Tetralogy of Fallot in the fetus: findings at targeted sonography

Prenatal diagnosis of a rare aortic arch anomaly with left aortic arch and right ductus arteriosus: Cross ribbon sign

Here, we report a fetus with a rare aortic arch anomaly with left aortic arch and right ductus arteriosus, which has not been reported so far. In this condition, the aorta extends to the left of the trachea as in normal, while the ductus arteriosus extends to the right of the trachea and joins the descending aorta posterior to the trachea, with a cross-ribbon sign.

Human fetal hearts with tetralogy of Fallot have altered fluid dynamics and forces

Studies have suggested the effect of blood flow forces in pathogenesis and progression of some congenital heart malformations. It is therefore of interest to study the fluid mechanic environment of the malformed prenatal heart, such as the tetralogy of Fallot (TOF), especially when little is known about fetal TOF. In this study, we performed patient-specific ultrasound-based flow simulations of three TOF and seven normal human fetal hearts. TOF right ventricles (RVs) had smaller end-diastolic volumes (EDVs) but similar stroke volumes (SVs), whereas TOF left ventricles (LVs) had similar EDVs but slightly increased SVs compared with normal ventricles. Simulations showed that TOF ventricles had elevated systolic intraventricular pressure gradient (IVPG) and required additional energy for ejection but IVPG elevations were considered to be mild relative to arterial pressure. TOF RVs and LVs had similar pressures because of equalization via ventricular septal defect (VSD). Furthermore, relative to normal, TOF RVs had increased diastolic wall shear stresses (WSS) but TOF LVs were not. This was caused by high tricuspid inflow that exceeded RV SV, leading to right-to-left shunting and chaotic flow with enhanced vorticity interaction with the wall to elevate WSS. Two of the three TOF RVs but none of the LVs had increased thickness. As pressure elevations were mild, we hypothesized that pressure and WSS elevation could play a role in the RV thickening, among other causative factors. Finally, the endocardium surrounding the VSD consistently experienced high WSS because of RV-to-LV flow shunt and high flow rate through the over-riding aorta. NEW & NOTEWORTHY Blood flow forces are thought to cause congenital heart malformations and influence disease progression. We performed novel investigations of intracardiac fluid mechanics of tetralogy of Fallot (TOF) human fetal hearts and found essential differences from normal hearts. The TOF right ventricle (RV) and left ventricle had similar and elevated pressure but only the TOF RV had elevated wall shear stress because of elevated tricuspid inflow, and this may contribute to the observed RV thickening. TOF hearts also expended more energy for ejection.

Role of the 3-Vessel and Trachea View in Antenatal Detection of Tetralogy of Fallot

Prenatal diagnosis of tetralogy of Fallot remains less frequent compared to other major congenital heart defects. In this study, we examined how often the 3-vessel and trachea view was abnormal in a large series of prenatally diagnosed cases of tetralogy of Fallot. In addition, we compared its sensitivity to that of the traditional outflow tract views for detection of tetralogy of Fallot. We found that both views were abnormal in all fetuses with tetralogy of Fallot, showing reversed aortic-to-pulmonary valve and aortic arch isthmus-to-ductus arteriosus ratios in the outflow tract and 3-vessel and trachea views, respectively. However, as a single measured marker, the enlarged aortic arch isthmus on the 3-vessel and trachea view appears to be the most sensitive for tetralogy of Fallot.

Simplifying ultrasound assessment of the fetal heart: Incorporating the complete Three Vessel View into routine screening

Introduction: As our experience and ultrasound resolution have improved significantly in last 30 years it is possible to detect most of the major cardiac abnormalities prenatally with high degree of accuracy.

Method: Current screening techniques have poor detection rate for congenital heart diseases (CHD) and nearly half of the major cardiac abnormalities mainly of Great Arteries goes unrecognised. A high detection rate for major CHDs can be achieved in a screening setting by improving techniques of routine screening in the low risk population.

