The fetal three-vessel and tracheal view revisited

The routine use of four-chamber screening of the fetal heart was pioneered in the early 1980s and has been shown to detect reliably mainly univentricular hearts in the fetus. Many conotruncal anomalies and ductal-dependent lesions may, however, not be detected with the four-chamber view alone and additional planes are needed. The three-vessel and tracheal (3VT) view is a transverse plane in the upper mediastinum demonstrating simultaneously the course and the connection of both the aortic and ductal arches, their relationship to the trachea and the visualization of the superior vena cava. The purpose of the article is to review the two-dimensional anatomy of this plane and the contribution of colour Doppler and to present a checklist to be achieved on screening ultrasound. Typical suspicions include the detection of abnormal vessel number, abnormal vessel size, abnormal course and alignment and abnormal colour Doppler pattern. Anomalies such as pulmonary and aortic stenosis and atresia, aortic coarctation, interrupted arch, tetralogy of Fallot, common arterial trunk, transposition of the great arteries, right aortic arch, double aortic arch, aberrant right subclavian artery, left superior vena cava are some of the anomalies showing an abnormal 3VT image. Recent studies on the comprehensive evaluation of the 3VT view and adjacent planes have shown the potential of visualizing the thymus and the left brachiocephalic vein during fetal echocardiography and in detecting additional rare conditions. National and international societies are increasingly recommending the use of this plane during routine ultrasound in order to improve prenatal detection rates of critical cardiac defects.

Loss of glypican-3 function causes growth factor-dependent defects in cardiac and coronary vascular development

Glypican-3 (Gpc3) is a heparan sulfate proteoglycan (HSPG) expressed widely during vertebrate development. Loss-of-function mutations cause Simpson-Golabi-Behmel syndrome (SGBS), a rare and complex congenital overgrowth syndrome with a number of associated developmental abnormalities including congenital heart disease. We found that Gpc3-deficient mice display a high incidence of congenital cardiac malformations like ventricular septal defects, common atrioventricular canal and double outlet right ventricle. In addition we observed coronary artery fistulas, which have not been previously reported in SGBS. Coronary artery fistulas are noteworthy because little is known about the molecular basis of this abnormality. Formation of the coronary vascular plexus in Gpc3-deficient embryos was delayed compared to wild-type, and consistent with GPC3 functioning as a co-receptor for fibroblast growth factor-9 (FGF9), we found a reduction in Sonic Hedgehog (Shh) mRNA expression and signaling in embryonic mutant hearts. Interestingly, we found an asymmetric reduction in SHH signaling in cardiac myocytes, as compared with perivascular cells, resulting in excessive coronary artery formation in the Gpc3-deficient animals. We hypothesize that the excessive development of coronary arteries over veins enables the formation of coronary artery fistulas. This work has broad significance to understanding the genetic basis of coronary development and potentially to molecular mechanisms relevant to revascularization following ischemic injury to the heart.

Ectopic origin of left coronary ostium from left ventricle, with occlusive membrane: a previously unreported anomaly, with an embryologic interpretation

Congenital atresia of the left main coronary artery, a condition in which the left main trunk is developed but has been occluded since birth, is a rare coronary anomaly. Herein, we describe this anomaly's association with a subannular location of an obliterated left main ostium in a patient with a bicuspid aortic valve and severe aortic stenosis. The patient underwent successful surgery. We discuss the embryologic implications of congenital atresia of the left main coronary artery, in view of the exceptional anatomic features of this condition. To our knowledge, this is the 1st report of a left coronary artery that was found to arise from the left ventricle.

[Surgical relevance of some aspects of heart's embriology]

We consider some aspects of cardiac embriology which explain the formation of pericardial cysts, anomalies of venae cavae, types of atrial septal defect (ostium primum, secundum, foramen ovale), anomalies in septal ventricular development by absence of structures to perform the septum (atrio-ventricularis communis, truncus arteriosus), lack of alineation (Taussig-Bing's complex, transposition of the great vessels, Eisenmenger's complex, Fallot's tetralogy) or interruption in their development (isolated ventricular septal defect). Finally the evolution of aortic arcs, ductus, aorta's istmus and anomalies in coronary arteries, are also considered.

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.

Management of sinus venosus defects

Sinus venosus defects are not atrial septal defects, but are intra-atrial communications outside of the boundaries of the atrial septum. The superior type is located above and separate from the fossal ovalis, usually adjacent to the superior vena cava and the right upper pulmonary vein. The inferior type is located near the orifice of the inferior vena cava and the right lower pulmonary vein. The goal of surgical repair is closure of the defect with unobstructed drainage of the pulmonary veins to the left atrium and of the vena cava to the right atrium. Numerous techniques have been described, particularly for the repair of the superior vena cava type of defect. Mortality and morbidity should be minimal. The risk of either vena cava or pulmonary vein obstruction is low. Sinus node dysfunction can occur postoperatively, particularly when an incision has been made across the superior vena cava/right atrial junction. There is little long-term data on the functional outcomes following repair of these defects.

