Development of the heart: (3) formation of the ventricular outflow tracts, arterial valves, and intrapericardial arterial trunks

Anatomy of the Ventricular Outflow Tracts: An Electrophysiology Perspective

Outflow tract ventricular arrhythmias are the most common type of idiopathic ventricular arrhythmia. A systematic understanding of the outflow tract anatomy improves procedural efficacy and enables electrophysiologists to anticipate and prevent complications. This review emphasizes the three-dimensional spatial relationships between the ventricular outflow tracts using seven anatomical principles. In turn, each principle is elaborated on from a clinical perspective relevant for the practicing electrophysiologist. The developmental anatomy of the outflow tracts is also discussed and reinforced with a clinical case.

Human Cardiac Development

Many aspects of heart development are topographically complex and require three-dimensional (3D) reconstruction to understand the pertinent morphology. We have recently completed a comprehensive primer of human cardiac development that is based on firsthand segmentation of structures of interest in histological sections. We visualized the hearts of 12 human embryos between their first appearance at 3.5 weeks and the end of the embryonic period at 8 weeks. The models were presented as calibrated, interactive, 3D portable document format (PDF) files. We used them to describe the appearance and the subsequent remodeling of around 70 different structures incrementally for each of the reconstructed stages. In this chapter, we begin our account by describing the formation of the single heart tube, which occurs at the end of the fourth week subsequent to conception. We describe its looping in the fifth week, the formation of the cardiac compartments in the sixth week, and, finally, the septation of these compartments into the physically separated left- and right-sided circulations in the seventh and eighth weeks. The phases are successive, albeit partially overlapping. Thus, the basic cardiac layout is established between 26 and 32 days after fertilization and is described as Carnegie stages (CSs) 9 through 14, with development in the outlet component trailing that in the inlet parts. Septation at the venous pole is completed at CS17, equivalent to almost 6 weeks of development. During Carnegie stages 17 and 18, in the seventh week, the outflow tract and arterial pole undergo major remodeling, including incorporation of the proximal portion of the outflow tract into the ventricles and transfer of the spiraling course of the subaortic and subpulmonary channels to the intrapericardial arterial trunks. Remodeling of the interventricular foramen, with its eventual closure, is complete at CS20, which occurs at the end of the seventh week. We provide quantitative correlations between the age of human and mouse embryos as well as the Carnegie stages of development. We have also set our descriptions in the context of variations in the timing of developmental features.

Double outlet right ventricle

This review article addresses the history, morphology, anatomy, medical management, and different surgical options for patients with double outlet right ventricle.

Nuclear import of Mas-related G protein-coupled receptor member D induces pathological cardiac remodeling

Alamandine (Ala), a ligand of Mas-related G protein-coupled receptor, member D (MrgD), alleviates angiotensin II (AngII)-induced cardiac hypertrophy. However, the specific physiological and pathological role of MrgD is not yet elucidated. Here, we found that MrgD expression increased under various pathological conditions. Then, MrgD knockdown prevented AngII-induced cardiac hypertrophy and fibrosis via inactivating Gα_i-mediacted downstream signaling pathways, including the phosphorylation of p38 (p-P38), while MrgD overexpression induced pathological cardiac remodeling. Next, Ala, like silencing MrgD, exerted its cardioprotective effects by inhibiting Ang II-induced nuclear import of MrgD. MrgD interacted with p-P38 and promoted its entry into the nucleus under Ang II stimulation. Our results indicated that Ala was a blocking ligand of MrgD that inhibited downstream signaling pathway, which unveiled the promising cardioprotective effect of silencing MrgD expression on alleviating cardiac remodeling. Video Abstract.

Single-cell and spatial transcriptomics: Advances in heart development and disease applications

Current transcriptomics technologies, including bulk RNA-seq, single-cell RNA sequencing (scRNA-seq), single-nucleus RNA-sequencing (snRNA-seq), and spatial transcriptomics (ST), provide novel insights into the spatial and temporal dynamics of gene expression during cardiac development and disease processes. Cardiac development is a highly sophisticated process involving the regulation of numerous key genes and signaling pathways at specific anatomical sites and developmental stages. Exploring the cell biological mechanisms involved in cardiogenesis also contributes to congenital heart disease research. Meanwhile, the severity of distinct heart diseases, such as coronary heart disease, valvular disease, cardiomyopathy, and heart failure, is associated with cellular transcriptional heterogeneity and phenotypic alteration. Integrating transcriptomic technologies in the clinical diagnosis and treatment of heart diseases will aid in advancing precision medicine. In this review, we summarize applications of scRNA-seq and ST in the cardiac field, including organogenesis and clinical diseases, and provide insights into the promise of single-cell and spatial transcriptomics in translational research and precision medicine.

Automated endocardial cushion segmentation and cellularization quantification in developing hearts using optical coherence tomography

Of all congenital heart defects (CHDs), anomalies in heart valves and septa are among the most common and contribute about fifty percent to the total burden of CHDs. Progenitors to heart valves and septa are endocardial cushions formed in looping hearts through a multi-step process that includes localized expansion of cardiac jelly, endothelial-to-mesenchymal transition, cell migration and proliferation. To characterize the development of endocardial cushions, previous studies manually measured cushion size or cushion cell density from images obtained using histology, immunohistochemistry, or optical coherence tomography (OCT). Manual methods are time-consuming and labor-intensive, impeding their applications in cohort studies that require large sample sizes. This study presents an automated strategy to rapidly characterize the anatomy of endocardial cushions from OCT images. A two-step deep learning technique was used to detect the location of the heart and segment endocardial cushions. The acellular and cellular cushion regions were then segregated by K-means clustering. The proposed method can quantify cushion development by measuring the cushion volume and cellularized fraction, and also map 3D spatial organization of the acellular and cellular cushion regions. The application of this method to study the developing looping hearts allowed us to discover a spatial asymmetry of the acellular cardiac jelly in endocardial cushions during these critical stages, which has not been reported before.