Conclusion: This article summarises the alternative strategies to examine the outflow tracts and Great Arteries, its correct interpretation and examples of abnormal views.

The impact of not having a ductus arteriosus on clinical outcomes in foetuses diagnosed with tetralogy of Fallot

BACKGROUND

Foetuses with simple tetralogy of Fallot almost universally have a patent ductus arteriosus. Two recently identified cases had an absent patent ductus arteriosus, requiring emergent intervention at birth. The objective of this study was to determine whether foetuses diagnosed with tetralogy of Fallot and no patent ductus arteriosus have poorer outcomes compared with those with tetralogy of Fallot+patent ductus arteriosus.

METHODS

All foetal cases of tetralogy of Fallot between January, 2000 and 2012 were retrospectively identified from The Hospital for Sick Children (Toronto, Canada) database. Cases - tetralogy of Fallot+no patent ductus arteriosus confirmed on postnatal echo - and controls - tetralogy of Fallot+patent ductus arteriosus, matched for gestational age - were identified from prenatal records, and both clinical and echocardiographic data were reviewed. Optimal outcome was defined as valve-sparing repair with no residual lesions. Student's t-tests and Fisher's exact χ2 were used to compare groups.

RESULTS

n=115 foetuses were diagnosed with tetralogy of Fallot: 11 (9%) had no patent ductus arteriosus, and were matched to 22 controls - mean gestational age at diagnosis 23.2±4.2 weeks, 23.4±6.6 weeks, respectively. Cases had a higher proportion of right aortic arches (64% versus 14%, p<0.001). Foetal and postnatal echocardiographic data did not reveal significant differences in branch pulmonary artery sizes, pulmonary valve sizes, or ventricular function. No differences were identified for cyanosis at birth (2/10 versus 7/20, p=0.67), or catheter intervention (5/10 versus 4/22, p=0.12). Optimal outcome rates were similar between cases and controls (4/11 (36%) versus 5/21 (24%), p=0.68).

CONCLUSIONS

The patent ductus arteriosus does not appear to have an impact on clinical outcome in foetuses with tetralogy of Fallot.

Assessment of the ductus arteriosus in fetuses with tetralogy of Fallot and the implication for postnatal management

OBJECTIVE

To describe the antenatal and neonatal echocardiographic morphology and flow pattern of the ductus arteriosus in patients with tetralogy of Fallot.

PATIENTS AND METHODS

We included patients with a prenatal diagnosis of tetralogy of Fallot between January 2006 and December 2012.

RESULTS

Among the 52 fetuses with tetralogy of Fallot the severity of right ventricular outflow obstruction was considered mild in 32, moderate in 14, and severe in 6. In the mild right ventricular outflow obstruction group (n = 32) all had normal ductal morphology and flow pattern, eight (25%) elected for termination of pregnancy and two died in the neonatal period from extracardiac causes. In the moderate right ventricular outflow obstruction group (n = 14) the fetuses had a small ductus arteriosus with antegrade but abnormal flow velocity, one (7%) elected for termination of pregnancy. Immediately after birth the ductus arteriosus was very small or already closed at echocardiographic examination. Two out of 13 patients (15%) developed severe hypoxic spells and underwent modified Blalock-Taussig shunt during the neonatal period. Six fetuses were considered to have severe right ventricular outflow obstruction with flow reversal in the ductus arteriosus, three (50%) of whom elected for termination of pregnancy. The other three newborns underwent modified Blalock-Taussig shunt.

CONCLUSION

In fetuses with tetralogy of Fallot, ductal diameter can be reduced even up to prenatal closure. Prenatal ductal morphology assessment may be useful for improving management of patients with moderate right ventricular outflow obstruction and small ductus arteriosus who may become cyanotic at birth.

