The incidence of congenital heart disease

Maternal folate deficiency affects proliferation, but not apoptosis, in embryonic mouse heart

Low dietary folate and deficiency of methylenetetrahydrofolate reductase (Mthfr) were reported to increase the risk for congenital heart defects, but contributory mechanisms have not been elucidated. Because low folate and absent MTHFR activity were shown to affect proliferation and apoptosis in developing neural tissue, we examined these processes in the myocardium of embryos from Mthfr +/+ and Mthfr +/- mice fed control diets (CD) or folic acid-deficient diets (FADD). Mice consumed the designated diets for 8 wk, from weaning and through pregnancy until they were killed. Embryos were assessed on gestational day 12.5 for myocardial proliferation by 5-bromo-2'-deoxyuridine (BrdU) labeling and for apoptosis by TdT-mediated dUTP nick end labeling staining and caspase 3/7 activity assays. FADD-treated dams had significantly higher resorption rates than CD-treated dams. Embryonic lengths and weights from FADD-treated dams were significantly lower than those from CD-treated dams; the smallest embryos were those of the Mthfr +/- dams that consumed the FADD, with effect of genotype tending to be significant (P = 0.09). The thickness of cardiac ventricular compact walls of embryos from FADD-treated dams was significantly reduced, and embryonic myocardium from FADD-treated dams had significantly fewer BrdU-labeled cells compared with CD-treated dams, with no differences in apoptosis due to the diets. Genotype did not affect proliferation or apoptosis. Our results suggest that proliferation of embryonic myocardium is sensitive to maternal dietary folate and that folate supplementation during pregnancy is important for normal heart development and prevention of heart defects.

How effectively can clinical examination pick up congenital heart disease at birth?

AIMS

To assess what proportion of all cardiac abnormality can be suspected at birth when all clinical examination before discharge is undertaken by a small stable team of clinicians.

METHODS

A prospective audit of all the 14 572 births in a maternity unit only staffed by nurse practitioners between 1996 and 2003.

RESULTS

1.2% of all babies born in the unit were found to have a structural defect (as confirmed by echocardiography) within a year of birth. The number not suspected before discharge declined over time, and only 6% were first suspected after discharge in the last four years of this eight year study. Four potentially life threatening conditions initially went unsuspected in 1996-8, but none after that. A policy of referring every term baby with a murmur at 1 day of age that was still present at 7-10 days resulted in 4.2% requiring cardiac referral; 54% of these babies still had a murmur when assessed one to two weeks later, and 33% had a structural defect. Parents said in independent, retrospectively conducted, interviews that they found it confidence building to have any possible heart defect identified early and the cause of any murmur clearly and authoritatively explained.

CONCLUSIONS

Effective screening requires experience and a clear, structured, referral pathway, but can work much better than most previous reports suggest. Whether staff bring a medical or nursing background to the task may well be of less importance.

Novel missense mutations (p.T596M and p.P1797H) in NOTCH1 in patients with bicuspid aortic valve

The bicuspid aortic valve (BAV) is the most common congenital cardiac malformation, occurring in 1-2% of the population. In a recent report, mutations in NOTCH1 a signaling and transcriptional regulator have been shown to cause BAV in two families. This study provides data on systematic sequencing in search for novel mutations in NOTCH1 gene in a large sample BAV. For the first time, we report results of a systematic mutation-analysis based on DNA-sequencing of all coding exons and adjacent splice consensus sequences of NOTCH1 gene. Our analyses revealed 57 NOTCH1 sequence variants. Twenty-one variants are located within exons and 36 within intronic or 5'-UTR sequences. Thirty-five variants were described previously as polymorphisms. The remaining 22, however, were neither listed in public SNP databases nor in the literature and were therefore considered novel. Seventeen variants were found only once (MAF = 1%), of these 15 were novel. Two sequence variants led to amino acid substitutions (p.T596M and p.P1797H) and are located in highly conserved regions of the NOTCH1 protein. In addition, these two mutations could not be detected in at least 327 healthy controls by using RFLP-analysis. The functional relevance of the other 13 novel and rare variants could not be proven without further functional examination. In this study, we provide a new evidence that the mutations in the NOTCH1 gene may trigger the underlying mechanism causing the valve calcification, especially in BAV. In conclusion, NOTCH1 gene mutations do not only play a role in familiar BAV, but can also be observed in approximately 4% of sporadic cases.

Aorta coarctation presenting with intracranial aneurysm rupture

Most vascular diseases have a tendency to affect both heart and the brain. Intracranial aneurysms are more often found in patients with aorta coarctation than in general population, and aneurysm rupture occurs much earlier in these patients. Here, we report a case of aorta coarctation which was diagnosed with its cerebrovascular complications. Before presenting with cerebrovascular complications, the disease can easily be diagnosed with physical examination and non-invasive radiological investigations like echocardiography or cardiac magnetic resonance imaging.

Indications and timing of pulmonary valve replacement after tetralogy of Fallot repair

Surgical management of tetralogy of Fallot results in anatomic and functional abnormalities in the majority of patients. Although right ventricular volume load due to severe pulmonary regurgitation can be tolerated for years, there is now evidence that the compensatory mechanisms of the right ventricular myocardium ultimately fail and that if the volume load is not eliminated or reduced the dysfunction might be irreversible. In light of that data and with better understanding of risk factors for adverse outcomes late after tetralogy of Fallot repair, many centers are now recommending early pulmonary valve replacement before symptoms of heart failure develop. This article reviews the pathophysiology of chronic right ventricular volume load after tetralogy of Fallot repair and the risks and benefits of pulmonary valve replacement. Finally, recommendations for timing and indications for pulmonary valve replacement are given.

Developmental Toxicity Induced by Inhalation Exposure of Pregnant Rats to N,N ‐Dimethylacetamide

Developmental toxicity of N,N-dimethylacetamide (DMAC) was examined by exposing pregnant rats by inhalation to DMAC vapor at 0 (control), 100, 300, 450 or 600 ppm (v/v) for 6 h/d during Gestation Days 6 through 19. Fetal body weight and the number of male live fetuses were significantly decreased, along with a tendency of the number of intrauterine deaths to increase. The number of fetuses with visceral and skeletal malformations was significantly increased in the 450 and 600 ppm groups, while the number of fetuses with anasarca as an external malformation was increased at 600 ppm. Observed cardiovascular malformations included ventricular septum defect, persistent truncus arteriosus, malpositioned subclavian branch and retroesophageal subclavian artery. Persistent truncus arteriosus was accompanied by ventricular septal defect (VSD). Incidences of the persistent truncus arteriosus, which was classified as a serious congenital heart disease affecting postnatal survival, were increased at 450 and 600 ppm. Increased liver weights and hepatocellular swelling occurred in the dams exposed to 300 ppm and above, whereas neither hepatocellular necrosis nor increased serum activity of liver transaminases was observed in any of the exposed groups. Maternal body weights were decreased at 450 and 600 ppm. The most sensitive signs of developmental toxicity appeared at the exposure level of 300 ppm which was also the level of slight maternal toxicity. The No-Observed-Adverse-Effect-Level (NOAEL) was determined as 100 ppm for the endpoints of fetal and maternal toxicities. The NOAEL of 100 ppm and the induction of serious cardiovascular malformations occurring at 450 ppm and above were discussed with reference to the existing occupational exposure limit for DMAC.

