The incidence of congenital heart disease

Activation of p38/MEF2C pathway by all-trans retinoic acid in cardiac myoblasts

Myocyte enhancer factor 2C (MEF2C) is a transcription factor particularly expressed in cardiac muscle. While the effects of all-trans retinoic acid (atRA) on embryonic heart are well described, the mechanism of atRA action on MEF2C activity in cardiomyocytes is less known. The aim of the present study was to investigate whether and how atRA regulates MEF2C activity in H9c2 rat ventricular cells. Here, our results, obtained from Western blot and protein kinase assays, showed that the phosphorylation of p38 mitogen-activated protein kinase (MAPK) and MEF2C was induced by atRA in H9c2 myocardial cells. And the result from luciferase assays showed that the transactivation activity of MEF2C was upregulated by p38. Furthermore, using confocal microscopy and immunoprecipitation, we found that atRA hastened p38 translocation into nuclei to interact with MEF2C, and SB202190 inhibited nuclear translocation of p38. These results suggest that atRA may mediate p38/MEF2C signaling pathway during heart development.

Outcomes following surgery for congenital heart disease in low-birthweight infants

AIM

To describe cardiac surgery, survival and outcomes for low-birthweight (< or = 2500 g) infants undergoing surgery for congenital heart disease.

METHODS

Using data from a prospectively collected population-based database of admissions to neonatal intensive care units in New South Wales and the Australian Capital Territory, we identified all low-birthweight infants undergoing cardiac surgery between 1992 and 2001. Infants with only a persistent ductus arteriosus were excluded. Two-year cardiac and neurodevelopmental outcome data were sought from hospital medical records.

RESULTS

A total of 121 low-birthweight infants underwent cardiac surgery, of whom 34% had a congenital syndrome or non-cardiac birth defect. Most (81%) underwent a palliative surgical procedure in the neonatal period. There were 19 early (15.7%) and 19 late deaths giving a 2-year mortality of 31%. Factors associated with mortality included birthweight below 1500 g (P = 0.006), low weight at surgery (P = 0.028) and Apgar score at 1 min (P = 0.019). No single factor predicted 30-day mortality. By 2 years of age, 27 (33% of survivors) were known to have neurodevelopmental delay. Although 22 children are known to be developing normally, the neurodevelopmental status of 34 children was not known.

CONCLUSIONS

These surgical data were comparable to previous single-institution studies. This group had a high risk of disability due to prematurity, low birthweight and associated conditions. There is a need to prospectively assess and manage neurodevelopmental outcomes in this group.

Identification of a novel role of ZIC3 in regulating cardiac development

Mutations in ZIC3 cause X-linked heterotaxy, a disorder characterized by abnormal lateralization of normally asymmetric thoracic and abdominal organs. Animal models demonstrate an early role for ZIC3 in embryonic left-right (LR) patterning. ZIC3 mutations have also been described in patients with isolated cardiovascular malformations. We wished to address the hypothesis that ZIC3 has plieotropic effects in development and may regulate cardiac development independent of its role in LR patterning. We observed significantly reduced expression of several markers of cardiac lineage commitment in Zic3(null/y) embryonic stem cells including atrial natriuretic factor (ANF), Nkx2.5 and Tbx5. Likewise, ANF expression-a molecular marker of trabecular myocardium and a direct target of multiple cardiac-specific transcription factors-was severely reduced in E9.5 Zic3 null hearts. Trabecular myocardium was reduced in these embryos. This finding was similar to that observed in embryos with cardiac-specific ablation of serum response factor (SRF), a direct transcriptional regulator of ANF expression. While ZIC3 by itself had no effect on the ANF promoter, it could bind to and inhibit a cardiac alpha-actin promoter through its zinc finger domains. We observed that ZIC3 could function as a coactivator of SRF on both cardiac alpha-actin and ANF promoters. The zinc fingers of ZIC3 and the mcm1, agamous deficiens SRF (MADS) box motif of SRF were found to mediate their physical and functional interactions. These findings reveal a novel role of ZIC3 in regulating cardiac gene expression and may explain, in part, the association of ZIC3 mutation with cardiovascular malformations.

Thoracic skeletal defects and cardiac malformations: a common epigenetic link?

Congenital heart defects (CHDs) are the most common birth defects in humans. In addition, cardiac malformations represent the most frequently identified anomaly in teratogenicity experiments with laboratory animals. To explore the mechanisms of these drug-induced defects, we developed a model in which pregnant rats are treated with dimethadione, resulting in a high incidence of heart malformations. Interestingly, these heart defects were accompanied by thoracic skeletal malformations (cleft sternum, fused ribs, extra or missing ribs, and/or wavy ribs), which are characteristic of anterior-posterior (A/P) homeotic transformations and/or disruptions at one or more stages in somite development. A review of other teratogenicity studies suggests that the co-occurrence of these two disparate malformations is not unique to dimethadione, rather it may be a more general phenomenon caused by various structurally unrelated agents. The coexistence of cardiac and thoracic skeletal malformations has also presented clinically, suggesting a mechanistic link between cardiogenesis and skeletal development. Evidence from genetically modified mice reveals that several genes are common to heart development and to formation of the axial skeleton. Some of these genes are important in regulating chromatin architecture, while others are tightly controlled by chromatin-modifying proteins. This review focuses on the role of these epigenetic factors in development of the heart and axial skeleton, and examines the hypothesis that posttranslational modifications of core histones may be altered by some developmental toxicants.

Comparing the clinical and economic effects of clinical examination, pulse oximetry, and echocardiography in newborn screening for congenital heart defects: A probabilistic cost-effectiveness model and value of information analysis

Objectives: Congenital heart defects (CHD) are an important cause of death and morbidity in early childhood, but the effectiveness of alternative newborn screening strategies in preventing the collapse or death—before diagnosis—of infants with treatable but life-threatening defects is uncertain. We assessed their effectiveness and efficiency to inform policy and research priorities.

Methods: We compared the effectiveness of clinical examination alone and clinical examination with either pulse oximetry or screening echocardiography in making a timely diagnosis of life-threatening CHD or in diagnosing clinically significant CHD. We contrasted their cost-effectiveness, using a decision-analytic model based on 100,000 live births, and assessed future research priorities using value of information analysis.