Coronary artery anomalies. Part I: Recent insights from molecular embryology

Congenital anomalies of the coronary arteries occur in 0.2-1.2% of the general population and may cause substantial cardiovascular morbidity and mortality. We review some of the advances that have been made both, in the understanding of the embryonic development of the coronary arteries (part I) and in the clinical diagnosis and management of their anomalies (part II). In this first part of our review we elucidate basic mechanisms of coronary vasculogenesis, angiogenesis and embryonic arteriogenesis. Moreover, we review the role of cellular progenitors such as epicardium-derived cells, cardiac neural crest cells and cells of the peripheral conduction system. Then we discuss the role of growths factors (such as FGV, HIF 1, PDGF B, TGFbeta1, VEGF, and VEGFR-2) and genes (such as FOG-2, VCAM-1, Bves, and RALDH2) at different states of coronary development. and we discuss the role of the cardiac neural crest in the concurrence of coronary anomalies with aortic root malformations. This part of the article is designed to review major determinants of coronary vascular development to provide a better understanding of the multiplicity of options and mechanisms that may give rise to coronary anomaly. To this end, we highlight results from experiments that provide insight in mechanisms of coronary malformation.

Coronary artery anomalies Part II: recent insights from clinical investigations

Congenital anomalies of the coronary arteries occur in 0.2-1.2% of the general population; they cause 12% of sports-related sudden cardiac deaths and 1.2% of non-sports-related deaths. We review some of the substantial advances that have been made both, in the understanding of the embryonic development of the coronary arteries and in the clinical diagnosis and management of their anomalies. In this second part of our review we elucidate recent approaches to defining coronary anomalies and provide information on their incidence and prognosis. In addition, we discuss the options for screening large populations for potentially lethal coronary malformations and elucidate the role of invasive diagnostic modalities such as intravascular ultrasound, flow wire and pressure wire. The clinical relevance of coronary anomalies is discussed particularly for the ill-defined group of anomalies that only occasionally cause severe clinical events comprising anomalous origination of a coronary artery from the opposite sinus (ACAOS), coronary artery fistulae and myocardial bridging. Finally, we provide an update on current diagnostic and therapeutic recommendations.

Coronary Artery and Orifice Development Is Associated With Proper Timing of Epicardial Outgrowth and Correlated Fas Ligand Associated Apoptosis Patterns

The proepicardial organ provides differentiated cell types to the myocardial wall and facilitates coronary development. Ingrowth of the coronary arteries into the aorta has recently been linked to apoptosis. This study was set up to examine the effect of an inhibition of epicardial outgrowth on apoptotic patterning and coronary development. Epicardial outgrowth was blocked at HH15-17 in quail embryos, which survived until HH25-35 (n=33). Embryos with complete inhibition of outgrowth did not survive after HH29. These embryos presented with thin compact myocardium, devoid of vessels. In embryos with delayed epicardial outgrowth the phenotype was less severe, and surviving embryos were studied up to HH35. In these embryos, myocardial vascularization was poor and apoptosis in the peritruncal region at HH30 was diminished. Embryos at HH35 displayed an abnormal coronary network and absent coronary orifices. In a further set of experiments (n=10), outgrowth was inhibited in chicken embryos at HH15, followed by transplantation of a quail proepicardial organ into the pericardial cavity to rescue cardiac phenotype. These chimeras were studied at HH29 and HH35. Myocardial development was restored; however, in 3 of 4 embryos (HH35), the coronary orifices were absent. Examination of double stainings of quail-chicken chimeras revealed that EPDCs produce Fas ligand as an apoptotic inductor at sites of coronary ingrowth. In the absence of proper timing of epicardial outgrowth, myocardial development and vascularization are disturbed. Also apoptosis in the peritruncal region is diminished. During later development, this leads to defective or absent connections of the coronary system to the systemic circulation.