Extracellular Matrix Remodeling and Organization in Developing and Diseased Aortic Valves

Heart valve disease is an important cause of morbidity and mortality worldwide. Little is known about valve disease pathogenesis, but increasing evidence implicates a genetic basis for valve disease, suggesting a developmental origin. Although the cellular and molecular processes involved in early valvulogenesis have been well described, less is known about the regulation of valve extracellular matrix (ECM) organization and valvular interstitial cell (VIC) distribution that characterize the mature valve structure. Histochemistry, immunohistochemistry, and electron microscopy were used to examine ECM organization, VIC distribution, and cell proliferation during late valvulogenesis in chicken and mouse. In mature valves, ECM organization is conserved across species, and developmental studies demonstrate that ECM stratification begins during late embryonic cusp remodeling and continues into postnatal life. Cell proliferation decreases concomitant with ECM stratification and VIC compartmentalization. Explanted, stenotic bicuspid aortic valves (BAVs) from pediatric patients were also examined. The diseased valves exhibited disruption of the highly organized ECM and VIC distribution seen in normal valves. Cusps from diseased valves were thickened with increased and disorganized collagens and proteoglycans, decreased and fragmented elastic fibers, and cellular disarray without calcification or cell proliferation. Taken together, these studies show that normal valve development is characterized by spatiotemporal coordination of ECM organization and VIC compartmentalization and that these developmental processes are disrupted in pediatric patients with diseased BAVs.

Forkhead transcription factors, Foxc1 and Foxc2, are required for the morphogenesis of the cardiac outflow tract

Previous studies have shown that Foxc1 and Foxc2, closely related Fox transcription factors, have interactive roles in cardiovascular development. However, little is known about their functional overlap during early heart morphogenesis. Here, we show that Foxc genes are coexpressed in a novel heart field, the second heart field, as well as the cardiac neural crest cells (NCCs), endocardium, and proepicardium. Notably, compound Foxc1; Foxc2 mutants have a wide spectrum of cardiac abnormalities, including hypoplasia or lack of the outflow tract (OFT) and right ventricle as well as the inflow tract, dysplasia of the OFT and atrioventricular cushions, and abnormal formation of the epicardium, in a dose-dependent manner. Most importantly, in the second heart field, compound mutants exhibit significant downregulation of Tbx1 and Fgf8/10 and a reduction in cell proliferation. Moreover, NCCs in compound mutants show extensive apoptosis during migration, leading to a failure of the OFT septation. Taken together, our results demonstrate that Foxc1 and Foxc2 play pivotal roles in the early processes of heart development, especially acting upstream of the Tbx1-FGF cascade during the morphogenesis of the OFT.

Cardiovascular malformations induced by prenatal exposure to phenobarbital in rats

The effects of prenatal exposure to phenobarbital (PB) on the cardiovascular system were examined in rat fetuses and pups. PB was administered at a dose of 80 or 120 mg/kg/day by gavage to Sprague Dawley (SD) rats on two consecutive gestational days (GD): 7-8, 8-9, 9-10, or 10-11. Fetuses were examined for cardiovascular malformations on GD 20. In addition, pups were examined for PB-induced cardiovascular malformations. Incidences of ventricular septal defect (VSD), overriding aorta, double outlet right ventricle and transposition of great arteries were significantly increased in the fetuses whose dams were administered PB at 120 mg/kg on GD 8-9, 9-10 or 10-11. GD 8-11 was the critical period for the cardiovascular malformations associated with administration of PB in rats. Various types of cardiovascular malformations were detected in pups from the PB-administered dam. Severe cardiovascular malformations induced by PB caused deaths on early postnatal days. However, slight malformations such as isolated VSD persisted until weaning, and did not affect postnatal viability.

Trends in diagnosis and prevalence of critical congenital heart defects in the Podkarpacie province in 2002–2004, based on data from the Polish Registry of Congenital Malformations

This paper presents results of data collection regarding congenital heart defects (CHD) for the Polish Registry of Congenital Malformations (PRCM) from the Podkarpacie province in 2002-2004. Routine methods (fetal echocardiography, clinical examination) and recently also unique methods (screening echocardiography and pulse oximetry) were used for early detection of critical cardiac malformations. Critical CHD were detected there in 107 newborns in 2002-2004, so the mean prevalence reached 1.71/1000. Within this group, death rate decreased from 8 deaths in 2002 to 2 deaths in 2004, mainly thanks to improved detection and treatment of CHD.

BMP and FGF regulatory pathways control cell lineage diversification of heart valve precursor cells

The atrioventricular heart valve leaflets and chordae tendineae are composed of diverse cell lineages and highly organized extracellular matrices that share characteristics with cartilage and tendon cell types in the limb buds and somites. During embryonic chicken valvulogenesis, aggrecan and sox9, characteristic of cartilage cells, are observed in the AV valve leaflets, in contrast to tendon-associated genes scleraxis and tenascin, present in the chordae tendineae. In the limb buds and somites, cartilage cell lineage differentiation is regulated by BMP2, while FGF4 controls tendon cell fate. The ability of BMP2 and FGF4 to induce similar patterns of gene expression in heart valve precursor cells was examined. In multiple assays of cells from prefused endocardial cushions, BMP2 is sufficient to activate Smad1/5/8 phosphorylation and induce sox9 and aggrecan expression, while FGF4 treatment increases phosphorylated MAPK (dpERK) signaling and promotes expression of scleraxis and tenascin. However, these treatments do not alter differentiated lineage gene expression in valve progenitors from fused cushions of older embryos. Together, these studies define regulatory pathways of AV valve progenitor cell diversification into leaflets and chordae tendineae that share inductive interactions and differentiation phenotypes with cartilage and tendon cell lineages.

NFATc1 expression in the developing heart valves is responsive to the RANKL pathway and is required for endocardial expression of cathepsin K

NFATc1 is necessary for remodeling endocardial cushions into mature heart valve leaflets and is also an essential effector of receptor activator of NFkappaB ligand (RANKL) signaling required for transcriptional activation of bone matrix remodeling enzymes during osteoclast differentiation. Therefore, developing heart valves were examined to determine if NFATc1 functions in the RANKL pathway during leaflet remodeling. Key components of RANKL signal transduction including RANKL, its receptor RANK, and the downstream remodeling enzyme cathepsin K (Ctsk) are expressed in the heart during valve remodeling and colocalize with NFATc1 in developing valve endocardium. However, the absence of tartrate-resistant acid phosphatase (TRAP) activity and the lack of F4/80-positive macrophage lineage contribution to the remodeling valves demonstrate that certain aspects of osteoclast RANKL function are not shared during valve formation. Analysis of NFATc1-/- mouse embryos shows that NFATc1 is specifically required for endocardial expression of RANKL and Ctsk during valve formation. In addition, RANKL treatment augments expression of NFATc1 and Ctsk in embryonic heart cultures, and the RANKL-mediated increase in Ctsk expression is dependent on NFATc1. Together, these results support a role for RANKL signaling during heart valve development and suggest that valve leaflet morphogenesis involves NFATc1-dependent expression of remodeling enzymes including Ctsk.

Transvenous Pacing Leads and Systemic Thromboemboli in Patients With Intracardiac Shunts

BACKGROUND

The risk of systemic thromboemboli associated with transvenous leads in the presence of an intracardiac shunt is currently unknown.

