Prenatal diagnosis of the fetal common arterial trunk. A case series

Fetal common arterial trunk is an anomaly represented by a unique arterial trunk that arouses from the base of the heart, and gives birth to systemic branches, both pulmonary and coronary, frequently associated with a ventricular septal defect (VSD) and has a poor prognosis. We present a series of 17 cases diagnosed in our tertiary center with different types of fetal common arterial trunk, its associated disorders, the evolution of the pregnancies, and of the neonates. We concluded that our cases support the fact that a complete intrauterine evaluation of each case of the common arterial trunk is impossible. The postnatal prognosis of the cases from our center was fatal, similar to most reports of the literature.

Prenatal differentiation between truncus arteriosus (Types II and III) and pulmonary atresia with ventricular septal defect

OBJECTIVE

To describe antenatal sonographic signs that help in the differentiation of truncus arteriosus Types II and III (TA-II/III) from pulmonary atresia with ventricular septal defect (PA-VSD).

METHODS

From a database of fetal echocardiographic examinations, we identified fetuses with sonographic features of a single great artery with VSD and relatively normal four-chamber view. Records were reviewed, comparing fetuses with TA-II/III and those with PA-VSD, with particular focus on: 1) characteristics of the overriding vessel, 2) appearance of the semilunar valves, 3) competence of the semilunar valves, 4) presence of major aortopulmonary collateral arteries (MAPCA), 5) main pulmonary artery being without antegrade flow, 6) site of arterial branching from the great artery and 7) other minor features, such as cardiac axis or associated anomalies.

RESULTS

Seventeen fetuses were identified, eight with TA-II/III and nine with PA-VSD. Among the eight fetuses with TA-II/III, seven had abnormal valves and six had valve regurgitation, compared with none of the nine PA-VSD fetuses. Five TA-II/III fetuses had early branching to supply the lungs, whereas most fetuses with PA-VSD had more distal branching. Notably, in six of the TA-II/III fetuses, the root of the single great artery originated predominantly from the right ventricle, while all but one of the PA-VSD fetuses had typical equal overriding of the VSD. The main pulmonary artery was without antegrade flow in two cases with PA-VSD. Finally, four cases with PA-VSD had MAPCA, in two of which this was identified prenatally.

CONCLUSION

Identification of abnormal arterial valves or valve regurgitation, site of origin of branching, presence of overriding of the great artery, a main pulmonary artery without antegrade flow and MAPCA are helpful in differentiating between TA-II/III and PA-VSD.

Cardiac arterial pole alignment is sensitive to FGF8 signaling in the pharynx

Morphogenesis of the cardiac arterial pole is dependent on addition of myocardium and smooth muscle from the secondary heart field and septation by cardiac neural crest cells. Cardiac neural crest ablation results in persistent truncus arteriosus and failure of addition of myocardium from the secondary heart field leading to malalignment of the arterial pole with the ventricles. Previously, we have shown that elevated FGF signaling after neural crest ablation causes depressed Ca2+ transients in the primary heart tube. We hypothesized that neural crest ablation results in elevated FGF8 signaling in the caudal pharynx that disrupts secondary heart field development. In this study, we show that FGF8 signaling is elevated in the caudal pharynx after cardiac neural crest ablation. In addition, treatment of cardiac neural crest-ablated embryos with FGF8b blocking antibody or an FGF receptor blocker rescues secondary heart field myocardial development in a time- and dose-dependent manner. Interestingly, reduction of FGF8 signaling in normal embryos disrupts myocardial secondary heart field development, resulting in arterial pole malalignment. These results indicate that the secondary heart field myocardium is particularly sensitive to FGF8 signaling for normal conotruncal development, and further, that cardiac neural crest cells modulate FGF8 signaling in the caudal pharynx.

Coronary artery embryogenesis in cardiac defects induced by retinoic acid in mice

BACKGROUND

Although normal coronary artery embryogenesis is well described in the literature, little is known about the development of coronary vessels in abnormal hearts.

