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Cor triatriatum sinister (CTS) is a rare congenital cardiac malformation. In CTS, a fibromuscular membrane subdivides the left atrium into 2 chambers. The communication between the 2 chambers is through 1 or more orifices in the dividing membrane. We present an interesting case of a 2-month-old infant with obstructed CTS membrane who first presented on account of poor feeding and failure to thrive. Echocardiography showed a persistent levoatrial cardinal vein (LACV) connecting the left atrium and the innominate vein. This allowed the proximal left atrial chamber to decompress its blood volume into the innominate vein and subsequently the superior vena cava. There was minimal prograde blood flow across the Cor triatriatum membrane, so the majority of pulmonary venous blood ultimately returned to the heart by way of the decompressing vertical vein into the systemic venous circulation. Surgical repair was performed with an uneventful postoperative course. The specific anatomical variant of Cor triatriatum found in our subject has rarely been reported.

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Bisphenol S (BPS) has been widely used as a substitute for bisphenol A in industrial manufacturing. However, the safety of BPS is controversial, and the mechanism by which BPS exerts cardiovascular toxicity remains unclear. In this study, zebrafish embryos, including wild-type zebrafish and transgenic (flk1:eGFP), (gata1:DsRed) and (cmlc2:eGFP) zebrafish at 2 h postfertilization (hpf), were exposed to BPS at concentrations of 1, 10 and 100 µg/L for 24, 48 and 72 h, respectively. The data showed that BPS accelerated the expansion of the common cardinal vein and inhibited lumen formation between 24 hpf and 72 hpf. Moreover, low-dose BPS disturbed cardiac muscle contraction by breaking the calcium balance in cardiac muscle cells according to the RNA-seq results. As a consequence, increased heart rate and irregular blood circulation were observed in the BPS treatment groups. This result suggested that BPS at environmental relevant concentrations caused cardiovascular toxicity during the development of zebrafish embryos, possibly being an important inducer of cardiovascular injury later in life. These findings provide insight into the rational and safe application of BPS.

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Tetralogy of Fallot is rarely associated with partially anomalous pulmonary venous connection. Unidentified partially anomalous pulmonary venous connection, however, might increase the risk of pulmonary valve replacement in repaired tetralogy of Fallot patients. Here, we present a case of a 19-year-old male who received a correction of tetralogy of Fallot 18 years ago and a rare type of partially anomalous pulmonary venous connection with levoatrial cardinal vein was identified during the follow-up period. The anomalous pulmonary veins were connected to the left hepatic vein and the right superior caval vein. Performing a pulmonary valve replacement, partially anomalous pulmonary venous connection was also corrected with a new approach using the venous plexus between the hepatic veins.

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Angioblasts that form the major axial blood vessels of the dorsal aorta and cardinal vein migrate toward the embryonic midline from distant lateral positions. Little is known about what controls the precise timing of angioblast migration and their final destination at the midline. Using zebrafish, we found that midline angioblast migration requires neighboring tissue rearrangements generated by somite morphogenesis. The somitic shape changes cause the adjacent notochord to separate from the underlying endoderm, creating a ventral midline cavity that provides a physical space for the angioblasts to migrate into. The anterior to posterior progression of midline angioblast migration is facilitated by retinoic acid-induced anterior to posterior somite maturation and the subsequent progressive opening of the ventral midline cavity. Our work demonstrates a critical role for somite morphogenesis in organizing surrounding tissues to facilitate notochord positioning and angioblast migration, which is ultimately responsible for creating a functional cardiovascular system.

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Congenital anomalies of the superior and inferior vena cava result from abnormal embryogenesis of cardinal veins. Duplication of superior vena cava (SVC) occurs in 0.3% of the general population of which only 8% drain into the left atrium. The prevalence of double inferior vena cava (IVC) is around 0.2-3%. The reported incidence of unilateral renal agenesis ranges from 1:1100 to 1:5000, and the association of double IVC with renal agenesis has been reported in only 11 cases in the literature. The conglomeration of such rare anomalies incidentally noted in a single patient is reported in this study. A 32-year-old man was referred to our department for Computed Tomography (CT) scan of the thorax. The patient was found to have dorsal kyphoscoliosis with hemivertebrae. The SVC was duplicated with the right SVC draining into the right atrium and the left SVC draining into the left atrium. The left kidney was not visualized in the abdomen. There was dual IVC with no intercommunicating interiliac vein. The right IVC maintained its normal course, while the left IVC continued as hemiazygos vein and joined left SVC in the thorax. Also noted was the aberrant origin of the right subclavian artery. This is the first reported case of combined superior and inferior vena caval anomalies along with left renal agenesis in a single patient in the literature. A review on the embryological basis is also described in this article.

