Clinical Presentation and Therapy of Atrioventricular Septal Defect.

Atrioventricular septal defects (AVSDs) consist of a number of cardiac malformations that result from abnormal development of the endocardial cushions. AVSDs occur in 0.19 of 1000 live births and constitute 4-5 % of congenital heart defects. AVSDs can be categorized as incomplete (or partial) or complete, and intermediate or transitional.

Molecular Pathways and Animal Models of Atrioventricular Septal Defect.

The development of a fully functional four-chambered heart is critically dependent on the correct formation of the structures that separate the atrial and ventricular chambers. Perturbation of this process typically results in defects that allow mixing of oxygenated and deoxygenated blood. Atrioventricular septal defects (AVSD) form a class of congenital heart malformations that are characterized by the presence of a primary atrial septal defect (pASD), a common atrioventricular valve (cAVV), and frequently also a ventricular septal defect (VSD). While AVSD were historically considered to result from failure of the endocardial atrioventricular cushions to properly develop and fuse, more recent studies have determined that inhibition of the development of other components of the atrioventricular mesenchymal complex can lead to AVSDs as well. The role of the dorsal mesenchymal protrusion (DMP) in AVSD pathogenesis has been well-documented in studies using animal models for AVSDs, and in addition, preliminary data suggest that the mesenchymal cap situated on the leading edge of the primary atrial septum may be involved in certain situations as well. In this chapter, we review what is currently known about the molecular mechanisms and animal models that are associated with the pathogenesis of AVSD.

Inflow Tract Development.

The development of the inflow tract is undoubtedly one of the most complex remodeling events in the formation of the four-chambered heart. It involves the creation of two separate atrial chambers, the formation of an atrial/atrioventricular (AV) septal complex, the incorporation of the caval veins and coronary sinus into the right atrium, and the remodeling events that result in pulmonary venous return draining into the left atrium. In these processes, the atrioventricular mesenchymal complex, consisting of the major atrioventricular (AV) cushions, the mesenchymal cap on the primary atrial septum (pAS), and the dorsal mesenchymal protrusion (DMP), plays a crucial role.

Molecular Pathways and Animal Models of Atrial Septal Defect.

The relative simplicity of the clinical presentation and management of an atrial septal defect belies the complexity of the developmental pathogenesis. Here, we describe the anatomic development of the atrial septum and the venous return to the atrial chambers. Experimental models suggest how mutations and naturally occurring genetic variation could affect developmental steps to cause a defect within the oval fossa, the so-called secundum defect, or other interatrial communications, such as the sinus venosus defect or ostium primum defect.

Cardiac Transcription Factors and Regulatory Networks.

Cardiac development is a fine-tuned process governed by complex transcriptional networks, in which transcription factors (TFs) interact with other regulatory layers. In this chapter, we introduce the core cardiac TFs including Gata, Hand, Nkx2, Mef2, Srf, and Tbx. These factors regulate each other's expression and can also act in a combinatorial manner on their downstream targets. Their disruption leads to various cardiac phenotypes in mice, and mutations in humans have been associated with congenital heart defects. In the second part of the chapter, we discuss different levels of regulation including cis-regulatory elements, chromatin structure, and microRNAs, which can interact with transcription factors, modulate their function, or are downstream targets. Finally, examples of disturbances of the cardiac regulatory network leading to congenital heart diseases in human are provided.

Revisiting Atrioventricular Septal Defects: Exploring Chromosomal Abnormalities, Cardiac and Extracardiac Anomalies in a Contemporary Prenatal Cohort.

To estimate if there is an association between partial AVSD with chromosomal abnormalities, cardiac and extracardiac malformations, and to report the outcomes of prenatally diagnosed AVSD in a large, contemporary cohort. This is a retrospective cohort study of 190 prenatally diagnosed fetal AVSD between 2014 and 2023. Type of AVSD (complete vs partial), additional cardiac findings, extracardiac findings, presence of a heterotaxy, results of prenatal karyotype, and pregnancy outcomes were documented and analyzed. A total of 190 cases of fetal AVSD were analyzed. Complete AVSDs comprised 141 (74.2%) of the cohort, while partial AVSDs comprised 49 (25.7%). Karyotype was completed in 131 cases, and in 98 (74.8%) cases chromosomal abnormalities were identified, with trisomy 21 being the most common (53/131, 40.5%). Complete AVSDs were associated with trisomy 21 (45.5%, p = 0.04), Isolated cases of complete AVSDs (p = 0.03). Partial AVSDs were associated with trisomy 18 (53.1%, p < 0.001). In cases of partial AVSDs with aneuploidies, 7 (70%) had an ostium primum defect and 20 (90.9%) of AV canal type VSD. Isolated partial AVSD had no clear association with aneuploidies. There were additional cardiac anomalies in 96 (50.5%) and extracardiac anomalies in 134 (70.5%) of the cohort. There were no differences between partial and complete AVSD in rate of additional cardiac and extracardiac anomalies. AVSD was part of a heterotaxy in 47 (24.7%) of cases, and heterotaxy was associated with complete AVSD in the majority of cases (43/47, 91.4%, p = 0.003). Fetal partial AVSDs are associated with trisomy 18. Fetal complete AVSDs, even isolated, are associated with trisomy 21. There were no differences in association of other aneuploidies, additional cardiac findings, or extracardiac anomalies between prenatally diagnosed complete AVSDs and partial AVSDs.