METHODS

We used an animal model of retinoic acid (RA)-evoked outflow tract malformations (e.g., double outlet right ventricle [DORV], transposition of the great arteries [TGA], and common truncus arteriosus [CTA]) to study the embryogenesis of coronary arteries using endothelial cell markers (anti-PECAM-1 antibodies and Griffonia simplicifolia I (GSI) lectin). These markers were applied to serial sections of staged mouse hearts to demonstrate the location of coronary artery primordia.

RESULTS

In malformations with a dextropositioned aorta, the shape of the peritruncal plexus, from which the coronary arteries develop, differed from that of control hearts. This difference in the shape of the early capillary plexus in the control and RA-treated hearts depends on the position of the aorta relative to the pulmonary trunk. In both normal and RA-treated hearts, there are several capillary penetrations to each aortic sinus facing the pulmonary trunk, but eventually only 1 coronary artery establishes patency with 1 aortic sinus.

CONCLUSIONS

The abnormal location of the vessel primordia induces defective courses of coronary arteries; creates fistulas, a single coronary artery, and dilated vessel lumens; and leaves certain areas of the heart devoid of coronary artery branches. RA-evoked heart malformations may be a useful model for elucidating abnormal patterns of coronary artery development and may shed some light on the angiogenesis of coronary artery formation.

Normal fate and altered function of the cardiac neural crest cell lineage in retinoic acid receptor mutant embryos

Mouse embryos lacking the retinoic acid (RA) receptors RARalpha1 and RARbeta suffer from a failure to properly septate (divide) the early outflow tract of the heart into distinct aortic and pulmonary channels, a phenotype termed persistent truncus arteriosus. This phenotype is associated with a failure in the development of the cardiac neural crest cell lineage, which normally forms the aorticopulmonary septum. In this study, we examined the fate of the neural crest lineage in RARalpha1/RARbeta mutant embryos by crossing with the Wnt1-cre and conditional R26R alleles, which together constitute a genetic lineage marker for the neural crest. We find that the number, migration, and terminal fate of the cardiac neural crest is normal in mutant embryos; however, the specific function of these cells in forming the aorticopulmonary septum is impaired. We furthermore show that the neural crest cells themselves do not utilize retinoid receptors and do not respond to RA during this process, but rather that the phenotype is cell non-autonomous for the neural crest cell lineage. This suggests that an alternative tissue in the vicinity of the outflow tract of the heart responds directly to RA, and thereby induces or permits the neural crest cell lineage to initiate aorticopulmonary septation.

A case of truncus arteriosus type II

A case of truncus arteriosus type II is reported. Truncus arterious is an uncommon congenital cardiac defect where a single great vessel exits the heart. Truncus arteriosus is usually fatal, if untreated. This defect occurs when the conus arteriosus and the truncus divide erroneously in the embryo. Palliative surgery in truncus arteriosus has been unsuccessful. Pulmonary banding has been tried and was ineffective and usually fatal. We operated on a nine-month-old (6200 g) male infant with a type II (Edwards-Collett) defect and a large ventricular septal defect. The pulmonary artery average pressure was 51 mmHg. We performed a cardiopulmonary bypass in the usual manner. Pulmonary arteries were resected from the truncal root, and primary end-to-end anastomosis of the truncal root to the ascending aorta was performed. Right ventricle to pulmonary artery continuity was provided using a valveless Gore-Tex graft. We lost our patient due to intractable pulmonary hypertension on the first postoperative day.