Single Cell Sequencing Reveals Mechanisms of Persistent Truncus Arteriosus Formation after PDGFRα and PDGFRβ Double Knockout in Cardiac Neural Crest Cells

Persistent truncus arteriosus (PTA) is an uncommon and complex congenital cardiac malformation accounting for about 1.2% of all congenital heart diseases (CHDs), which is caused by a deficiency in the embryonic heart outflow tract’s (OFT) septation and remodeling. PDGFRα and PDGFRβ double knockout (DKO) in cardiac neural crest cells (CNCCs) has been reported to cause PTA, but the underlying mechanisms remain unclear. Here, we constructed a PTA mouse model with PDGFRα and PDGFRβ double knockout in Pax3+ CNCCs and described the condensation failure into OFT septum of CNCC-derived cells due to disturbance of cell polarity in the DKO group. In addition, we further explored the mechanism with single-cell RNA sequencing. We found that two main cell differentiation trajectories into vascular smooth muscle cells (VSMCs) from cardiomyocytes (CMs) and mesenchymal cells (MSs), respectively, were interrupted in the DKO group. The process of CM differentiation into VSMC stagnated in a transitional CM I-like state, which contributed to the failure of OFT remodeling and muscular septum formation. On the other hand, a Penk+ transitional MS II cluster closely related to cell condensation into the OFT septum disappeared, which led to the OFT’s septation absence directly. In conclusion, the disturbance of CNCC-derived cells caused by PDGFRα and PDGFRβ knockout can lead to the OFT septation disorder and the occurrence of PTA.

Quadricuspid aortic valve and right ventricular type of myocardial bridging in an asymptomatic middle-aged woman: A case report

BACKGROUND

Quadricuspid aortic valve (QAV) is a very rare congenital cardiac defect with the incidence of 0.0125%-0.033% (< 0.05%) predominantly causing aortic regurgitation. A certain number of patients (nearly one-half) have abnormal function and often require surgery, commonly in their fifth or sixth decade. QAV usually appears as an isolated anomaly but may also be associated with other cardiac congenital defects. Echocardiography is considered the main diagnostic method although more and more importance is given to computed tomography (CT) and magnetic resonance imaging (MRI) as complementary methods.

CASE SUMMARY

A 60-year-old female patient was referred for transthoracic ultrasound of the heart as part of a routine examination in the treatment of arterial hypertension. She did not have any significant symptoms. QAV was confirmed and there were no elements of valve stenosis with moderate aortic regurgitation. At first, it seemed that in the projection of the presumed left coronary cusp, there were two smaller and equally large cusps along with two larger and normally developed cusps. Cardiac CT imaging was performed to obtain an even more precise valve morphology and it showed that the location of the supernumerary cusp is between the right and left coronary cusp, with visible central malcoaptation of the cusps. Also, coronary computed angiography confirmed the right-type of myocardial bridging at the distal segment of the left anterior descending coronary artery. Significant valve dysfunction often occurs in middle-aged patients and results in surgical treatment, therefore, a 1-year transthoracic echocardiogram control examination and follow-up was recommended to our patient.

CONCLUSION

This case highlights the importance of diagnosing QAV since it leads to progressive valve dysfunction and can be associated with other congenital heart defects which is important to detect, emphasizing the role of cardiac CT and MRI.

A pictorial account of the human embryonic heart between 3.5 and 8 weeks of development

Heart development is topographically complex and requires visualization to understand its progression. No comprehensive 3-dimensional primer of human cardiac development is currently available. We prepared detailed reconstructions of 12 hearts between 3.5 and 8 weeks post fertilization, using Amira® 3D-reconstruction and Cinema4D®-remodeling software. The models were visualized as calibrated interactive 3D-PDFs. We describe the developmental appearance and subsequent remodeling of 70 different structures incrementally, using sequential segmental analysis. Pictorial timelines of structures highlight age-dependent events, while graphs visualize growth and spiraling of the wall of the heart tube. The basic cardiac layout is established between 3.5 and 4.5 weeks. Septation at the venous pole is completed at 6 weeks. Between 5.5 and 6.5 weeks, as the outflow tract becomes incorporated in the ventricles, the spiraling course of its subaortic and subpulmonary channels is transferred to the intrapericardial arterial trunks. The remodeling of the interventricular foramen is complete at 7 weeks.

Sudden death of a post-partum female with anomalous origin of the coronary artery with bicuspid aortic valve

Modern techniques have enabled routine diagnosis of congenital cardiac defects, notwithstanding, there will be some that remain undiagnosed and asymptomatic until adulthood. But this is rarely the case with the patent foramen ovale, with the anomalous aortic origin of the left main coronary artery and bicuspid aortic valve. This case describes the sudden death of a female in her post-partum period due to cardiac tamponade following a ruptured aneurysm of the coronary artery at its origin at the sinus of Valsalva. Autopsy shows patent foramen ovale findings and anomalous aortic origin of coronary artery (AAOCA) and bicuspid aortic valve. The association of AAOCA with bicuspid aortic valve and patent foramen ovale is rare.

Diagnosis and therapeutic cardiac catheterization of symptomatic bicuspid aortic stenosis in the pediatric population

Bicuspid aortic valve (BAV) is the most common congenital heart disease with a prevalence of 0.5%–1.3% of the population. Many children with BAV are asymptomatic. Clinically relevant abnormal valve function usually occurs in adulthood. However, in rare cases, children can fail to thrive which requires valvular intervention. In this review, we will explore in more detail the anatomy of the BAV, clinical presentation of BAV, diagnosis of BAV, and its function by echocardiography, and indications for transcatheter intervention in the pediatric population.

Vessel structural stress mediates aortic media degeneration in bicuspid aortopathy: New insights based on patient-specific fluid-structure interaction analysis

This study aimed to assess the relationship between local mechanical stimuli and regional aortic tissue degeneration using fluid-structure interaction (FSI) analysis in patients with bicuspid aortic valve (BAV) disease. Nine patients underwent ascending aortic replacement were recruited. Tissues were collected to evaluate the pathology features in four regions, greater curvature (GC-region), posterior (P-region), anterior (A-region), and lesser curvature (LC-region). FSI analysis was performed to quantify vessel structural stress (VSS) and flow-induced parameters, including wall shear stress (WSS), oscillatory shear index (OSI), and particle relative residence time (RRT). The correlation between these biomechanical metrics and tissue degeneration was analyzed. Elastin in the medial layer and media thickness were thinnest and the gap between fibers was biggest in the GC-region, followed by the P-region and A-region, while the elastin and media thickness were thickest and the gap smallest in the LC-region. The collagen deposition followed a pattern with the biggest in the GC-region and least in the LC-region. There is a strong negative correlation between mean or peak VSS and elastin thickness in the arterial wall in the GC-region (r = -0.917; p = 0.001 and r = -0.899; p = 0.001), A-region (r = -0.748; p = 0.020 and r = -0.700; p = 0.036) and P-region (r = -0.773; p = 0.014 and r = -0.769; p = 0.015), and between mean VSS and fiber distance in the A-region (r = -0.702, p = 0.035). Moreover, strong negative correlation between mean or peak VSS and media thickness was also observed. No correlation was found between WSS, OSI, and RRT and aortic tissue degeneration in these four regions. These findings indicate that increased VSS correlated with local elastin degradation and aortic media degeneration, implying that it could be a potential biomechanical parameter for a refined risk stratification for patients with BAV.