METHODS AND RESULTS

To define this risk, we conducted a multicenter, retrospective cohort study of 202 patients with intracardiac shunts: Sixty-four had transvenous leads (group 1), 56 had epicardial leads (group 2), and 82 had right-to-left shunts but no pacemaker or implantable cardioverter defibrillator leads (group 3). Patient-years were accrued until the occurrence of systemic thromboemboli or study termination. Censoring occurred in the event of complete shunt closure, death, or loss to follow-up. Mean ages for groups 1, 2, and 3 were 33.9+/-18.0, 22.2+/-12.6, and 22.9+/-15.0 years, respectively. Respective oxygen saturations were 91.2+/-9.1%, 88.1+/-8.1%, and 79.7+/-6.7%. During respective median follow-ups of 7.3, 9.3, and 17.0 years, 24 patients had at least 1 systemic thromboembolus: 10 (15.6%), 5 (8.9%), and 9 (11.0%) in groups 1, 2, and 3, respectively. Univariate risk factors were older age (hazard ratio [HR], 1.05; P=0.0001), ongoing phlebotomy (HR, 3.1; P=0.0415), and an transvenous lead (HR, 2.4; P=0.0421). In multivariate, stepwise regression analyses, transvenous leads remained an independent predictor of systemic thromboemboli (HR, 2.6; P=0.0265). In patients with transvenous leads, independent risk factors were older age (HR, 1.05; P=0.0080), atrial fibrillation or flutter (HR, 6.7; P=0.0214), and ongoing phlebotomy (HR, 14.4; P=0.0349). Having had aspirin or warfarin prescribed was not protective. Epicardial leads were, however, associated with higher atrial (P=0.0407) and ventricular (P=0.0270) thresholds and shorter generator longevity (HR, 1.9; P=0.0176).

CONCLUSIONS

Transvenous leads incur a >2-fold increased risk of systemic thromboemboli in patients with intracardiac shunts.

Formation of the venous pole of the heart from an Nkx2-5-negative precursor population requires Tbx18

The venous pole of the mammalian heart is a structurally and electrically complex region, yet the lineage and molecular mechanisms underlying its formation have remained largely unexplored. In contrast to classical studies that attribute the origin of the myocardial sinus horns to the embryonic venous pole, we find that the sinus horns form only after heart looping by differentiation of mesenchymal cells of the septum transversum region into myocardium. The myocardial sinus horns and their mesenchymal precursor cells never express Nkx2-5, a transcription factor critical for heart development. In addition, lineage studies show that the sinus horns do not derive from cells previously positive for Nkx2-5. In contrast, the sinus horns express the T-box transcription factor gene Tbx18. Mice deficient for Tbx18 fail to form sinus horns from the pericardial mesenchyme and have defective caval veins, whereas the pulmonary vein and atrial structures are unaffected. Our studies define a novel heart precursor population that contributes exclusively to the myocardium surrounding the sinus horns or systemic venous tributaries of the developing heart, which are a source of congenital malformation and cardiac arrhythmias.

Bicuspid aortic valve: an innocent finding or a potentially life-threatening anomaly whose complications may be elicited by sports activity?

The bicuspid aortic valve is the most frequent congenital anomaly of the heart in adults. Since the 1970s, with the advent of two-dimensional echocardiography, the in-vivo diagnosis of bicuspid aortic valve has become easier and greater attention has been paid to this anomaly in normal young people, particularly in sportsmen because, from a theoretical point of view, physical exercise may stress the abnormal aortic valve, favouring an early deterioration of the valve itself, as well as a dilation of the ascending aorta. Although the bicuspid aortic valve may remain without clinical consequences for a lifetime, it may be responsible for severe complications such as aortic stenosis, aortic insufficiency, endocarditis and aortic dilation/dissection, sometimes requiring surgery. Moreover, the bicuspid aortic valve may be associated with other cardiovascular anomalies, mainly aortic coarctation. At present there are no prospective studies dealing with effect of physical training and competitive sports on the natural course of the bicuspid aortic valve. However, in order to take any decision about sports eligibility, sports physicians should perform an initial accurate staging of the bicuspid aortic valve, taking into account haemodynamic factors, aortic complications and associated significant cardiovascular anomalies. A strict follow-up, with serial cardiological controls, is mandatory as well as antibiotic prophylaxis for endocarditis, particularly in subjects engaged in contact sports.

Hearts and bones: shared regulatory mechanisms in heart valve, cartilage, tendon, and bone development

The mature heart valves are dynamic structures composed of highly organized cell lineages and extracellular matrices. The discrete architecture of connective tissue within valve leaflets and supporting structures allows the valve to withstand life-long functional demands and changes in hemodynamic forces and load. The dysregulation of ECM organization is a common feature of heart valve disease and can often be linked to genetic defects in matrix protein structure or developmental regulation. Recent studies have identified specific regulatory pathways that are active in the developing valve structures and also control cartilage, tendon, and bone development. This review will focus on the regulatory hierarchies that control normal and abnormal heart valve development in parallel with other connective tissue cell types.

Congenital heart diseases in small animals: part II. Potential genetic aetiologies based on human genetic studies

Comparative genetics provides veterinary researchers and clinicians with invaluable information for the understanding the possible genetic aetiologies and the disease process in congenital heart defects (CHDs) of dogs and cats. Although, the demand on this type of research has increased in the veterinary field, to date no fundamental genetic studies have been reported in the veterinary literature. In this second part of a two-part review, the general features and pathogenesis of major CHDs in humans and small animals are discussed. In addition, the known genetic aetiologies in human CHDs have been considered in parallel to CHDs in small animals.

Applied glycoproteomics—approaches to study genetic-environmental collisions causing protein-losing enteropathy

Protein-losing enteropathy (PLE), the loss of plasma proteins through the intestine, is a life-threatening symptom associated with seemingly unrelated conditions including Crohn's disease, congenital disorder of glycosylation, or Fontan surgery to correct univentricular hearts. Emerging commonalities between these and other disorders led us to hypothesize that PLE develops when genetic insufficiencies collide with simultaneous or sequential environmental insults. Most intriguing is the loss of heparan sulfate (HS) proteoglycans (HSPG) specifically from the basolateral surface of intestinal epithelial cells only during PLE episodes suggesting a direct link to protein leakage. Reasons for HSPG loss are unknown, but genetic insufficiencies affecting HSPG biosynthesis, trafficking, or degradation may be involved. Here, we describe cell-based assays we devised to identify key players contributing to protein leakage. Results from these assays confirm that HS loss directly causes protein leakage, but more importantly, it amplifies the effects of other factors, e.g., cytokines and increased pressure. Thus, HS loss appears to play a central role for PLE. To transfer our in vitro results back to the in vivo situation, we established methods to assess enteric protein leakage in mice and present several genetically deficient strains mimicking intestinal HS loss observed in PLE patients. Preliminary results indicate that mice with haploinsufficient genes involved in HS biosynthesis or HSPG trafficking develop intestinal protein leakage upon additional environmental stress. Our goal is to model PLE in vitro and in vivo to unravel the pathomechanisms underlying PLE, identify patients at risk, and provide them with a safe and effective therapy.

Pyramidal tract maturation after brain injury in newborns with heart disease

OBJECTIVE

Our objective was to quantify white matter tract development in term newborns with congenital heart disease, a population at high risk for perioperative brain injury, using magnetic resonance imaging diffusion tensor tractography (DTT).

METHODS

Twenty-five newborns with congenital heart disease were imaged before and after surgery, with a median of 2 weeks between serial magnetic resonance imaging examinations. DTT was performed to segment bilateral pyramidal tracts using semiautomated fiber tracking software, and manual region of interest measurements were taken for comparison.

