Congenital Coronary Blood Vessel Anomalies: Animal Models and the Integration of Developmental Mechanisms.

Coronary blood vessels are in charge of sustaining cardiac homeostasis. It is thus logical that coronary congenital anomalies (CCA) directly or indirectly associate with multiple cardiac conditions, including sudden death. The coronary vascular system is a sophisticated, highly patterned anatomical entity, and therefore a wide range of congenital malformations of the coronary vasculature have been described. Despite the clinical interest of CCA, very few attempts have been made to relate specific embryonic developmental mechanisms to the congenital anomalies of these blood vessels. This is so because developmental data on the morphogenesis of the coronary vascular system derive from complex studies carried out in animals (mostly transgenic mice), and are not often accessible to the clinician, who, in turn, possesses essential information on the significance of CCA. During the last decade, advances in our understanding of normal embryonic development of coronary blood vessels have provided insight into the cellular and molecular mechanisms underlying coronary arteries anomalies. These findings are the base for our attempt to offer plausible embryological explanations to a variety of CCA as based on the analysis of multiple animal models for the study of cardiac embryogenesis, and present them in an organized manner, offering to the reader developmental mechanistic explanations for the pathogenesis of these anomalies.

HIF-1α is required for development of the sympathetic nervous system.

The molecular mechanisms regulating sympathetic innervation of the heart during embryogenesis and its importance for cardiac development and function remain to be fully elucidated. We generated mice in which conditional knockout (CKO) of the Hif1a gene encoding the transcription factor hypoxia-inducible factor 1α (HIF-1α) is mediated by an Islet1-Cre transgene expressed in the cardiac outflow tract, right ventricle and atrium, pharyngeal mesoderm, peripheral neurons, and hindlimbs. These Hif1aCKO mice demonstrate significantly decreased perinatal survival and impaired left ventricular function. The absence of HIF-1α impaired the survival and proliferation of preganglionic and postganglionic neurons of the sympathetic system, respectively. These defects resulted in hypoplasia of the sympathetic ganglion chain and decreased sympathetic innervation of the Hif1aCKO heart, which was associated with decreased cardiac contractility. The number of chromaffin cells in the adrenal medulla was also decreased, indicating a broad dependence on HIF-1α for development of the sympathetic nervous system.

Anomalías congénitas de arterias coronarias, estudio de aquellas con Importancia hemodinámica / Evaluation of the hemodynamically significant congenital anomalies of coronary arteries

Resumen: Las anomalías de las arterias coronarias son poco frecuentes, con una prevalencia de 0,21- 5,79%. Su presentación clínica es amplia, pudiendo ser asintomáticas o presentarse como isquemia miocárdica y muerte súbita, la que puede estar ligada o no al ejercicio. Existen varias clasificaciones, siendo las más usadas las que las agrupan desde un punto de vista anatómico en relación con el segmento afectado (origen, curso o terminación) y desde el punto de vista funcional (hemodinámicamente significativa y no significativa). Actualmente la Tomografía Computada Cardiaca se considera el estándar de referencia, siendo de suma importancia su adecuada caracterización ya que, de requerir tratamiento, este generalmente es quirúrgico. El objetivo de este trabajo es identificar, caracterizar y clasificar las anomalías congénitas de las arterias coronarias por su importancia hemodinámica mediante la presentación de casos clínicos y revisión de la literatura.

Abstract: Coronary artery anomalies are rare, with a prevalence ranging from 0.21 to 5.79%. Their clinical presentation is variable; being either asymptomatic or presenting as myocardial ischemia and sudden death, which may or may not be linked to exercise. There are several classifications, the most commonly used being those that sort them from an anatomical point of view in relation to the affected segment (origin, course or termination) and from a functional point of view (hemodynamically significant and not significant). Currently, Cardiac Computed Tomography is considered the reference standard allowing an adequate characterization of the anomaly, which is highly relevant since, if treatment is needed, it usually involves surgery. The purpose of this review is to identify, characterize and classify congenital anomalies of the coronary arteries according to their hemodynamic significance through the presentation of clinical cases and review of the literature.

Imaging of congenital anomalies of the coronary arteries.