Histological regional analysis of the aortic root and thoracic ascending aorta: a complete analysis of aneurysms from root to arch

BACKGROUND

Although aortic root and ascending aortic aneurysms are treated the same, they differ in embryological development and pathological processes. This study examines the microscopic structural differences between aortic root and ascending aortic aneurysms, correlating these features to the macroscopic pathophysiological processes.

METHODS

We obtained surgical samples from ascending aortic aneurysms (n = 11), aortic root aneurysms (n = 3), and non-aneurysmal patients (n = 7), Aortic collagen and elastin content were examined via histological analysis, and immunohistochemistry techniques used to determine collagen I, III, and IV subtypes. Analysis was via observational features, and colour deconvolution quantification techniques.

RESULTS

Elastin fiber disruption and fragmentation was the most extensive in the proximal aneurysmal regions. Medial fibrosis and collagen density increased in proximal aneurysmal regions and aortic root aneurysms (p < 0.005). Collagen I was seen in highest quantity in aortic root aneurysms. Collagen I content was greatest in the sinus tissue regions compared to the valvular and ostial regions (p < 0.005) Collagen III and IV quantification did not vary greatly. The most susceptible regions to ultrastructural changes in disease are the proximal ascending aorta and aortic root.

CONCLUSIONS

The aortic root differs histologically from the ascending aorta confirming its unique composition in aneurysm pathology. These findings should prompt further evaluation on the influence of this altered structure on function which could potentially guide clinical management.

Dual role for CXCL12 signaling in semilunar valve development

Cxcl12-null embryos have dysplastic, misaligned, and hyperplastic semilunar valves (SLVs). In this study, we show that CXCL12 signaling via its receptor CXCR4 fulfills distinct roles at different stages of SLV development, acting initially as a guidance cue to pattern cellular distribution within the valve primordia during the endocardial-to-mesenchymal transition (endoMT) phase and later regulating mesenchymal cell proliferation during SLV remodeling. Transient, anteriorly localized puncta of internalized CXCR4 are observed in cells undergoing endoMT. In vitro, CXCR4+ cell orientation in response to CXCL12 requires phosphatidylinositol 3-kinase (PI3K) signaling and is inhibited by suppression of endocytosis. This dynamic intracellular localization of CXCR4 during SLV development is related to CXCL12 availability, potentially enabling activation of divergent downstream signaling pathways at key developmental stages. Importantly, Cxcr7-/- mutants display evidence of excessive CXCL12 signaling, indicating a likely role for atypical chemokine receptor CXCR7 in regulating ligand bioavailability and thus CXCR4 signaling output during SLV morphogenesis.

Anomalous coronary artery origin from the opposite sinus in patients with bicuspid aortic valve: comparison with tricuspid aortic valve

Objective

To compare the prevalence and patterns of anomalous coronary artery origin from the opposite sinus (ACAOS) in patients with bicuspid aortic valve (BAV) and tricuspid aortic valve (TAV).

Methods

Retrospective review of consecutive patients with surgically excised BAV and TAV was performed from 1994 to 2015. Clinical notes, echocardiograms, coronary angiograms, CT angiographies, and pathology reports were reviewed. ACAOS included right coronary artery from the left cusp, left circumflex artery from the right cusp and left main or left anterior descending artery from the right cusp.

Results

2371 (years 1994–2015) and 1679 (years 2009–2015) consecutive patients with pathology-confirmed BAV and TAV, respectively, and defined preoperative coronary anatomy were identified. A left dominant coronary circulation was present in 386 (18%) patients with BAV and 179 (11%) patients with TAV (p<0.001). ACAOS was identified in 43 (1.8%) patients with BAV and 15 (0.9%) patients with TAV, p=0.02. Among patients with BAV and ACAOS, the most common phenotype was right-left fusion (n=34, 79%) with present raphe (n=36, 84%), with no association between BAV phenotype and ACAOS type. On multivariate analysis, BAV status and size of the mid-ascending aorta were independently associated with ACAOS (OR 3.29; CI 1.26 to 8.6; p=0.02; OR 0.93; CI 0.87 to 0.98; p=0.01; respectively). Only two patients with ACAOS, one with BAV and one with TAV, had a perioperative coronary ischaemic event.

Conclusions

The prevalence of the potentially malignant ACAOS is significantly higher (threefold higher odds) in patients with BAV as compared with TAV, yet remains uncommon in absolute terms. Most patients with BAV and ACAOS had right-left cusp fusion and present raphe. Perioperative coronary events are rare in patients with ACAOS.

Setd5 is required in cardiopharyngeal mesoderm for heart development and its haploinsufficiency is associated with outflow tract defects in mouse

Congenital heart defects are a feature of several genetic haploinsufficiency syndromes, often involving transcriptional regulators. One property of haploinsufficient genes is their propensity for network interactions at the gene or protein level. In this article we took advantage of an online dataset of high throughput screening of mutations that are embryonic lethal in mice. Our aim was to identify new genes where the loss of function caused cardiovascular phenotypes resembling the 22q11.2 deletion syndrome models, that is, heterozygous and homozygous loss of Tbx1. One gene with a potentially haploinsufficient phenotype was identified, Setd5, thought to be involved in chromatin modification. We found murine Setd5 haploinsufficiency to be associated with double outlet right ventricle and perimembranous ventricular septal defect, although no genetic interaction with Tbx1 was detected. Conditional mutagenesis revealed that Setd5 was required in cardiopharyngeal mesoderm for progression of the heart tube through the ballooning stage to create a four-chambered heart.

Genetic and Developmental Contributors to Aortic Stenosis

Aortic stenosis (AS) remains one of the most common forms of valve disease, with significant impact on patient survival. The disease is characterized by left ventricular outflow obstruction and encompasses a series of stenotic lesions starting from the left ventricular outflow tract to the descending aorta. Obstructions may be subvalvar, valvar, or supravalvar and can be present at birth (congenital) or acquired later in life. Bicuspid aortic valve, whereby the aortic valve forms with two instead of three cusps, is the most common cause of AS in younger patients due to primary anatomic narrowing of the valve. In addition, the secondary onset of premature calcification, likely induced by altered hemodynamics, further obstructs left ventricular outflow in bicuspid aortic valve patients. In adults, degenerative AS involves progressive calcification of an anatomically normal, tricuspid aortic valve and is attributed to lifelong exposure to multifactoral risk factors and physiological wear-and-tear that negatively impacts valve structure-function relationships. AS continues to be the most frequent valvular disease that requires intervention, and aortic valve replacement is the standard treatment for patients with severe or symptomatic AS. While the positive impacts of surgical interventions are well documented, the financial burden, the potential need for repeated procedures, and operative risks are substantial. In addition, the clinical management of asymptomatic patients remains controversial. Therefore, there is a critical need to develop alternative approaches to prevent the progression of left ventricular outflow obstruction, especially in valvar lesions. This review summarizes our current understandings of AS cause; beginning with developmental origins of congenital valve disease, and leading into the multifactorial nature of AS in the adult population.

