Genetic study of congenital heart defects in Northern Ireland (1974-1978)

Evidence-Based Assessment of Congenital Heart Disease Genes to Enable Returning Results in a Genomic Study

BACKGROUND

Congenital heart disease (CHD) is the most common major congenital anomaly and causes significant morbidity and mortality. Epidemiologic evidence supports a role of genetics in the development of CHD. Genetic diagnoses can inform prognosis and clinical management. However, genetic testing is not standardized among individuals with CHD. We sought to develop a list of validated CHD genes using established methods and to evaluate the process of returning genetic results to research participants in a large genomic study.

METHODS

Two-hundred ninety-five candidate CHD genes were evaluated using a ClinGen framework. Sequence and copy number variants involving genes in the CHD gene list were analyzed in Pediatric Cardiac Genomics Consortium participants. Pathogenic/likely pathogenic results were confirmed on a new sample in a clinical laboratory improvement amendments-certified laboratory and disclosed to eligible participants. Adult probands and parents of probands who received results were asked to complete a post-disclosure survey.

RESULTS

A total of 99 genes had a strong or definitive clinical validity classification. Diagnostic yields for copy number variants and exome sequencing were 1.8% and 3.8%, respectively. Thirty-one probands completed clinical laboratory improvement amendments-confirmation and received results. Participants who completed postdisclosure surveys reported high personal utility and no decision regret after receiving genetic results.

CONCLUSIONS

The application of ClinGen criteria to CHD candidate genes yielded a list that can be used to interpret clinical genetic testing for CHD. Applying this gene list to one of the largest research cohorts of CHD participants provides a lower bound for the yield of genetic testing in CHD.

Genetic Basis of Human Congenital Heart Disease

Congenital heart disease (CHD) is the most common major congenital anomaly with an incidence of ∼1% of live births and is a significant cause of birth defect-related mortality. The genetic mechanisms underlying the development of CHD are complex and remain incompletely understood. Known genetic causes include all classes of genetic variation including chromosomal aneuploidies, copy number variants, and rare and common single-nucleotide variants, which can be either de novo or inherited. Among patients with CHD, ∼8%-12% have a chromosomal abnormality or aneuploidy, between 3% and 25% have a copy number variation, and 3%-5% have a single-gene defect in an established CHD gene with higher likelihood of identifying a genetic cause in patients with nonisolated CHD. These genetic variants disrupt or alter genes that play an important role in normal cardiac development and in some cases have pleiotropic effects on other organs. This work reviews some of the most common genetic causes of CHD as well as what is currently known about the underlying mechanisms.

Micro-computed tomography of isolated fetal hearts following termination of pregnancy: A feasibility study at 8 to 12 weeks' gestation

OBJECTIVES

To assess the feasibility of retrieval of intact human fetal hearts after first trimester surgical termination of pregnancy (TOP) and subsequent anatomical assessment by postmortem micro-computed tomography (micro-CT).

METHODS

In a cohort of consenting women undergoing surgical TOP between 8 and 13 weeks' gestation, we attempted the retrieval of the fetal heart from the suction material. Specimens were immersion fixed in 10% formaldehyde, scanned by iodine-enhanced micro-CT and cardiac anatomy assessed by a multidisciplinary team using 3D-multiplanar analysis.

RESULTS

The median gestational age at TOP was 10.7 weeks (range 8.3-12.9). In 57 (95.0%) out of 60 suction specimens, the heart could be retrieved. The median cardiac length was 5 mm (range 2-8 mm), in three (5.3%), the heart was too damaged to assess cardiac anatomy and in five (8.7%) only the four chambers could be examined. In the remaining 49 (86.0%) cases, a detailed assessment of cardiac anatomy was possible, showing a major defect in two (4.1%) and a minor defect in four (8.2%).

CONCLUSIONS

Fetal hearts can be retrieved after first trimester TOP being intact in the vast majority of cases. Iodine-enhanced, postmortem micro-CT can be used to assess cardiac anatomy from as early as 8 weeks and to describe heart abnormalities.

Congenital heart disease and chromossomopathies detected by the karyotype

OBJECTIVE:

To review the relationship between congenital heart defects and chromosomal abnormalities detected by the karyotype.

DATA SOURCES:

Scientific articles were searched in MEDLINE database, using the descriptors "karyotype" OR "chromosomal" OR "chromosome" AND "heart defects, congenital". The research was limited to articles published in English from 1980 on.

