Congenital Conotruncal Heart Defects Research Articles

Epigenetics of conotruncal congenital heart disease: Protocol for a systematic review and meta-analysis.

Conotruncal congenital heart defects (CTD) are a subset of congenital heart diseases (CHD) that involve structural anomalies of the right, left, or both cardiac outflow tracts. CHD is caused by multifactorial inheritance and changes in the genes or chromosomes. Recently, CHD was found to be due to epigenetic alterations, which are a combination of genetic and other environmental factors. Epigenetics is the study of how a gene's function changes as a result of environmental and behavioral influences. These causative factors can indirectly cause CHD by altering the DNA through epigenetic modifications. This is a protocol for a systematic review and meta-analysis that aims to explore whether the strength of association between various epigenetic changes and CTD types varies by race. Furthermore, to determine and compare the changes in gene expression of each mutation. Our protocol follows the Preferred Reporting Items for Systematic Reviews and Meta-Analyses Protocol (PRISMA-P) guidelines. A comprehensive pre-search has been developed in PubMed and PubMed's Medical Subject Headings (MeSH). The final search will be performed in June 2023 in PubMed, Embase, Scopus, Web of Science, Cochrane Library, CIANHL, and PsycInfo, without restrictions on publication years. The Covidence systematic review software will be used for blinded screening and selection. Conflicts will be resolved by a third, independent reviewer. The risk of bias in selected studies will be assessed using the National Heart, Lung, and Blood Institute (NHLBI) Quality Assessment Tool for Observational Cohort and Cross-Sectional Studies. The data to be extracted will cover basic information on the included studies, study sample size, number of patients with various types of epigenetic changes, number of patients with various CTD types, measures of association and their 95% confidence interval between each epigenetic change and each CTD. The protocol has been registered with the International Prospero Register of Systematic Review (PROSPERO) [CRD42023377597]. To the best of our knowledge, this protocol outlines the first systematic review and meta-analysis of the epigenetics of CTD. There is a growing body of evidence on epigenetics and its indirect involvement in disease by altering the DNA through epigenetic modifications in the genes associated with the causative factors for CHD. We will conduct a comprehensive and systematic search for literature in the above-mentioned seven core biomedical databases. It is very important to identify population-specific risk factors for CHD, which will have significant creative, custom-made, and effective prevention programs for the future generation.

Immunodeficiency Disorders in Congenital Heart Diseases (Review)

The study data of the last two decades on primary and secondary immunodeficiency in congenital heart defects (CHD) as a cause of frequent infectious complications before and after cardiac surgery are presented. Based on screenings of various levels, data are provided on the greater severity of immunological disorders in critical and cyanotic CHD in conotruncal defects compared with those in septal defects and stenotic defects. Violations were more often related to T-cell function and immunoglobulin deficiency (especially the IgG and IgG4 subgroups). Various types of primary immunodeficiency were found in 13 genetic syndromes in combination with CHD. The review discusses the possibility of using the technique of quantitative determination of DNA TREC and KREC — by-products of maturation of T- and B-cell receptors, which allows us to judge the defects of the T- and B-cell links of the immune system to predict infectious complications in children with CHD. The data of our own study of 200 infants with CHD (in 5% of cases with syndromic forms of CHD) are presented, where a decrease in TREC was found in 23.5% of cases, including all infants with syndromic forms, more often with cyanotic and conotruncal CHD and in children admitted in critical conditions. In children with reduced TREC values, infectious complications in the postoperative period were observed significantly more often than in children with normal indicators (36 and 3.6%, respectively). The analysis of publications confirmed the importance of TREC and KREC screening for targeted preoperative preparation in order to reduce postoperative complications and reduce the risk of mortality in CHD.