Results: Clinical examination alone, pulse oximetry, and screening echocardiography achieved 34.0, 70.6, and 71.3 timely diagnoses per 100,000 live births, respectively. This finding represents an additional cost per additional timely diagnosis of £4,894 and £4,496,666 for pulse oximetry and for screening echocardiography. The equivalent costs for clinically significant CHD are £1,489 and £36,013, respectively. Key determinants of cost-effectiveness are detection rates and screening test costs. The false-positive rate is very high with screening echocardiography (5.4 percent), but lower with pulse oximetry (1.3 percent) or clinical examination alone (.5 percent).

Conclusions: Adding pulse oximetry to clinical examination is likely to be a cost-effective newborn screening strategy for CHD, but further research is required before this policy can be recommended. Screening echocardiography is unlikely to be cost-effective, unless the detection of all clinically significant CHD is considered beneficial and a 5 percent false-positive rate acceptable.

Principles of genetic murine models for cardiac disease

It was only approximately 15 years ago that methodologies evolved to the point where we began to manipulate the genetic apparatus of the mouse such that proteins of the investigator's choice could be expressed in a 4-chambered, mammalian heart. Our abilities to express both normal and mutated proteins in the heart or to create genetic nulls in which the protein is not expressed at all continue to evolve. With the tools now available, one can target protein expression to the different cell types present in the heart, often at a particular time, and, in some cases, turn off the protein as development progresses or the animal ages. These abilities have enabled us to model many of the genetic mutations identified as causative for pediatric and/or adult cardiovascular disease and heart failure. Identifying the primary genetic cause is, more often than not, insufficient for designing effective therapeutics or interventions. Therefore, it is critical to be able to develop animal models that accurately recapitulate the pathogenic processes that ensue as a result of mutant gene expression or loss of protein expression. In this review, we discuss the nature, strengths, and weaknesses of the current set of tools for developing genetically manipulated mouse models, as well as the relevance of these models for understanding cardiovascular disease and illuminating potential therapeutic avenues.

Risk Factors Associated With Reoperation and Mortality in 252 Patients After Aortic Valve Replacement for Congenitally Bicuspid Aortic Valve Disease

BACKGROUND

We aimed to determine the risk factors associated with mortality in patients with congenitally bicuspid aortic valve disease and dilation (<5 cm) of the ascending aorta after aortic valve replacement.

METHODS

We reviewed 252 patients with bicuspid aortic valve undergoing aortic valve replacement at our institution from 1971 through 2000. Patients undergoing concomitant replacement of the ascending aorta were excluded.

RESULTS

The average patient age was 61 +/- 15 years; 66.3% were male, and 40.5% of patients had coronary artery disease. The ascending aorta was normal (<4.0 cm) in 60.3%, mildly dilated (4.0 to 4.4 cm) in 24.2%, and moderately dilated (4.5 to 4.9 cm) in 15.5% of patients. Patients with moderate aortic dilatation had significantly lower prevalence of coronary artery disease compared with patients with normal ascending aortas (20.5% and 45.4%; p = 0.006). Mean follow-up was 8.9 +/- 6.3 years. Long-term survival was significantly different across the three groups (p = 0.004). The 5-, 10-, and 15-year estimates were 78%, 59%, and 37%, respectively, in the normal aorta group; 88%, 77%, and 46%, respectively, in the mild aortic dilation group; and 92%, 83%, and 70%, respectively, in the moderate aortic dilation group. No significant difference in cardiac death was found among the groups (p = 0.08). The significant predictors of survival using the Cox regression model were coronary artery disease, age, decade of surgery, and ejection fraction. Aortic dilation was not significant after adjusting for these other variables. At follow-up, 18 patients required reoperation, 17 for aortic valve prosthesis failure and 1 for ascending aorta aneurysm.

CONCLUSIONS

The present study highlights the important adverse effect of concomitant coronary artery disease, advanced age, earlier decade of surgery, and reduced left ventricular ejection fraction on survival after aortic valve replacement for bicuspid aortic valve in patients with no or mild and moderate (<5 cm) dilation of the ascending aorta.

Combined loss of Hey1 and HeyL causes congenital heart defects because of impaired epithelial to mesenchymal transition

Congenital heart defects affect almost 1% of human newborns. Recently, mutations in Notch ligands and receptors have been found to cause a variety of heart defects in rodents and humans. However, the molecular effects downstream of Notch are still poorly understood. Here we report that combined inactivation of Hey1 and HeyL, two primary target genes of Notch, causes severe heart malformations, including membranous ventricular septal defects and dysplastic atrioventricular and pulmonary valves. These defects lead to congestive cardiac failure with high lethality. We found both genes to be coexpressed with Notch1, Notch2 and the Notch ligand Jagged1 in the endocardium of the atrioventricular canal, representing the primary source of mesenchymal cells forming membraneous septum and valves. Atrioventricular explants from Hey1/HeyL deficient mice exhibited impaired epithelial to mesenchymal transition. Although epithelial to mesenchymal transition was initiated regularly, full transformation into mesenchymal cells failed. This was accompanied by reduced levels of matrix metalloproteinase-2 expression and reduced cell density in endocardial cushions in vivo. We further show that loss of Hey2 leads to very similar deficiencies, whereas a Notch1 null mutation completely abolishes epithelial to mesenchymal transition. Thus, the Hey gene family shows overlap in controlling Notch induced endocardial epithelial to mesenchymal transition, a process critical for valve and septum formation.

Univentricular Heart

As early as 1699, Chemineau described a heart composed of 2 auricles but only 1 ventricle. 1 The univentricular heart has since fascinated the medical community. Unique in its complexity and scope, the univentricular heart has sparked intense debates about embryology and nomenclature, challenged our understanding of cardiovascular physiology and hemodynamics, and inspired some of the most creative surgical and interventional approaches in human history. The present report provides an overview of the nomenclature and classification of the univentricular heart, epidemiology and pathological subtypes, genetic factors, physiology, clinical features, diagnostic assessment, therapy, and postoperative sequelae. Although the present report touches on issues applicable to neonates and children with univentricular hearts, the focus is on information of interest and relevance to the adult cardiologist.

