is commonly estimated using inferior vena cava (IVC) diameter and its respirophasic variations. Although a guideline has been provided for estimation of RAP due to variation in IVC dimensions based on studies in Western subjects, echocardiographic values in Asian subjects are unknown., Methods and Results:  We studied 369 patients who underwent IVC ultrasound within 24h of right heart catheterization (RHC). The maximum and minimum IVC diameter during a respiratory cycle and the percent collapse after a sniff test were measured. These IVC parameters were compared with mean RAP measured on RHC. Receiver operating characteristic curves were generated for each IVC parameter to determine the optimal cut-off to detect RAP >10mmHg. The IVC maximum diameter cut-off for detecting RAP >10mmHg was 19mm (sensitivity, 75%; specificity, 78%) and the percent collapse cut-off was 30% (sensitivity, 75%; specificity, 83%). Both cut-offs were smaller than those previously reported in patients from Western countries. When the cut-off values from the existing guideline were applied to the present cohort, the sensitivity and specificity for normal RAP (0-5mmHg) were 38.6% and 74.2%, respectively, and 60.0% and 92.0% for elevated RAP (>10mmHg)., Conclusions:  The optimal IVC maximum diameter and percent collapse cut-offs to detect elevated RAP were smaller in Asian subjects than in a previously reported Western cohort.

Background: The echocardiographic assessment of circulatory function in sick newborn infants has the potential to improve patient care. However, measurements are prone to error and have not been sufficiently validated. Phase-contrast magnetic resonance imaging (MRI) provides highly validated measures of blood flow and has recently been applied to the newborn population. The aim of this study was to validate measures of left ventricular output and superior vena caval flow volume in newborn infants., Methods: Echocardiographic and MRI assessments were performed within 1 working day of each other in a cohort of newborn infants., Results: Examinations were performed in 49 infants with a median corrected gestational age at scan of 34.43 weeks (range, 27.43-40 weeks) and a median weight at scan of 1,880 g (range, 660-3,760 g). Echocardiographic assessment of left ventricular output showed a strong correlation with MRI assessment (R(2) = 0.83; mean bias, -9.6 mL/kg/min; limits of agreement, -79.6 to +60.0 mL/kg/min; repeatability index, 28.2%). Echocardiographic assessment of superior vena caval flow showed a poor correlation with MRI assessment (R(2) = 0.22; mean bias, -13.7 mL/kg/min; limits of agreement, -89.1 to +61.7 mL/kg/min; repeatability index, 68.0%). Calculating superior vena caval flow volume from an axial area measurement and applying a 50% reduction to stroke distance to compensate for overestimation gave a slightly improved correlation with MRI (R(2) = 0.29; mean bias, 2.6 mL/kg/min; limits of agreement, -53.4 to +58.6 mL/kg/min; repeatability index, 54.5%)., Conclusions: Echocardiographic assessment of left ventricular output appears relatively robust in newborn infant. Echocardiographic assessment of superior vena caval flow is of limited accuracy in this population, casting doubt on the utility of the measurement for diagnostic decision making., (Copyright © 2013 American Society of Echocardiography. Published by Mosby, Inc. All rights reserved.)