DATA SYNTHESIS:

Congenital heart disease is characterized by an etiologically heterogeneous and not well understood group of lesions. Several researchers have evaluated the presence of chromosomal abnormalities detected by the karyotype in patients with congenital heart disease. However, most of the articles were retrospective studies developed in Europe and only some of the studied patients had a karyotype exam. In this review, only one study was conducted in Latin America, in Brazil. It is known that chromosomal abnormalities are frequent, being present in about one in every ten patients with congenital heart disease. Among the karyotype alterations in these patients, the most important is the trisomy 21 (Down syndrome). These patients often have associated extra-cardiac malformations, with a higher risk of morbidity and mortality, which makes heart surgery even more risky.

CONCLUSIONS:

Despite all the progress made in recent decades in the field of cytogenetic, the karyotype remains an essential tool in order to evaluate patients with congenital heart disease. The detailed dysmorphological physical examination is of great importance to indicate the need of a karyotype.

Prognosis and Risk Factors for Congenital Airway Anomalies in Children with Congenital Heart Disease: A Nationwide Population-Based Study in Taiwan

BACKGROUND

The mortality risk associated with congenital airway anomalies (CAA) in children with congenital heart disease (CHD) is unclear. This study aimed to investigate the factors associated with CAA, and the associated mortality risk, among children with CHD.

METHODS

This nationwide, population-based study evaluated 39,652 children with CHD aged 0-5 years between 2000 and 2011, using the Taiwan National Health Insurance Research Database (NHIRD). We performed descriptive, logistic regression, Kaplan-Meier, and Cox regression analyses of the data.

RESULTS

Among the children with CHD, 1,591 (4.0%) had concomitant CAA. Children with CHD had an increased likelihood of CAA if they were boys (odds ratio [OR], 1.48; 95% confidence interval [CI], 1.33-1.64), infants (OR, 5.42; 95%CI, 4.06-7.24), or had a congenital musculoskeletal anomaly (OR, 3.19; 95%CI, 2.67-3.81), and were typically identified 0-3 years after CHD diagnosis (OR, 1.33; 95%CI 1.17-1.51). The mortality risk was increased in children with CHD and CAA (crude hazard ratio [HR], 2.05; 95%CI, 1.77-2.37), even after adjusting for confounders (adjusted HR, 1.76; 95%CI, 1.51-2.04). Mortality risk also changed by age and sex (adjusted HR and 95%CI are quoted): neonates, infants, and toddlers and preschool children, 1.67 (1.40-2.00), 1.93 (1.47-2.55), and 4.77 (1.39-16.44), respectively; and boys and girls, 1.62 (1.32-1.98) and 2.01 (1.61-2.50), respectively.

CONCLUSION

The mortality risk is significantly increased among children with CHD and comorbid CAA. Clinicians should actively seek CAA during the follow-up of children with CHD.

Prenatal Isolated Ventricular Septal Defect May Not Be Associated with Trisomy 21

The aim of this study was to examine if isolated fetal ventricular septal defect (VSD) is associated with trisomy 21. One hundred twenty six cases with prenatal VSD diagnosed by a pediatric cardiologist were reviewed. Cases with known risk factors for congenital heart disease, the presence of other major anomalies, soft signs for trisomy 21 or a positive screen test for trisomy 21 were excluded. Ninety two cases formed the study group. None of the cases in the study group had trisomy 21. The upper limit of prevalence for trisomy 21 in isolated VSD is 3%. When prenatal VSD is not associated with other major anomalies, soft markers for trisomy 21 or a positive nuchal translucency or biochemical screen, a decision whether to perform genetic amniocentesis should be individualized. The currently unknown association between isolated VSD and microdeletions and microduplications should be considered when discussing this option.

Unroofed coronary sinus in a patient with neurofibromatosis type 1

OBJECTIVE

To report the uncommon association between neurofibromatosis type 1 (NF1) and unroofed coronary sinus.

CASE DESCRIPTION

Girl with four years and six months old who was hospitalized for heart surgery. The cardiac problem was discovered at four months of life. On physical examination, the patient presented several café-au-lait spots in the trunk and the limbs and freckling of the axillary and groin regions. Her father had similar skin findings, suggesting the NF1 diagnosis. The cardiac evaluation by echocardiography disclosed an atrial septal defect of unroofed coronary sinus type. This cardiac finding was confirmed at surgery. The procedure consisted of the atrial septal defect repair with autologous pericardium.