Sox9 is required for precursor cell expansion and extracellular matrix organization during mouse heart valve development

Heart valve structures derived from mesenchymal cells of the endocardial cushions (ECs) are composed of highly organized cell lineages and extracellular matrix. Sox9 is a transcription factor required for both early and late stages of cartilage formation that is also expressed in the developing valves of the heart. The requirements for Sox9 function during valvulogenesis and adult valve homeostasis in mice were examined by conditional inactivation of Sox9 using Tie2-cre and Col2a1-cre transgenes. Sox9(flox/flox);Tie2-cre mice die before E14.5 with hypoplastic ECs, reduced cell proliferation and altered extracellular matrix protein (ECM) deposition. Sox9(flox/flox);Col2a1-cre mice die at birth with thickened heart valve leaflets, reduced expression of cartilage-associated proteins and abnormal ECM patterning. Thickened valve leaflets and calcium deposits, characteristic of valve disease, are observed in heterozygous adult Sox9(flox/+);Col2a1-cre mice. Therefore, Sox9 is required early in valve development for expansion of the precursor cell population and later is required for normal expression and distribution of valvular ECM proteins. These data indicate that Sox9 is required for early and late stages of valvulogenesis and identify a potential role for Sox9 in valve disease mechanisms.

Temporal and Anatomic Risk Profile of Brain Injury With Neonatal Repair of Congenital Heart Defects

BACKGROUND AND PURPOSE

Brain injury is common in newborns with congenital heart disease (CHD) requiring neonatal surgery. The purpose of this study is to define the risk factors for preoperative and postoperative brain injuries and their association with functional cardiac anatomic groups.

METHODS

Sixty-two neonates with CHD were studied with preoperative MRI, and 53 received postoperative scans. Clinical and therapeutic characteristics were compared in newborns with and without newly acquired brain injuries. A subset of 16 consecutive patients was monitored with intraoperative cerebral near-infrared spectroscopy.

RESULTS

Brain injury was observed in 56% of patients. Preoperative brain injury, seen in 39%, was most commonly stroke and was associated with balloon atrial septostomy (P=0.002). Postoperative brain injury, seen in 35%, was most commonly white matter injury and was particularly common in neonates with single-ventricle physiology and aortic arch obstruction (P=0.001). Risk factors associated with acquired postoperative brain injury included cardiopulmonary bypass (CPB) with regional cerebral perfusion (P=0.01) and lower intraoperative cerebral hemoglobin oxygen saturation during the myocardial ischemic period of CPB (P=0.008). In a multivariable model, new postoperative white matter injury was specifically associated with low mean blood pressure during the first postoperative day (P=0.04).

CONCLUSIONS

Specific modifiable risk factors can be identified for preoperative and postoperative white matter injury and stroke associated with neonatal surgery for CHD. The high incidence of postoperative injury observed despite new methodologies of CPB indicates the need for ongoing evaluation to optimize neurological outcome.

Nuchal Translucency and the Risk of Congenital Heart Disease

OBJECTIVE

To estimate whether nuchal translucency assessment is a useful screening tool for major congenital heart disease (CHD) in the absence of aneuploidy.

METHODS

Unselected patients with singleton pregnancies at 10(3/7) to 13(6/7) weeks of gestation were recruited at 15 U.S. centers to undergo nuchal translucency sonography. Screening characteristics of nuchal translucency in the detection of major CHD were determined using different cutoffs (2.0 or more multiples of the median [MoM], 2.5 or more MoM, 3.0 or more MoM).

RESULTS

A total of 34,266 euploid fetuses with cardiac outcome data were available for analysis. There were 224 cases of CHD (incidence 6.5 per 1,000), of which 52 (23.2%) were major (incidence 1.5 per 1,000). The incidence of major CHD increased with increasing nuchal translucency: 14.1 per 1,000, 33.5 per 1,000, and 49.5 per 1,000 at 2.0 or more MoM, 2.5 or more MoM, and 3.0 or more MoM cutoffs, respectively. Sensitivity, specificity, and positive predictive values were 15.4%, 98.4%, and 1.4% at 2.0 or more MoM; 13.5%, 99.4%, and 3.3% at 2.5 or more MoM; and 9.6%, 99.7%, and 5.0% at 3.0 or more MoM. Nuchal translucency of 2.5 or more MoM (99th percentile) had a likelihood ratio (95% confidence interval) of 22.5 (11.4-45.5) for major CHD. Based on our data, for every 100 patients referred for fetal echocardiography with a nuchal translucency of 99th percentile or more, three will have a major cardiac anomaly.

CONCLUSION

Nuchal translucency sonography in the first trimester lacks the characteristics of a good screening tool for major CHD in a large unselected population. However, nuchal translucency of 2.5 or more MoM (99th percentile or more) should be considered an indication for fetal echocardiography.

LEVEL OF EVIDENCE

II.

Microinjecting recombinant rainbow trout Ea4-peptide of pro-IGF-I into zebrafish embryos causes abnormal development in heart, red blood cells, and vasculature

E-peptides and mature insulin-like growth factors (IGFs) are produced from pre-pro-IGFs during post-translational processing and co-secreted into the circulation. Previously, we reported that introduction of a transgene encoding the secreted form of rainbow trout (rt) Ea4-peptide or human (h) Eb-peptide into newly fertilized eggs of medaka (Oryzias latipes) and zebrafish (Danio rerio) resulted in developmental defects in heart, red blood cells and vasculature. In addition to vasculature and red blood cell developmental defects, multiple phenocopies of heart developmental defects categorized by developmental arrest at cardiomyocyte, heart tube and heart looping stages were also observed. These results raise a question of whether rtEa4- or hEb-peptide exerts pleiotropic inhibitory effects on heart, vasculature and red blood cell development in fish embryos. To answer this question, various amounts of recombinant rtEa4-peptide were microinjected into zebrafish eggs at 1.5, 2.5 and 5.5 h post-fertilization (hpf). Although a dose-dependent developmental defect in heart, vasculature and red blood cells was observed in embryos microinjected with rtEa4-peptide at 1.5 and 2.5 hpf, the heart development in all of the microinjected embryos was arrested at the cardiomyocyte stage. Furthermore, the mRNA levels of Nkx2.5, GATA5, VEGF, GATA1 and GATA2 genes in defective embryos were significantly reduced by rtEa4-peptide. These results confirm our previous findings that rtEa4- or hEb-peptide exhibits pleiotropic effects in inhibiting heart, vasculature and red blood cell development in zebrafish embryos.

