This chapter is also covered by accompanying online material
Catherine Fredouille and Claudio Lombardi
CHAPTER CONTENTS
First step. Pathologies of position
Second step. Pathologies of the inlet
Third step. Pathologies of the outlet
We are now going to describe, the principle cardiac pathologies that are encountered prenatally.
First step. pathologies of position
Pathologies of position are the first we look for when examining the fetal heart. Beginning the examination abdominally, we observe the following.
Anomalies Of Visceral Positioning
In the case where the stomach and heart are not on the same side (Fig. 6.1), the anomaly is clear. More easily overlooked is the case where the stomach is positioned on the right of the fetus along with the heart, a situation which has the same pathologic relevance.
FIGURE 6.1 The apex of the heart towards the left and the stomach in the right side in a visceroatrial heterotaxia.
This implies a systematic verification of the left of the fetus, using the Situs wheel, not simply checking the homolaterality of the heart and stomach.
Situs anomalies often go unnoticed until the fetal pathologic or postnatal examinations.1 They are frequently associated with complex cardiopathies and only worsen the prognosis. These anomalies belong to the visceroatrial heterotaxias (VAH) group with risk of recurrence.
In VAH, gene lateralization anomalies2 encourage the formation of two homologous sides. Schematically, the fetus that presents with VAH, instead of having a normal left side and a normal right side has a “doubling,” which is neither really left nor right. These abdominal abnormalities are not systematic. They typically affect the liver which becomes median (Fig. 6.2) with the gall bladder situated to the right or left. The spleen, an organ normally found on the left, is classically absent (asplenia) in the case of a right isomerism, or multiple (polysplenia) in the case of a left isomerism. These anomalies are difficult to see with ultrasound (US), especially if we do not systematically verify the lateralization of the vessels and the organs at the abdominal level.
FIGURE 6.2 Median liver in a visceroatrial heterotaxia. Note on the right the apex of the heart, which is not normal.
At the same time, prenatally, it is impossible to identify two atrial appendages of the same type that would define a right or left isomerism. But this type of atrial appendage “absence” is often accompanied by anomalies of venous return corresponding to the appendage that is “missing.” In left isomerism (two left-type appendages, and therefore no atrium of the right type) the anomaly is found in the systemic venous return that normally would occur in the “missing” right atrium (RA). This is abnormal and is the reason why we can observe an azygos return (Fig. 6.3) with absence of the suprarenal section of the inferior vena cava (IVC), an element which can be recognized in US3 by a transverse (Fig. 6.4) or longitudinal (Fig. 6.5) view. In addition, this absence of the RA—which is the normal center for the principal elements of the conduction system—can provoke rhythm problems. In a right isomerism, where the left appendage is missing, we need to consider searching for anomalies related to pulmonary venous return(PVRs), i.e., total or partial PVR.
These anomalies, even discordant,4 justify the systematic verification of the abdominal vessels5 at the level of the transabdominal diameter (TAD), as well as the PVs which attach the heart to the lungs at the level of the four-chamber view.
FIGURE 6.3 Posterior view with a dilated azygos rejoining the superior vena cava (SVC).
FIGURE 6.4 Axial US view showing two vessels in front of and to the left of the spine, the aorta, and azygos.
FIGURE 6.5 Sagittal view showing two thoracic abdominal parallel vessels.
Early Gestation
Transabdominal is better than transvaginal imaging to detect fetal heart and stomach positioning on opposing sides. Identifying other anomalies of visceral position is difficult. Different morphology of atrial appendages can be better appreciated.6,7
Vessel Position Anomalies
In requiring verification of the vessels at the level of the TAD, following them through the “elevator”, then arriving at the four-chamber view, we can observe several possibilities.
Not one but two vessels in front and to the left of the spine on the TAD image
These are behind the LA in the four-chamber view (see Figs 6.4 and 6.5). This is the situation in an azygos venous return, classically observed in cases of left isomerism with the absence of a section of the IVC seen at the level of the TAD image.
Though not frequent, and yet of great interest, is the discovery of an infra-diaphragmatic confluent of a totally anomalous PVR (TAPR). When isolated, the TAPR can be seen to be recurrent within the same family. This has been observed in the form of a third abdominal vascular mass. It is part of the range of VAH syndromes, and often associated with other pathologic elements of this condition which can be far more difficult to diagnose.