Left Pulmonary Artery from the Ascending Aorta: A Case Report and Review of Published Cases

The left pulmonary artery arising from the ascending aorta is an infrequent finding. It may be found isolated or with intracardiac anomalies. We present a new case of the left pulmonary artery arising from the ascending aorta and pool these findings with those of previously reported cases. Associated cardiac, extracardiac, and syndromic findings are discussed along with the implications of these in the evaluation and management of this condition.

Endothelial TGF-β signaling instructs smooth muscle cell development in the cardiac outflow tract

The development of the cardiac outflow tract (OFT), which connects the heart to the great arteries, relies on a complex crosstalk between endothelial (ECs) and smooth muscle (SMCs) cells. Defects in OFT development can lead to severe malformations, including aortic aneurysms, which are frequently associated with impaired TGF-β signaling. To better understand the role of TGF-β signaling in OFT formation, we generated zebrafish lacking the TGF-β receptor Alk5 and found a strikingly specific dilation of the OFT: alk5-/- OFTs exhibit increased EC numbers as well as extracellular matrix (ECM) and SMC disorganization. Surprisingly, endothelial-specific alk5 overexpression in alk5-/- rescues the EC, ECM, and SMC defects. Transcriptomic analyses reveal downregulation of the ECM gene fibulin-5, which when overexpressed in ECs ameliorates OFT morphology and function. These findings reveal a new requirement for endothelial TGF-β signaling in OFT morphogenesis and suggest an important role for the endothelium in the etiology of aortic malformations.

Single-Cell RNA-Seq of the Developing Cardiac Outflow Tract Reveals Convergent Development of the Vascular Smooth Muscle Cells

Cardiac outflow tract (OFT) is a major hotspot for congenital heart diseases. A thorough understanding of the cellular diversity, transitions, and regulatory networks of normal OFT development is essential to decipher the etiology of OFT malformations. We performed single-cell transcriptomic sequencing of 55,611 mouse OFT cells from three developmental stages that generally correspond to the early, middle, and late stages of OFT remodeling and septation. Known cellular transitions, such as endothelial-to-mesenchymal transition, have been recapitulated. In particular, we identified convergent development of the vascular smooth muscle cell (VSMC) lineage where intermediate cell subpopulations were found to be involved in either myocardial-to-VSMC trans-differentiation or mesenchymal-to-VSMC transition. Finally, we uncovered transcriptional regulators potentially governing cellular transitions. Our study provides a single-cell reference map of cell states for normal OFT development and paves the way for further studies of the etiology of OFT malformations at the single-cell level.

Embryonic development of bicuspid aortic valves

Bicuspid aortic valve (BAV) is the most common congenital cardiac malformation, frequently associated with aortopathies and valvulopathies. The congenital origin of BAV is suspected to impact the development of the disease in the adult life. During the last decade, a number of studies dealing with the embryonic development of congenital heart disease have significantly improved our knowledge on BAV etiology. They describe the developmental defects, at the molecular, cellular and morphological levels, leading to congenital cardiac malformations, including BAV, in animal models. These models consist of a spontaneous hamster and several mouse models with different genetic manipulations in genes belonging to a variety of pathways. In this review paper, we aim to gather information on the developmental defects leading to BAV formation in these animal models, in order to tentatively explain the morphogenetic origin of the spectrum of valve morphologies that characterizes human BAV. BAV may be the only defect resulting from gene manipulation in mice, but usually it appears as the less severe defect of a spectrum of malformations, most frequently affecting the cardiac outflow tract. The genes whose alterations cause BAV belong to different genetic pathways, but many of them are direct or indirectly associated with the NOTCH pathway. These molecular alterations affect three basic cellular mechanisms during heart development, i.e., endocardial-to-mesenchymal transformation, cardiac neural crest (CNC) cell behavior and valve cushion mesenchymal cell differentiation. The defective cellular functions affect three possible morphogenetic mechanisms, i.e., outflow tract endocardial cushion formation, outflow tract septation and valve cushion excavation. While endocardial cushion abnormalities usually lead to latero-lateral BAVs and septation defects to antero-posterior BAVs, alterations in cushion excavation may give rise to both BAV types. The severity of the original defect most probably determines the specific aortic valve phenotype, which includes commissural fusions and raphes. Based on current knowledge on the developmental mechanisms of the cardiac outflow tract, we propose a unified hypothesis of BAV formation, based on the inductive role of CNC cells in the three mechanisms of BAV development. Alterations of CNC cell behavior in three possible alternative key valvulogenic processes may lead to the whole spectrum of BAV.

Stenotic lesions of pulmonary arteries: imaging evaluation using multidetector computed tomography angiography

Stenotic lesions of the pulmonary arteries can be congenital or acquired. Different etiologies may affect the pulmonary arteries, unilaterally or bilaterally, at different levels. The clinical scenario, age of presentation and the precipitating event may provide clues to the underlying etiology. Diagnosis is important as these lesions may have hemodynamic and clinical consequences. Multidetector computed tomography angiography allows for accurate depiction of these lesions along with a comprehensive assessment of the pulmonary arterial wall, intra- or extraluminal involvement, associated cardiac or extracardiac anomalies, effects secondary to pulmonary stenosis on the cardiac chambers as well as associated causative or resultant lung parenchymal changes.

Identification and analysis of KLF13 variants in patients with congenital heart disease

Background

The protein Kruppel-like factor 13 (KLF13) is a member of the KLF family and has been identified as a cardiac transcription factor that is involved in heart development. However, the relationship between KLF13 variants and CHDs in humans remains largely unknown. The present study aimed to screen the KLF13 variants in CHD patients and genetically analyze the functions of these variants.

Methods

KLF13 variants were sequenced in a cohort of 309 CHD patients and population-matched healthy controls (n = 200) using targeted sequencing. To investigate the effect of variants on the functional properties of the KLF13 protein, the expression and subcellular localization of the protein, as well as the transcriptional activities of downstream genes and physical interactions with other transcription factors, were assessed.

