Changes in pulmonary venous Doppler parameters in fetal cardiac defects

Fetal Pulmonary Venous Return: From Basic Research to the Clinical Value of Doppler Assessment

The fetal pulmonary circulation represents less than 25% of the fetal cardiac output. In comparison with the pulmonary arteries, studies on pulmonary veins are few and limited, and many questions remain to be answered. The literature reports that pulmonary veins play an important role in regulating vascular flow, forming an active segment of the pulmonary circulation. The development of more sophisticated ultrasonography technology has allowed the investigation of the extraparenchymal pulmonary veins and their waveform. The recognition of the pulmonary vein anatomy in echocardiography is important for the diagnosis of anomalous pulmonary venous connections, with a significant impact on prognosis. On the other hand, the identification of the normal pulmonary vein waveform seems to be a reliable way to study left heart function, with potential applicability in fetal and maternal pathology. Thus, the goal of this narrative review was to provide a clinically oriented perspective of the available literature on this topic.

Fetal Doppler Echocardiographic Assessment Predicts Severe Postnatal Obstruction in Total Anomalous Pulmonary Venous Connection

BACKGROUND

Obstructed total anomalous pulmonary venous connection (TAPVC) is a form of critical congenital heart disease that usually requires urgent postnatal intervention. Knowing which patients have severe obstruction can aid delivery planning. The authors previously developed a novel quantitative metric of pulmonary venous flow, the pulmonary venous variability index (PVVI). The aim of this study was to test the hypothesis that fetal PVVI and vertical vein Doppler velocities are associated with severe pulmonary vein obstruction postnatally.

METHODS

A retrospective cohort study of neonates with prenatally diagnosed TAPVC was performed. Patients who underwent fetal echocardiography at the Children's Hospital of Philadelphia with Doppler interrogation of the vertical vein were included for analysis. Twenty-nine patients met criteria (21 with heterotaxy, 18 with supracardiac TAPVC). The latest gestation fetal echocardiogram was used. Severe pulmonary vein obstruction was defined as preoperative death or urgent surgery or catheter-based intervention (first day of life). Measurements of PVVI, defined as (maximum velocity - minimum velocity)/mean velocity, were made offline. Wilcoxon rank sum models were used to assess the associations of severe obstruction and PVVI and maximum, mean, and minimum velocities.

RESULTS

The mean gestational age at the latest fetal echocardiographic examination was 35 weeks (range, 30-39 weeks). Twelve of the 29 patients (41%) met criteria for severe pulmonary vein obstruction. Lower PVVI was associated with greater risk for severe pulmonary venous obstruction (P = .008). The maximum, mean, and minimum velocities in the vertical vein were all significantly associated with severe pulmonary venous obstruction (P = .03, P = .03, and P = .007, respectively). Qualitative assessment of obstruction was not significantly associated with the outcome. Interobserver reliability for all vertical vein Doppler metrics was high (intraclass correlation coefficient > 0.9).

CONCLUSIONS

Fetal PVVI and maximum, mean, and minimum velocities are associated with severe postnatal pulmonary vein obstruction in TAPVC. Accurate prediction of obstructed TAPVC could allow safer delivery planning. Further research with larger sample sizes is needed to identify the ideal cutoff values for these Doppler measures.

Venous Flow Variation Predicts Preoperative Pulmonary Venous Obstruction in Children with Total Anomalous Pulmonary Venous Connection

BACKGROUND

Identifying preoperative pulmonary venous obstruction in total anomalous pulmonary venous connection is important to guide treatment planning and risk prognostication. No standardized echocardiographic definition of obstruction exists in the literature. Definitions based on absolute velocities are affected by technical limitations and variations in pulmonary venous return. The authors developed a metric to quantify pulmonary venous blood flow variation: pulmonary venous variability index (PVVI). The aim of this study was to demonstrate its accuracy in defining obstruction.