COMMENTS

NF1 is a common autosomal dominant disorder caused by mutations in the NF1 gene. Among the NF1 findings, congenital heart defects are considered unusual. In the literature review, there was no association between NF1 and unroofed coronary sinus, which is a rare cardiac malformation, characterized by a communication between the coronary sinus and the left atrium, resultant from the partial or total absence of the coronary sinus roof. It represents less than 1% of atrial septal defect cases. More reports are important to determine if this association is real or merely casual, since NF1 is a common condition.

Chromosomal abnormalities in patients with congenital heart disease

Background

Chromosomal abnormalities (CAs) are an important cause of congenital heart disease (CHD).

Objective

Determine the frequency, types and clinical characteristics of CAs identified in a sample of prospective and consecutive patients with CHD.

Method

Our sample consisted of patients with CHD evaluated during their first hospitalization in a cardiac intensive care unit of a pediatric referral hospital in Southern Brazil. All patients underwent clinical and cytogenetic assessment through high-resolution karyotype. CHDs were classified according to Botto et al. Chi-square, Fisher exact test and odds ratio were used in the statistical analysis (p < 0.05).

Results

Our sample consisted of 298 patients, 53.4% males, with age ranging from 1 day to 14 years. CAs were observed in 50 patients (16.8%), and 49 of them were syndromic. As for the CAs, 44 (88%) were numeric (40 patients with +21, 2 with +18, 1 with triple X and one with 45,X) and 6 (12%) structural [2 patients with der(14,21), +21, 1 with i(21q), 1 with dup(17p), 1 with del(6p) and 1 with add(18p)]. The group of CHDs more often associated with CAs was atrioventricular septal defect.

Conclusions

CAs detected through karyotyping are frequent in patients with CHD. Thus, professionals, especially those working in Pediatric Cardiology Services, must be aware of the implications that performing the karyotype can bring to the diagnosis, treatment and prognosis and for genetic counseling of patients and families.

Congenital heart defects and major structural noncardiac anomalies, Atlanta, Georgia, 1968 to 2005

OBJECTIVE

To identify the proportion of major structural noncardiac anomalies identified with congenital heart defects (CHDs).

STUDY DESIGN

Records of infants with CHDs in the Metropolitan Atlanta Congenital Defects Program who were born during the period 1968 through 2005 were classified as having isolated, syndromic, multiple CHD (ie, having an unrecognized pattern of multiple congenital anomalies or a recognized pattern of multiple congenital anomalies of unknown etiology), or laterality defects. Frequencies of associated noncardiac anomalies were obtained.

RESULTS

We identified 7984 live-born and stillborn infants and fetuses with CHDs. Among them, 5695 (71.3%) had isolated, 1080 (13.5%) had multiple, 1048 (13.1%) had syndromic, and 161 (2.0%) had laterality defects. The percentage of multiple congenital anomalies was highest for case with atrial septal defects (18.5%), cardiac looping defects (17.2%), and conotruncal defects (16.0%), and cases with atrioventricular septal defects represented the highest percentages of those with syndromic CHDs (66.7%).

CONCLUSIONS

Including those with syndromes and laterality defects, 28.7% of case infants with CHDs had associated major noncardiac malformations. Thus, infants with CHDs warrant careful examination for the presence of noncardiac anomalies.