Results

Two heterozygous variants, c.487C > T (P163S) and c.467G > A (S156N), were identified in two out of 309 CHD patients with tricuspid valve atresia and transposition of the great arteries, respectively. No variants were found among healthy controls. The variant c.467G > A (S156N) had increased protein expression and enhanced functionality compared with the wild type, without affecting the subcellular localization. The other variant, c.487C > T (P163S), did not show any abnormalities in protein expression or subcellular localization; however, it inhibited the transcriptional activities of downstream target genes and physically interacted with TBX5, another cardiac transcription factor.

Conclusion

Our results show that the S156N and P163S variants may affect the transcriptional function of KLF13 and physical interaction with TBX5. These results identified KLF13 as a potential genetic risk factor for congenital heart disease.

Mechano-biological adaptation of the pulmonary artery exposed to systemic conditions

Cardiac surgeries may expose pulmonary arterial tissue to systemic conditions, potentially resulting in failure of that tissue. Our goal was to quantitatively assess pulmonary artery adaptation due to changes in mechanical environment. In 17 sheep, we placed a pulmonary autograft in aortic position, with or without macroporous mesh reinforcement. It was exposed to systemic conditions for 6 months. All sheep underwent 3 ECG-gated MRI’s. Explanted tissue was subjected to mechanical and histological analysis. Results showed progressive dilatation of the unreinforced autograft, while reinforced autografts stabilized after two months. Some unreinforced pulmonary autograft samples displayed more aorta-like mechanical behavior with increased collagen deposition. The mechanical behavior of reinforced autografts was dominated by the mesh. The decrease in media thickness and loss of vascular smooth muscle cells was more pronounced in reinforced than in unreinforced autografts. In conclusion, altering the mechanical environment of a pulmonary artery causes changes in its mechano-biological properties.

What is the real cardiac anatomy?

The heart is a remarkably complex organ. Teaching its details to medical students and clinical trainees can be very difficult. Despite the complexity, accurate recognition of these details is a pre‐requisite for the subsequent understanding of clinical cardiologists and cardiac surgeons. A recent publication promoted the benefits of virtual reconstructions in facilitating the initial understanding achieved by medical students. If such teaching is to achieve its greatest value, the datasets used to provide the virtual images should themselves be anatomically accurate. They should also take note of a basic rule of human anatomy, namely that components of all organs should be described as they are normally situated within the body. It is almost universal at present for textbooks of anatomy to illustrate the heart as if removed from the body and positioned on its apex, the so‐called Valentine situation. In the years prior to the emergence of interventional techniques to treat cardiac diseases, this approach was of limited significance. Nowadays, therapeutic interventions are commonplace worldwide. Advances in three‐dimensional imaging technology, furthermore, now mean that the separate components of the heart can readily be segmented, and then shown in attitudinally appropriate fashion. In this review, we demonstrate how such virtual dissection of computed tomographic datasets in attitudinally appropriate fashion reveals the true details of cardiac anatomy. The virtual approach to teaching the arrangement of the cardiac components has much to commend it. If it is to be used, nonetheless, the anatomical details on which the reconstructions are based must be accurate. Clin. Anat. 32:288–309, 2019. © 2019 The Authors. Clinical Anatomy published by Wiley Periodicals, Inc. on behalf of American Association of Clinical Anatomists.

High incidence of ductal closure or narrowing at birth in patients with right ventricular outflow tract obstruction with normal orientation of the ductus arteriosus

BACKGROUND

Ductal patency is mandatory to manage patients with ductal-dependent pulmonary circulation. The aim of this study is to elucidate the morphological and haemodynamic features of ductus arteriosus with right ventricular outflow tract obstruction, and investigate the appropriate perinatal management.Patients and methodsPatients with prenatal diagnosis of right ventricular outflow tract obstruction at our institution between 2010 and 2015 were included in the study. Reverse orientation of the ductus arteriosus is defined as an inferior angle of 90°. We retrospectively reviewed the shape and flow pattern of ductus arteriosus and the clinical characteristics of the cases.

RESULTS

A total of 39 patients were enrolled. The shape was divided into normal orientation (n=15) and reverse orientation (n=24) of the ductus arteriosus. There was no significant difference in the type of oxygen saturation at birth and age at shunt operation between both the groups. However, the median narrowest diameter of ductus arteriosus in the normal orientation group was significantly smaller than that in the reverse orientation group (2.0 [1.0-5.4] versus 3.0 [1.3-4.4] mm, p&lt;0.05). In two patients of the normal orientation group, ductus arteriosus had closed at birth, and one of whom died because of severe cyanosis.

CONCLUSIONS

Normal orientation pattern might have high incidence of an early narrowing or closure of ductus arteriosus at birth. The critical patients need careful evaluation by repeated foetal echocardiography and further maternal interventions.

The proximal segment of the embryonic outflow (conus) does not participate in aortic vestibule development

OBJECTIVE

There is no consensus on the embryonic components or morphogenetic processes involved in mature ventricular outflow tract development. Our goal was to use in vivo labelling to investigate the prospective fate of the myocardium of each conal wall. The conal and atrioventricular cushion mesenchyme changes during transformation into mature structures and their role in apoptosis were also investigated.

METHODS

Plastic labels were placed at the cephalic and caudal conal limits of chicken embryo hearts (stage 22HH) and traced up to stage 36HH. Histological analyses, scanning electron microscopy and apoptotic detection using Lysotracker-Red were performed. The conal longitudinal length and medial displacement were registered. Muscle myosin was identified by immunofluorescence.

RESULTS

Labels positioned in the myocardium of each conal wall moved to the right ventricle (RV), shifting from the arterial subvalvular myocardial zone to the apex. No labels were found in the aortic vestibule. At stage 22HH, the conus was a tubular structure composed of myocardium and endocardium with scarce mesenchyme. The dorso-left conal myocardial wall gradually lost continuity and the free ends separated, while the myocardium was distributed to the RV free wall (24HH-28HH). At stage 22HH, conal crests were not observed, but they were apparent at the dorsal zone of the conus at stage 26HH; towards stage 30HH, they fused to form the supraventricular crest, and the pulmonary infundibulum was evident. The ventro-superior cushion of the AV canal was reorganized into the fibrous and muscular structures lined the aortic vestibule.

CONCLUSIONS

The posterior conus is an erroneous concept. The conal myocardium is reorganized in the free wall of the RV. Internally, the conal lumen is transformed into the pulmonary infundibulum. The aortic vestibule is formed from the ventro-superior cushion of the AV canal. Thus, the ventricular outflow tracts have different embryonic origins.