Aorta larger than pulmonary artery in the fetal 3-vessel view

OBJECTIVE

Fetal great artery asymmetry may accompany congenital heart disease. The fetal echocardiographic 3-vessel view (3VV) allows assessment of the superior vena cava, ascending aorta (AA), and main pulmonary artery (MPA). Our aim was to determine the association of congenital heart disease in fetuses with an AA/MPA ratio of greater than 1.

METHODS

We electronically searched our fetal echocardiographic database for studies performed between March 2002 and January 2008 that showed 3VVs with AA/MPA ratios of greater than 1 and correlated the findings with the presence of congenital heart disease.

RESULTS

In 2797 fetal echocardiograms, we identified 31 fetuses with normal 4-chamber views showing AA/MPA ratios of greater than 1 in the 3VV. Of 31 fetuses, 25 (81%) had tetralogy of Fallot (ToF) or a ToF variant, and 6 (19%) had an aortic valve abnormality or isolated dilatation of the AA.

CONCLUSIONS

Screening obstetric fetal sonography showing a 3VV AA/MPA ratio of greater than 1 suggests congenital heart disease and indicates the need for comprehensive fetal echocardiography.

A review of findings in fetal cardiac section drawings. Part 3: the 3-vessel-trachea view and variants

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 the 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 21 fetal heart 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.

Right aortic arch detected in fetal life

OBJECTIVE

To evaluate the prenatal distribution, associated conditions and outcome of the different types of right aortic arch (RAA) detected in fetal life.

METHODS

This was a retrospective review of all cases of RAA detected prenatally between 1998 and 2005 in two tertiary referral centers.

RESULTS

In the study period 71 cases of RAA were detected; 26 (37%) had RAA with aberrant left subclavian artery, 23 (32%) had RAA with mirror-image branching, 20 (28%) had RAA of unknown type and two (3%) had double aortic arch. While 20/26 cases with RAA and aberrant left subclavian artery were isolated findings, all 23 cases with RAA and mirror-image branching were associated with cardiac defects, namely tetralogy of Fallot (43%) or pulmonary atresia with ventricular septal defect (22%). Of the 20 cases with RAA, 19 of unknown type were associated with heterotaxy syndromes and had additional cardiac malformations and ambiguities of the situs. The two cases with DAA were isolated findings. Seven cases in our series (10%) had a microdeletion 22q11 and these were significantly associated with extracardiac malformations. The outcome in our series depended solely on the associated cardiac and extracardiac malformations, with the exception of one infant with isolated DAA, in whom a surgical correction was warranted.

CONCLUSIONS

RAA detected in fetal life is associated frequently with other cardiac/non-cardiac malformations, heterotaxy syndromes and microdeletions 22q11. The associated conditions vary depending on the branching type of the brachiocephalic vessels and the presence of extracardiac malformations.

Tomographic ultrasound imaging of the fetal heart: a new technique for identifying normal and abnormal cardiac anatomy

OBJECTIVE

In 2003 and 2004, the American College of Radiology, the American Institute of Ultrasound in Medicine, and the American College of Obstetricians and Gynecologists published guidelines for the standard ultrasound examination of the fetus. Each group recommended that the outflow tracts of the fetal heart be examined if technically feasible. One method to accomplish this task is to perform a free-hand sweep of the transducer beam directed in a transverse plane from the 4-chamber view to the fetal neck. One problem with this approach is that the examiner may not direct the beam transversely and, therefore, may not accurately identify the outflow tract anatomy.

METHODS

A new technology, tomographic ultrasound imaging (TUI), allows the examiner to obtain a volume data set that simultaneously displays multiple images at specific distances from the 4-chamber view. This study examined TUI technology for identifying normal and abnormal fetal cardiac anatomy with the use of either static or spatiotemporal image correlation volume data sets.

RESULTS

The 4 views used in the screening examination of the outflow tracts of the fetal heart (4-chamber, 5-chamber, 3-vessel, and tracheal views) could be identified with the use of TUI technology in fetuses between 13 and 40 weeks' gestation. Examples of fetuses with abnormal cardiac anatomy of the outflow tracts (tetralogy of Fallot, transposition of the great vessels, and pulmonary stenosis) all showed abnormal anatomy on TUI.