Exploring the interface between the first and second heart fields: Implications for cardiac septation

The embryonic heart elongates by progressive addition of second heart field (SHF) cardiac progenitor cells to the arterial and venous poles of the early heart tube, derived from the first heart field (FHF). The SHF gives rise to the right ventricle, outflow tract and part of the atrial myocardium. SHF-derived parts of the heart are hotspots of congenital heart defects (CHD) and perturbation of SHF deployment underlies a spectrum of CHD. These include atrial and ventricular septal defects that account for over 50% of CHD. Atrial septal structures originate in Tbx1 expressing cells in the posterior dorsal pericardial wall that activate the FHF regulator Tbx5 in response to retinoic acid (RA) signaling. Transient coexpression of Tbx1 and Tbx5 is followed by downregulation of the SHF program, and emergence of a sharp boundary between arterial and venous pole progenitor cells. A similar history of expression of both FHF and SHF regulators, followed by downregulation of the SHF program, demarcates boundary formation at the site of ventricular septation. Here we investigate the cellular and molecular mechanisms of ventricular septum morphogenesis. Using mouse genetics and a conditional dominant negative RA receptor, we show that RA signaling is also required at the heart field interface for morphogenesis of the muscular ventricular septum. Blocking RA signal reception in the SHF results in a bifid ventricular phenotype, identifying a novel RA-dependent zipper phase of ventricular septal morphogenesis. Additionally, blocking RA signal reception in the SHF results in conotruncal CHD. Together, our results point to the importance of RA signaling at the heart field interface for septal morphogenesis, providing new insights into the etiology of CHD.

Особенности проявления синдрома делеции 22Q11.2 хромосомы в раннем возрасте

DiGeorge syndrome is characterized by conotruncal heart defects, an immunodeficiency state, and underdeveloped parathyroid glands. Contemporary medicine describes more than 180 clinical forms of this disease, which are usually classified under the heading “chromosome 22q11.2 deletion syndrome” (D 82.1). Along with the above abnormalities, there are other malformations and pathological conditions in 22q11.2DS that not only complicate diagnosis, neonatal nursing, and further management, but also lead to an increased frequency of surgical interventions. This article presents 8 clinical cases of 22q11.2DS with multiple congenital disorders. The children under observation had malformations of the central nervous, maxillofacial, genitourinary, musculoskeletal systems, anorectal region, as well as diaphragmatic and inguinal hernias. Key words: multiple congenital disorders, 22q11.2 deletion syndrome, DiGeorge syndrome, conotruncal congenital heart defects, cleft lip and palate, anorectal malformations, hypoparathyroidism, delayed speech and psychomotor development, primary immunodeficiency

Aortopathy in Congenital Heart Disease.

Aortic dilatation is common in patients with congenital heart disease and is seen in patients with bicuspid aortic valve and those with conotruncal congenital heart defects. It is important to identify patients with bicuspid aortic valve at high risk for aortic dissection. High-risk patients include those with the aortic root phenotype and those with syndromic or familial aortopathies including Marfan syndrome, Loeys-Dietz syndrome, and Turner syndrome. Aortic dilatation is common in patients with conotruncal congenital heart defects and rarely results in aortic dissection.

162: Congenital cardiac defects and placental vascular malperfusion

There is growing evidence that abnormal early angiogenesis impacts pathogenesis of maternal hypertensive disorders, fetal growth restriction and congenital heart defects (CHD). The aim of this retrospective case control study is to assess the frequency of placental vascular malperfusion in congenital heart defects. Singleton pregnancies with isolated fetal CHD and delivery after 32 weeks that necessitated intervention with catheterization and or surgery in the first year of life were recruited from the Pediatric Cardiology database from April 2016 to April 2019. A control group without any congenital anomalies or diabetes, chronic hypertension, gestational hypertension, or preeclampsia were recruited from the Pathology data base. CHD was classified as groups: 1. right single ventricle morphology, 2. left single ventricle morphology, 3. transposition of the great vessels (TGA), 4. other conotruncal CHD, and 5. other CHD. Placental histopathology was classified as fetal vascular malperfusion (FVM), maternal vascular malperfusion (MVM), both FVM and MVM and neither. Chi square and t test were used as appropriate for statistical analysis. There were 37 patients and 45 controls included in the study. The CHD group had a decreased birth weight (BW) as compared to the control group. Placental vascular malperfusion and fetal vascular malperfusion were significantly increased in the CHD cases (33 % vs 62 %, Table 1). When compared to other CHD groups combined, CHD Groups 1 and 2 had a trend for any vascular malperfusion (80% vs 50%, p=0.09), (Table 2). Placental malperfusion overall and FVM were increased in CHD. These findings suggest interactions of the fetal cardiac and placental development pathways.View Large Image Figure ViewerDownload Hi-res image Download (PPT)

Projected Changes in Maternal Heat Exposure During Early Pregnancy and the Associated Congenital Heart Defect Burden in the United States.