Bicuspid aortic valve formation: Nos3 mutation leads to abnormal lineage patterning of neural crest cells and the second heart field

The bicuspid aortic valve (BAV), a valve with two instead of three aortic leaflets, belongs to the most prevalent congenital heart diseases in the world, occurring in 0.5-2% of the general population. We aimed to understand how changes in early cellular contributions result in BAV formation and impact cardiovascular outflow tract development. Detailed 3D reconstructions, immunohistochemistry and morphometrics determined that, during valvulogenesis, the non-coronary leaflet separates from the parietal outflow tract cushion instead of originating from an intercalated cushion. Nos3^-/- mice develop a BAV without a raphe as a result of incomplete separation of the parietal outflow tract cushion into the right and non-coronary leaflet. Genetic lineage tracing of endothelial, second heart field and neural crest cells revealed altered deposition of neural crest cells and second heart field cells within the parietal outflow tract cushion of Nos3^-/- embryos. The abnormal cell lineage distributions also affected the positioning of the aortic and pulmonary valves at the orifice level. The results demonstrate that the development of the right and non-coronary leaflets are closely related. A small deviation in the distribution of neural crest and second heart field populations affects normal valve formation and results in the predominant right-non-type BAV in Nos3^-/- mice.

Transcriptional regulation of cell shape during organ morphogenesis

The emerging field of transcriptional regulation of cell shape changes aims to address the critical question of how gene expression programs produce a change in cell shape. Together with cell growth, division, and death, changes in cell shape are essential for organ morphogenesis. Whereas most studies of cell shape focus on posttranslational events involved in protein organization and distribution, cell shape changes can be genetically programmed. This review highlights the essential role of transcriptional regulation of cell shape during morphogenesis of the heart, lungs, gastrointestinal tract, and kidneys. We emphasize the evolutionary conservation of these processes across different model organisms and discuss perspectives on open questions and research avenues that may provide mechanistic insights toward understanding birth defects.

HIRA directly targets the enhancers of selected cardiac transcription factors during in vitro differentiation of mouse embryonic stem cells

HIRA is a histone chaperone known to modulate gene expression through the deposition of H3.3. Conditional knockout of Hira in embryonic mouse hearts leads to cardiac septal defects. Loss of function mutation in HIRA, together with other chromatin modifiers, was found in patients with congenital heart diseases. However, the effects of HIRA on gene expression at earlier stages of cardiogenic mesoderm differentiation have not yet been studied. Differentiation of mouse embryonic stem cells (mESCs) towards cardiomyocytes mimics some of these early events and is an accepted model of these early stages. We performed RNA-Seq and H3.3-HA ChIP-seq on both WT and Hira-null mESCs and early cardiomyocyte progenitors of both genotypes. Analysis of RNA-seq data showed differential down regulation of cardiovascular development-related genes in Hira-null cardiomyocytes compared to WT cardiomyocytes. We found HIRA-dependent H3.3 deposition at these genes. In particular, we observed that HIRA influenced directly the expression of the transcription factors Gata6, Meis1 and Tbx2, essential for cardiac septation, through H3.3 deposition. We therefore identified new direct targets of HIRA during cardiac differentiation.

Intercalated cushion cells within the cardiac outflow tract are derived from the myocardial troponin T type 2 (Tnnt2) Cre lineage

BACKGROUND

The origin of the intercalated cushions that develop into the anterior cusp of the pulmonary valve (PV) and the noncoronary cusp of the aortic valve (AV) is not well understood.

RESULTS

Cre transgenes in combination with the Rosa TdTomato-EGFP reporter were used to generate three-dimensional lineage mapping of AV and PV cusps during intercalated cushion development. Tie2-Cre;EGFP was used to mark endothelial-derived mesenchymal cells, Wnt1-Cre;EGFP for cardiac neural crest and cardiac Troponin T (Tnnt2)Cre;EGFP, for myocardial lineage. The highest percentage of intercalated cushion cells at embryonic day (E) 12.5 was Tnnt2-Cre; EGFP positive; 68.0% for the PV and 50.0% AV. Neither Tnnt2 mRNA nor Tnnt2-Cre protein was expressed in the intercalated cushions; and the Tnnt2-Cre lineage intercalated cushion cells were also positive for the mesenchymal markers Sox9 and versican. Tnnt2-Cre lineage was present within the forming intercalated cushions from E11.5 and was present in the intercalated cushion derived PV and AV cusps and localized to the fibrosa layer at postnatal day 0.

CONCLUSIONS

Intercalated cushions of the developing outflow tract are populated with Tnnt2-Cre derived cells, a Cre reporter previously used for tracing and excision of myocardial cells and not previously associated with mesenchymal cells. Developmental Dynamics 247:1005-1017, 2018. © 2018 Wiley Periodicals, Inc.

Notch-Tnf signalling is required for development and homeostasis of arterial valves

Aims

Congenital anomalies of arterial valves are common birth defects, leading to valvar stenosis. With no pharmaceutical treatment that can prevent the disease progression, prosthetic replacement is the only choice of treatment, incurring considerable morbidity and mortality. Animal models presenting localized anomalies and stenosis of congenital arterial valves similar to that of humans are critically needed research tools to uncover developmental molecular mechanisms underlying this devastating human condition.

Methods and results

We generated and characterized mouse models with conditionally altered Notch signalling in endothelial or interstitial cells of developing valves. Mice with inactivation of Notch1 signalling in valvar endothelial cells (VEC) developed congenital anomalies of arterial valves including bicuspid aortic valves and valvar stenosis. Notch1 signalling in VEC was required for repressing proliferation and activating apoptosis of valvar interstitial cells (VIC) after endocardial-to-mesenchymal transformation (EMT). We showed that Notch signalling regulated Tnfα expression in vivo, and Tnf signalling was necessary for apoptosis of VIC and post-EMT development of arterial valves. Furthermore, activation or inhibition of Notch signalling in cultured pig aortic VEC-promoted or suppressed apoptosis of VIC, respectively.

Conclusion

We have now met the need of critical animal models and shown that Notch-Tnf signalling balances proliferation and apoptosis for post-EMT development of arterial valves. Our results suggest that mutations in its components may lead to congenital anomaly of aortic valves and valvar stenosis in humans.