Coronary arteries in fetal life: physiology, malformations and the "heart-sparing effect"

The present knowledge of coronary arteries in prenatal diagnosis is reviewed with a focus on three aspects: the physiology and visualization of coronary flow, malformations involving the coronary arteries, and the "heart-sparing effect". Visualization of coronary arteries in a healthy human fetus is possible in real-time and colour Doppler during the last 10 wk of gestation when ultrasound conditions are excellent. Visualization at an earlier gestational age (up to 13 wk) is feasible mainly in association with malformations and impending hypoxia. The main coronary malformations that can be visualized in utero are the ventriculo-coronary communications in fetuses with pulmonary atresia. In the last few years, interest has been focused on the "heart-sparing effect", defined as the increased perfusion of the coronary arteries in fetuses with severe growth restriction and abnormal Doppler velocimetry in the peripheral vessels. Increased perfusion detectable with colour and pulsed Doppler is a late sign of fetal compromise in hypoxaemia. It confirms animal experiments that have demonstrated dilatory reserves of the fetal coronary arteries under chronic hypoxaemia. The outcome of 21 fetuses showing the "heart-sparing effect" before 32 wk gestation was poor: nine fetuses died in utero and two after birth, the median weight at birth was 630 g. In summary, our knowledge of the coronary arteries in the fetus is based on the diagnostic means used in prenatal diagnosis. New information in this field may also contribute to a better understanding of coronary heart disease later in life.

Localized atresia of the coronary sinus a short distance proximal to its ostium

Atresia of the ostium of the coronary sinus (CS) is a well-recognized abnormality. We report the incidental finding of atresia of the distal portion of the CS, a short distance proximal to its ostium in a 39-week-old neonate, which, as far as we are aware, has not been previously reported.

Prenatal diagnosis of tetralogy of Fallot associated with a fistula from the left coronary artery to the left atrium

In a fetus at 20 weeks gestation, we found a large fistula from the left coronary artery to the left atrium in association with tetralogy of Fallot. Postnatally, the therapeutic issues were complex because of prematurity, low birth weight, decreased flow of blood to the lungs, and volume overload of the left ventricle because of the huge fistula. At three months, the baby underwent repair of tetralogy of Fallot, with surgical ligation of the fistula, but the baby died postoperatively.

Echocardiographic evaluation, management and outcomes of bilateral arterial ducts and complex congenital heart disease: 16 years' experience

Bilateral arterial ducts represent an uncommon form of pulmonary or systemic blood supply associated with complex congenital cardiac disease. We sought to determine the role of high-resolution cross-sectional echocardiography and color flow Doppler ultrasonography in assessing this condition, as well as to describe the management and outcome in a group of patients. A retrospective review was conducted of 11 newborns identified over a 16-year period as having bilateral arterial ducts. Pulmonary atresia associated with non-confluent pulmonary arteries was the dominant lesion, with the heterotaxy syndrome also frequently being recognized. Echocardiography best identified the source of blood supply to either the pulmonary or systemic circulations, allowing differentiation from collateral vessels. Stenosis of the right or left pulmonary artery at the initial site of ductal insertion needs careful evaluation on follow-up. Management of patients with this condition remains a challenge, as indicated by the poor outcomes observed in our series.

Coronary arteriogenesis and differentiation of periarterial Purkinje fibers in the chick heart: is there a link?

In the following review, we outline the cellular ontogeny and time course of coronary artery development within the vertebrate heart. Our eventual focus will be the potential role of arteriogenesis in the differentiation of a subset of specialized conduction cells in the chick heart. We begin by briefly outlining early heart formation, showing how the outermost layer of the looped, tube heart--the epicardium--is of extracardiac origin and provides the progenitor cells to the entire vascular bed. Subsequently, we summarize the events of coronary arterial development that follow epicardialization. Finally, we discuss work in the chick that indicates how arteries form pioneering, directional conduits through ventricular tissue, adjacent to which myocardial cells differentiate to form the most peripheral component of the avian conduction system--a network of periarterial Purkinje fibers.

Congenital heart defects and coronary anatomy

Coronary artery anomalies are a well recognized feature of many cardiac malformations and have been catalogued in a number of reviews. This overview concentrates on 1) the interplay between congenital heart defects and coronary morphogenesis, examining how some of the embryology fits with the experiments of nature encountered in clinical practice; and 2) the influence of coronary anatomy on patient management. This overview uses, as examples, pulmonary atresia with intact ventricular septum, complete and congenitally corrected transpositions of the great arteries, and tetralogy of Fallot.

Cellular precursors of the coronary arteries

Coronary vessels develop from a primary vascular network that differentiates in the subepicardium through a process of vasculogenesis, that is, self-assembly of mesenchymal vascular progenitors. Further growth of the subepicardial vascular plexus through a complex process of angiogenesis, vascular remodeling, and arterialization of specific branches gives rise to the definitive coronary system. This report is intended to summarize current knowledge on the origin of the coronary vascular progenitors and to provide new insights suggested by recent findings. It has been established that the mesenchymal precursors of the vascular smooth muscle cells and the adventitial fibroblasts originate from an epithelial-mesenchymal transformation of the epicardial mesothelium. We report herein experimental evidence that the precursors of the coronary endothelium are also epicardium-derived cells (EPDCs). The evidence shown includes co-localization of mesothelial and endothelial molecular markers as well as cell lineage studies performed through direct labeling of the epicardial cells. If this proposal is confirmed, the early EPDCs might be found to have a competence similar to that shown by the recently discovered bipotential vascular progenitor cells, which are able to differentiate into endothelium or smooth muscle depending on their exposure to VEGF or PDGF-BB. It is conceivable that the earliest EPDCs differentiate into endothelial cells in response to myocardially secreted VEGF, while subsequent EPDCs, recruited by the nascent capillaries via PDGFRbeta signaling, differentiate into percytes and smooth muscle cells.