RESULTS

Significant maturational rates of increasing fractional anisotropy (median, 4.4% per week) and decreasing mean diffusivity (D(av)) (median, -2.0% per week) in the pyramidal tract were measured in infants without brain injury. Fractional anisotropy maturation rates were highest in newborns with normal scans, intermediate (median, 2.4% per week) in those with postoperative injury, and lowest (median, 0.9% per week) in those with preoperative injury, indicating a significant trend across brain injury groups (p = 0.015). D(av) maturation rates did not differ across injury groups (p = 0.15). Manual region of interest measures showed greater variability in serial measurements, and no significant differences were identified between injury groups, suggesting that DTT may provide more sensitive measures.

INTERPRETATION

DTT is feasible in term newborns and may help to characterize abnormal white matter tract development following acquired brain injury.

Maternal MTHFR 677C>T is a risk factor for congenital heart defects: effect modification by periconceptional folate supplementation

AIMS

Periconceptional folate supplementation prevents neural tube defects and possibly congenital heart defects (CHD) as well. The search for candidate genes involved in the folate metabolism includes the methylenetetrahydrofolate reductase (MTHFR) 677C > T polymorphism. We studied the association between MTHFR 677C > T variants and CHD risk. The interaction with periconceptional folate supplementation was also investigated.

METHODS AND RESULTS

A case-control study and a family-based transmission disequilibrium test (TDT) were conducted to explore this association. In 133 triads, the TDT revealed no association of the fetal 677T allele with the development of a heart defect. In 158 mothers with a CHD-affected child, the maternal MTHFR 677CT and TT genotypes in combination with no use of periconceptional folate supplements were associated with, respectively, a three-fold (OR 3.3 95% CI 1.46-7.32) and six-fold (OR 6.3 95% CI 2.32-17.27) increased risk for conotruncal heart defects in offspring. In a case-only study, the interaction between periconceptional folate supplementation and maternal MTHFR genotype was significant (P = 0.012).

CONCLUSION

The maternal MTHFR 677C > T variants are a risk factor for CHD in offspring, confined to conotruncal heart defects. A gene-environment interaction between maternal MTFHR 677CT and TT genotypes with periconceptional folate supplementation was observed. These findings provide a mechanism of the protective role of folate and support the thesis that periconceptional folate supplementation might prevent CHD.

Quantitative trait loci modifying cardiac atrial septal morphology and risk of patent foramen ovale in the mouse

Atrial septal defect (ASD) is a common congenital heart disease (CHD) occurring in 5 to 7 per 10,000 live births. Mutations in 5 human genes (NKX2.5, TBX5, GATA4, MYHC, ACTC) are known to cause dominant ASD, but these account for a minority of cases. Human and mouse data suggest that ASD exists in an anatomical continuum with milder septal variants patent foramen ovale (PFO) and atrial septal aneurysm, strongly associated with ischemic stroke and migraine. We have previously shown in inbred mice that the incidence of PFO strongly correlates with length of the interatrial septum primum, defining a quantitative trait underlying PFO risk. To better understand genetic causation of atrial septal abnormalities, we mapped quantitative trait loci (QTL) influencing septal morphology using mouse strains (QSi5 and 129T2/SvEms) maximally informative for PFO incidence and 3 quantitative septal anatomical traits including septum primum length. [QSi5x129T2/SvEms]F2 intercross animals (n=1437) were phenotyped and a whole genome scan performed at an average 17-cM interval. Statistical methodology scoring PFO as a binary phenotype was developed as a confirmatory mapping technique. We mapped 7 significant and 6 suggestive QTL modifying quantitative phenotypes, with 4 supported by binary analysis. Quantitative traits, although strongly associated with PFO (P<0.001), correlated poorly with each other and in all but 1 case QTL for different traits were nonoverlapping. Thus, multiple anatomical processes under separate genetic control contribute to risk of PFO. Our findings demonstrate the feasibility of modeling the genetic basis of common CHD using animal genetic and genomic technologies.

Assessment of myocardial function of the systemic right ventricle in patients with D-transposition of the great arteries after atrial switch operation by tissue Doppler echocardiography

INTRODUCTION

The long-term follow-up of patients with D-transposition of the great arteries after atrial switch operation shows specific problems such as tricuspid valve insufficiency, rhythm disturbances and failure of the morphologic right ventricle in systemic position. Assessment of the myocardial contractility of the subaortic right ventricle by conventional echocardiography is limited. The usage of tissue Doppler echocardiography with strain combined with strain rate imaging provides a new approach for quantitative analysis of longitudinal myocardial function. The aim of this study was to assess patterns of wall motion and regional contractile function of the systemic right ventricle in patients after atrial switch operation for D-transposition of the great arteries and to compare them to those of normal subjects.

PATIENTS AND METHODS

Twenty-four patients with Dtransposition of the great arteries after atrial switch operation with a mean age of 21.3 (range, 13 to 31) years and a postoperative period of 16.9 years were examined and compared to 22 control individuals with a mean age of 21.5 (range, 3 to 43) years. Tissue Doppler studies were obtained from apical 4- chamber view to determine regional systolic (Syst(T)) and diastolic (E(T), A(T)) velocities as well as E(T)/A(T) ratio at the basal free wall. The presystolic isovolumic contraction peak was assessed and the ratio of the presystolic peak velocity to the isovolumic acceleration time as the IVA index was calculated. Strain and peak systolic and diastolic strain rates were assessed on basal, middle and apical segments of the right ventricular free wall. Data obtained from the morphologic right systemic ventricle in patients were compared to those derived from the left and the right ventricle in controls.

RESULTS

The right ventricular free wall systolic velocities were significantly reduced in patients compared to velocities obtained from the normal right and left ventricle. On the other hand, the IVA index was only reduced in patients compared to the IVA index in the normal subpulmonary right ventricle. Compared to data obtained from the normal systemic left ventricle, the IVA index in patients was not significantly different. In contrast, strain and strain rate parameters in all analyzed segments mostly showed a highly significant reduction compared to normal right and left ventricular data.

CONCLUSION

Tissue Doppler echocardiography is a promising tool for the evaluation of regional myocardial contractile function of the morphologic right systemic ventricle in patients following atrial switch operation for D-transposition of the great arteries. Presystolic, systolic and diastolic regional ventricular function was reduced in the systemic right ventricle. However, further comparative studies using other quantitative parameters of global and regional myocardial function derived from cardiac catheterization or MRI should be performed in order to evaluate the reliability of tissue Doppler echocardiography for the assessment of global right ventricular function in these patients.

Detection rate of early fetal echocardiography and in utero development of congenital heart defects

OBJECTIVE

The purpose of this study was to evaluate the detection rate of early fetal echocardiography and the in utero development of congenital heart defects (CHD).

METHODS

Cases were selected from all singleton pregnancies between 1997 and 2003 in which detailed fetal 2-dimensional and color-coded Doppler echocardiography was performed in our prenatal unit between 11 weeks' and 13 weeks 6 days' gestation; 2165 cases with complete outcome parameters were analyzed.

RESULTS

During this study period, CHD were diagnosed in 46 fetuses. Between 11 and 13 weeks' gestation, 29 CHD were diagnosed (11 weeks, 9 cases; 12 weeks, 8 cases; and 13 weeks, 12 cases); 9 CHD were found in the second trimester and 2 in the third trimester. The in utero detection rate of fetal echocardiography was 86.96% (n = 40). Six additional CHD (13.04%) were detected postnatally. The spectrum of detected CHD changed with advancing gestational age and was different from the postnatal detected heart defects.