Early Gestation
The detection of venous anomalies is very limited and not the object of the early study.
Anomalies of organ or vessel position at the abdominal level, which are present in VAH, are elements of orientation
These are easier to diagnose than the frequent complex CHD associated with them. Often affecting the inlet and outlet, VAH cardiopathies found in the inlet are essentially represented by a unique atrium (UA) frequently associated with AVSD or unique ventricle (UV). In the outlet they are often seen as PA with OS, with or without the great vessels being transposed.8
To this end, the discovery of an AVSD in a patient having a normal karyotype should immediately lead us to consider VAH.9
Visceroatrial heterotaxias present in the form of associations of anomalies of position, inlet, and outlet having a normal karyotype.
Early Gestation
The diagnosis of a RAA is possible. Use of power Doppler or B/E-flow is of value. Differential diagnosis with double aortic arch could be difficult.10–12
The descending aorta is found—not in front and to the left—but on the right of the spine in the four-chamber view
A right descending aorta after a right aortic arch facilitates our diagnosis when we remember to look for it systematically using the four-chamber view. It is an excellent warning sign of conotruncal cardiopathies (CTC) (Fig. 6.6),13 the most direct indications for which should only be seen at the outlet level (Fig. 6.7). In addition, this sign, when the standard karyotype is normal, points us towards 22q11 deletion (Fig. 6.8).
FIGURE 6.6 “Pediatric” four-chamber view showing a right descending aorta, the axis of the heart (at 60°), and the dilated coronary sinus. We can already see that the VSD predominates in ejection.
FIGURE 6.7 Tetralogy of Fallot in trisomy 21 with an arch and right descending aorta. Note the large aorta and the small PT.
FIGURE 6.8 Posterior view of heart–lung block (HLB) with the right descending aorta with MAPCA under the probe. This fetus has a 22q11 deletion.
Anomalies Concerning The Position Of The Heart
The heart is in the right hemithorax (Fig. 6.9), conserving its apex to the left. This case is often associated with a left diaphragmatic hernia (Fig. 6.10). Diaphragmatic hernias are particularly seen in forms of this pathology which are part of a general group of syndromes, (e.g., Fryn syndrome). Associated CHD can also exist here, which would also be generally conotruncal.
FIGURE 6.9 Ultrasound view showing the liver in the left hemithorax in a diaphragmatic hernia. The apex of the heart turns towards the left.
FIGURE 6.10 Macroscopic view showing liver and intestine in the right hemithorax in a diaphragmatic hernia. The apex of the heart turns towards the left.
Early Gestation
The detection of congenital diaphragmatic hernia (CDH) is possible but in a significant number of cases the diaphragmatic defect is still too small to allow the stomach to be displaced upwards.14,15
Anomalies That Modify The Axis Of The Heart
The interventricular septum (IVS), which marks the boundary between the right and left inlet tracts, represents the axis of the heart on the four-chamber view. It normally makes a medium-sized angle of 45° with the anteroposterior axis and reflects the balance between the inlet tracts. The right inlet tract is composed of the RA and the inlet section of the RV, while the left inlet tract is composed of the LA and the inlet section of the LV. Any modification of this axis should be observed by the operator during examination using the four-chamber view (Fig. 6.11). Pathologically it is perhaps the asymmetry of the chambers causing an important modification of the axis which attracts our attention.16
FIGURE 6.11 Logo of the heart axis.
The angle can be clearly superior to 45 with a distinct asymmetry of the chambers
This is seen in severe hypoplasias of the left tract (Figs 6.12 and 6.13) as well as in Ebstein disease. Here (Fig. 6.14) the dilatation of the RA can be enormous due to an incompetent tricuspid valve. This is especially true due to the fact that the septal valve remains stuck to the septum much more than it normally would, enlarging the atrium, which then appears larger than the ventricle. Forms of this anomaly observed prenatally are often severe.
FIGURE 6.12 Macroscopic view where the axis is at an angle greater than 45° in a hypoplasic LV caused by mitral atresia.
FIGURE 6.13 Ultrasound view where the axis is at an angle greater than 45° in a hypoplasic LV.
FIGURE 6.14 Ultrasound view of a macroscopic four-chamber view in Ebstein disease.
