Molecular Pathways and Animal Models of Tetralogy of Fallot and Double Outlet Right Ventricle.

Tetralogy of Fallot and double-outlet right ventricle are outflow tract (OFT) alignment defects situated on a continuous disease spectrum. A myriad of upstream causes can impact on ventriculoarterial alignment that can be summarized as defects in either i) OFT elongation during looping morphogenesis or ii) OFT remodeling during cardiac septation. Embryological processes underlying these two developmental steps include deployment of second heart field cardiac progenitor cells, establishment and transmission of embryonic left/right information driving OFT rotation and OFT cushion and valve morphogenesis. The formation and remodeling of pulmonary trunk infundibular myocardium is a critical component of both steps. Defects in myocardial, endocardial, or neural crest cell lineages can result in alignment defects, reflecting the complex intercellular signaling events that coordinate arterial pole development. Importantly, however, OFT alignment is mechanistically distinct from neural crest-driven OFT septation, although neural crest cells impact indirectly on alignment through their role in modulating signaling during SHF development. As yet poorly understood nongenetic causes of alignment defects that impact the above processes include hemodynamic changes, maternal exposure to environmental teratogens, and stochastic events. The heterogeneity of causes converging on alignment defects characterizes the OFT as a hotspot of congenital heart defects.

Anatomic Risk Factors for Reintervention After Arterial Switch Operation for Taussig-Bing Anomaly.

BACKGROUND: This study aimed to determine the factors related to reintervention, especially for pulmonary stenosis (PS), in patients with Taussig-Bing anomaly (TBA) after the arterial switch operation. METHODS: This retrospective study included 34 patients with TBA who underwent the arterial switch operation between 1993 and 2018. Preoperative anatomic and physiologic differences and long-term outcomes were determined using a case-matched control with transposition of the great arteries with ventricular septal defect and TBA with an anterior and rightward aorta. RESULTS: At arterial switch operation, median age was 43 days (range, 16 to 102) and median body weight was 3.6 kg (range, 2.8 to 3.8 kg). Aortic arch obstruction and coronary anomalies were present in 64% and 41% of patients, respectively. The hospital mortality rate was 11%, including one cardiac death, and the late mortality rate was 2.9%. Furthermore, 41% patients underwent 26 reinterventions for PS. Patients undergoing PS-related reintervention had a significantly larger native pulmonary artery to aortic annulus size ratio than patients not receiving reintervention (1.69 vs 1.41, P = .02). This ratio was the only predictor of PS-related reintervention; it was significantly higher in the TBA group than in the transposition of great arteries/ventricular septal defect group. The PS-related reintervention was required more in the TBA group than in the transposition of great arteries/ventricular septal defect group. CONCLUSIONS: Regardless of complex coronary anatomy and associated anomalies, early and late survival were acceptable. Postoperative PS was strongly associated with having a larger native pulmonary valve, suggesting that an optimal surgical reconstruction was required for achieving an appropriate aortopulmonary anatomic relationship during the arterial switch operation.

An unusual presentation of developmental anomalies of the cardiovascular system including tetralogy of fallot, double outlet right ventricle, patent foramen ovale and persistent right aortic arch in a Friesian calf.

BACKGROUND: Congenital heart diseases are occasionally encountered in the bovine species. Ventricular septal defects (VSD) and atrial septal defects (ASD) are reported to be the most common; however, a vast collection have been reported [1, 2]. Congenital heart diseases is thought to represent less than 3% of all congenital abnormalities in calves [3]. Various cardiac anomalies arise due to defective embryologic development such as defects of the septae or the cardiac chambers [2]. The exact aetiology of these congenial heart anomalies remains to be fully elucidated [4]. VSDs appear to be the most common congenital cardiac anomaly in calves. Other diseases can be subdivided into cyanotic (e.g. ASD or patent ductus arteriosus) and non-cyanotic (e.g. tetralogy of fallot or eisenmengers complex) [5, 6]. An exceptional presentation of an array of congenital anomalies was identified in a Friesian heifer calf. To the authors' knowledge this concurrent collection of congenital abnormalities has never been reported in this species. CASE PRESENTATION: A 3-day old Friesian heifer presented with a history since birth of regurgitation post feeding. The main finding on clinical examination was tachypnoea with a holosystolic murmur. Echocardiography identified a VSD, patent foramen ovale (PFO) (both with left to right blood flow) and tricuspid insufficiency. The calf was subsequently euthanised and underwent gross post-mortem examination. A persistent right aortic arch (PRAA) was identified. The cardiac anomalies identified on the echocardiogram were confirmed along with additional abnormalities; double outlet right ventricle (DORV), partial transposition of the great vessels, pulmonic stenosis, hypoplasia of the right branch of the pulmonary artery and right ventricular hypertrophy. The final diagnosis was Tetralogy of Fallot with DORV, PFO and PRAA. The lungs appeared oedematous and congested due to cardiac malfunction and cranioventral aspiration pneumonia. Free serous fluid was identified in the thoracic cavity. Unilateral renal agenesis of the left kidney was an incidental finding but is of note due to its coexistence with the cardiac abnormalities. CONCLUSIONS: This is an unusual case as it features numerous congenital abnormalities that appeared to negate each other allowing capability with life. To the authors' knowledge, this collection of concurrent cardiac anomalies has not been previously reported in bovines.