Pulmonary Valve Morphology in Patients with Bicuspid Aortic Valves

The aortic and pulmonary valve share a common developmental origin from the embryonic arterial trunk. Bicuspid aortic valve is the most common congenital anomaly and can occur isolated as well as in association with other congenital heart disease (CHD). Data on pulmonary valve morphology in these cases are scarce. In this study, we aimed to determine pulmonary valve morphology in hearts with BAV associated with CHD. In 83 post-mortem heart specimens with BAV and associated CHD, pulmonary valve morphology was studied and related to BAV morphology. In 14/83 (17%) hearts, the pulmonary valve was affected, bicuspid in 8/83 (10%), dome-shaped in 3/83 (4%) and atretic in 3/83 (4%). In specimens with a bicuspid pulmonary valve, 5/8 (63%) had a strictly bicuspid aortic valve (without raphe), 2/3 hearts (67%) with dome-shaped pulmonary valves and 2/3 hearts (67%) with atretic pulmonary valves had BAV without raphe. Six out of eight (75%) specimens with a bicuspid pulmonary valve had a perimembranous ventricular septal defect (VSD). 4/8 (50%) specimens with a bicuspid pulmonary valve were associated with chromosomal abnormalities: 3 (38%) had trisomy 18 and 1 (13%) had trisomy 13. In BAV with associated CHD, abnormal pulmonary valve morphology was observed in 17% of the hearts. The majority of hearts with abnormal pulmonary valve morphology had a Type B bicuspid aortic valve (without raphe). Bilateral semilunar valvular disease is associated with Type B BAVs and in many cases related to chromosomal abnormalities. As this study was performed in post-mortem specimens with high frequency of associated CHD, caution is warranted with application of these results to the general BAV population.

Association Between Tetralogy of Fallot and Tracheobronchial Branching Abnormalities: A New Clue for Pathogenesis?

Background

In our practice, we noticed an increased frequency of tracheobronchial branching abnormalities (TBAs) in patients with tetralogy of Fallot (ToF). This study aimed to determine whether an association exists between congenital TBAs and ToF with or without pulmonary atresia.

Methods and Results

The frequency of TBAs on chest computed tomography was assessed in 55 patients with ToF without pulmonary atresia, 34 patients with ToF with pulmonary arteria, and 100 control patients. We then looked for a possible association between TBAs and pulmonary artery branch hypoplasia, the presence of major aortopulmonary collateral arteries, and the presence of the chromosome 22q11 deletion. TBAs were significantly more frequent in patients with ToF with or without pulmonary atresia than in the control group (any TBAs, 21% versus 2% [P<0.001]; bronchial situs anomalies, 6% versus 0% [P=0.002]; right tracheal bronchus, 4% versus 0% [P=0.04]; left eparterial bronchus, 8% versus 0% [P=0.005]); and tended to be more frequent in those with ToF without pulmonary atresia than in those with ToF with pulmonary atresia (any TBAs, 27% versus 12% [P=0.11]; left eparterial bronchus, 13% versus 0% [P=0.04]). TBAs were readily multiple (8 patients of 19 with TBA) and concerned essentially the upper lobes. TBAs were not associated with pulmonary branch hypoplasia, major aortopulmonary collateral arteries, or the chromosome 22q11 deletion.

Conclusions

We demonstrated a significantly increased frequency of tracheobronchial abnormalities in patients with ToF with or without pulmonary atresia compared with a control group. These results suggest an interaction between abnormalities in conotruncal septation and tracheobronchial branching and may provide a new clue to the pathogenesis of conotruncal heart diseases.

Multiple Roles of Pitx2 in Cardiac Development and Disease

Cardiac development is a complex morphogenetic process initiated as bilateral cardiogenic mesoderm is specified at both sides of the gastrulating embryo. Soon thereafter, these cardiogenic cells fuse at the embryonic midline configuring a symmetrical linear cardiac tube. Left/right bilateral asymmetry is first detected in the forming heart as the cardiac tube bends to the right, and subsequently, atrial and ventricular chambers develop. Molecular signals emanating from the node confer distinct left/right signalling pathways that ultimately lead to activation of the homeobox transcription factor Pitx2 in the left side of distinct embryonic organ anlagen, including the developing heart. Asymmetric expression of Pitx2 has therefore been reported during different cardiac developmental stages, and genetic deletion of Pitx2 provided evidence of key regulatory roles of this transcription factor during cardiogenesis and thus congenital heart diseases. More recently, impaired Pitx2 function has also been linked to arrhythmogenic processes, providing novel roles in the adult heart. In this manuscript, we provide a state-of-the-art review of the fundamental roles of Pitx2 during cardiogenesis, arrhythmogenesis and its contribution to congenital heart diseases.

Evidence of subannular and left ventricular morphological differences in patients with bicuspid versus tricuspid aortic valve stenosis: magnetic resonance imaging-based analysis

Objectives

Prospective analysis of left ventricular (LV) morphological/functional parameters in patients with bicuspid versus tricuspid aortic valve (TAV) stenosis undergoing aortic valve replacement (AVR) surgery.

Methods

A total of 190 consecutive patients with BAV ( n  = 154) and TAV stenosis ( n  = 36) (mean age 61 ± 8 years, 65% male) underwent AVR ± concomitant aortic surgery from January 2012 through May 2015. All patients underwent preoperative cardiac magnetic resonance imaging in order to evaluate: (i) left ventricular outflow tract (LVOT) dimensions, (ii) length of anterior mitral leaflet (AML), (iii) end-systolic and end-diastolic LV wall thickness, (iv) LV area, (v) LV end-systolic and end-diastolic diameters (LVESD, LVEDD), (vi) LV end-diastolic and end-systolic volumes (LVEDV, LVESV) and (vii) maximal diameter of aortic root. These parameters were compared between the two study groups.

Results

The LVOT diameter was significantly larger in BAV patients (21.7 ± 3 mm in BAV vs 18.9 ± 3 mm in TAV, P  < 0.001). Moreover, BAV patients had significantly longer AML (24 ± 3 mm in BAV vs 22 ± 4 mm in TAV, P  = 0.009). LVEDV and LVESV were significantly larger in BAV patients (LVEDV: 164.9 ± 68.4 ml in BAV groups vs 126.5 ± 53.1 ml in TAV group, P  = 0.037; LVESV: 82.1 ± 57.9 ml in BAV group vs 52.9 ± 25.7 ml in TAV group, P  = 0.008). A strong linear correlation was found between LVOT diameter and aortic annulus diameter in BAV patients ( r  = 0.7, P  < 0.001), whereas significantly weaker correlation was observed in TAV patients ( r  = 0.5, P  = 0.006, z  = 1.65, P  = 0.04). Presence of BAV morphology was independently associated with larger LVOT diameters (OR 9.0, 95% CI 1.0-81.3, P  = 0.04).

Conclusions

We found relevant differences in LV morphological/functional parameters between BAV and TAV stenosis patients. Further investigations are warranted in order to determine the cause of these observed differences.