The inlet chambers remain symmetric
However, their angle can attain 60° in forms of tetralogy of Fallot (ToF) where the heart takes on the form of a “boot” due to the overriding of the aorta upon the VSD (Fig. 6.15; see also Fig. 6.5).
FIGURE 6.15 Macroscopic view of a case of tetralogy of Fallot with the heart in the classic “boot” shape with an axis of 60°.
The angle can be inferior to 45°
This is the case in hypoplasia of the RV called pulmonary atresia with intact septum (PA with IS) (Figs 6.16 and 6.17) that is to say without VSD.17 Care should be taken not to confuse this condition with pulmonary atresia with open septum (PA with OS), which is a major form of CTC caused by the anterior swing of the conal septum and which has a constant VSD. In the case of PA with IS (exterior to the small size of the PT and RV) fistulae can exist within the coronary circulation on the wall of the RV which are visible on the RV wall in fetal pathology (Fig. 6.18) and translate by multiple aliasing on Doppler. Their hemodynamic consequence can bring about uterine death.18
FIGURE 6.16 Anterior view of the HLB of PA with IS with an axis at an angle less than 45°.
FIGURE 6.17 Ultrasound four-chamber view of PA with IS.
FIGURE 6.18 Anterior view of the HLB of PA with IS. Note the fistulae.
The axis can be negative with the apex of the heart to the right
This could be due to a heart that is a mirror image with complete situs inversus (Fig. 6.19). While cardiac situs inversus is associated with an abdominal situs inversus, this anomaly, which falls in the category of VAH, often remains unnoticed. A dextrorotation due to an atrioventricular discordance with a normal atrial situs can also displace the apex towards the right.
FIGURE 6.19 Complete situs inversus seen on a thoracic view; the apex of the heart is to the right.
Early Gestation
The cardiac axis tend to be higher (levorotation) at 12 weeks. It is increased in some CHD, for example, ToF.19,20
Second step. pathologies of the inlet
To each key point, one or several pathologies corresponds:
• Point 3: heart on the diaphragm, attached by the inferior PV.
• Point 4: four chambers.
• Point 5: chambers that are balanced and concordant.
• Point 6: crux of the heart with permeable and offset rings.
Point 3: Heart On The Diaphragm
If we do not discipline ourselves to always use the inferior PVs as our reference point—and separate to the axial errors already described in lateral swings—we can miss an extremely serious anomaly concerning PVR. TAPVR is seen as either:
• Associated with a complex cardiopathy like VAH (described earlier),5 especially in those cases of right isomerism (Fig. 6.20; see also Fig. 6.8), or
FIGURE 6.20 Posterior view of the HLB showing a TAPVR with a sub-diaphragmatic confluent (C).
• Isolated but total,21 posing a serious problem after birth, and even bringing on post- or neonatal death if there has been no diagnosis. Familial forms of this pathology exist, and here again we see the importance of the initial medical history which looks for a family history of early cardiac surgery (most often in partial forms of the disease), or unexplained neonatal deaths (which could occur in undiagnosed complete forms of TAPVR) (Fig. 6.21). This research can be helped by Doppler, which is necessary in the case of a small LA but only after we are sure that the four-chamber view has been verified axially and is optimal.
FIGURE 6.21 “Blocked” TAPVR with an above-diaphragmatic confluent finishing in the SVC. This newborn died at one month.
Early Gestation
Anomalies of PVR are not diagnosed.
Point 4: If We Cannot Distinguish The Four Chambers
In this situation we can identify the following:
Three chambers
Three chambers in the case of a UA or UV. The diagnosis of UA, frequently associated with AVSD, should not pose a particular problem in the total absence of an interauricular wall without a flap valve. This should lead us to search for Ellis–van Creveld syndrome (Fig. 6.22).
FIGURE 6.22 Right posterior view of the fetal heart with Ellis–van Creveld syndrome showing a UA overhanging a complete AVSD. Note the dysplasia of the bridging leaflets.
The case of a UV is more delicate because of the difficulty in differentiating a UV from an extreme ventricular hypoplasia, in particular that of the left. In this case, the papillary muscle of the RV, which is large, is often mistaken as the IVS. But in these cases, careful analysis of the four-chamber view will not allow us to find balanced chambers with a normal crux of the heart.