BackgroundMore intense and longer‐lasting heat events are expected in the United States as a consequence of climate change. This study aimed to project the potential changes in maternal heat exposure during early pregnancy (3–8 weeks post conception) and the associated burden of congenital heart defects (CHDs) in the future.Methods and ResultsThis study expanded on a prior nationwide case‐control study that evaluated the association between CHDs and maternal heat exposure during early pregnancy in summer and spring. We defined multiple indicators of heat exposure, and applied published odds ratios obtained for the matching season of the baseline (1995–2005) into the projection period (2025–2035) to estimate potential changes in CHD burden throughout the United States. Increases in maternal heat exposure were projected across the United States and to be larger in the summer. The Midwest will potentially have the highest increase in summer maternal exposure to excessively hot days (3.42; 95% CI, 2.99–3.88 per pregnancy), heat event frequency (0.52; 95% CI, 0.44–0.60) and heat event duration (1.73; 95% CI, 1.49–1.97). We also found large increases in specific CHD subtypes during spring, including a 34.0% (95% CI, 4.9%–70.8%) increase in conotruncal CHD in the South and a 38.6% (95% CI, 9.9%–75.1%) increase in atrial septal defect in the Northeast.ConclusionsProjected increases in maternal heat exposure could result in an increased CHD burden in certain seasons and regions of the United States.

Genetic Imbalances in Argentinean Patients with Congenital Conotruncal Heart Defects

Congenital conotruncal heart defects (CCHD) are a subset of serious congenital heart defects (CHD) of the cardiac outflow tracts or great arteries. Its frequency is estimated in 1/1000 live births, accounting for approximately 10–30% of all CHD cases. Chromosomal abnormalities and copy number variants (CNVs) contribute to the disease risk in patients with syndromic and/or non-syndromic forms. Although largely studied in several populations, their frequencies are barely reported for Latin American countries. The aim of this study was to analyze chromosomal abnormalities, 22q11 deletions, and other genomic imbalances in a group of Argentinean patients with CCHD of unknown etiology. A cohort of 219 patients with isolated CCHD or associated with other major anomalies were referred from different provinces of Argentina. Cytogenetic studies, Multiplex-Ligation-Probe-Amplification (MLPA) and fluorescent in situ hybridization (FISH) analysis were performed. No cytogenetic abnormalities were found. 22q11 deletion was found in 23.5% of the patients from our cohort, 66% only had CHD with no other major anomalies. None of the patients with transposition of the great vessels (TGV) carried the 22q11 deletion. Other 4 clinically relevant CNVs were also observed: a distal low copy repeat (LCR)D-E 22q11 duplication, and 17p13.3, 4q35 and TBX1 deletions. In summary, 25.8% of CCHD patients presented imbalances associated with the disease.

Rare copy number variants in patients with congenital conotruncal heart defects.