Congenital abnormalities of the coronary arteries are extremely variable and include anomalies of their origin (atresia, anomalies of origin from the aorta or from the pulmonary artery), the course of the epicardiac coronary branches (intramural, myocardial bridge) and distal connections (coronary-cardiac chamber fistulae). In pediatric practice, the diagnosis relies on ultrasound which should be supplemented by additional cardiac imaging in most cases. Multidetector CT is the most widely used imaging technique to identify abnormal courses and relationships with the greater vessels. In this paper, the important diagnostic and prognostic features in the interpretation of coronary imaging in pediatric practice is discussed.

Congenital coronary artery anomalies: a bridge from embryology to anatomy and pathophysiology--a position statement of the development, anatomy, and pathology ESC Working Group.

Congenital coronary artery anomalies are of major significance in clinical cardiology and cardiac surgery due to their association with myocardial ischaemia and sudden death. Such anomalies are detectable by imaging modalities and, according to various definitions, their prevalence ranges from 0.21 to 5.79%. This consensus document from the Development, Anatomy and Pathology Working Group of the European Society of Cardiology aims to provide: (i) a definition of normality that refers to essential anatomical and embryological features of coronary vessels, based on the integrated analysis of studies of normal and abnormal coronary embryogenesis and pathophysiology; (ii) an animal model-based systematic survey of the molecular and cellular mechanisms that regulate coronary blood vessel development; (iii) an organization of the wide spectrum of coronary artery anomalies, according to a comprehensive anatomical and embryological classification scheme; (iv) current knowledge of the pathophysiological mechanisms underlying symptoms and signs of coronary artery anomalies, with diagnostic and therapeutic implications. This document identifies the mosaic-like embryonic development of the coronary vascular system, as coronary cell types differentiate from multiple cell sources through an intricate network of molecular signals and haemodynamic cues, as the necessary framework for understanding the complex spectrum of coronary artery anomalies observed in human patients.

The anatomy and development of normal and abnormal coronary arteries.

At present, there is significant interest in the morphology of the coronary arteries, not least due to the increasingly well-recognised association between anomalous origin of the arteries and sudden cardiac death. Much has also been learnt over the last decade regarding the embryology of the arteries. In this review, therefore, we provide a brief introduction into the recent findings regarding their development. In particular, we emphasise that new evidence, derived using the developing murine heart, points to the arterial stems growing out from the adjacent sinuses of the aortic root, rather than the arteries growing in, as is currently assumed. As we show, the concept of outgrowth provides an excellent explanation for several of the abnormal arrangements encountered in the clinical setting. Before summarising these abnormal features, we draw attention to the need to describe the heart in an attitudinally appropriate manner, following the basic rule of human anatomy, rather than describing the cardiac components with the heart in the "Valentine" orientation. We then show how the major abnormalities involving the coronary arteries in humans can be summarised in terms of abnormal origin from the pulmonary circulation, abnormal aortic origin, or fistulous communications between the coronary arteries and the cardiac cavities. In the case of abnormal aortic origin, we highlight those malformations known to be associated with sudden cardiac death.

Coronary arterial development: a review of normal and congenitally anomalous patterns.

Coronary artery development is a delicate, complex, and finely tuned process that includes multiple interactions among many pathways, especially in the pericardium and the developing myocardium. There still exists some controversy on the exact origin of certain cellular components. Nevertheless, an understanding of this extremely important developmental process is paramount in identifying some of the causes of anomalous coronary development. There are different patterns of anomalous coronary arteries, with variable risk of myocardial ischemia, malignant arrhythmias, and sudden cardiac death. These anomalies can be broadly categorized into 2 basic anatomic subsets: those with origin of the anomalous coronary artery from the opposite aortic sinus, and those with origin of the anomalous coronary artery from the pulmonary artery. Diagnosis and management of such patterns continues to be challenging. A good knowledge of the normal and abnormal coronary artery development could potentially help us explore new avenues in the treatment of ischemic heart disease as well as anomalous coronary arteries.

Left main coronary atresia in a child with absent pulmonary valve syndrome: early entrapment of an innocent bystander.

Atresia of the left main coronary artery is a rare anomaly that, if left untreated, has an unfavorable outcome. We hereby report left main coronary artery atresia in a child with tetralogy of Fallot with absent pulmonary valve and discuss the possible developmental basis of the association.

Nitric oxide synthase-3 deficiency results in hypoplastic coronary arteries and postnatal myocardial infarction.