Role of growth factors in coronary morphogenesis

This communication briefly reviews the role of angiogenic growth factors in myocardial vessel formation during development. The earliest signs of vascularization are the migration and differentiation of angioblasts from the epicardium and subepicardium into the myocardium. A regulator of this process is vascular endothelial growth factor (VEGF), which is probably triggered by hypoxia. The subsequent formation of vascular tubes is regulated by multiple growth factors: VEGF family members, fibroblast growth factors (FGFs), and angiopoietins and their receptors. Our studies on explanted quail hearts reveal that these growth factors are interdependent. We also have shown that a harmonic interplay of growth factors characterizes early postnatal development in rats. Neutralizing antibodies to either basic FGF (bFGF) or VEGF inhibit capillary formation, whereas arteriolar growth is markedly inhibited by bFGF, but not VEGF, neutralizing antibodies. Arteriolar diameter is also increased when anti-bFGF and anti-VEGF are administered in combination. Thus, the hierarchical development of the arteriolar vasculature depends on both of these growth factors; however, the establishment of arterioles, as reflected by length density, is dependent on bFGF but not on VEG. Finally, stretch of cardiac myocytes and endothelial cells serves as a stimulus for increases in growth factor and receptor proteins. We have shown that cyclic stretch of either cell type increases VEGF, and that endothelial cells respond to stretch by up-regulation of VEGF receptor-2 (VEGFR-2), and Tie-2 receptor. These results indicate that both mechanical and metabolic factors are primary stimuli for coronary angiogenesis.

The role of the epicardium and neural crest as extracardiac contributors to coronary vascular development

At species-specific times in embryonic development, the pro-epicardial organ appears as an outcropping of the mesothelial body wall, near the sinus venosus-liver region. The pro-epicardial vesicles attach to the myocardium, flatten, and join to form the epicardium. The epicardium shows epithelial-mesenchymal transformation: cells detach from the epithelium, fill the subepicardial space, and invade the heart tube. Epicardium-derived cells migrate as far as the core of the endocardial cushions, which differentiate into the atrioventricular valve leaflets. In the cardiac wall, other epicardium-derived cells differentiate into interstitial fibroblasts and adventitial and smooth muscle cells of the coronary arteries. Using neural crest tracings in mouse embryos (Wnt1-Cre-lacZ), we studied the patterning of cardiac neural crest cells during development. Participation of neural crest cells in the formation of the vascular media could not be excluded, although epicardium-derived cells have hitherto been considered responsible for formation of the coronary arterial smooth muscle cells. The endothelial cells of the coronary network derive mostly from the endothelium of the sinus venosus-liver region by vasculogenesis and angiogenesis. However, an epicardium-derived cell origin of some endothelial cells cannot be ruled out. The coronary vasculature is closely related to the differentiating Purkinje network, but isolated epicardium-derived cells are also associated with Purkinje cells. After ablating the pro-epicardial organ in quail embryos, we found severe malformations in the myocardial architecture, leading to the hypothesis that epicardium-derived cells give instructive signals to the myocardium for proper differentiation of the compact and the trabeculated compartments.

Cardiovascular defects associated with abnormalities in midline development in the Loop-tail mouse mutant

Loop-tail (Lp) is a naturally occurring mouse mutant that develops severe neural tube defects. In this study, we describe complex cardiovascular defects in Lp homozygotes, which include double-outlet right ventricle, with obligatory perimembranous ventricular septal defects, and double-sided aortic arch, with associated abnormalities in the aortic arch arteries. Outflow tract and aortic arch defects are often related to abnormalities in the cardiac neural crest, but using molecular and anatomic markers, we show that neural crest migration is normal in Lp/Lp embryos. On the other hand, the heart fails to loop normally in Lp/Lp embryos, in association with incomplete axial rotation and reduced cervical flexion. As a consequence, the ventricular loop is shifted posteromedially relative to its position in wild-type embryos. This suggests that the observed cardiac alignment defects in the Lp mutant may be secondary to failure of neural tube closure and incomplete axial rotation. Double-sided aortic arch is a rare finding among mouse models. In humans, it is usually an isolated malformation, only rarely occurring in combination with other cardiac defects. We suggest that the double-sided arch arises as a primary defect in the Lp mutant, unrelated to the alignment defects, perhaps reflecting a role for the (as-yet-unknown) Lp gene in maintenance/regression of the aortic arch system.