Previous studies using different cardiac phenotypes, technologies and designs suggest a burden of large, rare or de novo copy number variants (CNVs) in subjects with congenital heart defects. We sought to identify disease-related CNVs, candidate genes, and functional pathways in a large number of cases with conotruncal and related defects that carried no known genetic syndrome. Cases and control samples were divided into two cohorts and genotyped to assess each subject's CNV content. Analyses were performed to ascertain differences in overall CNV prevalence and to identify enrichment of specific genes and functional pathways in conotruncal cases relative to healthy controls. Only findings present in both cohorts are presented. From 973 total conotruncal cases, a burden of rare CNVs was detected in both cohorts. Candidate genes from rare CNVs found in both cohorts were identified based on their association with cardiac development or disease, and/or their reported disruption in published studies. Functional and pathway analyses revealed significant enrichment of terms involved in either heart or early embryonic development. Our study tested one of the largest cohorts specifically with cardiac conotruncal and related defects. These results confirm and extend previous findings that CNVs contribute to disease risk for congenital heart defects in general and conotruncal defects in particular. As disease heterogeneity renders identification of single recurrent genes or loci difficult, functional pathway and gene regulation network analyses appear to be more informative. Birth Defects Research 109:271-295, 2017. © 2017 Wiley Periodicals, Inc.

DGCR6 at the proximal part of the DiGeorge critical region is involved in conotruncal heart defects.

Cardiac anomaly is one of the hallmarks of DiGeorge syndrome (DGS), observed in approximately 80% of patients. It often shows a characteristic morphology, termed as conotruncal heart defects. In many cases showing only the conotruncal heart defect, deletion of 22q11.2 region cannot be detected by fluorescence in situ hybridization (FISH), which is used to detect deletion in DGS. We investigated the presence of genomic aberrations in six patients with congenital conotruncal heart defects, who show no deletion at 22q11.2 in an initial screening by FISH. In these patients, no abnormalities were identified in the coding region of the TBX1 gene, one of the key genes responsible for the phenotype of DGS. However, when copy number alteration was analyzed by high-resolution array analysis, a small deletion or duplication in the proximal end of DiGeorge critical region was detected in two patients. The affected region contains the DGCR6 and PRODH genes. DGCR6 has been reported to affect the expression of the TBX1 gene. Our results suggest that altered dosage of gene(s) other than TBX1, possibly DGCR6, may also be responsible for the development of conotruncal heart defects observed in patients with DGS and, in particular, in those with stand-alone conotruncal heart defects.

Progresses on relationship of conotruncal heart defects and retinoic acid signaling pathway

Congenital conotruncal heart defects (CHD),including tetralogy of Fallot (TOF),double outlet of right ventricle(DORV),transposition of the great arteries(TGA),persistent truncus arteriosus (PTA),is a variety of common and serious congenital cardiovascular diseases which are threatenting to the health of neonates and infants.Previous studies have demostrated that TBX1 contricuted to some of the CHD.Recent studies have also confirmed that retinoic acid signaling pathway plays a curcial role of development of CHD.Further studies have also found that TGF-β2 differential expression is closely related with phenotypic polymorphism of conotruncal heart defects in retinoic acid receptor mutant mice,of which the mechanism is not yet clear.This paper provides an overview of the relationship between TBX1-RA signaling pathway and congenital conotruncal heart defects and TGF-β2-RA and CHD during the development of CHD. Key words: Retinoic acid receptor; Transforming growth factor; Gene TBX1 ; Signaling pathway; Conotruncal heart defect

Investigation of copy number variation in children with conotruncal heart defects.

BackgroundCongenital heart defects (CHD) are the most prevalent group of structural abnormalities at birth and one of the main causes of infant morbidity and mortality. Studies have shown a contribution of the copy number variation in the genesis of cardiac malformations.ObjectivesInvestigate gene copy number variation (CNV) in children with conotruncal heart defect.MethodsMultiplex ligation-dependent probe amplification (MLPA) was performed in 39 patients with conotruncal heart defect. Clinical and laboratory assessments were conducted in all patients. The parents of the probands who presented abnormal findings were also investigated.ResultsGene copy number variation was detected in 7/39 patients: 22q11.2 deletion, 22q11.2 duplication, 15q11.2 duplication, 20p12.2 duplication, 19p deletion, 15q and 8p23.2 duplication with 10p12.31 duplication. The clinical characteristics were consistent with those reported in the literature associated with the encountered microdeletion/microduplication. None of these changes was inherited from the parents.ConclusionsOur results demonstrate that the technique of MLPA is useful in the investigation of microdeletions and microduplications in conotruncal congenital heart defects. Early diagnosis of the copy number variation in patients with congenital heart defect assists in the prevention of morbidity and decreased mortality in these patients.