Four+ chambers
Seeing a small, supplementary, rounded chamber at the left atrioventricular angle (Fig. 6.23; see also Fig 6.6) is witness to a most often dilated coronary sinus (CS) by a persistent left subclavian vein (LSCV). The importance of this dilatation and its eventual repercussions22 depend on the association of the LSCV with an abnormal PVR found flowing there. Erroneous diagnoses of AVSD have been made in the case of a dilated CS in the presence of an imperfect four-chamber view (Fig. 6.24).23
FIGURE 6.23 Macroscopic view of the four chambers with a dilated CS in trisomy 21. Note the LIAVV without defect (marked by *).
FIGURE 6.24 Ultrasound view of a posterior swing cutting a dilated CS. This can be mistaken for AVSD.
Five chambers
We should be aware of the existence of a very rare doubling of the left atrial chamber: the triatrial heart.24 This “antechamber” receives the PV and is in communication with the LA by a tight orifice, which brings about the same effect as that of mitral stenosis with eventual repercussions on the development of the left tracts.
Early Gestation
The detection is possible; however, a careful analysis of four chambers would be better a few weeks later in some cases. Dilated coronary sinus is not present.
Point 5: Asymmetric Or Discordant Chambers
If the chambers are asymmetric we can distinguish a variety of architectural malformations
Right ventricular hypoplasia due to PA with IS (see Fig. 6.18) is found more often than tricuspid atresia (Fig. 6.25). In tricuspid atresia—certain cases have been published showing this condition to be associated with 22q11 deletion25—the right AV valve is closed but, due to the persistence of the bulbar ventricular foramen ensuring communication between the left and right outlet, the great vessels can be balanced. They are, however, often transposed.
FIGURE 6.25 Tricuspid atresia seen within a macroscopic four-chamber view showing a dead-ended orifice.
With different degrees of severity and variable causes26, left ventricular hypoplasia has a poor prognosis.27 According to the level where the obstacle is found, the left chamber lumen will be seen (or not seen) and the left chamber wall might be hyperechogenic. Atresia or a tightening stenosis of the aorta creates an obstacle, the struggle against which causes fibroelastosis (Fig. 6.26).28 This fibroelastosis can be seen as an hyperechogenicity.
FIGURE 6.26 Macroscopic four-chamber view of the heart with aortic atresia and fibroelastosis.
Ebstein anomalies (Fig. 6.27; see also Fig. 6.14) are associated with an often enlarged RA due to “atrialization” of the septal leaflet of the tricuspid valve. RV function can be very much reduced.
FIGURE 6.27 Macroscopic view of the heart with Ebstein's disease showing the right inlet tract open.
Early Gestation
Disproportion of chambers is most commonly a nonspecific finding to monitor and reassess later. It can represent a temporary finding in an otherwise normal heart.29–34 There is an adverse outcome for PA-IVS, TA, TS, and HLHS.
!!! Attention !!!
A discreet asymmetry at a gestational age of 20–22 weeks has been described as a warning sign of coarctation of the aorta.35 This pathology can be critical at birth. If there is the slightest suspicion, you should not hesitate to consult a pediatric cardiologist who can then follow the patient.
In cases where the chambers are discordant
An atrioventricular discordance is rare and defined as the communication between the RA and a ventricle of the left type (which has a smooth septum), while the left atrium (that which receives the PV) communicates with a ventricle of the right type (which has trabeculations). This anomaly, which is relatively easy to appreciate in fetal pathology, is visible through a rigorous study of the atrioventricular concordance in the four-chamber view. A discordance that is visible in the inlet, and thus atrioventricular, will lead us to look for an associated ventriculoarterial discordance. This double discordance was called the “corrected TGV” (Fig. 6.28).36 Theoretically, without any early or notable consequence, it is frequently associated with other pathologies—VSD, pulmonary stenosis, rhythm trouble—which justify the search for these concordances.
FIGURE 6.28 Macroscopic view of the HLB having a double discordance or “corrected transposition”.
Point 6: Rings That Are Impermeable Or Not Offset
The atrioventricular valves should be permeable. It is necessary to collect images of the four-chamber view with the valves closed and opened. They are impermeable in two pathologies: mitral (Fig. 6.29) or tricuspid (see Fig. 6.25) atresias.
FIGURE 6.29 Macroscopic four-chamber view of a heart with mitral atresia.