Neural crest is involved in development of abnormal myocardial function

Around 85% of embryos homozygous for the splotch (Sp2H) allele (Sp2H/Sp2H), a Pax3 mutation, develop persistent truncus arteriosus (PTA), a defect related to the cardiac neural crest. These embryos die by 14.5 days post coitum. In an investigation of the cause of lethality in these embryos, we used digital video imaging microscopy to examine beating embryonic hearts in situ at 13.5 dpc. The hearts of Sp2H/Sp2H embryos with PTA clearly showed poor function when compared with normal litter mates. Contractile force was examined in detergent-skinned ventricular muscle strips from Sp2H/Sp2H embryos at ages 12.5 and 13.5 dpc. There was no significant difference in the maximum force or in myosin content between Sp2H/Sp2H and control groups, indicating no significant dysfunction of the contractile apparatus in hearts from Sp2H/Sp2H embryos. Ca2+ transients were examined in enzymatically-dissociated ventricular myocytes and were significantly reduced in defective hearts, indicating that reduced cardiac function in Sp2H/Sp2H embryos with PTA was due to impaired excitation-contraction (EC) coupling. Ca2+ currents were examined using the perforated patch clamp technique. The magnitude of the Ca2+ current was found to be reduced by approximately 3.2-fold in Sp2H/Sp2H hearts with PTA compared to normal. Since the sarcoplasmic reticulum is sparse or absent in the embryonic heart, the impaired EC coupling was due to the reduction in Ca2+ current. These observations suggest that neural crest abnormalities result in a defect in EC coupling, causing depressed myocardial function and death in utero from cardiac failure. Interestingly, Sp2H/Sp2H hearts without PTA had normal EC coupling. These results indicated that impaired EC coupling was secondary to the Pax3 mutation. The findings in this report indicate an important role for the neural crest in the development of normal myocardial function, and represent the first demonstration of impaired excitation-contraction coupling in a genetically-defined embryonic mammalian model of a cardiac structural defect.

Truncus arteriosus malformation: a developmental arrest at Carnegie stage 14

The pathogenesis of truncus arteriosus malformation has been ascribed to deficiency of conotruncal ridges, failure to form a pulmonary conus, absence of the aortopulmonary septum, or hemodynamic factors. To re-examine this issue, we reviewed the morphology of 28 hearts with truncus arteriosus malformation and compared the findings to the sequences of cardiogenesis in 351 normal human embryos of the Carnegie Embryological Collection. All malformed hearts had an absent muscular outflow tract (conal) septum. The truncal valve had four commissures and/or raphes, a fused commissure, in seven cases, three in 20, and uncertain status in one. All but one heart had fibrous continuity between the anterior mitral leaflet and the truncal valve. In embryos, the outflow tract was circular and lined by a layer of cardiac jelly early in Carnegie stage 14 but acquired an elliptical configuration and four cushions, with fusion of the two larger, by stage 16. Semilunar valve leaflets form at the downstream end of the cushions. The more frequent occurrence of three rather than four commissures in the truncal valve associated with absence of a conal septum suggests that the embryonic outflow tract failed to acquire an elliptical shape and cushions that could fuse to subdivide the outflow tract and the semilunar valves anatomically. The presence of truncal valve leaflets shows that three or four cushions did form and the usual presence of mitral-truncal valve fibrous continuity supports otherwise normal outflow tract development. We conclude that a failure or delay of the circular outflow tract of early Carnegie stage 14 to acquire the elliptical configuration needed to induce formation of four cushions, two of which fuse to subdivide the outflow tract and semilunar valve primordia, is the cause of truncus arteriosus malformation.

A single major-gene defect underlying cardiac conotruncal malformations interferes with myocardial growth during embryonic development: studies in the CTD line of keeshond dogs

The common forms of isolated congenital heart disease are usually not inherited in a Mendelian pattern, and most are considered multifactorial threshold traits. A large subset consisting of a group of malformations of the ventricular outflow region, termed "conotruncal defects" (CTDs), include subarterial ventricular septal defects, tetralogy of Fallot, and persistent truncus arteriosus. Similar aggregations of CTDs have been reported in human families and in the keeshond breed of dog. The results of our early breeding experiments utilizing noninbred keeshonds were not consistent with any hypothesis of a fully penetrant monogenic inheritance. Here we report a recent series of genetic and embryologic studies conducted after more than 10 generations of selective inbred matings between affected-CTD-line dogs. The results are now consistent with a defect at a single autosomal locus, the Mendelian pattern of transmission having been obscured prior to selective inbreeding by genetic background. On the basis of morphometric embryologic studies, the mutant CTD allele causes conotruncal malformations in homozygous animals by interfering with myocardial growth in the conotruncus during the critical window when the conotruncal cushions fuse to form the conotruncal septum.