Lack of Association Between Folate Receptor Autoantibodies and Conotruncal Congenital Heart Defects

Conotruncal cardiac defects are partially prevented by maternal folic acid supplementation. However, the biochemical mechanism is unknown. Maternal autoantibodies to folate receptors, previously associated with increased risk for neural tube defects, also may account for this effect. This study aimed to examine the titers of folate receptor-blocking autoantibodies in mothers of children with conotruncal congenital heart defects and to compare them with those in the general population. Serum samples were obtained from 22 women whose pregnancies were complicated by conotruncal congenital heart malformations. Groups of samples were analyzed for autoantibodies against [(3)H] folic acid-labeled folate receptors, quantitative amounts of immunoglobulin G (IgG) and IgM autoantibodies to the folate receptor, and for ability to block-bind folic acid to receptors. No elevated levels of antibodies binding to [(3)H] folic acid-labeled folate receptors were found. No difference was found in antifolate receptor alpha-IgG or IgM median levels between cases (261 vs. 240μg/mL) and control subjects (773 vs. 924μg/mL). There was no increased blocking of folic acid binding between cases [0.69ng/mL; 95% confidence interval (CI), 0.006-0.01] and control subjects (0.69ng/mL; 95% CI, 0.003-0.013). Although epidemiologic evidence suggests that periconceptual folic acid may prevent many conotruncal congenital heart defects, the current study suggests that this effect is unlikely to be explained by the presence of maternal autoantibodies to folate receptor. These data suggest that a strategy of screening women for such autoantibodies will not identify a high-risk group of women to target for supplemental folic acid to prevent congenital heart defects.

Tbx1, subpulmonary myocardium and conotruncal congenital heart defects

Conotruncal congenital heart defects, including defects in septation and alignment of the ventricular outlets, account for approximately a third of all congenital heart defects. Failure of the left ventricle to obtain an independent outlet results in incomplete separation of systemic and pulmonary circulation at birth. The embryonic outflow tract, a transient cylinder of myocardium connecting the embryonic ventricles to the aortic sac, plays a critical role in this process during normal development. The outflow tract (OFT) is derived from a population of cardiac progenitor cells called the second heart field that contributes to the arterial pole of the heart tube during cardiac looping. During septation, the OFT is remodeled to form the base of the ascending aorta and pulmonary trunk. Tbx1, the major candidate gene for DiGeorge syndrome, is a critical transcriptional regulator of second heart field development. DiGeorge syndrome patients are haploinsufficient for Tbx1 and present a spectrum of conotruncal anomalies including tetralogy of Fallot, pulmonary atresia, and common arterial trunk. In this review, we focus on the role of Tbx1 in the regulation of second heart field deployment and, in particular, in the development of a specific population of myocardial cells at the base of the pulmonary trunk. Recent data characterizing additional properties and regulators of development of this region of the heart, including the retinoic acid, hedgehog, and semaphorin signaling pathways, are discussed. These findings identify future subpulmonary myocardium as the clinically relevant component of the second heart field and provide new mechanistic insight into a spectrum of common conotruncal congenital heart defects.

64 Risk of Congenital Heart Defects for Children Conceived Following Assisted Reproductive Technologies. A Population Based Evaluation