The verification of the offsetting of the atrioventricular valves is an important step that should be part of the examination using the four-chamber view. In fact, the absence of offsetting, or the linear insertion of atrioventricular valves (LIAVV), is a marker common to all levels of the spectrum of AVSD. This spectrum goes from the continued persistence of the initial atrioventricular canal in the form of a complete AVSD (Figs 6.30 and 6.31) to the LIAVV without defect, which we have described both anatomically and through US.37,38 This spectrum then passes through partial AVSD with the interatrial defect of the ostium primum type and mitral cleft, or a partial AVSD with an inlet defect. The close relationship between AVSD and trisomy 21 is well known (Fig. 6.32).
FIGURE 6.30 Embryological diagram of the “verticalized” heart seen from the left. The AVSD is still complete.
FIGURE 6.31 Macroscopic view of the “verticalized” heart. Opening of the left inlet showing a large defect with two bridging leaflets over the crest.
FIGURE 6.32 Ultrasound view of a trisomic 21 fetus. There is a complete AVSD in this apical incidence. Note the linear aspect of the bridging leaflet.
In the case of complete AVSD, the common valves, inferior and superior (Figs 6.33 and 6.34), bridge the AVSD from above. Dependent on the degree of severity within the spectrum, we can eventually visualize a septum intermedium which appears echogenic (Fig. 6.35). Sometimes the bridging leaflets are attached to the crest of the AVSD (Fig. 6.36). This takes into account the differences between the US aspect of the common valve without attachments (see Figs 6.33–6.35), opening and closing like a single wing of a seagull, and the attached bridging leaflet (Fig. 6.37; see also Fig. 6.36) which beats like the two wings of a seagull (Fig. 6.38).
FIGURE 6.33 Diagram of a major form of complete AVSD.
FIGURE 6.34 Macroscopic view of a major form of complete AVSD with the probe under the bridging leaflet (the “one wing” of a seagull).
FIGURE 6.35 Diagram of a view of a complete AVSD with the septum intermedium.
FIGURE 6.36 Diagram of a view of a complete AVSD with the septum intermedium and attached to the bridging leaflet on the crest of the VSD like two wings of a seagull.
FIGURE 6.37 Diagram of a view of a partial AVSD with an ASD ostium primum.
FIGURE 6.38 A seagull flying over the Mediterranean.
In the case of partial AVSD, a defect is described as either ASD of the ostium primum type, (Figs 6.39 and 6.40) or VSD of the inlet type (Figs 6.41 and 6.42). In both cases the atrioventricular leaflets appear to be inserted at the same level. There can be a mitral cleft, but here as well, there is no offsetting.
FIGURE 6.39 Embryological diagram seen from the left of a partial AVSD with ASD ostium primum. iad, interatrial defect.
FIGURE 6.40 Macroscopic view of the vertical fetal heart opened to the left showing the ASD and mitral cleft. The probe passes through the “chicane” of the foramen ovale.
FIGURE 6.41 Diagram of a view of a partial AVSD with an inlet VSD.
FIGURE 6.42 Macroscopic view of a HLB with an inlet VSD (probe) of a partial AVSD in a trisomic 21 fetus.
Next to partial AVSD with defects, we have described a minor form of AVSD, which we named the LIAVV without defect (Figs 6.43–6.45; see also Fig. 6.23),37 which can now be observed by US (Fig. 6.46).38
FIGURE 6.43 Diagram of LIAVV without defect.
FIGURE 6.44 Macroscopic view of the four chambers of a fetal heart with trisomy 21 and LIAVV without defect. Note the ballooning septal tricuspid leaflet (marked by *).
FIGURE 6.45 Histologic view of the four chambers of a fetal heart with trisomy 21 and LIAVV without defect. The septal leaflets insert (*) at the same level.
FIGURE 6.46 Ultrasound view of the four chambers of a fetal heart with trisomy 21 and LIAVV without defect. Note the ballooning septal tricuspid leaflet.
There is a lack of the normal offsetting. (Figs 6.47 and 6.48).
FIGURE 6.47 Crux of the heart with normal offsetting in an US scan.
FIGURE 6.48 Crux of the heart with normal offsetting in macroscopy.
In normal hearts, the offsetting of the atrioventricular valves is constant, whereas in all forms of the AVSD spectrum we observe a linear insertion of these atrioventricular valves which makes them look like the wings of a seagull (see Fig. 6.38).