Relation of early hemodynamic changes to final cardiac phenotype and survival after neural crest ablation in chick embryos

BACKGROUND

Microcinephotography was used to study a model of persistent truncus arteriosus created in chick embryos by ablation of premigratory neural crest destined for the third and fourth aortic arch arteries as well as the septum of the cardiac outflow tract.

METHODS AND RESULTS

Twenty-five control embryos and 105 of 202 experimental embryos were filmed on day 3 of incubation and then reincubated. The remaining 97 experimental embryos were not filmed because of twisting of the embryos, but they were reincubated. There was no difference in either the survival rate (p greater than 0.23) from day 3 to day 11 of incubation or the incidence of persistent truncus arteriosus (p greater than 0.08) between the filmed and the nonfilmed embryos. Incomplete looping of the cardiac tube observed in experimental embryos during early cardiogenesis correlated with a right ventricular origin of the outflow vessels in the definitive heart. Hemodynamic measurements indicated that there was no difference in heart rate, ejection fraction, systolic and diastolic areas, stroke volume, and cardiac output between controls and the experimental group as a whole. However, embryos that did not survive to day 11 had decreased stroke volume (p less than 0.001) and cardiac output (p less than 0.001), whereas embryos that survived to day 11 with cardiac malformations had increased stroke volume and cardiac output in early embryogenesis.

CONCLUSIONS

Increased stroke volume and cardiac output may be necessary factors for survival in embryos with cardiac dysmorphogenesis and probably are associated with dilation of the ventricular portion of the cardiac tube, which leads to malalignment of the outflow vessel or vessels.

Reduced L-type calcium current in the embryonic chick heart with persistent truncus arteriosus

Calcium currents were examined in an experimental model in the embryonic chick heart with a congenital malformation known as persistent truncus arteriosus. This is a severe defect characterized by failure of conotruncal and aorticopulmonary septation of the embryonic heart tube. As a result, no separation into the aortic and pulmonary arteries occurs, and there is a common outflow tract. The hearts with persistent truncus arteriosus had a 26% greater ventricular to whole embryo weight, which indicated that the ventricles were enlarged. Both the low-threshold T-type (ICa.T) and the 1,4-dihydropyridine-sensitive L-type (ICa.L) Ca2+ currents were present in the ventricular myocytes from hearts at day 11 of incubation. However, day 11 hearts with persistent truncus arteriosus showed a twofold reduction in the peak magnitude of ICa.L at a test potential of + 10 mV without a concomitant reduction in the number of L channels detected by 1,4-dihydropyridine antagonist [(+)[3H]PN200-110] and agonist (Bay K 8644) receptor binding. The results indicated that an L channel regulatory mechanism other than protein synthesis was affected. These changes are consistent with responses to conditions of excessive hemodynamic burden that have been characterized in adult hearts.

Facial dysmorphologic and skeletal cephalometric findings associated with conotruncal cardiac anomalies. off

Anomalous conotruncal cardiac morphology and facial dysmorphology have been associated with neural crest-pharyngeal arch abnormalities. To assess these associations, 20 patients 3 to 18 years old with tetralogy of Fallot (TOF) or persistent truncus arteriosus (PTA) were evaluated by cardiologic, facial dysmorphic, and cephalometric criteria. The average number of facial abnormalities of neural crest derivation was two, while pharyngeal arch derivative abnormalities were observed with an average of five defects per subject. The total group had many more facial malformations than normal populations (P less than .00001). The occurrence of defects was not significantly different between TOF and PTA patients. Thirteen TOF patients 8 years, 9 months to 18 years, 10 months old (x = 13 years, 4 months) had lateral cephalograms analyzed for skeletal relationships. The TOF patients exhibited higher than usual distribution of dolichofacial growth patterns (6 of 13), Class II skeletal relationships (6 of 13), mandibular retrusion (7 of 13), and maxillary protrusion (6 of 13). Trends were not absolute, since opposite patterns were individually expressed, and referencing by race tended to show more normal values for respective groups.