Background: Children conceived after ART have higher risks for adverse birth outcomes. Insufficient data exist regarding the specific risk for CHD. Objective: To estimate the risk associated with Assisted Reproductive Technologies (ART) for congenital heart defects (CHD), CHD without chromosomal abnormalities and CHD subgroups defined based on anatomo-embryologic criteria. Methods: We used data from the Paris Registry of Congenital Malformations on 5,599 cases of CHD and 3,985 malformed controls including a heterogeneous group of malformations for which no known associations with ART were reported in literature. ART included inductors of ovulation only, in vitro fertilization and intracytoplasmic sperm injection. Results: Exposure to ART (all methods combined) was higher for cases than controls (4.7% vs. 3.6%, p=0.008) and was associated with a 40% increase in the maternal age, socioeconomic factors and year of birth-adjusted odds of CHD without chromosomal abnormalities (Adjusted-OR 1.4, 95%CI 1.1-1.7). ART was specifically associated with significant increases in the odds of malformations of great vessels and outflow tracts (Adjusted-OR 1.7, 95%CI 1.2-2.4), of anomalies of atria and atrial septal defects (Adjusted-OR 1.8, 95%CI 1.1-2.8) and of conotruncal CHD and double outlet right ventricle (Adjusted-OR 1.7, 95%CI 1.1-2.7). In general, we found specific associations between methods of ART and subgroups of CHD. Conclusion: Risk of CHD was higher in children exposed to ART as compared to malformed controls. This association seems to vary according to the method of ART and type of CHD and may be due to ART per se and/or the underlying infertility of couples.

Obituary of Dr. Angelo Di George

Obituary of Dr. Angelo Di George

A deletion and a duplication in distal 22q11.2 deletion syndrome region. Clinical implications and review

BackgroundIndividuals affected with DiGeorge and Velocardiofacial syndromes present with both phenotypic diversity and variable expressivity. The most frequent clinical features include conotruncal congenital heart defects, velopharyngeal insufficiency, hypocalcemia and a characteristic craniofacial dysmorphism. The etiology in most patients is a 3 Mb recurrent deletion in region 22q11.2. However, cases of infrequent deletions and duplications with different sizes and locations have also been reported, generally with a milder, slightly different phenotype for duplications but with no clear genotype-phenotype correlation to date.MethodsWe present a 7 month-old male patient with surgically corrected ASD and multiple VSDs, and dysmorphic facial features not clearly suggestive of 22q11.2 deletion syndrome, and a newborn male infant with cleft lip and palate and upslanting palpebral fissures. Karyotype, FISH, MLPA, microsatellite markers segregation studies and SNP genotyping by array-CGH were performed in both patients and parents.ResultsKaryotype and FISH with probe N25 were normal for both patients. MLPA analysis detected a partial de novo 1.1 Mb deletion in one patient and a novel partial familial 0.4 Mb duplication in the other. Both of these alterations were located at a distal position within the commonly deleted region in 22q11.2. These rearrangements were confirmed and accurately characterized by microsatellite marker segregation studies and SNP array genotyping.ConclusionThe phenotypic diversity found for deletions and duplications supports a lack of genotype-phenotype correlation in the vicinity of the LCRC-LCRD interval of the 22q11.2 chromosomal region, whereas the high presence of duplications in normal individuals supports their role as polymorphisms. We suggest that any hypothetical correlation between the clinical phenotype and the size and location of these alterations may be masked by other genetic and/or epigenetic modifying factors.

Are Black and Hispanic Infants with Specific Congenital Heart Defects at Increased Risk of Preterm Birth?

Congenital heart defects (CHDs) are a leading cause of infant morbidity and mortality. Infants with CHDs have increased risk of preterm birth (PTB) compared to infants without birth defects. Although non-Hispanic (NH) Blacks are more likely to be born preterm and Hispanics have rates similar to those of PTB to NH-Whites, it is unknown if this pattern is present for infants with specific types of CHDs. Our intent was to determine if defect-specific risk of PTB varies by maternal race/ethnicity among infants with CHDs. We conducted a retrospective cohort study with 14,888 singleton infants from the Florida Birth Defects Registry, born in 1998-2003 to resident NH-White, NH-Black, and Hispanic women aged 15-49, diagnosed with 11 CHDs. Covariates were taken from Florida live birth certificates. PTB was defined as 20-36 weeks of gestation. Odds ratios (OR) and P-values were calculated from defect-specific multivariable logistic regression models; statistical significance was set at P < 0.002. The greatest risk of PTB was for NH-Black infants with conotruncal CHDs. NH-Blacks with common truncus, transposition of the great vessels, and tetralogy of Fallot had increased risk of PTB compared to NH-Whites (OR = 4.8, P = 0.015; OR = 3.1, P = 0.004; and OR = 2.0, P = 0.005, respectively). Hispanics with conotruncal CHDs had almost a twofold risk of PTB compared to NH-Whites (P > 0.002). NH-Blacks with tricuspid valve atresia/stenosis had 4.1 times (P = 0.034) and Hispanics had 2.1 times (P = 0.314) the risk for PTB compared to NH-Whites. NH-Blacks with hypoplastic left heart syndrome had 2.0 times (P = 0.047) the risk for PTB as NH-Whites. Both NH-Black and Hispanic infants with CHDs may be at increased risk of PTB, depending on the type of CHD, but the etiology is unknown. Future research is needed to further examine this complex relationship.