A yet unpublished large prospective study has also shown that in certain CTCs we can find a LIAVV with defect. This confirms fetal pathologic observations that have been seen in these hearts (Fig. 6.49).
!!! Attention !!!
Before concluding that there is an inlet anomaly, an asymmetry or an abnormal insertion of the valves, you must be certain—and clearly confirm—that the four-chamber view is strictly axial and situated at the optimal level.
FIGURE 6.49 Four-chamber view of the HLB of a fetus with tetralogy of Fallot. Note there is a LIAVV (marked by *). The defect is seen in the outlet.
There are two criteria for assuring the quality of this view which should be visualized on the same image plane. They are:
• The arrival of the two inferior PVs in the LA.
• The visualization of one (or two) complete rib(s) depending on the incidence.
At the level of the TAD and the optimal four-chamber view, the presence of at least one complete rib confirms the axial nature of the view.
Early Gestation
The AVSD is best detected by a high-frequency linear probe or transvaginal probe. Routine study of the flow across the tricuspid valve is highly recommended: absence of TR is a good indicator that there is no AVSD.
Third step. pathologies of the outlet
Often outlet pathologies are suspected due to certain small warning signs observed on the four-chamber view. These include:
• A right descending aorta (see Figs 6.6–6.8).
• The axis of the heart at 60° (see Figs 6.6 and 6.15), with balanced ventricular outlet chambers, and a heart in the form of a “boot” as seen in severe forms of tetralogy of Fallot.
At the outlet level these different pathologies touch each of the key points, which include:
• Point 7: two balanced outlet chambers separated by an outlet septum with an intact, normal alignment.
• Point 8: two crossed vessels.
• Point 9: outlet tracts that are balanced and concordant.
• Point 10: a regular aortic arch.
Point 7: Pathology
The presence of a defect of the alignment in the outlet septum is a direct warning sign of CTC. If the defect is situated on the trabeculated outlet section of the IVS (Fig. 6.50) it is essentially a VSD with a misalignment, which destroys the septal–aortic continuity at the level of the junction between the muscle of the IVS and the fibrous aortic wall.
FIGURE 6.50 The fetal heart opened to the left. The probe pushes along the aortic wall into the right ventricle.
This type of large outlet VSD (Figs 6.51 and 6.52) is characteristic of CTCs and is the most frequent type of VSD associated with CTC. If it is associated with an anterior swing of the conal septum, depending on the degree of swing, it can result in different forms of tetralogy of Fallot through to PA with OS (Fig. 6.53).
FIGURE 6.51 Macroscopic LV–Ao views: large misalignment VSD in a tetralogy of Fallot with an overriding aorta compared to a normal heart.
FIGURE 6.52 Ultrasound view of a large overriding aorta.
FIGURE 6.53 Another US view of a large overriding aorta.
Far rarer is a VSD of CTC involving the infundibular septum, which is smaller and more difficult to see, except in the “SOS” view, which is what we call the sagittal LV–Ao view. Infundibular VSDs are situated at a distance from the membranous septum and are more often associated with CTC caused by a posterior swing. (Fig. 6.54) The milder forms are coarctation syndromes (narrowing of the aorta associated with an outlet VSD); major forms are interruption of the aorta. When the VSD is not seen right away, an asymmetry of the great vessels when the admission chambers are balanced should draw us to this region, allowing us to discern this defect.
FIGURE 6.54 Lateral left view of the outlet tract. An infundibulum VSD is more frequent in cases of a posterior swing. Note the crest situated between the forceps which forms an obstacle to the aortic outlet.
Constant VSD in conotruncal cardiopathies is for the most part caused by misalignment.
Verifying septal–aortic continuity and the balance of vessels (having the same diameter) eliminates the possibility of a large majority of the CTC spectrum, especially the most common or severe types, such as ToF, and PA with OS.
Early Gestation
Detection of ToF is possible in most of the cases, but the US practitioner could miss cases when pulmonary vessel is of normal size. Suspicion can arise from a more leftward cardiac axis.
Diagnosis can be made based on the substantial anatomic details that allow for accurate diagnosis.39,40
Only a few cases of APVS are reported, since the full spectrum of anatomic details manifests later in gestation.