METHODS

All patients with total anomalous pulmonary venous connection at a single institution were identified. Echocardiograms were reviewed, and maximum (V_max), mean (V_mean), and minimum (V_min) velocities along the pulmonary venous pathway were measured. PVVI was defined as (V_max - V_min)/V_mean. These metrics were compared with pressures measured on cardiac catheterization. Echocardiographic measures were then compared between patients with and without clinical preoperative obstruction (defined as a need for preoperative intubation, catheter-based intervention, or surgery within 1 day of diagnosis), as well as pulmonary edema by chest radiography and markers of lactic acidosis. One hundred thirty-seven patients were included, with 22 having catheterization pressure recordings.

RESULTS

V_max and V_mean were not different between patients with catheter gradients ≥ 4 and < 4 mm Hg, while PVVI was significantly lower and V_min higher in those with gradients ≥ 4 mm Hg. The composite outcome of preoperative obstruction occurred in 51 patients (37%). Absolute velocities were not different between patients with and without clinical obstruction, while PVVI was significantly lower in patients with obstruction. All metrics except V_max were associated with pulmonary edema; none were associated with blood gas metrics.

CONCLUSIONS

The authors developed a novel quantitative metric of pulmonary venous flow, which was superior to traditional echocardiographic metrics. Decreased PVVI was highly associated with elevated gradients measured by catheterization and clinical preoperative obstruction. These results should aid risk assessment and diagnosis preoperatively in patients with total anomalous pulmonary venous connection.

[Doppler Sonography during Pregnancy - DEGUM Quality Standards and Clinical Applications]

Doppler sonography is widely established in prenatal medicine and obstetrics and is commonly used in screening for aneuploidy and preeclampsia during the first trimester. More importantly, during the 2nd and 3 rd trimester, it is used in the assessment of fetal health as well as the surveillance of underlying fetal conditions such as IUGR and anemia. Correct use of the method is vital for correct data interpretation and the inferred clinical decision process. Therefore, we aim to provide all users of doppler sonography with a guide for meeting the required quality standards. These quality standards will further be the basis of DEGUM-certified training courses. In the first part, we will introduce the technical principles of the method and potential error sources, vascular disciplines to which the method can be applied, analysis of the spectral curves, patient safety and the needed requirements for successful certification.

A novel parameter for pulmonary blood flow during palliative procedures: velocity time integral of the pulmonary vein†

OBJECTIVES

The main goal of palliative procedures for congenital heart defects is adequate pulmonary blood flow (PBF), but precise intraoperative PBF evaluation is sometimes difficult. The purpose of this preliminary study was to investigate the usefulness of velocity time integral of the pulmonary vein (PV-VTI) measured by transoesophageal echocardiography (TOE) at the time of palliative procedure as a parameter for PBF.

METHODS

Case histories of 63 patients who underwent palliative procedures (bilateral pulmonary artery banding in 18 patients, main pulmonary artery banding in 22 patients and systemic-to-pulmonary artery shunt in 23 patients) and whose intraoperative PV-VTI was measured by TOE from 2011 to 2017 at our centre were retrospectively reviewed. Low-body-weight infants, cases in which cardiopulmonary bypass was used and cases that were anatomically difficult to measure were excluded.

RESULTS

PV-VTIs measured at 4 orifices of the pulmonary veins were all significantly decreased in both the bilateral pulmonary artery banding and main pulmonary artery banding groups and increased in the systemic-to-pulmonary artery shunt group immediately after the procedure. There were significant correlations between the velocity time integrals of both right and left pulmonary veins and arterial oxygen saturation (r = 0.564 and 0.703). Nine patients (6 bilateral pulmonary artery banding and 3 systemic-to-pulmonary artery shunt) required unplanned early reoperation due to inadequate PBF; their PV-VTIs were significantly different from those of patients not requiring reoperation. No major complications related to TOE occurred postoperatively.