MEKK4 regulates developmental EMT in the embryonic heart

Congenital heart malformations occur at a rate of one per one hundred births and are considered the most frequent birth defects. This high incidence of cardiac defects underscores the complex developmental processes required to form the first functioning organ in mammals. The molecular cues which govern heart development are poorly defined and require an improved understanding in order to advance repair strategies for heart defects. The cytoplasmic MAP kinase kinase kinase, MEKK4, is a critical effector in cellular stress responses; however, the function of MEKK4 during embryonic development and cardiogenesis is not well understood. We have identified MEKK4 as a critical signaling molecule during cardiovascular development. We report the detection of MEKK4 transcripts to early myocardium, endocardium and to cardiac cushion cells that have executed epithelial to mesenchymal transformation (EMT). These observations suggest that MEKK4 may function during production of the cushion mesenchyme as required to create valves and the septated heart. We used a kinase inactive form of MEKK4(MEKK4(KI)) in an in vitro assay that recapitulates in vivo EMT, and show that MEKK4(KI) attenuates mesenchyme production. However, addition of a constitutively active MEKK4 into ventricular explants, a system that does not normally undergo EMT, is not able to cause mesenchymal cell outgrowth. Thus, the kinase activity of MEKK4 is essential, but not sufficient, to support developmental EMT. This knowledge provides a basis to understand how MEKK4 may integrate signaling cascades controlling heart development.

Malformation rate and sex ratio in 412 children conceived with epididymal or testicular sperm

BACKGROUND

Follow-up studies of children conceived after ICSI using epididymal or testicular sperm are important due to a still more extensive use of immature male germ cells for ICSI. It is, however, difficult to evaluate the potential risks of malformations of children born after ICSI, overcoming the natural fertilization processes, due to methodological limitations.

METHODS

Follow-up study including all children born in Denmark and Norway following ICSI in Denmark, using epididymal or testicular sperm, was done. A questionnaire was sent to the parents between 3 months and 7 years after delivery.

RESULTS

Of 341 couples, 329 returned the questionnaire giving a response rate of 96.5%. The study included 412 children, 225 girls and 187 boys, giving a sex ratio (males/males + females) of 45.4% compared with 53.1% in Danish children conceived after conventional IVF without ICSI (P < 0.005). Among a total of 14 (3.4%; 95% confidence interval (CI): 1.9%-5.7%) major malformations, three boys with hypospadias were the most remarkable finding (1.6%; 95% CI: 0.33-4.7%).

CONCLUSIONS

An increased frequency of hypospadias in the male offsprings was seen compared with the general population. Apart from this, no increased major malformation rate was detected in ICSI children conceived with epididymal or testicular sperm when compared with malformation rates for IVF or spontaneously conceived children reported in the literature. The sex ratio was significantly lower for ICSI children conceived with epididymal or testicular sperm when compared with children conceived with conventional IVF.

MTRR 66A>G polymorphism in relation to congenital heart defects

BACKGROUND

Evidence is accumulating that periconceptional folic acid supplementation may prevent congenital heart defects (CHD). The methionine synthase reductase (MTRR) enzyme restores methionine synthase (MTR) enzyme activity and therefore plays an essential role in the folate- and vitamin B(12)-dependent remethylation of homocysteine to methionine. We studied the influence of the MTRR 66A>G polymorphism on CHD risk. In addition, possible interaction between this variant and plasma methylmalonic acid (MMA) concentrations, as an indicator of intracellular vitamin B(12) status, was investigated.

METHODS

Case-control and case-parental studies were conducted to explore this association. In total, 169 CHD patients and 213 child controls, and 159 mothers with a CHD-affected child and 245 female controls were included.

RESULTS

The maternal MTRR 66AG and GG vs. AA genotypes revealed an odds ratio (OR) of 1.3 (95% CI 0.72-2.20) and 1.3 (0.71-2.37), respectively. Family-based transmission disequilibrium analysis did not reveal a significant association of the foetal 66G allele with the development of a heart defect in children (chi(2)=2.94, p=0.086). Maternal 66GG genotype in combination with high MMA concentration (above the 80th percentile) was associated with a three-fold (OR 3.3, 95% CI 0.86-12.50) increased risk for all types of CHD in offspring.

CONCLUSIONS

These data indicate that maternal MTRR 66A>G polymorphism is not a risk factor for CHD. Maternal MTRR 66GG genotype with compromised vitamin B(12) status may possibly result in increased CHD risk. In addition to folate, vitamin B(12) supplementation may contribute to the prevention of CHD.

Congenital heart disease in the general population: changing prevalence and age distribution

BACKGROUND

Empirical data on the changing epidemiology of congenital heart disease (CHD) are scant. We determined the prevalence, age distribution, and proportion of adults and children with severe and other forms of CHD in the general population from 1985 to 2000.

METHODS AND RESULTS

Where healthcare access is universal, we used administrative databases that systematically recorded all diagnoses and claims. Diagnostic codes conformed to the International Classification of Disease, ninth revision. Severe CHD was defined as tetralogy of Fallot, truncus arteriosus, transposition complexes, endocardial cushion defects, and univentricular heart. Prevalence of severe and other CHD lesions was determined in 1985, 1990, 1995, and 2000 using population numbers in Quebec. Children were subjects <18 years of age. The prevalence was 4.09 per 1000 adults in the year 2000 for all CHD and 0.38 per 1000 (9%) for those with severe lesions. Female subjects accounted for 57% of the adult CHD population. The median age of all patients with severe CHD was 11 years (interquartile range, 4 to 22 years) in 1985 and 17 years (interquartile range, 10 to 28 years) in 2000 (P<0.0001). The prevalence of severe CHD increased from 1985 to 2000, but the increase in adults was significantly higher than that observed in children. In the year 2000, 49% of those alive with severe CHD were adults.

CONCLUSIONS

The prevalence in adults and median age of patients with severe CHD increased in the general population from 1985 to 2000. In 2000, there were nearly equal numbers of adults and children with severe CHD.