Reverse flow in umbilical artery can be detected, and PAVSD can be identified.41,42
As in AVSD, there is a CTC malformation spectrum. Faced with each and every form of CTC we should research the possibility of a 22q11 deletion if the standard karyotype is normal.43
The major form of this spectrum is the persistence of the common arterial trunk (CAT) (Fig. 6.55) where the infundibular or conal septum is absent; a unique outlet vessel overrides the VSD. The PT arises from the CAT soon after the ring, which is frequently displastic.
FIGURE 6.55 Fetal HLB with CAT. Note the “boot” shape of the heart responsible for the 60° axis.
Other CTCs are differentiated by size and position of the great vessels relative to the VSD:
• The minor form is an isolated outlet VSD.
• In the case of an anterior swing (Fig. 6.56) of the conal or infundibular septum, and depending on the degree of this swing, we move from a minor to a major form of tetralogy of Fallot. At the extreme end is PA with OS. These cardiopathies are very frequent in fetal pathology, where they are seen to evolve,44 and represent 55% of cases of CTC.
FIGURE 6.56 Diagram of the CTC spectrum caused by an anterior swing: From tetralogy of Fallot to PA with OS.
• In the case of a posterior swing (Fig. 6.57), the aortic flow is seen to proportionally diminish at the degree of the swing with stenosis (in minor forms) to interruptions (major forms) of certain sections of the aortic arch. This can be explained by the multiple and specific embryonic origins of these different segments. The minor form is the coarctation syndrome which associates a partial stenosis (or coarctation of the aorta) with an outlet VSD. The major form occurs when the aortic arch is interrupted (IAA) (Fig. 6.58), which itself exists in several forms (about 14% of fetal CTC, but it is associated in 80% of cases of 22q11 deletion where the IAA has been visualized as being of the B type).43 This form of IAA is characterized by the interruption (illustrated by the dotted lines in Figure 6.58) occurring between the left primitive carotid artery and the left subclavian artery (Fig. 6.59). In IAA attention should be given to the unusual “vertical” aspect of the ascending aorta before the interruption of its arch.
FIGURE 6.57 Diagram of the CTC spectrum caused by a posterior swing: From syndrome of coarctation to interruption of the aortic arch (IAA).
FIGURE 6.58 Heart–lung block showing a type B IAA. Note the steepness of the ascending aorta and the absence of continuity between the primitive left carotid and the arterial canal.
FIGURE 6.59 Diagram of the different levels of IAA.
• In anomalies involving asymmetry in the size of the vessels we can add the variable degree involved in malpositioning of these vessels above the IVS. These positional errors can be of such importance that it is difficult to differentiate a tetralogy of Fallot in which less than 50% of the aorta receives a flow from the RV from a double outlet right ventricle in which the PT and the aorta primarily exit out of the RV.
Certain particularities of CTC chiefly evoke a 22q11 deletion: a right aortic arch; a type B2 IAA (see Fig. 6.58); the presence of main aortopulmonary collateral arteries (MAPCA) (Fig. 6.60) in PA with OS; and an absence of the ductus arteriosus (DA). In addition, 30% of fetuses present with associated renal anomalies.43
!!! Attention !!!
The discovery of an outlet cardiopathy in a fetus with a standard normal karyotype in the context of oligohydramnios leads us immediately to consider 22q11 deletion because 30% are associated with a renal anomaly.
FIGURE 6.60 Posterior view of a HLB in a PA with OS. MAPCA coming out of the aorta to the right and the left lungs.
Point 8: The Verification Of The Crossing Over Of The Great Vessels Is A Critical Moment
Early Gestation
CAT and DORV are detectable. Differental diagnosis in some cases is postponed.
It is here that we can allay suspicion of a complete TGV—an obsession of the fetal US practitioner. TGV occurs in an otherwise normal fetus whose prognosis depends on the prenatal diagnosis of this cardiopathy.45,46 Anatomically, TGV is described as ventriculoarterial discordance (Figs 6.61 and 6.62). The origin of the aorta occurs in the RV, more anterior than the PT in the LV at the center of the heart. This results in an almost parallel direction of the two vessels (Fig. 6.63) as they proceed towards their junction with the descending aorta (Figs 6.64 and 6.65).
FIGURE 6.61 Macroscopic view of TGV.
FIGURE 6.62 Ultrasound incidence in TGV.