The inheritance of conotruncal malformations: a review and report of two siblings with tetralogy of Fallot with pulmonary atresia

Congenital heart defects (CHD) are a group of structural abnormalities that in humans have a combined incidence of approximately 1%. It is estimated that 4-5% of CHD are associated with chromosome abnormalities, 1-2% are associated with single gene syndromes, 1-2% are due to known teratogens, with the rest presumably determined multifactorially. We report on a brother and sister with tetralogy of Fallot with pulmonary atresia, and review the inheritance of familial conotruncal anomalies. We feel the small number of family clusters and the rare instances of consanguinity in non-syndromal conotruncal defects are consistent with multifactorial determination. While it is prudent in counseling families with 2 or more individuals with conotruncal CHD to raise the possibility of single gene inheritance, we believe that current empiric recurrence risk estimates most accurately reflect their risks.

Abstract 2335: Transposition Of The Great Arteries And Double Outlet Right Ventricle Have Related Early Developmental Origins: Fundamental Insights From In Vivo Imaging

Congenital heart defects (CHD) are the most common birth defect. Proper retinoic acid (RA) signaling is required for normal development, and RA excess produces conotruncal CHD such as transposition of the great arteries (TGA) and double outlet right ventricle (DORV). We hypothesized that origins and evolution of TGA and DORV follow specific developmental patterns, definable in vivo by noninvasive ultrasound biomicroscopy (UBM)-Doppler imaging. Timed-pregnant ICR mice were injected with 70 mg/kg IP RA at 8.5 days post-conception (E8.5). Individual embryos were tracked with 40 MHz UBM-Doppler longitudinally on 5 consecutive days (E11.5–15.5: N=34 injected, N=8 uninjected controls). CHD included TGA (24%) and DORV (21%, all with right aorta, left pulmonary artery), as well as ventricular septal defect (VSD, defined at E15.5) and double-inlet left ventricle. External gross examination and histology confirmed ~90% concordance of UBM diagnosis of CHD, here (at E15.5) and in separate experiments (E11.5–15.5, N=111). All E11.5 embryos showed normal cardiac looping, with a normal unseptated heart and outflow tract (OFT) - the truncus arteriosus -arising from the right ventricle/bulbus cordis. Of embryos destined for TGA, 7/8 showed partial septation of the distal truncus into parallel OFT at E12.5; 4 showed DORV at E12.5 before evolving into TGA by E13.5. Of embryos destined for DORV, 6/7 showed partial septation of the distal truncus into parallel OFT at E12.5 as well. Thus, abnormal septation commences in the more distal truncus arteriosus as early as E12.5. In contrast, embryos destined for normal OFT development showed partial OFT septation in spiral (non-parallel) fashion, with complete/near-complete OFT septation and morphology at E13.5. All TGA/DORV embryos displayed normal cardiac function. CONCLUSIONS. TGA and DORV are developmentally related, differing only in complete (TGA) vs. incomplete (DORV) leftward truncal shift. Given normal heart, proximal OFT, and cardiac function, flow streams do not explain TGA/DORV morphogenesis. Corresponding to 4–6 weeks’ human gestation, these first in vivo data support longstanding hypotheses of TGA/DORV embryogenesis, and implicate RA signaling in the pathogenesis of abnormal truncal septation and shift.