Persistent truncus arteriosus in the Splotch mutant mouse

The Splotch mutant mouse shows defects in neural crest-derived cell populations. The septation of the truncus arteriosus and the development of the aortic arch-derived blood vessels was studied in homozygotes of the Splotch mutant allele Sp1H. It is shown that in homozygous mutant embryos, the septation of the truncus arteriosus does not proceed normally, resulting in persistent truncus arteriosus. The ostium of the persistent truncus arteriosus opens to the right ventricle. Frequently, variations of the aortic arch-derived blood vessels are observed. The development of the thymus, the parathyroid and the ultimobranchial bodies are also variably affected in mutants. These results provide indirect evidence, that cells contributing to the aortic arches and the septum of the truncus arteriosus in mice are derived from the neural crest. The Splotch mutant mouse is proposed to be an animal model for persistent truncus arteriosus. The implications of the vascular malformations for the midgestational death of this mutant are discussed.

Pathogenesis of persistent truncus arteriosus and dextroposed aorta in the chick embryo after neural crest ablation

To investigate the contribution of cranial neural crest cells to the developing cardiovascular system in the chick embryo, cauterization of various regions of cranial neural crest was performed. Five regions may be distinguished, each of which contributes mesenchyme to pharyngeal (branchial) arches 1 through 4 and 6. Ablation of arch 3, 4, and 6 regions resulted in a high incidence of persistent truncus arteriosus (PTA) associated with anomalies of the aortic arch. Dextroposed aorta (DPA) or anomalies of the inflow tract were found in all ablation groups. Although anomalies of the aortic arch arteries were induced in all ablation groups and were usually associated with intracardiac anomalies, those of the third and right fourth aortic arch were most frequent in the arch 4 and arch 4 + 6 groups. Anomalies of the sixth aortic arch were most frequent after extensive ablations that included the arch 6 region. We speculate that PTA is a direct result of the decreased population of mesenchymal cells derived from the arch 3 through 6 neural crest regions. DPA or anomalies of the inflow tract may be related to altered hemodynamics due to anomalies induced by neural crest ablation. Anomalies of the aortic arch arteries may be caused by either the direct or indirect process.

Cardiovascular anomalies in DiGeorge syndrome and importance of neural crest as a possible pathogenetic factor

One hundred sixty-one cases of DiGeorge syndrome (111 previously reported in which details concerning individual patients were given and 50 observed) were analyzed for occurrence and type of cardiovascular anomalies. Only 5 patients had a normal heart. Interrupted aortic arch type B was the major anomaly in 48 patients and persistent truncus arteriosus in 37. Therefore, in about half of the patients with DiGeorge syndrome the major anomaly was one that is rare. Conversely, of those patients with interrupted aortic arch, 68% had DiGeorge syndrome, as did 33% of all patients with truncus arteriosus. Although tetralogy of Fallot was also seen often in DiGeorge syndrome (10 patients), these cases represented less than 2% of the total number of cases of tetralogy of Fallot. Similarly, less than 1% of children with isolated ventricular septal defect or transposition of the great arteries had DiGeorge syndrome. The primary cardiovascular anomaly always involved the aortic arch system or the arterial pole of the heart. Recent studies show that neural crest cells play a crucial role in development of pharyngeal (bronchial) pouch derivatives, e.g., thymus and parathyroid glands, as well as the aortic arches and the truncoconal part of the heart. These studies and present observations support the view that DiGeorge syndrome and the associated cardiovascular anomalies are due to an abnormal developmental process involving the neural crest. Curiously, no instances of aortopulmonary septal defect or anomalous origin of a pulmonary artery from the ascending aorta (hemitruncus) have been associated with DiGeorge syndrome.(ABSTRACT TRUNCATED AT 250 WORDS)

The teratogenic effects of a bis(dichloroacetyl)diamine on hamster embryos. Aortic arch anomalies and the pathogenesis of the DiGeorge syndrome