CONCLUSIONS

Early fetal echocardiography is feasible and allows the detection of most CHD. Congenital heart defects vary in appearance at different stages of pregnancy and may evolve in utero with advancing gestational age. Therefore, early fetal echocardiography should always be followed by echocardiography at mid gestation.

Early fetal echocardiography: heart biometry and visualization of cardiac structures between 10 and 15 weeks' gestation

OBJECTIVE

The purpose of this prospective cross-sectional study was to compile normative data about biometry of the fetal heart and great vessels between 10 and 15 weeks in 123 normal singleton pregnancies. Additionally, we investigated the different methods and the optimal examination time of early fetal echocardiography.

METHODS

The interrogated parameters included total heart diameter; heart area and circumference; right and left ventricular diameter; diameter, circumference, and area of the thorax; and diameter of the aorta and pulmonary trunk. Visualization of the 4-chamber view, 3-vessel view, origin and crossover of the great arteries, aortic arch, ductus arteriosus, superior and inferior venae cavae, and pulmonary veins was analyzed, and the success rates by transvaginal sonography (TVS) and transabdominal sonography (TAS) were calculated.

RESULTS

Complete evaluation of the fetal heart was impossible at 10 weeks; the total success rate increased from 45% at 11 weeks to 90% between 12 and 14 weeks and 100% at 15 weeks. Between 10 and 13 weeks, TVS was superior to TAS. At 14 weeks, both methods were similar to each other, and at 15 weeks, TAS allowed adequate visualization of all structures. Linear regression analysis showed a significant correlation between the interrogated parameters and gestational age, crown-rump length, and biparietal diameter (P < .05). The ratio of right and left ventricular diameters and the ratio of pulmonary trunk and aortic diameters were constant.

CONCLUSIONS

Early fetal heart evaluation by TVS or TAS or both is reasonable and feasible. Our normative data could be helpful for understanding the normal development of the fetal heart and great arteries and for detection of cardiac defects in early pregnancy.

Ventricular septal defect with secondary left ventricular-to-right atrial shunt is associated with a higher risk for infective endocarditis and a lower late chance of closure

OBJECTIVE

Although ventricular septal aneurysm may diminish or even close the shunt through the ventricular septal defect (VSD), developing a left ventricular-to-right atrial (LV-RA) shunt may be unfavorable. This study sought to clarify this issue on the basis of an extended observation of such patients.

METHODS

Sixty-eight patients (1201 patient-years) who had small perimembranous VSD and LV-RA shunt and were not operated on before 6 years of age were studied.

RESULTS

The onset age of LV-RA shunt was 5.8 +/- 3.3 years, with clinical improvement later observed in 23 (34%). The murmur disappeared and showed spontaneous closure in 5 (7%). Seven episodes of infective endocarditis occurred in 6 (8.7%, or 58 per 10000 patient-years), with 2 receiving surgery. Another 4 received surgery during follow-up. With echocardiography, aneurysmal transformation involving the anterior and septal leaflets of tricuspid valve (double sac) was found in 56 (85%), whereas only the septal leaflet (single sac) was involved in 10. Patients with double sac were less likely to show improvement, whereas patients who had superior QRS axis and were female showed clinical improvement more frequently.

CONCLUSIONS

VSD with secondary LV-RA shunt is associated with a higher risk for infective endocarditis but still has a low chance for late improvement and even closure.

Pregnancy Outcomes in Women With Congenital Heart Disease

Background— Pregnant women with congenital heart disease are at increased risk for cardiac and neonatal complications, yet risk factors for adverse outcomes are not fully defined.

Methods and Results— Between January 1998 and September 2004, 90 pregnancies at age 27.7±6.1 years were followed in 53 women with congenital heart disease. Spontaneous abortions occurred in 11 pregnancies at 10.8±3.7 weeks, and 7 underwent elective pregnancy termination. There were no maternal deaths. Primary maternal cardiac events complicated 19.4% of ongoing pregnancies, with pulmonary edema in 16.7% and sustained arrhythmias in 2.8%. Univariate risk factors included prior history of heart failure (odds ratio [OR], 15.5), NYHA functional class ≥2 (OR, 5.4), and decreased subpulmonary ventricular ejection fraction (OR, 7.7). Independent predictors were decreased subpulmonary ventricular ejection fraction and/or severe pulmonary regurgitation (OR, 9.0) and smoking history (OR, 27.2). Adverse neonatal outcomes occurred in 27.8% of ongoing pregnancies and included preterm delivery (20.8%), small for gestational age (8.3%), respiratory distress syndrome (8.3%), intraventricular hemorrhage (1.4%), intrauterine fetal demise (2.8%), and neonatal death (1.4%). A subaortic ventricular outflow tract gradient >30 mm Hg independently predicted an adverse neonatal outcome (OR, 7.5). Cardiac risk assessment was improved by including decreased subpulmonary ventricular systolic function and/or severe pulmonary regurgitation (OR, 10.3) in a previously proposed risk index developed in pregnant women with acquired and congenital heart disease.

Conclusions— Maternal cardiac and neonatal complication rates are considerable in pregnant women with congenital heart disease. Patients with impaired subpulmonary ventricular systolic function and/or severe pulmonary regurgitation are at increased risk for adverse cardiac outcomes.

Ras-related signaling pathways in valve development: ebb and flow

Congenital heart defects affect approximately 1 in every 100 live births, and deficits in the formation of the mitral, tricuspid, and outflow tract valves account for 20-25% of all cardiac malformations. Mutations in genes that affect Ras signaling have been identified in individuals with congenital valve disease associated with Noonan syndrome and neurofibromatosis type 1. Dissection of Ras-related signaling pathways during valvulogenesis provides seminal insight into cellular and molecular mechanisms that contribute to congenital heart disease.

Mutations in myosin heavy chain 11 cause a syndrome associating thoracic aortic aneurysm/aortic dissection and patent ductus arteriosus

We have recently described two kindreds presenting thoracic aortic aneurysm and/or aortic dissection (TAAD) and patent ductus arteriosus (PDA) and mapped the disease locus to 16p12.2-p13.13 (ref. 3). We now demonstrate that the disease is caused by mutations in the MYH11 gene affecting the C-terminal coiled-coil region of the smooth muscle myosin heavy chain, a specific contractile protein of smooth muscle cells (SMC). All individuals bearing the heterozygous mutations, even if asymptomatic, showed marked aortic stiffness. Examination of pathological aortas showed large areas of medial degeneration with very low SMC content. Abnormal immunological recognition of SM-MHC and the colocalization of wild-type and mutant rod proteins in SMC, in conjunction with differences in their coimmunoprecipitation capacities, strongly suggest a dominant-negative effect. Human MYH11 gene mutations provide the first example of a direct change in a specific SMC protein leading to an inherited arterial disease.

T-box transcription factors and their roles in regulatory hierarchies in the developing heart

T-box transcription factors are important players in the molecular circuitry that generates lineage diversity and form in the developing embryo. At least seven family members are expressed in the developing mammalian heart, and the human T-box genes TBX1 and TBX5 are mutated in cardiac congenital anomaly syndromes. Here, we review T-box gene function during mammalian heart development in the light of new insights into heart morphogenesis. We see for the first time how hierarchies of transcriptional activation and repression involving multiple T-box factors play out in three-dimensional space to establish the cardiac progenitors fields, to define their subservient lineages, and to generate heart form and function.