Proper coronary vascular development and heart morphogenesis depend on interaction of GATA-4 with FOG cofactors

GATA-family transcription factors are critical to the development of diverse tissues. In particular, GATA-4 has been implicated in formation of the vertebrate heart. As the mouse Gata-4 knock-out is early embryonic lethal because of a defect in ventral morphogenesis, the in vivo function of this factor in heart development remains unresolved. To search for a requirement for Gata4 in heart development, we created mice harboring a single amino acid replacement in GATA-4 that impairs its physical interaction with its presumptive cardiac cofactor FOG-2. Gata4(ki/ki) mice die just after embryonic day (E) 12.5 exhibiting features in common with Fog2(-/-) embryos as well as additional semilunar cardiac valve defects and a double-outlet right ventricle. These findings establish an intrinsic requirement for GATA-4 in heart development. We also infer that GATA-4 function is dependent on interaction with FOG-2 and, very likely, an additional FOG protein for distinct aspects of heart formation.

Pathogenesis of single right coronary artery and pulmonic stenosis in English Bulldogs

English Bulldogs are the most common breed to have pulmonic stenosis. Previous studies showed that this congenital heart abnormality in Bulldogs frequently is caused by a circumpulmonary left coronary artery originating from a single right coronary artery. Fetal anasarca also occurs often in Bulldogs and might represent congestive heart failure, but the cause is unknown. To determine if fetal anasarca is associated with a coronary anomaly and pulmonic stenosis, major coronary arteries were studied in 6 bulldog puppies with fetal anasarca. Five of the puppies had normal coronary arteries, and this led to the conclusion that fetal anasarca usually is not associated with major coronary abnormalities or pulmonic stenosis. The 6th puppy had single right coronary artery with circumpulmonary left coronary artery and moderate subvalvular pulmonic stenosis. Serial section histology suggests that the underlying cause of this syndrome is malformation of the left aortic sinus (of Valsalva) and inversion of the proximal segment of the left main coronary artery.

Epicardial outgrowth inhibition leads to compensatory mesothelial outflow tract collar and abnormal cardiac septation and coronary formation

In the present study, we investigated the modulatory role of the epicardium in myocardial and coronary development. Epicardial cell tracing experiments have shown that epicardium-derived cells are the source of interstitial myocardial fibroblasts, cushion mesenchyme, and smooth muscle cells. Epicardial outgrowth inhibition studies show abnormalities of the compact myocardial layer, myocardialization of cushion tissue, looping, septation, and coronary vascular formation. Lack of epicardial spreading is partly compensated by mesothelial outgrowth over the conotruncal region. Heterospecific epicardial transplant is able to partially rescue the myocardial development, as well as septation and coronary formation.

Embryology of congenital ventriculo-coronary communications: a study on quail-chick chimeras

Ventriculo-coronary arterial communications are rare congenital heart defects which have been explained traditionally on the basis of abnormal persistence of such communications found in the normal developing heart. Recent studies, however, have suggested that these embryonic communications might be an incidental finding rather than a normal feature. Thus, it has been suggested that congenital ventriculo-coronary communications do not represent remnants of normal embryonic vessels, but rather represent acquired lesions. In the present study, hearts were constructed in embryonic chicks in which the coronary vasculature was almost completely derived from a quail-donor. After immunohistochemical staining of the quail-derived coronary endothelium, chimeric hearts were analysed with respect to the presence of embryonic ventriculo-coronary communications, and with respect to the origin of these structures from either coronary arteries or endocardium. The results demonstrate the normal presence of ventriculo-coronary communications in avian embryonic hearts. They show, furthermore, that these structures are of coronary endothelial origin. The findings are in accord with the traditional view on the pathogenesis of congenital ventriculo-coronary communications. The roles of elevated ventricular pressure, abnormal remodelling of the developing myocardium, and of abnormal growth of the coronary vasculature are discussed relative to the pathogenesis of congenital ventriculo-coronary communications.

Compartment-selective sensitivity of cardiovascular morphogenesis to combinations of retinoic acid receptor gene mutations

Several aspects of normal cardiovascular development require signaling by the vitamin A metabolite retinoic acid. We have previously established germ-line mutations in mice in the genes that encode the RAR alpha 1, RAR beta, and RXR alpha retinoic acid receptors as a means of studying the function of these receptors in vivo. Although mutation of RXR alpha results in fetal ventricular defects, the RAR alpha 1 and RAR beta mutations are apparently nonphenotypic in the heart and elsewhere. In this study, we have established and analyzed combinations of these receptor gene mutations. Malformations of the ventricular chamber (chamber hypoplasia and muscular ventricular septal defects), conotruncus (double-outlet right ventricle, transposition, and membranous ventricular septal defects), aortic sac (persistent truncus arteriosus and aorticopulmonary window), and aortic arch-derived arteries were recovered in various combinations of the RAR alpha 1, RAR beta, and RXR alpha gene mutations. Depending on the combination of receptor mutations, selective defects were obtained in specific cardiovascular compartments, suggestive of differential expression or function of each receptor within domains of the developing heart.