Evidence in favor of linkage to human chromosomal regions 18q, 5q and 13q for bicuspid aortic valve and associated cardiovascular malformations

The aim of this study was to identify regions of the genome that harbor genes influencing inheritance of bicuspid aortic valve (BAV) and/or associated cardiovascular malformation (CVM). Aortic valve disease is an important clinical problem, which often results in valve replacement, the second most common cardiac surgery in the United States. In every age group, a majority of cases of valve disease involves a BAV. BAV is the most common CVM with a reported prevalence of 1-2%. Heritability studies indicate that BAV determination is almost entirely genetic. We used a family-based genome-wide linkage analysis with microsatellite markers. Parametric and nonparametric analyses were performed with the software GENEHUNTER and SOLAR (Sequential Oligogenic Linkage Analysis Routines). Thirty-eight families (353 subjects) with BAV and/or associated CVM were assessed. Each participant underwent a standardized echocardiographic examination. The highest LOD score, 3.8, occurred on chromosome 18q between markers D18S68 and D18S1161. Two other chromosomal regions, 5q15-21 (between D5S644 and D5S2027) and 13q33-qter (between D13S1265 and 13qter), exhibited suggestive evidence of linkage (LOD > 2.0). Further, two previously reported linkage peaks on 9q34 and 17q24 were replicated in family specific analyses. No significant X chromosome linkage peaks were identified. In this genome-wide scan we demonstrate for the first time, that BAV and/or associated CVM exhibit linkage to chromosomes 18q, 5q and 13q. These regions likely contain genes whose mutation results in BAV and/or associated CVM indicating their important role in valvulogenesis and cardiac development.

Essential functions of Alk3 during AV cushion morphogenesis in mouse embryonic hearts

Accumulated evidence has suggested that BMP pathways play critical roles during mammalian cardiogenesis and impairment of BMP signaling may contribute to human congenital heart diseases (CHDs), which are the leading cause of infant morbidity and mortality. Alk3 encodes a BMP specific type I receptor expressed in mouse embryonic hearts. To reveal functions of Alk3 during atrioventricular (AV) cushion morphogenesis and to overcome the early lethality of Alk3(-/-) embryos, we applied a Cre/loxp approach to specifically inactivate Alk3 in the endothelium/endocardium. Our studies showed that endocardial depletion of Alk3 severely impairs epithelium-mesenchymal-transformation (EMT) in the atrioventricular canal (AVC) region; the number of mesenchymal cells formed in Tie1-Cre;Alk3(loxp/loxp) embryos was reduced to only approximately 20% of the normal level from both in vivo section studies and in vitro explant assays. We showed, for the first time, that in addition to its functions on mesenchyme formation, Alk3 is also required for the normal growth/survival of AV cushion mesenchymal cells. Functions of Alk3 are accomplished through regulating expression/activation/subcellular localization of multiple downstream genes including Smads and cell-cycle regulators. Taken together, our study supports the notion that Alk3-mediated BMP signaling in AV endocardial/mesenchymal cells plays a central role during cushion morphogenesis.

Exercise prescription for patients with a Fontan circulation: current evidence and future directions

It is well documented that children with a Fontan circulation have a reduced exercise capacity. One of the modalities to improve exercise capacity might be exercise training. We performed a systematic literature review on the effects of exercise training in patients with a Fontan circulation. Six published studies were included that reported on the effects of exercise training in 40 patients. All studies had a small sample size and/or did not include a control group.Based on the six published studies we can conclude that children who have undergone a Fontan operation and who are in a stable haemodynamic condition can safely participate in an exercise training programme and that exercise training results in an improved exercise capacity. However, more research is needed to establish the optimal exercise mode, dose-response relation, and the effects of exercise training on cardiac function, peripheral muscle function, physical activity, and health-related quality of life. (Neth Heart J 2007;15:142-7.).

The genetics of cardiac birth defects

Congenital heart disease likely results from a complex mixture of environmental and genetic factors. Recent work has elucidated rare single gene mutations that cause a variety of cardiac defects, but the etiologies of more common disease remains unknown. Here, we review the known genetic causes of cardiac malformations and discuss future approaches for addressing sporadic congenital heart disease as a complex trait.

The paradoxical patent ductus arteriosus

The ductus arteriosus (DA) is a vessel whose patency is required for fetal survival but is incompatible with postnatal life. Because of developmental insufficiency, the DA in preterm infants often fails to close in a condition known as patent DA (PDA). Although COX inhibitors can be used to close the PDA by lowering circulating prostaglandin levels, their effectiveness is correlated with birth weight, and severely premature infants often require surgical repair. Paradoxically, targeted deletion of COX pathway components in mice results in PDA. In this issue of the JCI, Yokoyama et al. describe dual roles for prostaglandins in DA development and closure, offering new insights into the mechanism of negative effects of COX inhibitors that may influence the treatment of severely premature infants with PDA and lead to improvement of their outcomes (see the related article beginning on page 3026).

Patent Foramen Ovale: Assessment, Clinical Significance and Therapeutic Options

Foramen ovale plays an important function in the fetus but is of no physiologic significance after birth and closes in most individuals. In about one fourth of the population, however, foramen ovale remains open for life and has been associated with cerebrovascular accidents, especially in younger patients, presumably through paradoxical embolism. Patent foramen ovale (PFO) has also been associated with hypoxia, migraine headaches and neurologic findings of decompression illness in scuba divers. Availability of transesophageal echocardiography and its frequent use in the management of patients with stroke has lead to frequent detection of PFO. In addition, the recent development of devices and techniques for percutaneous closure of PFO has resulted in widespread enthusiasm for such interventions, even when a clear etiologic role for PFO may not be established. In the United States, the Federal Drug Administration (FDA) has approved two such devices through compassionate investigational device exemption without adequate data from large randomized clinical studies. Other such devices are undergoing evaluation in clinical trials. Expert opinions have been helpful for clinical decision making in management of patients with PFO associated with stroke, hypoxia, decompression sickness and migraine headaches.

Ventricular Septal Defects

Ventricular septal defects are the most common congenital heart defect. They vary greatly in location, clinical presentation, associated lesions, and natural history. The present article describes the clinical aspects of ventricular septal defects and current management strategies.