In vivo cell biology: following the zebrafish trend

A deeper understanding of the mechanisms of cell behavior is essential if we want to comprehend how an organism develops and functions. Changes in cellular processes, including the orientation of cell divisions, cell shape, polarity, differentiation and migration, account for tissue rearrangements during development and homeostasis. The in vivo relevance of in vitro findings is being constantly debated and the need for in vivo systems becoming more pressing. The zebrafish (Danio rerio) might become the vertebrate system of choice for a wide spectrum of biological questions that need to be investigated in vivo at cellular and subcellular resolutions. Here, we discuss some recent studies in which the zebrafish was used to gain insight into cell-biological mechanisms. Although this model system has been predominantly appreciated for its amenability to forward genetics, current advances in imaging technology and an increasing number of transgenic lines are bringing it closer to its full potential.

Rotation of the myocardial wall of the outflow tract is implicated in the normal positioning of the great arteries

Congenital heart defects frequently involve a failure of outflow tract (OFT) formation during development. We analyzed the remodeling of the OFT, using the y96-Myf5-nlacZ-16 transgene, which marks a subpopulation of myocardial cells of the pulmonary trunk. Expression analyses of reporter transcript and protein suggest that the myocardial wall of the OFT rotates before and during the formation of the great arteries. Rotational movement was confirmed by Di-I injection experiments with cultured embryos. We subsequently examined the expression of the transgene in mouse models for OFT defects. In hearts with persistent truncus arteriosus (PTA), double outlet right ventricle (DORV), or transposition of the great arteries, rotation of the myocardial wall of the OFT is arrested or fails to initiate. This is observed in Splotch (Pax3) mutants with PTA or DORV and may be a result of defects in neural crest migration, known to affect OFT septation. However, in Pitx2deltac mutant embryos, where cardiac neural crest cells are present in the heart, PTA and DORV are again associated with a rotation defect. This is also seen in Pitx2deltac mutants, which have transposition of the great arteries. Because Pitx2c is involved in left-right signaling, these results suggest that embryonic laterality affects rotation of the myocardial wall during OFT maturation. We propose that failure of normal rotation of OFT myocardium may underlie major forms of congenital heart disease.

Screening of 99 Danish Patients with Congenital Heart Disease forGATA4Mutations

Congenital heart disease (CHD) affects nearly 1% of the population, but only few genes involved in human CHD are presently known. Germ-line mutations in the zinc finger transcription factor GATA4 have been associated with familial cases of atrial and ventricular septal defects and pulmonary stenosis. We have screened 99 unrelated Danish patients with different CHD phenotypes to evaluate the prevalence of GATA4 mutations in CHD. No pathogenic mutations were found among the patients, suggesting that GATA4 mutations are relatively rare among CHD patients. Thus, the diagnostic importance of GATA4 mutations may be confined to familial cases or specific subgroups of CHD phenotypes.

La importancia de la ecocardiografía fetal en la detección y el manejo de las malformaciones cardiacas congénitas

Using present-day high-resolution ultrasound scanners, it is possible to visualize and study the heart during the different stages of fetal growth in patients at risk of some forms of congenital heart disease. Detailed anatomical knowledge of cardiac structures combined with the accurate interpretation of echocardiographic images made during fetal development enable early diagnosis of particular forms of congenital disease that have serious pathophysiologic consequences. In addition, it also becomes possible to select the most appropriate nature and timing of delivery, and to organize early treatment for the newborn. Any decision taken on how to treat a fetus in which a congenital cardiac abnormality has been identified must be taken by a multidisciplinary team. This will help in coordinating the measures that must be taken after delivery and, in the near future, in implementing intrauterine surgery. Fetal echocardiography is establishing itself as a valuable tool in the management of the various types of congenital malformation, which together comprise the main cause of death among the newborn. In addition, the technique can be used to confirm and broaden our knowledge of the natural history of cardiac malformations, which are the most common congenital malformations. There is no doubt that the application and understanding of this imaging technology will increase the survival rate of newborns with specific congenital cardiac abnormalities, and will have a significant impact on long-term clinical outcome and quality of life in these patients.

Four-dimensional ultrasonography of the fetal heart using a novel Tomographic Ultrasound Imaging display

OBJECTIVE

The objective of this study was to investigate the feasibility of examining the fetal heart with Tomographic Ultrasound Imaging (TUI) using four-dimensional (4D) volume datasets acquired with spatiotemporal image correlation (STIC).

MATERIAL AND METHODS

One hundred and ninety-five fetuses underwent 4D ultrasonography (US) of the fetal heart with STIC. Volume datasets were acquired with B-mode (n=195) and color Doppler imaging (CDI) (n=168), and were reviewed offline using TUI, a new display modality that automatically slices 3D/4D volume datasets, providing simultaneous visualization of up to eight parallel planes in a single screen. Visualization rates for standard transverse planes used to examine the fetal heart were calculated and compared for volumes acquired with B-mode or CDI. Diagnoses by TUI were compared to postnatal diagnoses.

RESULTS

(1) The four- and five-chamber views and the three-vessel and trachea view were visualized in 97.4% (190/195), 88.2% (172/195), and 79.5% (142/195), respectively, of the volume datasets acquired with B-mode; (2) these views were visualized in 98.2% (165/168), 97.0% (163/168), and 83.6% (145/168), respectively, of the volume datasets acquired with CDI; (3) CDI contributed additional diagnostic information to 12.5% (21/168), 14.2% (24/168) and 10.1% (17/168) of the four- and five-chamber and the three-vessel and trachea views; (4) cardiac anomalies other than isolated ventricular septal defects were identified by TUI in 16 of 195 fetuses (8.2%) and, among these, CDI provided additional diagnostic information in 5 (31.3%); (5) the sensitivity, specificity, positive- and negative-predictive values of TUI to diagnose congenital heart disease in cases where both B-mode and CDI volume datasets were acquired prenatally were 92.9%, 98.8%, 92.9% and 98.8%, respectively.

CONCLUSION

Standard transverse planes commonly used to examine the fetal heart can be automatically displayed with TUI in the majority of fetuses undergoing 4D US with STIC. Due to the retrospective nature of this study, the results should be interpreted with caution and independently confirmed before this methodology is introduced into clinical practice.

Twin-to-twin transfusion syndrome, vein of galen malformation, and transposition of the great arteries in a pair of monochorionic twins: coincidence or related association?

The pathogenetic mechanisms leading to the development of congenital heart disease and congenital intracranial arteriovenous malformation are still unclear. We report on a monochorionic twin pregnancy with twin-to-twin transfusion syndrome (TTTS), in which vein of Galen malformation (VGM) was diagnosed in the donor twin and transposition of the great arteries (TGA) in the recipient twin. The development of TTTS, VGM, and TGA in a single monochorionic pregnancy could be pure coincidence, but there might also be a causative link. We discuss the possible contribution of genetic factors, fetal flow fluctuations, vascular endothelial growth factors, and the process of twinning itself to the development of these congenital anomalies.

Diagnosis and prognosis of fetuses with double outlet right ventricle

OBJECTIVES

To examine the echocardiographic features, associated anomalies, and outcomes of fetuses diagnosed with double outlet right ventricle (DORV).

METHODS

Fetuses with DORV were identified from 987 fetal echocardiograms performed from August 1, 2002 to August 1, 2004. The medical records of 19 fetuses with DORV were reviewed.

