Ebstein\'s anomaly is a congenital malformation of the tricuspid valve characterized by abnormal attachment of the valve leaflets, resulting in varying degrees of valve dysfunction. The anatomic hallmarks of this entity are the downward displacement of the attachment of the septal and posterior leaflets of the tricuspid valve. Additional intracardiac malformations are common. From an embryological point of view, the cavity of the future right atrium does not have a direct orifice connected to the developing right ventricle. This chapter provides an overview of current insight into how this connection is formed and how malformations of the tricuspid valve arise from dysregulation of molecular and morphological events involved in this process. Furthermore, mouse models that show features of Ebstein\'s anomaly and the naturally occurring model of canine tricuspid valve malformation are described and compared to the human model. Although Ebstein\'s anomaly remains one of the least understood cardiac malformations to date, the studies summarized here provide, in aggregate, evidence for monogenic and oligogenic factors driving pathogenesis.

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.

Ablation of accessory pathways in patients with Ebstein\'s anomaly can be challenging. Despite increasing experience and advances in mapping technology, success is limited and recurrence rates can be high. To date, high-density electroanatomic mapping has not been studied in this anatomical substrate. We present a pediatric case of Ebstein\'s anomaly in which high-density mapping in Ebstein\'s anomaly was a useful additional tool to improve the outcome of catheter ablation.

Ebstein\'s anomaly is a rare congenital cardiac disease which is often associated with various other cardiac anomalies. However, its association with total anomalous pulmonary venous connection is extremely rare with only one case reported so far in the English literature. We report the first successful surgical correction of both Ebstein\'s anomaly and total anomalous pulmonary venous connection in an adult patient. Such complex scenarios may pose unique challenges in management which require a judicious approach.
UNASSIGNED: The online version contains supplementary material available at 10.1007/s12055-023-01664-8.

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A circular shunt is a poor prognostic factor associated with Ebstein\'s anomaly. Targeting the constriction of the ductus arteriosus (DA) in order to limit or resolve the circular shunt, has been shown to improve fetal outcomes. Prenatal non-steroidal anti-inflammatory drugs (NSAIDs) have been known to constrict the DA. Recently, prenatal NSAIDs have been used for that purpose in the treatment of circular shunt. Limited research shows that it may be an effective treatment leading to improved fetal outcomes. In this article, we did an extensive review of literature to describe this therapy\'s effectiveness and outcomes. 82% of fetuses were able to achieve ductal constriction with prenatal NSAID therapy. For fetuses who achieved ductal constriction, fetal demise was less likely (6%) when compared to those who were unable to achieve the same (50%). Of all the fetuses with hydrops, 50% had resoluation of hydrops with prenatal NSAID treatment.

Due to the heterogeneity of anatomic anomalies in Ebstein\'s anomaly (EA), particularly in the subset of patients with atrial septal defect (ASD), hemodynamic changes, which ultimately cause left ventricular (LV) deterioration remain unclear. The current study aimed to investigate the effect of concomitant ASD on LV function using cardiovascular magnetic resonance (CMR) imaging in patients with EA.
This study included 31 EA patients with ASD, 76 EA patients without ASD, 35 patients with simple ASD and 40 healthy controls. Left/right ventricular (RV, the RV was defined as a summation of the functional RV and atrialized RV in EA patients) volumes and functional parameters, LV strain parameters, and echocardiogram indices were compared among the four groups. Associations between variables were evaluated via Spearman or Pearson correlation analyses. The association between risk factors and LV ejection fraction (EF) was determined via multivariate linear regression analysis.
Both EA patients and ASD patients had a higher RV/LV end-diastolic volume (RVEDV/LVEDV) as well as lower LV and RV ejection fractions (LVEF/RVEF) compared to healthy controls (all p < 0.05). Moreover, the EA patients with ASD had a significantly higher RVEDV/LVEDV and a lower LVEF and RVEF than those without ASD (all p < 0.05). Multivariate linear regression analysis revealed that the presence of ASD was independently associated with LVEF (β = - 0.337, p < 0.001). The RVEDV/LVEDV index was associated with LVEF (r = - 0.361, p < 0.001). Furthermore, the LV longitudinal peak diastolic strain rate (PDSR) was lower in EA patients with ASD than those without ASD, patients with simple ASD, and healthy controls (p < 0.05).
Concomitant ASD is an important risk factor of LV dysfunction in patients with EA, and diastolic dysfunction is likely the predominate mechanism related to LV dysfunction.