FIGURE 6.63 Right posterior view of a heart after ablation of the auricles and the great vessels. Arrows indicate the trajectory of the vessels in rejoining the descending aorta in TGV.
FIGURE 6.64 Ultrasound incidence in TGV. A view close to the three-vessel view (3VT).
FIGURE 6.65 Anatomic correlation of Figure 6.64.
The US diagnosis of TGV means that we must check the emergence of the vessels from each ventricle, noting that:
• Out of the LV comes a vessel which will rejoin the descending aorta and rapidly divide, thus it is the PT.
• Out of the anterior RV emerges a vessel which joins the descending aorta after a long anteroposterior trajectory (Fig. 6.66). This vessel gives rise to the vessels of the neck, thus it is an aorta.
FIGURE 6.66 Ultrasound incidence in TGV. Sagittal, the aorta is seen to begin not in the center of the heart but in a ventricle situated behind the sternum.
An isolated right or left ventriculo-arterial discordance is a vital clue to orient our diagnosis towards that of TGV.
Early Gestation
The aorta and pulmonary artery are imaged in the same view with color flow modalities without tilting the transducer; visualization of the cross of great vessel is easier.28
The differential diagnosis between complete and correct transposition could be postponed.
Point 9: A Lack Of Balance Can Involve Several Elements
A lack of balance between the chambers
This might already have been seen on the four-chamber view when we paid attention to checking the permeability of the atrioventricular rings. This is the case in left tract hypoplasias (see Figs 6.12 and 6.13) which are more frequent than those concerning the right hypoplasias (Figs 6.16 and 6.17).
Vessel imbalance
Though seen while viewing a single vessel—e.g., a large arch, a small PT (Fig. 6.67), or one that is not seen at all—it is often better appreciated when observing two vessels on the same image, the arterial duct view (Fig. 6.68) or the three-vessel view. This imbalance makes searching for an outlet VSD a priority, which, if found, leads us to a diagnosis of CTC.
FIGURE 6.67 Large aorta, small PA. Tetralogy of Fallot. Look for the outlet VSD.
FIGURE 6.68 Ductus arteriosus view. Large PT, small aorta. If the four-chamber view is in equilibrium look for a VSD (CTC by posterior swing). If the four-chamber view is not in equilibrium verify if there is a hypoplasia of the left tracts.
In studying vessel imbalance through the three-vessel view it is important to appreciate the direction of flow of the two vessels in Doppler; this is essential in certain cardiopathies called duct-dependent. Normally both the aortic and DA flow is directed towards the descending aorta. This vascularization, which ends with the physiologic closing of the DA in the hours following birth, is called duct-dependent. This problem is one for the pediatric cardiologists but its US visualization is relatively simple.
The confirmation of convergent flow of aorta and DA in the three-vessel view is essential.47 A reverse flow is always pathologic, indicating a retrograde vascularization of the PT or the Ao.48
Early Gestation
Pulmonary and aortic stenosis are difficult to detect and diagnose as ultrasound findings may be subtle or absent. It is possibly a progression to ventricular and great artery hypoplasia.
Bidirectional flow in one or both great arteries is associated with a poor prognosis.
Critical aortic stenosis is easily recognized by the modified size and contractility of the left ventricle.49–52
Point 10: Irregular Aortic Arch
We have already spoken of large arches which are noticeable in different forms of tetralogy of Fallot where they are associated with VSD. Though the irregularities of the aortic arch are subtle, they can eventually be examined using the three-vessel view.
Coarctations of the isthmus of the aorta is a pathology that often becomes critical with the closing of the arterial duct. This pathology is difficult to recognize by direct signs but can be suspected due to its effects on the hemodynamics. This causes a type of ventricular asymmetry, noted at a gestational age of 22 weeks in the absence of any other pathology.35
Coarctation of the horizontal aorta is characteristic of Turner's syndrome52 (karyotype primarily 45X0).
Attention
Do not confuse coarctations with the syndromes of coarctation CTC caused by a posterior swing of the conal septum, which are always associated with a VSD.
The third step necessitates static and dynamic studies based on multiple views that are complementary, which include the measurement of the diameters of the great vessels.
The three-vessel view necessitates color Doppler to check the direction of the flow towards the descending aorta.
Early Gestation
Detection and diagnosis of aortic coartation and IAA is limited.
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