Apoptosis in the developing mouse heart

Apoptosis occurs at high frequency in the myocardium of the developing avian cardiac outflow tract (OFT). Up- or down-regulating apoptosis results in defects resembling human conotruncal heart anomalies. This finding suggested that regulated levels of apoptosis are critical for normal morphogenesis of the four-chambered heart. Recent evidence supports an important role for hypoxia of the OFT myocardium in regulating cell death and vasculogenesis. The purpose of this study was to determine whether apoptosis in the outflow tract myocardium occurs in the mouse heart during developmental stages comparable to the avian heart and to determine whether differential hypoxia is also present at this site in the murine heart. Apoptosis was detected using a fluorescent vital dye, Lysotracker Red (LTR), in the OFT myocardium of the mouse starting at embryonic day (E) 12.5, peaking at E13.5-14.5, and declining thereafter to low or background levels by E18.5. In addition, high levels of apoptosis were detected in other cardiac regions, including the apices of the ventricles and along the interventricular sulcus. Apoptosis in the myocardium was detected by double-labeling with LTR and cardiomyocyte markers. Terminal deoxynucleotidyl transferase-mediated deoxyuridinetriphosphate nick end-labeling (TUNEL) and immunostaining for cleaved Caspase-3 were used to confirm the LTR results. At the peak of OFT apoptosis in the mouse, the OFT myocardium was relatively hypoxic, as indicated by specific and intense EF5 staining and HIF1alpha nuclear localization, and was surrounded by the developing vasculature as in the chicken embryo. These findings suggest that cardiomyocyte apoptosis is an evolutionarily conserved mechanism for normal morphogenesis of the outflow tract myocardium in avian and mammalian species.

Making or breaking the heart: from lineage determination to morphogenesis

The cues governing cardiac cell-fate decisions, cardiac differentiation, and three-dimensional morphogenesis are rapidly being elucidated. Several themes are emerging that are relevant for childhood and adult heart disease and the growing field of stem cell biology. This review will consider our current understanding of cardiac cell-fate determination and cardiogenesis--largely derived from developmental studies in model organisms and human genetic approaches--and examine future implications for diagnosis, prevention, and treatment of heart disease in the young and old.

Tgfbeta signaling is required for atrioventricular cushion mesenchyme remodeling during in vivo cardiac development

The transforming growth factorbeta (Tgfbeta) signaling pathway plays crucial roles in many biological processes. To understand the role(s) of Tgfbeta signaling during cardiogenesis in vivo and to overcome the early lethality of Tgfbr2(-/-) embryos, we applied a Cre/loxp system to specifically inactivate Tgfbr2 in either the myocardium or the endothelium of mouse embryos. Our results show that Tgfbr2 in the myocardium is dispensable for cardiogenesis in most embryos. Contrary to the prediction from results of previous in vitro collagen gel assays, inactivation of Tgfbr2 in the endocardium does not prevent atrioventricular cushion mesenchyme formation, arguing against its essential role in epithelium-mesenchyme transformation in vivo. We further demonstrate that Tgfbeta signaling is required for the proper remodeling of the atrioventricular canal and for cardiac looping, and that perturbation in Tgfbeta signaling causes the double-inlet left ventricle (DILV) defect. Thus, our study provides a unique mouse genetic model for DILV, further characterization of which suggests a potential cellular mechanism for the defect.

Prevalence of congenital heart disease in schoolchildren of sub-Saharan Africa, Mozambique

A survey conducted by cardiologists in Mozambique provided an opportunity for assessing the prevalence of congenital heart disease in public school children in Maputo. After randomization, a total of 2170 children were examined. Five children had clinical and echographic evidence of congenital heart disease, corresponding to a prevalence of 2.3 in 1000 (95% confidence interval: 1.0 to 5.4), 80% newly discovered during the survey. These findings confirm that congenital heart disease is at least as common in this South African black community as in Caucasians. Early detection of these cardiac diseases in children is important in order to prevent serious complications and to institute endocarditis prevention.

Molecular and cellular basis of congenital heart disease

The cellular and molecular basis of congenital heart disease (CHD) is an evolving area of rapid discovery. This article introduced the basic mechanisms underlying cardiac development and CHD in order to permit a clear understanding of current diagnostics and therapeutics and their future development. It is clear that although significant advances have been made in understanding mechanisms controlling heart formation, the direct causes of CHD remain poorly defined. Future studies tha delineate the complexity of these mechanisms are required to provide a comprehensive understanding of the etiologies of CHD. Such understanding will lead to the development of novel approaches to prevention and therapy.

Report of the Tennessee Task Force on Screening Newborn Infants for Critical Congenital Heart Disease

A member of the Tennessee state legislature recently proposed a bill that would mandate all newborn infants to undergo pulse oximetry screening for the purpose of identifying those with critical structural heart disease before discharge home. The Tennessee Task Force on Screening Newborn Infants for Critical Congenital Heart Defects was convened on September 29, 2005. This group reviewed the current medical literature on this topic, as well as data obtained from the Tennessee Department of Health, and debated the merits and potential detriments of a statewide screening program. The estimated incidence of critical congenital heart disease is 170 in 100,000 live births, and of those, 60 in 100,000 infants have ductal-dependent left-sided obstructive lesions with the potential of presentation by shock or death if the diagnosis is missed. Of the latter group, the diagnosis is missed in approximately 9 in 100,000 by fetal ultrasound assessment and discharge examination and might be identified by a screening program. Identification of the missed diagnosis in these infants before discharge could spare many of them death or neurologic sequelae. Four major studies using pulse oximetry screening were analyzed, and when data were restricted to critical left-sided obstructive lesions, sensitivity values of 0% to 50% and false-positive rates of between 0.01% and 12% were found in asymptomatic populations. Because of this variability and other considerations, a meaningful cost/benefit analysis could not be performed. It was the consensus of the task force to provide a recommendation to the legislature that mandatory screening not be implemented at this time. In addition, we determined that a very large, prospective, perhaps multistate study is needed to define the sensitivity and false-positive rates of lower-limb pulse oximetry screening in the asymptomatic newborn population and that there needs to be continued partnering between the medical community, parents, and local, state, and national governments in decisions regarding mandated medical care.