RESULTS

Nineteen fetuses were diagnosed with DORV. The pregnancy was terminated in 15.8% (3/19) of cases. Postnatal assessment was not obtained in 26.3% (5/19) cases. Accurate prenatal diagnosis of the relationship of the ventricular septal defect (VSD) with the great arteries was achieved in 14 of 14 cases (100%). Chromosomal abnormalities (21.4%), abnormalities of body situs (35.7%), and other extracardiac abnormalities were diagnosed in association. Only 4 of 13 (30.8%) infants with confirmed DORV survived beyond 28 days.

CONCLUSIONS

DORV is found in fetuses with a large spectrum of associated cardiac and extracardiac lesions. The overall prognosis for fetuses with DORV is poor throughout the spectrum of these lesions, not only related to the primary lesion but also depending on the associated intra- and extracardiac abnormalities. While the complexity of the heart disease in fetuses with DORV makes detailed fetal diagnosis challenging, it can be accomplished with a high degree of accuracy.

Cardiovascular phenotyping of fetal mice by noninvasive high-frequency ultrasound facilitates recovery of ENU-induced mutations causing congenital cardiac and extracardiac defects

As part of a large-scale noninvasive fetal ultrasound screen to recover ethylnitrosourea (ENU)-induced mutations causing congenital heart defects in mice, we established a high-throughput ultrasound scanning strategy for interrogating fetal mice in utero utilizing three orthogonal imaging planes defined by the fetus’ vertebral column and body axes, structures readily seen by ultrasound. This contrasts with the difficulty of acquiring clinical ultrasound imaging planes which are defined by the fetal heart. By use of the three orthogonal imaging planes for two-dimensional (2D) imaging together with color flow, spectral Doppler, and M-mode imaging, all of the major elements of the heart can be evaluated. In this manner, 10,091 ENU-mutagenized mouse fetuses were ultrasound scanned between embryonic days 12.5 and 19.5, with 324 fetuses found to die prenatally and 425 exhibiting cardiovascular defects. Further analysis by necropsy and histology showed heart defects that included conotruncal anomalies, obstructive lesions, and shunt lesions as well as other complex heart diseases. Ultrasound imaging also identified craniofacial/head defects and body wall closure defects, which necropsy revealed as encephalocele, holoprosencephaly, omphalocele, or gastroschisis. Genome scanning mapped one ENU-induced mutation associated with persistence truncus arteriosus and holoprosencephaly to mouse chromosome 2, while another mutation associated with cardiac defects and omphalocele was mapped to mouse chromosome 17. These studies show the efficacy of this novel ultrasound scanning strategy for noninvasive ultrasound phenotyping to facilitate the recovery of ENU-induced mutations causing congenital heart defects and other extracardiac anomalies.

Cardiac computed tomography compared to transthoracic echocardiography in the management of congenital heart disease

OBJECTIVES

To compare cardiac CT and transthoracic echocardiography (TTE) as diagnostic utilities in congenital heart disease (CHD) and to determine their advantages and limitations.

BACKGROUND

TTE is widely used in the evaluation of CHD. Recent reports suggested an increasing role of CT. However, there are few quantitative data on its diagnostic accuracy.

METHODS

We investigated a total of 162 patients (51.24% male; mean age: 16.06 +/-+/- 17.92) with congenital heart defects, who underwent electron beam CT (EBCT) and TTE between March 2002 and June 2005. We retrospectively analyzed a total of 667 findings, stratified for age and anatomic categories.

RESULTS

EBCT and TTE findings are concordant in patients below 1 year of age (85.43% agreement). EBCT had poor sensitivity and specificity in detecting anomalies of cardiac chambers (0.68, 0.58), but was useful for great arteries (0.91, 0.85). Furthermore, sensitivity and specificity were remarkably different in systemic venous return (0.93, 0.3) and coronary vessels (0.8, 0.33) because of "false positive" findings, which were later found to be most likely real findings not detectable by reference standard. The opposite was true for cardiac valves (0.66, 0.89) and septa (0.76, 0.91).

CONCLUSIONS

EBCT delineates findings related to systemic venous return and coronary vessels well due to simultaneous visualization of complex anatomy. This advantage does not seem to apply in patients below 1 year of age with better acoustic windows. TTE was found more suitable for cardiac valves and septal defects because of the availability of flow imaging.

Nurse specialists in adult congenital heart disease: the current status in Europe

AIM

Recommendations for the management of adults with congenital heart disease indicate that specialist referral centres should employ nurse specialists who are trained and educated in the care for these patients. We surveyed the involvement, education and activities of nurse specialists in the care for adults with congenital cardiac anomalies in Europe.

METHODS

The Euro Heart Survey on Adult Congenital Heart Disease has previously showed that 20 out of 48 specialist centres (42%) have nurse specialists affiliated with their programme. Fifteen of these 20 centres (75%) validly completed a web-based survey tool.

RESULTS

Specialist centres had a median number of 2 nurse specialists on staff, corresponding with 1 full-time equivalent. In most centres, the nurse specialists were also affiliated with other cardiac care programmes, in addition to congenital heart disease. The involvement of nurse specialists was not related to the caseload of inpatients and outpatient visits. Physical examination was the most prevalent activity undertaken by nurse specialists (93.3%), followed by telephone accessibility (86.7%), patient education (86.7%), co-ordination of care (73.3%), and follow-up after discharge (73.3%). Patient education covered mainly prevention and prophylaxis of endocarditis (100%), cardiovascular risk factors (92.3%), sport activities (92.3%), the type and characteristics of the heart defect (92.3%), the definition and aetiology of endocarditis (84.6%), cardiac risk in case of pregnancy (84.6%), and heredity (84.6%). Two third of the nurse specialists were involved in research.

CONCLUSION

This survey revealed gaps in the provision of care for these patients in Europe and demonstrated that there is room for improvement in order to provide adequate chronic disease management. The results of this study can be used by individual hospitals for benchmarking.

Atrioventricular cushion transformation is mediated by ALK2 in the developing mouse heart

Developmental abnormalities in endocardial cushions frequently contribute to congenital heart malformations including septal and valvular defects. While compelling evidence has been presented to demonstrate that members of the TGF-beta superfamily are capable of inducing endothelial-to-mesenchymal transdifferentiation in the atrioventricular canal, and thus play a key role in formation of endocardial cushions, the detailed signaling mechanisms of this important developmental process, especially in vivo, are still poorly known. Several type I receptors (ALKs) for members of the TGF-beta superfamily are expressed in the myocardium and endocardium of the developing heart, including the atrioventricular canal. However, analysis of their functional role during mammalian development has been significantly complicated by the fact that deletion of the type I receptors in mouse embryos often leads to early embryonal lethality. Here, we used the Cre/loxP system for endothelial-specific deletion of the type I receptor Alk2 in mouse embryos. The endothelial-specific Alk2 mutant mice display defects in atrioventricular septa and valves, which result from a failure of endocardial cells to appropriately transdifferentiate into the mesenchyme in the AV canal. Endocardial cells deficient in Alk2 demonstrate decreased expression of Msx1 and Snail, and reduced phosphorylation of BMP and TGF-beta Smads. Moreover, we show that endocardial cells lacking Alk2 fail to delaminate from AV canal explants. Collectively, these results indicate that the BMP type I receptor ALK2 in endothelial cells plays a critical non-redundant role in early phases of endocardial cushion formation during cardiac morphogenesis.