Increased nuchal translucency in trisomy 21 fetuses: relationship to narrowing of the aortic isthmus

Pathological examination of the great vessels was performed in 34 trisomy 21 fetuses after surgical termination of pregnancy at 11-16 weeks of gestation. In each case, the external diameters of eight segments of the great vessels were measured. The aortic valve and the ascending aorta were wider than in normal fetuses, whilst the aortic isthmus was narrower. The degree of narrowing of the isthmus was significantly greater in fetuses with high nuchal translucency thickness and it is possible that there is a causal association between the two.

[Morphofunctional correlation in congenital anomalies of the coronary arteries. I. Coronary artery fistulas]

In order to explain the congenital coronary arteries malformations, the authors review the recent concepts on the coronary artery morphogenesis, based in the findings that in the human embryo, these arteries evolve from three sources: 1) endothelial aortic buds, 2) cavitary cellular groups from pericardial origin and with angiogenic character, which migrate to the cardiac zones where the coronary arteries will be distributed, and 3) the intramyocardial sinusoids. The anatomic and histologic cardiac alterations will be reflected in modifications of the coronary artery pattern. The coronary artery fistulae are formed by the persistence of the sponge structure of the myocardial wall, present in the early ontogenic steps of the cardiac development; such fistulae alter the normal functions of the coronary vascular tree and are capable to cause angina pectoris to the patient through diverse mechanisms: absence of capillarization, steal phenomenon aggravated by the altered coronary arteries properties when aneurysm or vascular channels are developed. The authors suggest a classification of the congenital coronary arteries anomalies: I. Anomalous origin in the sinus of Valsalva (anomalous and ectopic origin), II. Malformations of the coronary branches (in number, distribution and wall anomalies) and III. Anomalous connection of the coronary arteries: fistulae and persistence of the intramyocardial sinusoids isolated or communicated to left and right ventricles. The latter are frequently associated with aortic or pulmonary valve atresia. They do not cause myocardial ischemia and are formed secondary to the intracavitary elevated pressure which maintained the persistence, dilatation and communication of the ventricular chambers with such sinusoids and coronary arteries in the case of pulmonary valve atresia and with coronary veins in the case of aortic valve atresia.

Development of the cardiac coronary vascular endothelium, studied with antiendothelial antibodies, in chicken-quail chimeras

The endothelium of the coronary vascular system has been described in the literature as originating from different sources, varying from aortic endothelium for the main coronary stems, endocardium for the intramyocardial network, and sinus venosus lining for the venous part of the coronary system. Using an antibody against quail endothelial cells (alpha-MB1), we investigated the development of the coronary vascular system in the quail (Hamburger and Hamilton stages 15 to 35) and in a series of 36 quail-chicken chimeras. In the chimeras, pieces of quail epicardial primordium and/or liver tissue were transplanted into the pericardial cavity of a chicken host. The results showed that the coronary vascular endothelial distribution closely followed the formation of the epicardial covering of the heart. However, pure epicardial primordium transplants did not lead to endothelial cell formation, whereas a liver graft with or without an epicardial contribution did have this capacity. The first endothelial cells were seen to reach the heart at the sinus venosus region, subsequently spreading through the inner curvature to the atrioventricular sulcus and the outflow tract and, last of all, over the ventricular surfaces. At these sites, the precursor cells and small vessels were seen to invade the sinus venosus wall, the ventricular and atrial myocardium, and the mesenchymal border of the aortic orifice. Connections with the endocardium of the heart tube were only observed in the right ventricular outflow region. Initially, the connections with the aortic endothelium were multiple, but later in development only two of these connections persisted to form the proximal part of the two main coronary arteries. Connections to the pulmonary orifice were never observed. Our transplantation data showed that the entire coronary endothelial vasculature originated from an extracardiac source. Moreover, using the developing subepicardial layer as a matrix, we showed that the endothelial cells reached the heart from the liver region. Ingrowth into the various cardiac segments was also observed. Implications for the relation to specific congenital cardiac malformations are discussed.

[The single coronary artery]

Single coronary artery is a fairly rare entity which may nevertheless be found in 0.4 per cent of coronary arteriograms. The authors report 3 cases seen in 2 departments of cardiology. In each patient, despite the existence of definite cardiovascular risk factors, this distribution was a factor worsening coronary ischemia, leading to complete thrombosis in one case. Although most often a chance discovery, a review of the literature justifies the attribution to this anomaly of the onset of angina, infarction or even sudden death.