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An 86-year old asymptomatic male was incidentally found to have a variant of levoatrial cardinal vein (LACV) forming a complete venous ring. This is the first report of this variant. Although rare, the ability to identify LACV in the adult population is clinically significant because it may result in bi-directional shunt and the development of symptoms is an indication for intervention.

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BACKGROUND: The hypoplastic coronary sinus (CS) is a rare anomaly of the cardiac venous system, wherein some of the tributaries fail to join the CS. These tributaries usually drain into atrial chambers through dilated thebesian channels. We report the first case where the tributaries are draining into the right superior vena cava (SVC). CASE SUMMARY: A case of ischemic cardiomyopathy with severe LV systolic dysfunction with NYHA class III symptoms was taken for CRTD implantation. CS venogram after direct cannulation from left subclavian access revealed a hypoplastic CS. The part of CS beyond the attachment of the oblique vein of the left atrium to CS (distal to the posterolateral vein) formed a common channel and was draining into the right-sided SVC. The posterolateral vein was of sufficient caliber so that an left ventricle (LV) lead could be implanted, and the CRTD procedure could be completed. DISCUSSION: Hypoplastic CS though has no pathological significance in the normal population but for CRT it can become a significant limitation. Tributaries of CS draining into right SVC are the rarest of the finding, the channel draining most likely is a remnant of the splanchnic plexus around the embryonic foregut that usually has a temporary communication with cardinal veins during intrauterine growth. This communication somehow has persisted and resulted in a channel between coronary vein and the SVC, which may be referred to as coronary veno-cardinal vein.

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We present a rare case of a levoatrial cardinal vein identified during the work-up of a patient with coarctation of the aorta. Early diagnosis and repair in the neonatal period prevented future manifestations of left-to-right shunt and the need for reoperations, in contrast with the later-age presentation of this congenital anomaly. An integrative approach was crucial for prompt detection, intraoperative confirmation and complete one-stage repair.

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A double left brachiocephalic vein is an uncommon anatomic variation. Among these, a accessory branch with preaortic course is extremely rare. In this case, both branches of the left brachiocephalic vein were anterior to the aortic arch. We describe the computed tomography findings with volume-rendering imaging of this rare anatomic variation.

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Cor triatriatum sinister is a very rare cardiac anomaly that may lead to pulmonary hypertension, right ventricular dilation, and eventually right heart failure. We report a case of a toddler who presented with respiratory distress and cardiomegaly and was found to have cor triatriatum sinister with a restrictive communication, decompressing vertical vein, pulmonary hypertension, severe tricuspid regurgitation, and severe right ventricular dysfunction. She underwent a successful surgical repair, with normalisation of right ventricular function and pulmonary artery pressure.

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Levoatrial cardinal vein (LACV) is anomalous connection between left atrium or pulmonary veins and systemic veins such as innominate vein or superior vena cava. This persistence of splanchnic circulation occurs when there is left-sided obstructive cardiac lesions such as hypoplastic left heart or mitral atresia. In this report we present three cases of LACV with well-developed left heart, without any obstructive lesions. All our cases presented with pulmonary arterial hypertension (PAH) and had associated intracardiac shunt such as ventricular/atrial septal defect and supracardiac partial anomalous pulmonary venous connection. Apart from the above shunts, LACV contributed to PAH in these cases. It is important to detect and report LACV as this may require surgical correction along with other defects. If LACV goes undetected during imaging workup, it may cause persistent PAH postoperatively.

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The two vascular systems of our body are the blood and the lymphatic vasculature. Our understanding of the genes and molecular mechanisms controlling the development of the lymphatic vasculature network has significantly improved. The availability of novel animal models and better imaging tools led to the identification of lymphatics in tissues and organs previously thought to be devoid of them. Similarly, the classical textbook list of established functional roles of the lymphatic system has been expanded by the addition of novel findings. In this review we provide a historical perspective of some of the important landmarks that opened the doors to researchers working in this field. We also summarize some of the current views about embryonic lymphangiogenesis, particularly about the source(s), commitment, and differentiation of lymphatic endothelial cells.

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Blood vessels and the lymphatic vasculature are extensive tubular networks formed by endothelial cells that have several indispensable functions in the developing and adult organism. During growth and tissue regeneration but also in many pathological settings, these vascular networks expand, which is critically controlled by the receptor EphB4 and the ligand ephrin-B2. An increasing body of evidence links Eph/ephrin molecules to the function of other receptor tyrosine kinases and cell surface receptors. In the endothelium, ephrin-B2 is required for clathrin-dependent internalization and full signaling activity of VEGFR2, the main receptor for vascular endothelial growth factor. In vascular smooth muscle cells, ephrin-B2 antagonizes clathrin-dependent endocytosis of PDGFRß and controls the balanced activation of different signal transduction processes after stimulation with platelet-derived growth factor. This review summarizes the important roles of Eph/ephrin molecules in vascular morphogenesis and explains the function of ephrin-B2 as a molecular hub for receptor endocytosis in the vasculature.