A study of the teratogenic effects of Fertilysin, a bis(dichloroacetyl)diamine, on hamster embryos was undertaken for a comparison of Fertilysin-induced malformations with the DiGeorge syndrome of human patients, a rare birth defect characterized by thymic and parathyroid gland agenesis, abnormal facies, and aortic arch malformations. In treated hamsters, malformations of the aortic arches were found to be consistently produced, and many of these anomalies could not be explained by conventional methods of analysis. A pathogenetic scheme to classify malformations of the aortic arch and great vessels is offered, including a revision of Celoria and Patton's classification of interrupted aortic arches. It is suggested that the DiGeorge syndrome is a syndrome of truncated pharyngeal arch development with two general forms: 1) agenesis of or incomplete development of the sixth pharyngeal arch with pulmonic circulation through the fifth arch; 2) agenesis of or incomplete development of the fifth and sixth pharyngeal arches with pulmonic circulation through the fourth arch. The third aortic arch may descend into the thorax under these circumstances.

Dependence of thymus development on derivatives of the neural crest

Elimination of limited areas of the cephalic neural crest in stage 9 or 10 chick embryos markedly reduced the size of the thymus gland or resulted in its absence. Small thymic lobes contained both thymocytes and epithelial cells but showed delayed development. Parathyroid and thyroid glands sometimes were reduced in size or missing from the normal location on one or both sides. Heart defects were consistently present. Thymus development may depend on direct interaction of mesenchymal derivatives of the neural crest with pharyngeal epithelium. Multiple defects, such as the Di George syndrome, may result from failure of neural crest derivatives to migrate and interact properly.

Pathogenesis of persistent truncus arteriosus in light of observations made in a dog embryo with the anomaly

Among 36 embryos obtained from a strain of Keeshond dogs in which there is a large incidence of spontaneously occurring conotruncal anomalies, a specimen with persistent truncus arteriosus, type 1 was found. The embryo had a crown-rump length of 20 mm. The specimen was serially sectioned and a wax plate reconstruction was made of the heart and proximal great vessels at a magnification of X100. The truncal valve was quadricuspid and dysplastic; associated anomalies were a right subclavian artery arising anomalously from the descending aorta, a single coronary artery, an absent ductus arteriosus and a small persistent left cranial (superior) vena cava. The truncus cushions were hypoplastic, had failed to fuse and each had simply produced an arterial cusp. The observations made on this embryo support the view that in persistent truncus arteriosus there is failure of septation of the truncus arteriosus. No evidence was found in favor of the concept that persistent truncus arteriosus represents a form of tetralogy of Fallot with atresia of the subpulmonary infundibulum and partial or complete absence of the aorticopulmonary septum.

Anatomical study of truncus arteriousus communis with embryological and surgical considerations

Twelve specimens of truncus arteriosus communis have been studied anatomically, with special reference to the conal anatomy and to the associated cardiac anomalies which can create additional problems if surgical repair is planned. A wide spectrum of conal morphology has been observed, suggesting that differential conal absorption is a developmental characteristic of truncus arteriousus as well as of transposition complexes. The invariable absence of septation of the ventricular infundibula and semilunar valves, in spite of the variable anatomy of the free wall of the conus, indicates that all types of truncus arteriosus, ontogenetically, should be considered as a single undivided conotruncus. Various types of ventircular septal defect were found: (a) ventricular septal defect with absent crista, in which no remnants of conal septum are present; (b) supracristal ventricular septal defect, in which vestigial conal septum is seen in front of the membranous septum; (c) bulloventricular foramen, associated with univentricular origin of the truncus from the right ventricle. Frequent associated anomalies are underdevelopment of the aortic arch, truncal valve malformations, and obstructive ventricular septal defect. The AV conduction system studied in one case showed an arrangement similar to Fallot's tetralogy with the His bundle and the left bundle-branch in a safe position behind the posteroinferior rim of the defect. The postoperative fate of the frequently abnormal truncal valve and the theoretical indications for total repair for Type IV truncus are also discussed.