Tetralogy of Fallot, cardiac hypertrophy, pulmonary hypertension, and anomalies of great vessels in fetuses and neonates of WKY/NCrj rats

We examined anatomically the hearts, lungs, and great vessels of 269 WKY/NCrj rats at three fetal and three neonatal stages. Severe pulmonary valve thickening was present in 16 and ventricular septal defects with overriding of the aorta in 15 of the 90 near-term fetuses and in 10 and nine, respectively, of the 79 neonates at 2-4 d of age. These abnormalities occurred together (tetralogy of Fallot) in seven of the near-term fetuses and in five of the neonates. A narrow pulmonary outflow tract was present in 55% of the fetuses and in 56% of the neonates. The wall of the pulmonary arterial branch was abnormally thick in 19% of the fetuses and in 26% of the neonates, most of which did not have septal defects. In about 80% of the fetuses, the middle latitudinal muscle bundle of the ventricular septum was not continuous with the left ventricular free wall, but rather with the right; after birth, it was discontinuous with both free walls. The heart was abnormally heavy in 49% of the 79 neonates. In about half of the heavy hearts, there were no septal defects or pulmonary valvular and arterial lesions. There were double aortic arches in four and right aortic arches in six of the total WKY fetuses and neonates; the ductus arteriosus was abnormally small in 47% and the aorta was large in 51% of the near-term fetuses. This constellation of congenital heart disease is genetic in origin, but altered by hemodynamics late in fetal life.

Coronary arterial and sinusal anatomy in hearts with a common arterial trunk

Eighty-four specimens of common arterial trunk were studied with special reference to the arrangement of the leaflets in relation to the atrioventricular valves, the origin of the coronary arteries in relation to the arterial sinuses, and the epicardial course of the coronary arteries. Fourteen normal hearts were used for comparison. In the hearts with common arterial trunk, the location and level of the coronary artery orifices (as well as the relationship of the truncal root to the area of fibrous continuity with the mitral valve) are different from those in normal hearts. In none of the hearts with common arterial trunk (particularly the 53 hearts with three leaflets in the truncal valve) did the appearance of the truncal valve approximate that of a normal aortic valve. Among the 22 hearts with four leaflets, there was a high incidence of coronary artery orifices in opposite sinuses (17/22 or 77.3%) and a low incidence of coronary artery orifices in adjacent sinuses (2/22 or 9.1%). These results suggest that the formation of the truncal valve is independent of the formation of the coronary orifices. Its leaflets are not predestined to become part of either the aortic valve or the pulmonary valve.

Anomalous origins of left anterior descending and circumflex coronary arteries from separate orifices in the right coronary sinus

A case is described of a 69-year-old man with angina pectoris who was found at coronary angiography to have all three coronary arteries arising by separate orifices from the right coronary sinus. This appears to be a previously unreported anomaly. The embryological origin and mechanisms of angina in coronary arterial anomalies are discussed.

[Intercoronary anastomoses of congenital origin. Apropos of a case]

Homo- or heterolateral intercoronary anastomoses are usually present in the normal heart. Owing to their small caliber they cannot be visualized at coronary arteriography, but they may become visible in case of obstructive coronary lesion. Congenital intercoronary anastomoses are entirely different. A case of intercoronary anastomosis between the right coronary artery and the circumflex artery, without any coronary lesion, is presented. This is an exceptional variant, only 12 cases of which were found in the literature. The anastomosis was located in the atrioventricular sulcus in 11 cases and in the interventricular sulcus in 1 case. This "abnormality" can be distinguished from collateral arteries by its angiographic features, and it does not reflect an underlying coronary disease. It may play a protective role if lesions develop on one of the two vessels it links together.

[2 cases of agenesis of the left coronary trunk in adults]

Agenesis of the left main coronary artery is a congenital condition the prognosis of which is reputed to be good in adults, provided no associated heart disease is present. The first case reported here illustrates the benign character of the anomaly. In contrast, the second case shows that when associated with proximal atheromatous stenosis of the single right coronary artery the anomaly may have catastrophic consequences. The anatomical variants and morbid associations of left main coronary artery agenesis are described.

Dual connection of the left anterior descending coronary artery to the left and right coronary arteries

Origin of the left anterior descending coronary artery from the right coronary artery is a well-described but rare congenital coronary anomaly. In this report, we describe two cases in which the mid left anterior descending coronary artery is connected to the right coronary artery through an intraseptal connecting vessel, while the proximal left anterior descending coronary artery originates normally from the left main coronary artery. This previously unreported pattern suggests partial persistence of the peritruncal ring, which occurs during normal embryologic development of the coronary circulation. Even though it is classically described as an epicardial structure, the vascular pattern in our cases suggests that the peritruncal ring may have an intramural segment in some individuals.