Cardiac malformations are increased in infants of mothers with epilepsy

We aimed to ascertain the prevalence of cardiac malformation (CM) and its association with antenatal exposure to an antiepileptic drug (AED) in infants of mothers with epilepsy (IMEs). Women with epilepsy (WWE) are enrolled in Kerala Registry of Epilepsy and Pregnancy (KREP) in the prepregnancy or early pregnancy period and are followed up with a standard protocol until the IMEs are 6 years old. At 3 months postpartum, a cardiologist, blinded to the AED exposure, carried out a clinical examination and echocardiography on all live-born babies. Patent foramen ovale (PFO) and interatrial septal defects of < 5 mm in size were excluded from CM. Details of maternal epilepsy, folate usage, AED exposure in the first trimester, and newborn characteristics were abstracted from the records of the KREP. We examined 462 babies. Maternal epilepsy was generalized in 201 (43.50%) or localization related in 241 (52.2%). The AED exposure was monotherapy in 262 (56.7%)--carbamazepine (112), valproate (71), phenobarbitone (43), phenytoin (31), and clonazepam (2)--and polytherapy in 126 (27.3%). Seventy-four infants (16.01%) had no AED exposure. There were 36 infants with CM (7.8%; 95% confidence interval: 5.5-10.6). CMs included atrial septal defect (26; 72.2%), tetrology of Fallot (3; 8.3%), patent ductus arteriosus and pulmonic stenosis (2 each; 5.6%), and ventricular septal defect, tricuspid regurgitation, transposition of great arteries (1 each; 2.8%). CMs were significantly more for IMEs with premature birth (p < .003). There was no association between CM and maternal age, epilepsy syndrome, seizure frequency during pregnancy, and folate use. CMs were more frequent with polytherapy (13; 10.3%) compared to monotherapy (17; 6.5%). Those with valproate exposure had a trend (not statistically significant) toward higher frequency of CM compared to IMEs on other AEDs as monotherapy.

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.

Obstetric outcome of 6346 pregnancies with infants affected by congenital heart defects

OBJECTIVE

To evaluate whether pregnancies with infants affected by congenital heart defects are associated with adverse obstetric and perinatal outcome.

STUDY DESIGN

In a prospective population-based cohort study from Sweden (1992-2001), 6346 singleton pregnancies with infants affected by congenital heart defects were, after suitable adjustments, compared to all delivered women.

RESULTS

The prevalence of cardiovascular defects was 9.1 per 1000 births. Among them, mothers of 6346 infants (71%) had information on maternal smoking habits and maternal height and weight in early pregnancy that enabled the calculation of BMI. All cases with known chromosomal abnormalities and/or maternal pre-existing diabetes were excluded. Eighty-four percent (n=5338) had an isolated cardiovascular defect. Severe types occurred in 21.7% (n=1378). In the group of pregnancies with infants affected by congenital heart defects as compared to all delivered women, there was an increased risk of the following outcomes (adjusted OR (95%CI)): pre-eclampsia (1.21 (1.06-1.37)), cesarean section (1.91 (1.79-2.03)), instrumental delivery (1.21 (1.10-1.34)), pre-term delivery (2.58 (2.39-2.79)), small-for gestational age (1.96 (1.77-2.16)), meconium aspiration (1.51 (1.28-1.77)), and fetal distress (1.38 (1.17-1.63)).

CONCLUSIONS

Pregnancies with infants affected by congenital heart defects are associated with several obstetric and neonatal complications.

Genetics in zebrafish, mice, and humans to dissect congenital heart disease: insights in the role of VEGF

Heart development and the establishment of a functional circulatory circuit are complex biological processes in which subtle perturbations may result in catastrophic consequences of cardiovascular birth defects. Studies in model organisms, most notably the mouse and the zebrafish, have identified genes that also cause these life-threatening defects when mutated in humans. Gradually, a framework for the genetic pathway controlling these events is now beginning to emerge. However, the puzzling phenotypic variability of the cardiovascular disease phenotype in humans and the recent identification of phenotypic modifiers using model organisms indicates that other genetic loci might interact to modify the disease phenotype. To illustrate this, we review the role of vascular endothelial growth factor (VEGF) during vascular and cardiac development and stress how zebrafish and mouse genetic studies have helped us to understand the role this growth factor has in human disease, in particular in the Di-George syndrome.

Maternal obesity and infant heart defects

OBJECTIVE

This study determined whether obese women have an increased risk of cardiovascular defects in their offspring compared with average weight women.

RESEARCH METHODS AND PROCEDURES

In a case-control study, prospectively collected information was obtained from Swedish medical health registers. The study included 6,801 women who had infants with a cardiovascular defect and, as controls, all delivered women (N = 812,457) during the study period (1992 to 2001). Infants with chromosomal anomalies or whose mothers had pre-existing diabetes were excluded. Obesity was defined as BMI >29 kg/m(2), and morbid obesity was defined as BMI >35 kg/m(2). Comparisons were made with average weight women (BMI = 19.8 to 26 kg/m(2)).