Rosiglitazone antagonizes vascular endothelial growth factor signaling and nuclear factor of activated T cells activation in cardiac valve endothelium

Nuclear factor of activated T cells, Cytoplasmic 1 (NFATc1) is required for heart valve formation. Vascular endothelial growth factor (VEGF) signaling, mediated by NFATc1 activation, positively regulates growth of valvular endothelial cells. However, regulators of VEGF/NFATc1 signaling in valve endothelium are poorly understood. Peroxisome proliferator-activated receptor gamma (PPARgamma) inhibits NFATc1 activity in T cells and cardiomyocytes, but it is not known if PPARgamma controls NFATc1 function in endothelial cells. The authors hypothesize PPARgamma antagonizes VEGF signaling in valve endothelium by inhibiting NFATc1. Endothelial cells isolated from human valve leaflet tissue were shown by immunocytochemistry to express the endothelial-specific markers von Willebrand factor (vWF) and platelet endothelial cell adhesion molecule (PECAM)-1. VEGF-induced proliferation and migration of human pulmonary valve endothelial cells (HPVECs) were inhibited by rosiglitazone (ROSI), a specific ligand of PPARgamma activation, suggesting that PPARgamma disrupts VEGF signaling in the valve endothelium. ROSI also antagonized VEGF-mediated NFATc1 nuclear translocation in HPVECs, suggesting that PPARgamma inhibits VEGF signaling of NFATc1 activation in the valve. The effect of ROSI on nonvalve human umbilical vein endothelial cells (HUVECs) was tested in parallel and a similar inhibition of NFATc1 activation was observed. These data provide the first demonstration that ROSI negatively regulates VEGF signaling in the valve endothelium by a mechanism involving NFATc1 activation and nuclear translocation.

Neurocognitive consequences of surgically corrected congenital heart defects: A review

With advances in surgical procedures, neuropsychological assessment after congenital heart defects and pre, peri- and/or postoperative predictors of adverse outcome has become an important focus in research. We aim to summarize neuropsychological sequelae associated with different types of congenital heart defects, critically review the methodology used in more than 20 empirical studies that were retrieved from biomedical electronic search engines, and identify possible directions for future research. Despite the lack of adequate control groups and long-term studies, there seem to be some cognitive deficits. The largest group of children with isolated congenital heart defects present with normal intellectual capacities. However, they tend to show language deficits and motor dysfunction. Although performances on memory tasks are good, unambiguous conclusions concerning their attentional and executive functioning are still lacking. Serious behavioral problems are not an issue. In addition to a detailed description of the (neuro) psychological consequences of pediatric cardiac surgery, an overview of the predictors of the cognitive defects is provided.

Évolution du diagnostic prénatal, des interruptions de grossesse et de la mortalité périnatale des enfants avec cardiopathie congénitale

OBJECTIVE

To examine population-based overall and malformation-specific trends in the prenatal diagnosis, pregnancy termination, and perinatal mortality for congenital heart disease (CHD) during a period of rapid progress in prenatal diagnosis and medical management of CHD and to explore the impact of prenatal diagnosis on early neonatal mortality for specific (isolated) cardiac malformations.

METHODS

A total of 1982 cases of CHD, which were not associated with a known chromosomal anomaly, were obtained from the Paris Registry of Congenital Malformations. Main outcome measures were trends in the proportions diagnosed and terminated prior to birth, stillbirth and early (<1 day, one-week) neonatal mortality for (1) all cases; (2) all cases excluding isolated ventricular septal defects; and (3) malformation-specific trends for transposition of great arteries, hypoplastic left heart syndrome, coarctation of aorta, and tetralogy of Fallot. Analyses included cusum and binomial regression models for analysis of the trends during 1983-2000.

RESULTS

Prenatal diagnosis rates for CHD increased from 23.0% (95%CI: 19.0-27.4) in 1983-1988 to 47.3% (95%CI: 43.8-50.8) in 1995-2000. Termination rates increased between 1983 and 1989 (9.9%; 95%CI: 7.2-13.2) and 1989 and 1994 (14.7%; 95%CI: 12.3-17.4) but seemed to remain stable thereafter. Other than for hypoplastic left heart syndrome, pregnancy termination was exceptional for the other 3 specific malformations examined. Early neonatal mortality decreased to less than a third in the period 1995-2000 as compared with 1983-1989 (risk ratio, first week mortality: 0.31; 95%CI: 0.18-0.53). First week mortality was significantly lower for cases of transposition of great arteries diagnosed before birth (risk difference: 15.4%; 95% CI: 4.0-26.7).

CONCLUSION

Progress in clinical management, together with policies for increased access to prenatal diagnosis, has resulted in both a substantial increase in the prenatal diagnosis and considerable reductions in early neonatal mortality of CHD in the Parisian population.

Rendering in fetal cardiac scanning: the intracardiac septa and the coronal atrioventricular valve planes

OBJECTIVE

In this study we aimed to apply spatio-temporal image correlation (STIC) rendering to visualize the virtual planes of the interventricular and interatrial septa (IVS, IAS) as well as the atrioventricular (AV) annuli plane just distal to the semilunar valves (coronal atrioventricular (CAV) plane) in normal and pathological fetal hearts, to ascertain whether these planes add to fetal cardiac examination.

METHODS

Unselected gravidae presenting for anatomy scan or patients referred for fetal echocardiography in the second and third trimesters of pregnancy with suspected or diagnosed cardiac malformation were scanned using the five planes technique with the STIC modality to obtain cardiac volume sets for each patient. Rendering capabilities were employed to obtain the 'virtual planes' to evaluate the IVS, IAS, AV annuli, and size and alignment of the great vessels.

RESULTS

A total of 136 normal scans were performed to establish a learning curve for STIC acquisition and post-processing rendering and analysis. An additional 35 cases with cardiac anomalies were accrued. In 131/136 (96.3%) normal scans the IAS and IVS were visualized successfully, while in 127/136 (93.4%) normal fetuses the CAV plane was successfully visualized. In 13 anomalous cases the IVS plane improved ventricular septal defect (VSD) evaluation, and in four the IAS plane contributed to foramen ovale evaluation. The modality improved visualization of the septa and the assessment of the defects, as well as the foramen ovale flap and pattern of movement of the foramen ovale. In five cases the CAV plane improved evaluation of the alignment of the major vessels in relation to the AV annuli, and in three the evaluation of the semilunar valves, with or without malalignment of the great vessels.

CONCLUSIONS

Rendering STIC technology allows the visualization of virtual planes (IAS, IVS, AV annuli-CAV plane), which can clarify our understanding of anatomical defects and may improve communication with the management team and family.