CONCLUSIONS

The PV-VTI measured by TOE during palliative procedures reflected the change of PBF and could help identify patients at higher risk of early reoperation due to inadequate PBF. This parameter may be a useful additional tool for evaluating intraoperative PBF.

Sonographic Pulmonary Abnormalities in Fetuses With Hypoplastic Left Heart Syndrome and Intact Atrial Septum Undergoing Attempted Atrial Septostomy In Utero

Fetuses with hypoplastic left heart syndrome (HLHS) and intact atrial septum are a particular subset of HLHS neonates with high perinatal mortality. The reported mortality in these patients is 50% to 70%, even with prenatal diagnosis. Prenatal left atrial and pulmonary venous hypertension results in abnormal pulmonary vascular and parenchymal development. The goal of this study was to compare the sonographic appearance of the lungs in fetuses with HLHS/intact atrial septum to neonatal outcome and/or pathology in cases where in utero intervention was performed to open the atrial septum. We found that lung inhomogeneity on ultrasound corresponded to peripheral lymphatic dilatation at autopsy and was associated with a dismal prognosis even when in utero intervention was successful.

A Simple Rule for Prenatal Diagnosis of Total Anomalous Pulmonary Venous Return

The objective of this series was to describe a simple rule for prenatal diagnosis of total anomalous pulmonary venous return (TAPVR). Fourteen fetuses had a prenatal diagnosis of TAPVR by the simple rule, including the following components: (1) the major criterion, which was the absence of a connection between the pulmonary vein and the left atrium; and (2) at least 1 of the following minor criteria: (a) the presence of a vascular confluence behind the atria, (b) abnormal spectral Doppler waveforms in the pulmonary veins, (c) a smooth posterior wall of the left atrium, (d) increased retroatrial space, (e) a dilated coronary sinus (cardiac type), (f) a dilated superior vena cava or brachiocephalic vein, and (g) an additional vessel on the 3-vessel/3-vessel and trachea view or a vertical descending vein. All were accurately diagnosed, and none were missed by the diagnosis. In summary, the simple rule described is helpful in increasing the number of accurate prenatal diagnoses of TAPVR.

Fetal left brachiocephalic vein in normal and abnormal conditions

OBJECTIVES

To establish values of fetal left brachiocephalic vein (LBCV) dimensions during normal pregnancy and determine whether routine assessment of the LBCV may help in identifying fetuses with congenital abnormalities of this vessel.

METHODS

Fetal LBCV was assessed prospectively during ultrasound examinations in 431 normal singleton pregnancies. The visualization rate of the transverse view of the upper fetal chest at the level of drainage of the LBCV into the superior vena cava (SVC) by two-dimensional (2D) and 2D plus color Doppler ultrasound was evaluated. Reference ranges of LBCV diameter during non-complicated pregnancies were established. Interobserver and intraobserver measurement variability was analyzed. In addition, a retrospective review of the hospital medical records of 91 pregnancies with fetuses diagnosed with LBCV abnormalities was performed.

RESULTS

Sonographic assessment of the fetal LBCV was consistently achieved in the second and third trimesters and in some fetuses in the first trimester of pregnancy. In normal fetuses LBCV diameter increased significantly throughout pregnancy, with a mean value of 0.7 mm at 11 weeks and 4.9 mm at term. Dilation of the fetal LBCV was noted in five cases of intracranial arteriovenous malformation and six cases of supracardiac type total anomalous pulmonary venous connection. Abnormal course of the LBCV was noted in 12 fetuses. In 63 fetuses with a persistent left SVC and a right SVC the LBCV was absent.

CONCLUSION

This is the first study describing an effective sonographic approach for the assessment of fetal LBCV dimensions during pregnancy. The normative data may provide an additional means of detecting rare anomalies of systemic and pulmonary veins during pregnancy.