Normal and anomalous coronary arteries: definitions and classification

Results of a comprehensive survey of the literature concerning coronary artery anatomy, embryology, and pathophysiology show the lack of an adequate definition of normal coronary arteries. To fill this gap, the present review considers the available data concerning the embryogenesis of the coronary arteries and proposes a new definition of normality that refers to essential anatomic features. The concepts of normal variant versus anomaly are introduced, based on a statistical definition of the normal range (99% of the presentations observed in a normal, unselected population). Coronary anomalies are defined as those patterns found in less than 1% of the cases. The wide spectrum of coronary abnormalities is then organized according to a comprehensive classification scheme. For clinical purposes the conceptual difference between anatomic and pathophysiologic anomalies is stressed. The current paucity of experimental studies concerning normal and abnormal embryogenesis of the coronary arteries is found to be the major limitation to an understanding of this subject.

The inadequacy of existing theories on development of the proximal coronary arteries and their connexions with the arterial trunks

Coronary arterial development was studied in complete microseries of 20 human embryos and microseries of the hearts from 18 rat embryos. We never observed more than two coronary arterial orifices; these always originated from the facing aortic sinuses. In the human embryos these coronary orifices were variably identified between 16-19 mm crown-rump length, but were invariably present above 19 mm crown-rump length. In rat embryos, the orifices were variably identified at 13-17 mm and invariably present above 17 mm crown-rump length. In both human and rat embryos the left coronary orifice was observed significantly earlier. In all the embryos septation at arterial orifice level was complete. At the stages in which identification of the coronary orifices was variable, the proximal epicardial segments of the left and right coronary arteries could usually already be identified, in human as well as in rat embryos. On the other hand, a coronary orifice was never seen in the absence of a proximal coronary artery. At all stages studied (in human embryos from 10 mm crown-rump length and in rat embryos from 11 mm crown-rump length) vascular structures could be identified in the epicardial covering of the heart. The present theories on proximal coronary artery development are inadequate to explain either these data or the known possible congenital abnormalities of the coronary arteries. Our study offers a detailed chronology of development of these proximal coronary arteries and mostly supports dual coronary arterial development. The process by which the coronary orifices are brought into contact with the main coronary arteries still remains to be explained.

Abnormalities of the coronary circulation in pulmonary atresia and intact ventricular septum

To identify developmental aspects and establish morphologic criteria useful for clinical recognition of sinusoids and coronary artery abnormalities in pulmonary atresia and intact ventricular septum, we studied 17 autopsy hearts with this lesion. Hearts from age- and weight-matched infants served as controls. There were two stillborn fetuses, 12 full-term neonates, and 3 infants. None of the eight hearts with normal or large-sized right ventricular chambers had sinusoids or coronary artery abnormalities. Five of nine hearts with small right ventricular chambers had sinusoids; all five lacked trabecular and outlet portions of the ventricle. Four of these five contained major coronary artery abnormalities: atrophy of one or both coronaries proximal to a communication between a sinusoid and the coronary artery. We conclude (1) there is a strong association between the presence of sinusoids and coronary anomalies, supporting the developmental concept of abnormal persistence of embryonic right ventricular sinusoid--coronary artery communications in pulmonary atresia and intact ventricular septum; (2) the absence of trabecular and outlet portions of the small right ventricle indicates a strong possibility of coronary artery abnormalities; and (3) this initial report of a fully-developed lesion in a mid-gestation fetus documents that the coronary artery problem may arise early in fetal life.

Malformation of the venous sinus in human embryos

2 human embryos of stages XV and XVII are studied, in which the persistence of the left vitelline vein opening into the venous sinus (sinus venosi cordis) is described.

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.

Anomalous origin of the left coronary artery from the right pulmonary artery

A previously unknown coronary artery anomaly is reported: origin of the left coronary artery from the right pulmonary artery. This unusual anomaly can probably be explained by the theory of dual embryonic development of the coronary arteries from angioblastic buds in the truncus arteriosus. It is thought that these buds anastomose with a capillary network that is developing on the surface of the ventricles. Complete repair of this lesion with restoration of a two-coronary artery system was accomplished in a 10-month-old baby. The coronary artery was detached from the pulmonary artery, with a button of pulmonary artery being retained around the coronary artery ostium. Direct systemic arterial flow to the left coronary artery was established by anastomosis of the left coronary to the right subclavian artery.

Partial anomalous systemic venous return: report of surgical treatment in two cases

Two cases of anomalous systemic venous return were correctly diagnosed preoperatively and repaired by intracardiac baffle. These cases are of interest because of their anatomy, embryology, and the surgical method chosen to correct them.