Cyclic flexure and laminar flow synergistically accelerate mesenchymal stem cell-mediated engineered tissue formation: Implications for engineered heart valve tissues

Bone marrow-derived mesenchymal stem cells (BMSCs) are relatively accessible and exhibit a pluripotency suitable for cardiovascular applications such as tissue-engineered heart valves (TEHVs). Recently, Sutherland et al. [From stem cells to viable autologous semilunar heart valve. Circulation 2005; 111(21): 2783-91] demonstrated that BMSC-seeded TEHV can successfully function as pulmonary valve substitutes in juvenile sheep for at least 8 months. Toward determining appropriate mechanical stimuli for use in BMSC-seeded TEHV cultivation, we investigated the independent and coupled effects of two mechanical stimuli physiologically relevant to heart valves-cyclic flexure and laminar flow (i.e. fluid shear stress)-on BMSC-mediated tissue formation. BMSC isolated from juvenile sheep were expanded and seeded onto rectangular strips of nonwoven 50:50 blend poly(glycolic acid) (PGA) and poly(l-lactic acid) (PLLA) scaffolds. Following 4 days static culture, BMSC-seeded scaffolds were loaded into a novel flex-stretch-flow (FSF) bioreactor and incubated under static (n=12), cyclic flexure (n=12), laminar flow (avg. wall shear stress=1.1505 dyne/cm(2); n=12) and combined flex-flow (n=12) conditions for 1 (n=6) and 3 (n=6) weeks. By 3 weeks, the flex-flow group exhibited dramatically accelerated tissue formation compared with all other groups, including a 75% higher collagen content of 844+/-278 microg/g wet weight (p<0.05), and an effective stiffness (E) value of 948+/-233 kPa. Importantly, collagen and E values were not significantly different from values measured for vascular smooth muscle cell (SMC) -seeded scaffolds incubated under conditions of flexure alone [Engelmayr et al. The independent role of cyclic flexure in the early in vitro development of an engineered heart valve tissue. Biomaterials 2005; 26(2): 175-87], suggesting that BMSC-seeded TEHV can be optimized to yield results comparable to SMC-seeded TEHV. We thus demonstrated that cyclic flexure and laminar flow can synergistically accelerate BMSC-mediated tissue formation, providing a basis for the rational design of in vitro conditioning regimens for BMSC-seeded TEHV.

Bridging the gap between anatomy and molecular genetics for an improved understanding of congenital heart disease

Birth defects are the leading cause of infant mortality and malformations in congenital heart disease (CHD) are among the most prevalent and fatal of all birth defects. Yet the molecular mechanisms leading to CHD are complex and the causes of the cardiac malformations observed in humans are still unclear. In recent years, the pivotal role of certain transcription factors in heart development has been demonstrated, and gene targeting of cardiac-specific transcription factor genes in animal models has provided valuable insights into heart anomalies. Nonetheless results in these models can be species specific, and in humans, germline mutations in transcription factor genes can only account for some cases of CHD. Furthermore, most patients do not have family history of CHD. There is, therefore, a need for a better understanding of the mechanisms in both normal cardiac development and the formation of malformations. The combining of expertise in cardiac anatomy, pathology, and molecular genetics is essential to adequately comprehend developmental abnormalities associated with CHD. To help elucidate genetic alterations in affected tissues of malformed hearts, we carried out genetic analysis of cardiac-specific transcription factor genes from the Leipzig collection of formalin-fixed malformed hearts. Working with this morphologically well-characterized archival material not only provided valuable genetic information associated with disease, but enabled us to put forward a hypothesis of somatic mutations as a novel molecular cause of CHD. Knowledge of cause and disease mechanism may allow for intervention that could modify the degree of cardiac malformations or development of new approaches for prevention of CHD.

Regionalized sequence of myocardial cell growth and proliferation characterizes early chamber formation

Increase in cell size and proliferation of myocytes are key processes in cardiac morphogenesis, yet their regionalization during development of the heart has been described only anecdotally. We have made quantitative reconstructions of embryonic chicken hearts ranging in stage from the fusion of the heart-forming fields to early formation of the chambers. These reconstructions reveal that the early heart tube is recruited from a pool of rapidly proliferating cardiac precursor cells. The proliferation of these small precursor cells ceases as they differentiate into overt cardiomyocytes, producing a slowly proliferating straight heart tube composed of cells increasing in size. The largest cells were found at the ventral side of the heart tube, which corresponds to the site of the forming ventricle, as well as the site where proliferation is reinitiated. The significance of these observations is 2-fold. First, they support a model of early cardiac morphogenesis in 2 stages. Second, they demonstrate that regional increase in size of myocytes contributes significantly to chamber formation.

Analysis of Fibroblast growth factor 15 cis-elements reveals two conserved enhancers which are closely related to cardiac outflow tract development

Fibroblast growth factor 15 (Fgf15) is expressed in the developing mouse central nervous system and pharyngeal arches. Fgf15 mutant mice showed defects of the cardiac outflow tract probably because of aberrant behavior of the cardiac neural crest cells. In this study, we examined cis-elements of the Fgf15 gene by transient transgenic analysis using lacZ as a reporter. We identified two enhancers: one directed lacZ expression in the hindbrain/spinal cord and the other in the posterior midbrain (pmb), rhombomere1 (r1) and pharyngeal epithelia. Interestingly, human genomic regions which are highly homologous to these two mouse enhancers showed almost the same enhancer activities as those of mice in transgenic mouse embryos, indicating that the two enhancers are conserved between humans and mice. We also showed that the mouse and human pmb/r1 enhancer can regulate lacZ expression in chick embryos in almost the same way as in mouse embryos. We found that the lacZ expression domain with this enhancer was expanded by ectopic Fgf8b expression, suggesting that this enhancer is regulated by Fgf8 signaling. Moreover, over-expression of Fgf15 resulted in up-regulation of Fgf8 expression in the isthmus/r1. These findings suggest that a reciprocal positive regulation exists between Fgf15 and Fgf8 in the isthmus/r1. Together with cardiac outflow tract defects in Fgf15 mutants, the conservation of enhancers in the hindbrain/spinal cord and pharyngeal epithelia suggests that human FGF19 (ortholog of Fgf15) is involved in early development and the distribution of cardiac neural crest cells and is one of the candidate genes for congenital heart defects.