Reference guide to the stages of chick heart embryology

Cardiac progenitors of the splanchnic mesoderm (primary and secondary heart field), cardiac neural crest, and the proepicardium are the major embryonic contributors to chick heart development. Their contribution to cardiac development occurs with precise timing and regulation during such processes as primary heart tube fusion, cardiac looping and accretion, cardiac septation, and the development of the coronary vasculature. Heart development is even more complex if one follows the development of the cardiac innervation, cardiac pacemaking and conduction system, endocardial cushions, valves, and even the importance of apoptosis for proper cardiac formation. This review is meant to provide a reference guide (Table 1) on the developmental timing according to the staging of Hamburger and Hamilton (1951) (HH) of these important topics in heart development for those individuals new to a chick heart research laboratory. Even individuals outside of the heart field, who are working on a gene that is also expressed in the heart, will gain information on what to look for during chick heart development. This reference guide provides complete and easy reference to the stages involved in heart development, as well as a global perspective of how these cardiac developmental events overlap temporally and spatially, making it a good bench top companion to the many recently written in-depth cardiac reviews of the molecular aspects of cardiac development.

Cardiovascular malformations among preterm infants

OBJECTIVE

Preterm birth and cardiovascular malformations are the 2 most common causes of neonatal and infant death, but there are no published population-based reports on the relationship between them. We undertook this study to determine the prevalence and spectrum of cardiovascular malformations in a preterm population, the prevalence of prematurity among infants with cardiovascular malformations, and the influence of prematurity and cardiovascular malformations on outcomes.

METHODS

We based the study on the population of the former Northern Health Region of England. We identified all live-born infants with cardiovascular malformations diagnosed in the first 1 year of life from the regional pediatric cardiology database, which includes the gestational age and details of the diagnosis. We limited ascertainment to malformations diagnosed by the age of 12 months. Infants with isolated patent ductus arteriosus or atrial septal defect were excluded, to avoid ascertainment bias. Infants with ventricular septal defect were classified according to whether they required surgery in the first 1 year. There are no population data on gestational ages for all births in our population for the era of this study; therefore, we used data published in the literature for populations similar to our own to predict that 0.4% of live births occur at <28 weeks of gestation, 0.9% at 28 to 31 weeks, and 6% at 32 to 36 weeks. Overall, 7.3% of live-born infants are preterm.

RESULTS

Of 521619 live-born infants in 1987-2001, 2964 had cardiovascular malformations (prevalence: 5.7 cases per 1000 live births). Cardiovascular malformations were present at 5.1 cases per 1000 term infants and 12.5 cases per 1000 preterm infants. The odds ratio (OR) for a cardiovascular malformation in prematurity was 2.4 (95% confidence interval [CI]: 2.2-2.7). We found that 474 infants (16%) with cardiovascular malformations were born at <37 weeks of gestation, giving an OR for prematurity among infants with a cardiovascular malformation of 2.4 (95% CI: 2.2-2.7). More infants were born preterm with diagnoses of pulmonary atresia with ventricular septal defect (23%), complete atrioventricular septal defect (22%), and coarctation of the aorta, tetralogy of Fallot, and pulmonary valve stenosis (each 20%). Fewer were born preterm with diagnoses of pulmonary atresia and intact ventricular septum (7%), transposition of the great arteries (8%), and single ventricle (9%). We found that 18% of infants with ventricular septal defect requiring surgery were preterm, compared with 13% in the nonsurgical group. Preterm infants with ventricular septal defect required surgery in 30% of cases, compared with 23% of term infants with ventricular septal defect. These figures show that the excess of cardiovascular malformations among preterm infants cannot be explained by greater ascertainment of minor ventricular septal defects. In our denominator population, 646 live-born infants were recognized as having trisomy 21, and gestational age data were available for 609. Of these, 149 (25%; 95% CI: 21-28%) were preterm. Approximately two thirds of infants with complete atrioventricular septal defect have trisomy 21. Complete atrioventricular septal defect was no more common among preterm infants with trisomy 21 (16%) than among term infants with trisomy 21. However, the increased incidence of prematurity among infants with trisomy 21 probably explains some of the excess of preterm births among infants with complete atrioventricular septal defect. Only 4 (11%) of 38 infants with 22q11 deletion were born preterm. None of those infants had pulmonary atresia with ventricular septal defect; therefore, 22q11 deletion does not explain the excess of preterm births in pulmonary atresia with ventricular septal defect. The OR for death in the first 1 year in the presence of a cardiovascular malformation was 4.4 (95% CI: 3.1-5.5) overall; ORs were 1.8 at <28 weeks of gestation, 3.7 at 28 to 31 weeks, 11.0 at 32 to 36 weeks, and 35.6 at term.

CONCLUSIONS

This study showed that preterm infants have more than twice as many cardiovascular malformations as do infants born at term and that 16% of all infants with cardiovascular malformations are preterm. It also showed, not surprisingly, that there is an increased mortality rate among infants born preterm with a cardiovascular malformation. The additional effect of cardiovascular malformations on mortality rates is most marked for term and near-term infants, for whom mortality rates are otherwise low. The excess of cardiovascular malformations among preterm infants is intriguing but not easy to explain. Previous studies of birth weight among infants with cardiovascular malformations reported a significant increase in the likelihood of being small for gestational age among infants with tetralogy of Fallot, complete atrioventricular septal defect, hypoplastic left heart, or large ventricular septal defect. There is an obvious relationship between birth weight and gestational age, and those studies also showed an increased prevalence of prematurity among infants with tetralogy of Fallot, pulmonary stenosis, aortic stenosis, coarctation of the aorta, complete atrioventricular septal defect, or ventricular septal defect. There is also a high prevalence of cardiovascular malformations among late stillbirths, with major differences in the number and spectrum of cardiovascular malformations, compared with those seen in postnatal life. In particular, there is a greater incidence of coarctation of the aorta, double-inlet left ventricle, hypoplastic left heart, truncus arteriosus, double-outlet right ventricle, and atrioventricular septal defect among stillbirths. This spectrum of malformations is similar to that in our study and to those in other reports. Whether the increased prevalence of cardiovascular malformations among preterm infants and the increase in stillbirths suggest clues to the cause is difficult to say. The influence of preterm birth should be taken into account in risk assessment and risk stratification for surgical repair.

Incidencia de las cardiopatías congénitas en Navarra (1989-1998)

INTRODUCTION AND OBJECTIVES

Congenital cardiopathies are the most common forms of congenital malformation. They occur in between 5.2 and 12.5 in every thousand live births. The aim of this study was to describe the incidence and nature of congenital heart disease in the Spanish region of Navarra during a specified time period (1989-1998).

PATIENTS AND METHOD

The study involved all children with congenital heart disease among the 47 783 born in the region in the specified time period.

RESULTS

The incidence was 8.96 per thousand live births, with 90% having one of the 10 most common types of cardiac malformation. The accumulative percentage diagnosed was 25.3% in the first 24 hours of life, 45% in the first week, 65% in the first month, and 83.1% during the first year. Some 30.8% of cases of congenital heart disease required invasive treatment: 25.4% underwent surgery and 6.4%, cardiac catheterization.

CONCLUSIONS

The incidence of congenital heart disease in Navarra falls within the range reported for developed countries. The level of care provided in this region is good, as demonstrated by existing diagnostic capabilities and treatment provision.

Cardiac development: new concepts

Understanding normal development is a prerequisite to unraveling the mechanisms that underlie congenital heart disease, a critical step if one is to design rational new therapies. Over the past 20 years, human molecular genetics and developmental biology have provided a group of powerful tools to uncover a number of now well-defined pathways. There is now a confluence of new technologies and experimental systems that may allow for a more profound understanding in the near future.