AIMS: Hypoplastic coronary artery disease is a rare congenital abnormality that is associated with sudden cardiac death. However, molecular mechanisms responsible for this disease are not clear. The aim of the present study was to assess the role of nitric oxide synthase-3 (NOS3) in the pathogenesis of hypoplastic coronary arteries. METHODS AND RESULTS: Wild-type (WT), NOS3(-/-), and a novel cardiac-specific NOS3 overexpression mouse model were employed. Deficiency in NOS3 resulted in coronary artery hypoplasia in foetal mice and spontaneous myocardial infarction in postnatal hearts. Coronary artery diameters, vessel density, and volume were significantly decreased in NOS3(-/-) mice at postnatal day 0. In addition, NOS3(-/-) mice showed a significant increase in the ventricular wall thickness, myocardial volume, and cardiomyocyte cell size compared with WT mice. Lack of NOS3 also down-regulated the expression of Gata4, Wilms tumour-1, vascular endothelial growth factor, basic fibroblast growth factor and erythropoietin, and inhibited migration of epicardial cells. These abnormalities and hypoplastic coronary arteries in the NOS3(-/-) mice were completely rescued by the cardiac-specific overexpression of NOS3. CONCLUSION: Nitric oxide synthase-3 is required for coronary artery development and deficiency in NOS3 leads to hypoplastic coronary arteries.

Neural crest cells are required for correct positioning of the developing outflow cushions and pattern the arterial valve leaflets.

AIMS: Anomalies of the arterial valves, principally bicuspid aortic valve (BAV), are the most common congenital anomalies. The cellular mechanisms that underlie arterial valve development are poorly understood. While it is known that the valve leaflets derive from the outflow cushions, which are populated by cells derived from the endothelium and neural crest cells (NCCs), the mechanism by which these cushions are sculpted to form the leaflets of the arterial valves remains unresolved. We set out to investigate how NCCs participate in arterial valve formation, reasoning that disrupting NCC within the developing outflow cushions would result in arterial valve anomalies, in the process elucidating the normal mechanism of arterial valve leaflet formation. METHODS AND RESULTS: By disrupting Rho kinase signalling specifically in NCC using transgenic mice and primary cultures, we show that NCC condensation within the cardiac jelly is required for correct positioning of the outflow cushions. Moreover, we show that this process is essential for normal patterning of the arterial valve leaflets with disruption leading to a spectrum of valve leaflet patterning anomalies, abnormal positioning of the orifices of the coronary arteries, and abnormalities of the arterial wall. CONCLUSION: NCCs are required at earlier stages of arterial valve development than previously recognized, playing essential roles in positioning the cushions, and patterning the valve leaflets. Abnormalities in the process of NCC condensation at early stages of outflow cushion formation may provide a common mechanism underlying BAV, and also explain the link with arterial wall anomalies and outflow malalignment defects.

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.

Successful surgical treatment of a gigantic congenital coronary artery fistula immediately after birth.

A foetus was prenatally diagnosed with a gigantic (12 mm) coronary artery fistula (CAF) from the left anterior descending (LAD) coronary artery to right ventricular apex at 38 weeks of gestation. LAD was dilated to 10 mm with partial aneurysmal changes. Because of concern for sudden ischaemic cardiogenic shock soon after birth, the child was electively delivered by caesarean section, with surgical fistula closure subsequently performed 1 h after birth. We also highly suspected the presence of a clinically significant accessory diagonal branch just around the fistula, thus direct fistula closure from outside the heart without cardiopulmonary bypass was abandoned and cardiopulmonary bypass was initiated. The terminal end of LAD was carefully opened, and the fistula was directly closed with four pairs of 6-0 polypropylene mattress sutures under cardioplegic arrest, while the opened terminal end of LAD was also repaired with plegetted 6-0 polypropylene mattress and over-and-over sutures. After 4 days of post-surgical extracorporeal life support for over-systemic pulmonary hypertension, the patient recovered without complications. Although postoperative echocardiography 5 months after the operation showed normal cardiac function without ventricular asynergy, the dilated and aneurysmal LAD remained unchanged.

The cytoplasmic domain of TGFßR3 through its interaction with the scaffolding protein, GIPC, directs epicardial cell behavior.