Sequential segmental analysis of the crocodilian heart

Differences between hearts of crocodilians and those of mammals and birds are only partly understood because there is no standardised approach and terminology for describing cardiac structure. Whereas most reptiles have an undivided ventricle, crocodilians have a fully septated ventricle. Their hearts, therefore, are more readily comparable with the hearts of mammals and birds. Here, we describe the heart of a crocodile (Crocodylus noliticus). We use the versatile sequential segmental approach to analysis, juxtaposing several key views of the crocodilian heart to the comparable views of human hearts. In crocodiles, the atrial and ventricular septums are complete but, unlike in placental mammals, the atrial septum is without an oval fossa. The myocardial component of the crocodilian ventricular septum dominates, but the membranous septum likely makes up a greater proportion than in any mammal. In the crocodile, the aortic trunk takes its origin from the left ventricle and is not wedged between the atrioventricular junctions. Consequently, there is a common atrioventricular junction, albeit with separate right and left atrioventricular valvar orifices. As in mammals, nonetheless, the crocodilian left atrioventricular valvar orifice is cranial to the right atrioventricular valvar orifice. By applying a method of analysis and terminology usually restricted to the human heart, we build from the considerable existing literature to show neglected and overlooked shared features, such as the offset between the left and right atrioventricular valvar orifices. Such commonalities are surprising given the substantial evolutionary divergence of the archosaur and synapsid lineages, and likely reflect evolutionarily shared morphogenetic programmes.

Variations in structure of the outflow tract of the human embryonic heart: A new hypothesis for generating bicuspid aortic semilunar valves

Outflow tract development of the heart is complex. The presence, differential growth and interactions of the various tissues through space and time contribute to the final development of the tract. This paper presents a novel interpretation of observations of outflow tract development, in particular of the aortic and pulmonary semilunar valves in embryos from the Shaner Collection at the University of Alberta. Three-dimensional reconstructions assist in the visualization of the spatial relationships of the developing valve tissues. In some embryos the aortic intercalated valve swelling is displaced proximally, giving rise to a bicuspid aortic semilunar valve more distally. In addition, the developing valve tissue first appears external to the myocardial cuff. The pulmonary semilunar valve regions appear to be more normal. This paper thus proposes a novel mechanism for generating a bicuspid aortic valve and also supports the idea that there is some independence of the aortic and pulmonary regions from each other during development.

Two Rare Vascular Rings With Ductal Origin of the Left Pulmonary Artery: A Previously Unrecognized Syndrome?

We report two neonates with distal ductal origin of the left pulmonary artery who also had rare vascular rings comprised of a left aortic arch and right arterial duct with a midline/rightward descending aorta. To the best of our knowledge, this association has not previously been described, although other abnormalities of the left pulmonary artery in the setting of vascular rings have been reported. We review the embryology, utility of imaging, and clinical course.

The Increasing Prevalence in Intersex Variation from Toxicological Dysregulation in Fetal Reproductive Tissue Differentiation and Development by Endocrine-Disrupting Chemicals

An increasing number of children are born with intersex variation (IV; ambiguous genitalia/hermaphrodite, pseudohermaphroditism, etc.). Evidence shows that endocrine-disrupting chemicals (EDCs) in the environment can cause reproductive variation through dysregulation of normal reproductive tissue differentiation, growth, and maturation if the fetus is exposed to EDCs during critical developmental times in utero. Animal studies support fish and reptile embryos exhibited IV and sex reversal when exposed to EDCs. Occupational studies verified higher prevalence of offspring with IV in chemically exposed workers (male and female). Chemicals associated with endocrine-disrupting ability in humans include organochlorine pesticides, poly-chlorinated biphenyls, bisphenol A, phthalates, dioxins, and furans. Intersex individuals may have concurrent physical disorders requiring lifelong medical intervention and experience gender dysphoria. An urgent need exists to determine which chemicals possess the greatest risk for IV and the mechanisms by which these chemicals are capable of interfering with normal physiological development in children.

In Vivo Cardiotoxicity Induced by Sodium Aescinate in Zebrafish Larvae

Sodium aescinate (SA) is a widely-applied triterpene saponin product derived from horse chestnut seeds, possessing vasoactive and organ-protective activities with oral or injection administration in the clinic. To date, no toxicity or adverse events in SA have been reported, by using routine models (in vivo or in vitro), which are insufficient to predict all aspects of its pharmacological and toxicological actions. In this study, taking advantage of transparent zebrafish larvae (Danio rerio), we evaluated cardiovascular toxicity of SA at doses of 1/10 MNLC, 1/3 MNLC, MNLC and LC₁₀ by yolk sac microinjection. The qualitative and quantitative cardiotoxicity in zebrafish was assessed at 48 h post-SA treatment, using specific phenotypic endpoints: heart rate, heart rhythm, heart malformation, pericardial edema, circulation abnormalities, thrombosis and hemorrhage. The results showed that SA at 1/10 MNLC and above doses could induce obvious cardiac and pericardial malformations, whilst 1/3 MNLC and above doses could induce significant cardiac malfunctions (heart rate and circulation decrease/absence), as compared to untreated or vehicle-treated control groups. Such cardiotoxic manifestations occurred in more than 50% to 100% of all zebrafish treated with SA at MNLC and LC₁₀. Our findings have uncovered the potential cardiotoxicity of SA for the first time, suggesting more attention to the risk of its clinical application. Such a time- and cost-saving zebrafish cardiotoxicity assay is very valid and reliable for rapid prediction of compound toxicity during drug research and development.

Coronary anatomy as related to bicuspid aortic valve morphology

OBJECTIVE

Variable coronary anatomy has been described in patients with bicuspid aortic valves (BAVs). This was never specified to BAV morphology, and prognostic relevance of coronary vessel dominance in this patient group is unclear. The purpose of this study was to evaluate valve morphology in relation to coronary artery anatomy and outcome in patients with isolated BAV and with associated aortic coarctation (CoA).

METHODS

Coronary anatomy was evaluated in 186 patients with BAV (141 men (79%), 51±14 years) by CT and invasive coronary angiography. Correlation of coronary anatomy was made with BAV morphology and coronary events.

RESULTS

Strictly bicuspid valves (without raphe) with left-right cusp fusion (type 1B) had more left dominant coronary systems compared with BAVs with left-right cusp fusion with a raphe (type 1A) (48% vs. 26%, p=0.047) and showed more separate ostia (28% vs. 9%, p=0.016). Type 1B BAVs had more coronary artery disease than patients with type 1A BAV (36% vs. 19%, p=0.047). More left dominance was seen in BAV patients with CoA than in patients without (65% vs. 24%, p<0.05).

CONCLUSIONS

The incidence of a left dominant coronary artery system and separate ostia was significantly related to BAVs with left-right fusion without a raphe (type 1B). These patients more often had significant coronary artery disease. In patients with BAV and CoA, left dominancy is more common.