CONCLUSIONS

Tomographic ultrasound imaging technology enables the fetal examiner to evaluate the 4-chamber view and the outflow tracts in a systematic manner to identify normal and abnormal cardiac anatomy.

Three-dimensional and four-dimensional fetal echocardiography: a new frontier

PURPOSE OF REVIEW

One of the difficulties of conventional two-dimensional cardiac imaging is the inability to examine fetal cardiac anatomy from multiple angle planes. Three-dimensional and four-dimensional ultrasound allows the fetal examiner to more accurately accomplish this task. Currently, multiple disciplines may be involved in the examination of the fetal heart (pediatric cardiologists, obstetricians, maternal-fetal medicine specialists, and radiologists). The three-dimensional and four-dimensional imaging equipment used by these specialty physicians varies greatly. The purpose of this communication is to review techniques using three-dimensional and four-dimensional imaging that the pediatric cardiologist may not be exposed to in the clinical environment, however, in consulting with colleagues needs to have an understanding of these imaging modalities.

RECENT FINDINGS

The reconstruction of cardiac structures using this technology allows the examiner to view cardiac anatomy in a manner that was limited by previous two-dimensional imaging. Volume datasets are obtained in the three-dimensional static mode (no cardiac motion) or using four-dimensional - the three-dimensional heart is observed contracting during one or multiple cardiac cycles. Therefore, the fourth dimension is time. Using either three-dimensional or four-dimensional technology datasets are acquired, followed by image reconstruction. The image reconstruction enables the examiner to evaluate a two-dimensional image using multiple views, evaluate intracardiac anatomy at different depth planes, and recreate casts of blood flow of the chambers and great vessels.

SUMMARY

This new technology has enhanced the ability of the examiner to identify normal and complex fetal heart anatomy during the early second to the late third trimesters of pregnancy.

Prenatal sonographic diagnosis of tetralogy of fallot

The objective of this report was to emphasize the sonographic findings of tetralogy of Fallot (TOF) during the prenatal period. Four fetuses with TOF were prenatally diagnosed at gestational ages of 25, 28, 25, and 32 weeks. Based on this small series, prenatal sonographic findings suggestive of TOF may be summarized as follows: (1) a large aortic root, which is the most common prenatal sonographic finding, (2) a small pulmonary artery or stenosis of the right ventricular outflow tract, (3) a ventricular septal defect in the outlet portion of the septum, (4) an overriding aorta, which is best seen in the long-axis view, and (5) right ventricular hypertrophy. Other findings such as hydrops fetalis or polyhydramnios may also be helpful especially in the case of dysplastic pulmonary valves. The demonstration of a normal aortic root would render the presence of TOF unlikely. TOF with pulmonary atresia can be confused with truncus arteriosus, in which both pulmonary arteries arise from the ascending aorta. How-ever, with careful examination along the course of the ascending aorta, there are no branches arising from the aorta in TOF.

Fetal sonographic diagnosis of aortic arch anomalies

Aortic arch anomalies refer to congenital abnormalities of the position or branching pattern, or both of the aortic arch. Although aortic arch anomalies are not uncommon, reports on their prenatal diagnosis are scarce. Insight into the hypothetical arch model is crucial to understanding anomalies of the aortic arch in the fetus. Recognition of the trachea, three major vessels, ductus arteriosus and descending aorta in the axial views of the upper mediastinum is necessary for a complete fetal cardiac assessment. Clues to aortic arch anomalies include abnormal position of the descending aorta, absence of the normal 'V'-shaped confluence of the ductal and aortic arches, a gap between the ascending aorta and main pulmonary artery in the three-vessel view, and an abnormal vessel behind the trachea with or without a vascular loop or ring around the trachea. Meticulous attention to anatomic landmarks will lead to successful prenatal diagnosis of important vascular rings making early postnatal management possible.