UNASSIGNED: Ebstein\'s anomaly occurs when there is an apical displacement of the tricuspid valve with septal and posterior valve leaflets tethering. This condition often occurs in association with other congenital, structural, or conduction system diseases, including intracardiac shunts, valvular lesions, arrhythmias, accessory conduction pathways, and first-degree atrioventricular (AV) block. We present for the first time a case of a patient with Ebstein\'s anomaly who presented with second-degree Mobitz II AV block and was successfully treated with conduction system pacing (CSP) due to her young age and the likelihood of a long-term high percentage of pacing.
UNASSIGNED: We present a case of a 42-year-old lady with a background of complex congenital heart disease, including severe pulmonary stenosis, Ebstein anomaly, and atrial septal defect (ASD). She required complex surgical intervention, including tricuspid valve (TV) repair and subsequently replacement, ASD closure, and pulmonary balloon valvuloplasty. She presented to our hospital with symptomatic second-degree Mobitz II AV block (dizziness, shortness of breath, and exercise intolerance) and right bundle branch block (RBBB) on her baseline ECG. Her echocardiogram showed dilated right ventricle (RV) and left ventricle (LV) with low normal LV systolic function. Due to her young age and the likelihood of a long-term high percentage of RV pacing, we opted for CSP after a detailed discussion and patient consent. The distal HIS position is the preferred pacing strategy at our centre. We could not cross the TV with the standard Medtronic C315 HIS catheter, so we had to use the deflectable C304 HIS catheter. Mapping and pacing of the distal HIS bundle were achieved by Medtronic Selectsecure 3830, 69 cm lead. HIS bundle pacing led to the correction of both second-degree Mobitz II AV block and pre-existing RBBB. The implantation was uneventful, and the patient was discharged home the next day without any acute complications.
UNASSIGNED: Distal HIS pacing is feasible in patients with surgically treated complex Ebstein anomaly and heart block. This approach can normalize the QRS complex with a high probability of preserving or improving LV function.

BACKGROUND: Severe neonatal Ebstein\'s anomaly (EA) and tricuspid valve dysplasia (TVD) are associated with high perinatal morbidity and mortality. The authors recently demonstrated left ventricular (LV) dysfunction and dyssynchrony to be prevalent in affected newborns and to contribute to poor outcomes. The aim of this study was to investigate the impact of patent ductus arteriosus (PDA) closure, spontaneous or surgical ligation, or right ventricular exclusion (Starnes procedure) on LV performance in neonatal EA and TVD.
METHODS: Neonates with EA or TVD encountered from 2004 to 2018 at three institutions were identified. Pre- and postoperative LV function was assessed using two-dimensional, Doppler-derived deformation (six-segment vector velocity imaging) and two measures of mechanical dyssynchrony (the SD of time to peak and global dyssynchrony index), and values were compared using paired t test analysis or the Wilcoxon rank sum test.
RESULTS: Before the intervention, LV function was impaired in the PDA (n = 18) and Starnes (n = 6) groups and was similar between groups. After PDA closure, LV performance did not change. After the Starnes procedure, however, LV function, including synchrony, improved significantly: fractional area change from 45 ± 5% to 58 ± 8% (P = .003), global circumferential strain from -18.2 ± 5.0% to -32.5 ± 5.5% (P = .01), cardiac index from 1.9 ± 0.3 to 3.9 ± 1.5 L/min/m2 (P = .05), and circumferential strain dyssynchrony (dyssynchrony index from 0.19 ± 0.09 to 0.04 ± 0.02 [P = .009] and SD of time to peak from 59.8 ± 18.5 to 29.9 ± 8.2 [P = .02]).
CONCLUSIONS: The Starnes procedure results in early improvements in LV dysfunction and dyssynchrony, not observed after PDA closure in neonatal severe EA and TVD, which may benefit critically unwell neonates.

Ebstein\'s anomaly, a rare congenital heart disease, is distinguished by the failure of embryological delamination of the tricuspid valve leaflets from the underlying primitive right ventricle myocardium. Gaining insight into the genetic basis of Ebstein\'s anomaly allows a more precise definition of its pathogenesis. In this study, two distinct cohorts from the Chinese Han population were included: a case-control cohort consisting of 82 unrelated cases and 125 controls without cardiac phenotypes and a trio cohort comprising 36 parent-offspring trios. Whole-exome sequencing data from all 315 participants were utilized to identify qualifying variants, encompassing rare (minor allele frequency < 0.1% from East Asians in the gnomAD database) functional variants and high-confidence (HC) loss-of-function (LoF) variants. Various statistical models, including burden tests and variance-component models, were employed to identify rare variants, genes, and biological pathways associated with Ebstein\'s anomaly. Significant associations were noted between Ebstein\'s anomaly and rare HC LoF variants found in genes related to the matrisome, a collection of extracellular matrix (ECM) components. Specifically, 47 genes with HC LoF variants were exclusively or predominantly identified in cases, while nine genes showed such variants in the probands. Over half of unrelated cases (n = 42) and approximately one-third of probands (n = 12) were found to carry one or two LoF variants in these prioritized genes. These results highlight the role of the matrisome in the pathogenesis of Ebstein\'s anomaly, contributing to a better understanding of the genetic architecture underlying this condition. Our findings hold the potential to impact the genetic diagnosis and treatment approaches for Ebstein\'s anomaly.