Risk factors for the recurrence of left atrioventricular valvular regurgitation after surgical repair of partial and transitional atrioventricular septal defect.

Background: Left atrioventricular valvular regurgitation (LAVVR) recurrence after partial and transitional atrioventricular septal defect (AVSD) repair is the main risk factor associated with reoperation or mortality. The purpose of this study was to identify risk factors associated with the recurrence of LAVVR after surgical repair of transitional and partial AVSD at a single institution. Methods: A hundred and fifty-seven patients who underwent anatomical repair for partial and transitional AVSD from January 2013 to December 2021 were included in our institutional database. Demographic characteristics, operative information, comorbidities, complications, and outcomes were retrieved from electronic medical records. Echocardiographic evaluations included cardiac dimensions, the degree of LAVVR, and the anatomy of the atrioventricular valve. Results: After a median follow-up period of 5.8 years, 40 patients had recurrent moderate or even more severe LAVVR. Compared with patients without recurrent LAVVR, those experiencing LAVVR recurrence were more likely to have larger preoperative left atrial (LA) size and larger left ventricular (LV) size after standardization, larger left atrioventricular valve (LAVV) cleft width, higher proportions of preoperative moderate or even more severe LAVVR, and immediately postoperative mild to moderate or even more severe LAVVR. Univariate Cox regression analysis showed that age at first repair, height, LA size after standardization, LV size after standardization, the severity of preoperative LAVVR, immediately postoperative LAVVR, and the LAVV cleft width more than 1cm were risk factors for recurrent LAVVR (P<0.05 for all). Multivariable Cox regression analysis showed that mild to moderate or even more severe LAVVR postoperatively [hazard ratio (HR) 9.53, 95% confidence interval (CI): 3.78-24.01; P<0.001], the width of LAVV cleft more than 1 cm (HR: 3.90, 95% CI: 1.80-8.48; P<0.001) and age at first repair (HR: 0.45, 95% CI: 0.31-0.66; P<0.001) were independently associated with the recurrence of LAVVR. Conclusions: The width of LAVV cleft, mild to moderate or even more severe LAVVR immediately after surgery, and age at initial surgery are risk factors for recurrent LAVVR. The presence of recurrent LAVVR necessitates proactive surveillance to facilitate timely reintervention.

Application of neural networks in prenatal diagnosis of atrioventricular septal defect.

Background: There is no relevant study on landmarks detection, one of the Convolutional Neural Network algorithms, in the field of fetal echocardiography (FE). This study aimed to explore whether automatic landmarks detection could be used in FE correctly and whether the atrial length (AL) to ventricular length (VL) ratio (AVLR) could be used to diagnose atrioventricular septal defect (AVSD) prenatally. Methods: This was an observational study. Two hundred and seventy-eight four-chamber views in end diastole, divided into the normal, AVSD, and differential diagnosis groups, were retrospectively included in this study. Seven landmarks were labeled sequentially by the experts on these images, and all images were divided into the training and test sets for normal, AVSD, and differential diagnosis groups. U-net, MA-net, and Link-net were used as landmark prediction neural networks. The accuracy of the landmark detection, AL, and VL measurements, as well as the prenatal diagnostic effectiveness of AVLR for AVSD, was compared with the expert labeled. Results: U-net, MA-net, and Link-net could detect the landmarks precisely (within the localization error of 0.09 and 0.13 on X and Y axis) and measure AL and VL accurately (the measured pixel distance error of AL and VL were 0.12 and 0.01 separately). AVLR in AVSD was greater than in other groups (P<0.0001), but the statistical difference was not obvious in the complete, partial, and transitional subgroups (P>0.05). The diagnostic effectiveness of AVLR calculated by three models, area under receiver operating characteristic curve could reach 0.992 (0.968-1.000), was consistent with the expert labeled. Conclusions: U-net, Link-net, and MA-net could detect landmarks and make the measurements accurately. AVLR calculated by three neural networks could be used to make the prenatal diagnosis of AVSD.

Role of ECG in the Accidental Finding of an Atrioventricular Septal Defect in an Asymptomatic Patient Undergoing Cosmetic Surgery.

Electrocardiogram (ECG) is an important diagnostic tool in identifying congenital heart disease (CHD), as demonstrated by this case of a 48-year-old female who presented for a preoperative evaluation for cosmetic surgery. ECG showed a right bundle branch block (RBBB) and first-degree atrioventricular (AV) block, and further testing revealed a primum atrial septal defect (ASD) with mitral valve anterior leaflet cleft and a membranous ventricular septal defect (VSD). She underwent successful surgical repair and was discharged home without complications. This case highlights the importance of performing additional tests like echocardiography or other imaging modalities in cases of abnormal ECG findings to accurately diagnose the underlying heart condition and ensure proper treatment.