Computational fluid dynamics of developing avian outflow tract heart valves

Hemodynamic forces play an important role in sculpting the embryonic heart and its valves. Alteration of blood flow patterns through the hearts of embryonic animal models lead to malformations that resemble some clinical congenital heart defects, but the precise mechanisms are poorly understood. Quantitative understanding of the local fluid forces acting in the heart has been elusive because of the extremely small and rapidly changing anatomy. In this study, we combine multiple imaging modalities with computational simulation to rigorously quantify the hemodynamic environment within the developing outflow tract (OFT) and its eventual aortic and pulmonary valves. In vivo Doppler ultrasound generated velocity profiles were applied to Micro-Computed Tomography generated 3D OFT lumen geometries from Hamburger-Hamilton (HH) stage 16-30 chick embryos. Computational fluid dynamics simulation initial conditions were iterated until local flow profiles converged with in vivo Doppler flow measurements. Results suggested that flow in the early tubular OFT (HH16 and HH23) was best approximated by Poiseuille flow, while later embryonic OFT septation (HH27, HH30) was mimicked by plug flow conditions. Peak wall shear stress (WSS) values increased from 18.16 dynes/cm(2) at HH16 to 671.24 dynes/cm(2) at HH30. Spatiotemporally averaged WSS values also showed a monotonic increase from 3.03 dynes/cm(2) at HH16 to 136.50 dynes/cm(2) at HH30. Simulated velocity streamlines in the early heart suggest a lack of mixing, which differed from classical ink injections. Changes in local flow patterns preceded and correlated with key morphogenetic events such as OFT septation and valve formation. This novel method to quantify local dynamic hemodynamics parameters affords insight into sculpting role of blood flow in the embryonic heart and provides a quantitative baseline dataset for future research.

In vitro hemodynamic investigation of the embryonic aortic arch at late gestation

This study focuses on the dynamic flow through the fetal aortic arch driven by the concurrent action of right and left ventricles. We created a parametric pulsatile computational fluid dynamics (CFD) model of the fetal aortic junction with physiologic vessel geometries. To gain a better biophysical understanding, an in vitro experimental fetal flow loop for flow visualization was constructed for identical CFD conditions. CFD and in vitro experimental results were comparable. Swirling flow during the acceleration phase of the cardiac cycle and unidirectional flow following mid-deceleration phase were observed in pulmonary arteries (PA), head-neck vessels, and descending aorta. Right-to-left (oxygenated) blood flowed through the ductus arteriosus (DA) posterior relative to the antegrade left ventricular outflow tract (LVOT) stream and resembled jet flow. LVOT and right ventricular outflow tract flow mixing had not completed until approximately 3.5 descending aorta diameters downstream of the DA insertion into the aortic arch. Normal arch model flow patterns were then compared to flow patterns of four common congenital heart malformations that include aortic arch anomalies. Weak oscillatory reversing flow through the DA junction was observed only for the Tetralogy of Fallot configuration. PA and hypoplastic left heart syndrome configurations demonstrated complex, abnormal flow patterns in the PAs and head-neck vessels. Aortic coarctation resulted in large-scale recirculating flow in the aortic arch proximal to the DA. Intravascular flow patterns spatially correlated with abnormal vascular structures consistent with the paradigm that abnormal intravascular flow patterns associated with congenital heart disease influence vascular growth and function.

A review of findings in fetal cardiac section drawings, Part 2: high abdominal views

OBJECTIVE

The goal of this presentation is to review some of the common and rare fetal heart abnormalities and to provide an easy approach to these findings with schematic drawings.

METHODS

Over the past 10 years, we collected cases in which the common views of the heart were abnormal and the differential diagnoses that existed for each. This presentation shows the normal sonographic sections and then variations of these sections and the associated anomalies. We used illustrative drawings to present these findings, enabling us to point out the main sonographic features of abnormalities of the heart.

RESULTS

This work reviews 4 fetal abnormalities in schematic drawings.

CONCLUSIONS

This short review highlights several of the anomalies that can be recognized on the common sonographic views. The drawings tend to simplify the findings but should serve as a basis for those doing fetal echocardiography when they encounter an unusual finding.