The epicardium is a major contributor of the cells that are required for the formation of coronary vessels. Mice lacking both copies of the gene encoding the Type III Transforming Growth Factor ß Receptor (TGFßR3) fail to form the coronary vasculature, but the molecular mechanism by which TGFßR3 signals coronary vessel formation is unknown. We used intact embryos and epicardial cells from E11.5 mouse embryos to reveal the mechanisms by which TGFßR3 signals and regulates epicardial cell behavior. Analysis of E13.5 embryos reveals a lower rate of epicardial cell proliferation and decreased epicardially derived cell invasion in Tgfbr3(-/-) hearts. Tgfbr3(-/-) epicardial cells in vitro show decreased proliferation and decreased invasion in response to TGFß1 and TGFß2. Unexpectedly, loss of TGFßR3 also decreases responsiveness to two other important regulators of epicardial cell behavior, FGF2 and HMW-HA. Restoring full length TGFßR3 in Tgfbr3(-/-) cells rescued deficits in invasion in vitro in response TGFß1 and TGFß2 as well as FGF2 and HMW-HA. Expression of TGFßR3 missing the 3 C-terminal amino acids that are required to interact with the scaffolding protein GIPC1 did not rescue any of the deficits. Overexpression of GIPC1 alone in Tgfbr3(-/-) cells did not rescue invasion whereas knockdown of GIPC1 in Tgfbr3(+/+) cells decreased invasion in response to TGFß2, FGF2, and HMW-HA. We conclude that TGFßR3 interaction with GIPC1 is critical for regulating invasion and growth factor responsiveness in epicardial cells and that dysregulation of epicardial cell proliferation and invasion contributes to failed coronary vessel development in Tgfbr3(-/-) mice.

Developmental defects of coronary vasculature in rat embryos administered bis-diamine.

BACKGROUND: Conotruncal anomalies are often associated with abnormal coronary arteries. Although bis-diamine is known to induce conotruncal defects, its pathological effects on coronary vascular development have not been demonstrated. This study sought to assess the teratogenic effects of bis-diamine on coronary vascular development and the pathogenesis of this anomalous association. METHODS AND RESULTS: A single 200 mg dose of bis-diamine was administered to pregnant Wistar rats at 10.5 days of gestation. Fifty-two embryos from 10 mother rats underwent morphological analysis of the coronary arteries. Three embryos each were removed from four mothers on embryonic days (ED) 14.5, 15.5, 16.5, and 17.5 and used for immunohistochemical studies using the anti-vascular cell adhesion molecule (VCAM)-1 antibody. Conotruncal anomalies were detected in 48 of 52 embryos, and an aplastic or hypoplastic left coronary artery was found in all of them. In control embryos at ED 16.5, VCAM-1-positive epicardial cells were transformed into mesenchymal cells in vascular plexus, which appeared to differentiate into the endothelial cells of coronary vasculature. In the heart at ED 17.5, coronary vasculature was well developed and connected with coronary ostia near the aorta. However, poor epicardial-mesenchymal transformation and subsequent differentiation was revealed in bis-diamine-treated embryos at EDs 16.5 and 17.5, causing abnormal development of the coronary vasculature and incomplete connections with coronary ostia of the aorta. CONCLUSIONS: Anomalous coronary arteries in the bis-diamine-treated embryos are induced by the disruption of epicardial-mesenchymal transformation and subsequent poor development of coronary vasculature. Incomplete hatching of the coronary ostium is associated with abnormal truncal division.

Imaging of coronary artery anomalies.

Coronary artery anomalies (CAA) are uncommon congenital variations in coronary anatomy, occurring in 0.2% to 1.2% of the general population, the majority of which are detected incidentally and have little clinical significance. A minority of CAA, primarily due to an interarterial course, is clinically significant, and may present with symptoms of myocardial ischemia, malignant ventricular arrhythmias, and even sudden cardiac death. Until recently, CAA were primarily detected at catheter coronary angiography. With recent advances in multidetector computed tomography (CT) technology and the use of electrocardiographic gating, coronary CT angiography provides an exquisite omnidimensional display of the anomalous coronary arteries and their relation to the adjacent structures noninvasively, and is the diagnostic test of choice. Understanding CAA morphology and clinical significance of CAA is important for establishing a diagnosis, and is essential for appropriate patient management and treatment planning.

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.