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Glutaredoxin 2 is a vertebrate specific oxidoreductase of the thioredoxin family of proteins modulating the intracellular thiol pool. Thereby, glutaredoxin 2 is important for specific redox signaling and regulates embryonic development of brain and vasculature via reversible oxidative posttranslational thiol modifications. Here, we describe that glutaredoxin 2 is also required for successful heart formation. Knock-down of glutaredoxin 2 in zebrafish embryos inhibits the invasion of cardiac neural crest cells into the primary heart field. This leads to impaired heart looping and subsequent obstructed blood flow. Glutaredoxin 2 specificity of the observed phenotype was confirmed by rescue experiments. Active site variants of glutaredoxin 2 revealed that the (de)-glutathionylation activity is required for proper heart formation. Our data suggest that actin might be one target during glutaredoxin 2 regulated cardiac neural crest cell migration and embryonic heart development. In summary, this work represents further evidence for the general importance of redox signaling in embryonic development and highlights additionally the importance of glutaredoxin 2 during embryogenesis.

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Initial embryonic determination of artery or vein identity is regulated by genetic factors that work in concert to specify the endothelial cell׳s (EC) fate, giving rise to two structurally unique components of the circulatory loop. The Shh/VEGF/Notch pathway is critical for arterial specification, while the orphan receptor nr2f2 (COUP-TFII) has been implicated in venous specification. Studies in mice have shown that nr2f2 is expressed in venous but not arterial ECs, and that it preferentially induces markers of venous cell fate. We have examined the role of nr2f2 during early arterial-venous development in the zebrafish trunk. We show that expression of a subset of markers of venous endothelial identity requires nr2f2, while the expression of nr2f2 itself requires sox7 and sox18 gene function. However, while sox7 and sox18 are expressed in both the cardinal vein and the dorsal aorta during early trunk development, nr2f2 is expressed only in the cardinal vein. We show that Notch signaling activity present in the dorsal aorta suppresses expression of nr2f2, restricting nr2f2-dependent promotion of venous differentiation to the cardinal vein.

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Persistent left superior vena cava, usually an incidental finding, is the most common thoracic vein anatomical variation draining into the coronary sinus. Central venous catheter procedures may be complicated secondary to the presence of a persistent left superior vena cava, leading to life-threatening complications such as arrhythmias, cardiogenic shock, and cardiac arrest. We present a case of persistent superior vena cava diagnosed on transthoracic echocardiogram (TTE) in a patient with congestive heart failure. A dilated coronary sinus was identified on TTE, followed by injection of agitated saline into the left antecubital vein resulting in filling of the coronary sinus prior to the right atrium-an indication of persistent left superior vena-cava. This also was confirmed on cardiac computed tomography. Such a diagnosis is critical in patients who may undergo central venous catheter procedures such as our patient's potential requirement for an implantable cardiovertor defibrillator due to severe global left ventricular systolic dysfunction. The presence of a persistent left superior vena cava should always be suspected when the guidewire takes a left-sided downward course towards the right atrium at the level of the coronary sinus. Therefore, special attention should be paid to the imaging work-up prior to central venous catheter procedures.

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The formation and lumenization of blood vessels has been studied in some detail, but there is little understanding of the morphogenetic mechanisms by which endothelial cells (ECs) forming large caliber vessels aggregate, align themselves and finally form a lumen that can support blood flow. Here, we focus on the development of the zebrafish common cardinal veins (CCVs), which collect all the blood from the embryo and transport it back to the heart. We show that the angioblasts that eventually form the definitive CCVs become specified as a separate population distinct from the angioblasts that form the lateral dorsal aortae. The subsequent development of the CCVs represents a novel mechanism of vessel formation, during which the ECs delaminate and align along the inner surface of an existing luminal space. Thereby, the CCVs are initially established as open-ended endothelial tubes, which extend as single EC sheets along the flow routes of the circulating blood and eventually enclose the entire lumen in a process that we term 'lumen ensheathment'. Furthermore, we found that the initial delamination of the ECs as well as the directional migration within the EC sheet depend on Cadherin 5 function. By contrast, EC proliferation within the growing CCV is controlled by Vascular endothelial growth factor C, which is provided by circulating erythrocytes. Our findings not only identify a novel mechanism of vascular lumen formation, but also suggest a new form of developmental crosstalk between hematopoietic and endothelial cell lineages.

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