RESULTS

In the group of obese mothers, there was an increased risk for cardiovascular defects compared with the average weight mothers [adjusted odds ratio (OR) = 1.18; 95% CI, 1.09 to 1.27], which was slightly more pronounced for the severe types of cardiovascular defects (adjusted OR = 1.23; 95% CI, 1.05 to 1.44). With morbid obesity, the OR for cardiovascular defects was 1.40 (95% CI, 1.22 to 1.64), and for severe cardiovascular defects, the OR was 1.69 (95% CI, 1.27 to 2.26). There was an increased risk for all specific defects studied among the obese women, but only ventricular septal defects and atrial septal defects reached statistical significance.

DISCUSSION

In this sample, a positive association was found between maternal obesity in early pregnancy and congenital heart defects in the offspring. A suggested explanation is undetected type 2 diabetes in early pregnancy, but other explanations may exist.

Risk factors in congenital heart disease

A case-control study was conducted to investigate the risk factors of congenital heart disease (CHD). The cases were 346 children with CHD who were admitted to a university hospital in Tehran from 1995 to 2000 and controls (n=346) were randomly selected from children without CHD who were admitted during the same period. The medical records of both cases and controls were reviewed. Ten risk factors were studied and found to be more prevalent among cases (47%) than controls (35%, p < 0.005). Extracardiac malformations (OR, 31.1; CI95, 15.9-60.9; p < 0.001) and chromosomal abnormalities (OR, 34.05; CI95, 23.3-49.8; p < 0.001) were significant risk factors for CHD. Dysmorphic syndromes (p < 0.05) and CHD in siblings (p < 0.001) were also significant risk factors. Maternal illness and drug use in the first trimester of pregnancy, maternal history of previous abortions and stillbirths, parental consanguinity, and parental cardiac lesions were not significant risk factors for CHD in offspring. Results suggest that genetic factors more than environmental or reproductive factors can increase the occurrence of cardiac defects.

The incidence of congenital heart disease

This study was designed to determine the reasons for the variability of the incidence of congenital heart disease (CHD), estimate its true value and provide data about the incidence of specific major forms of CHD. The incidence of CHD in different studies varies from about 4/1,000 to 50/1,000 live births. The relative frequency of different major forms of CHD also differs greatly from study to study. In addition, another 20/1,000 live births have bicuspid aortic valves, isolated anomalous lobar pulmonary veins or a silent patent ductus arteriosus. The incidences reported in 62 studies published after 1955 were examined. Attention was paid to the ways in which the studies were conducted, with special reference to the increased use of echocardiography in the neonatal nursery. The total incidence of CHD was related to the relative frequency of ventricular septal defects (VSDs), the most common type of CHD. The incidences of individual major forms of CHD were determined from 44 studies. The incidence of CHD depends primarily on the number of small VSDs included in the series, and this number in turn depends upon how early the diagnosis is made. If major forms of CHD are stratified into trivial, moderate and severe categories, the variation in incidence depends mainly on the number of trivial lesions included. The incidence of moderate and severe forms of CHD is about 6/1,000 live births (19/1,000 live births if the potentially serious bicuspid aortic valve is included), and of all forms increases to 75/1,000 live births if tiny muscular VSDs present at birth and other trivial lesions are included. Given the causes of variation, there is no evidence for differences in incidence in different countries or times.

The genetic basis of pediatric cardiovascular disease

Congenital heart disease (CHD), cardiomyopathy, and vasculopathies are common causes of mortality and morbidity in pediatrics, including the perinatal period. This article reviews evidence that single gene defects cause many of the pediatric heart diseases. Vasculopathies discussed include Marfan's syndrome, supravalvar aortic stenosis and Williams' syndrome, Alagille's syndrome, and hereditary telangiectasia, the Osler-Weber-Rendu syndrome. Genetic causes of hypertrophic cardiomyopathy caused by sarcomeric protein mutations (beta-cardiac myosin heavy chain) and of dilated cardiomyopathy secondary to structural protein deficiencies (dystrophin) are presented. Defects in proteins essential for myocardial energy production such as oxidative phosphorylation proteins and fatty acid oxidation genes that cause cardiomyopathy or sudden death are described. Gene ablation models in mice, such as RXR alpha and homeobox gene knockouts, which result in cardiac phenotypes resembling human congenital heart disease, are described. Familial types of human CHD which are being investigated for genetic causes by positional cloning methods and known cytogenetic causes of CHD, including the CATCH-22 syndrome and monosomy at 22q11, are presented. General lessons and principles derived from these new and exciting discoveries in human cardiovascular development are surmised.