A novel NR2F2 loss-of-function mutation predisposes to congenital heart defect.

Congenital heart defect (CHD) is the most common type of birth defect in humans and a leading cause of infant morbidity and mortality. Previous studies have demonstrated that genetic defects play a pivotal role in the pathogenesis of CHD. However, the genetic basis of CHD remains poorly understood due to substantial genetic heterogeneity. In this study, the coding exons and splicing boundaries of the NR2F2 gene, which encodes a pleiotropic transcription factor required for normal cardiovascular development, were sequenced in 168 unrelated patients with CHD, and a novel mutation (c.247G > T, equivalent to p.G83X) was detected in a patient with double outlet right ventricle as well as ventricular septal defect. Genetic scanning of the mutation carrier's relatives available showed that the mutation was present in all affected family members but absent in unaffected family members. Analysis of the index patient's pedigree displayed that the mutation co-segregated with CHD, which was transmitted as an autosomal dominant trait with complete penetrance. The nonsense mutation was absent in 230 unrelated, ethnically-matched healthy individuals used as controls. Functional deciphers by using a dual-luciferase reporter assay system revealed that the mutant NR2F2 protein had no transcriptional activity as compared with its wild-type counterpart. Furthermore, the mutation abrogated the synergistic transcriptional activation between NR2F2 and GATA4, another core cardiac transcription factor associated with CHD. This study firstly associates NR2F2 loss-of-function mutation with an increased susceptibility to double outlet right ventricle in humans, which provides further significant insight into the molecular mechanisms underpinning CHD, suggesting potential implications for genetic counseling of CHD families and personalized treatment of CHD patients.

Double outlet right ventricle with subpulmonary ventricular septal defect (Taussig-Bing anomaly) and other complex congenital cardiac malformations in an American Quarter Horse foal.

A 4-week-old American Quarter Horse colt presented with a recent history of diarrhea and decreased activity level. On initial physical examination, the animal was bright and alert and major findings were limited to a loud systolic heart murmur radiating widely over both sides of the thorax. While in the hospital, the clinical condition of the foal warranted further imaging to determine the cause and extent of cardiac disease. A variety of congenital cardiac malformations were identified during echocardiographic examination and autopsy, including a double outlet right ventricle and a subpulmonary interventricular septal defect (Taussig-Bing anomaly), ventricular inversion with atrioventricular discordance, tricuspid valve atresia, a septum primum interatrial septal defect, mitral valve dysplasia with a cleft in the septal mitral valve cusp, aortic, and subaortic stenosis, tubular hypoplasia of the ascending aorta and the aortic arch, a patent ductus arteriosus, an aberrant circumflex coronary artery, and aberrant left and right subclavian arteries. Echocardiographic and postmortem findings of the cardiac defects in this foal are presented and discussed.

MESP1 loss­of­function mutation contributes to double outlet right ventricle.

Congenital heart disease (CHD) is the most common form of birth defect in humans, and remains a leading non­infectious cause of infant mortality worldwide. An increasing number of studies have demonstrated that genetic defects serve a pivotal role in the pathogenesis of CHD, and mutations in >60 genes have been causally associated with CHD. CHD is a heterogeneous disease and the genetic basis of CHD in the majority of patients remains poorly understood. In the present study, the coding exons and flanking introns of the mesoderm posterior 1 (MESP1) gene, which encodes a basic helix­loop­helix transcription factor required for normal cardiovascular development, were sequenced in 178 unrelated patients with CHD. The available relatives of the index patient carrying an identified mutation and 200 unrelated, ethnically­matched healthy individuals, who were used as controls, were genotyped for MESP1. The functional characteristics of the MESP1 mutation were determined using a dual­luciferase reporter assay system. As a result, a novel de novo heterozygous MESP1 mutation, p.Q118X, was identified in an index patient with double outlet right ventricle (DORV) and a ventricular septal defect. The nonsense mutation was absent in the 400 reference chromosomes and the altered amino acid was completely conserved evolutionarily across species. Functional assays indicated that the mutant MESP1 protein had no transcriptional activity when compared with its wild­type counterpart. The present study firstly provided experimental evidence supporting the concept that a MESP1 loss­of­function mutation may contribute to the development of DORV in humans, which presents a significant insight into the molecular pathogenesis of CHD. The results highlight the potential implications for the genetic counseling and personalized treatment of patients with CHD.

Double-outlet right ventricle revisited.

OBJECTIVES: Double-outlet right ventricle is a form of ventriculoarterial connection. The definition formulated by the International Society for Nomenclature of Paediatric and Congenital Heart Disease is based on hearts with both arterial trunks supported in their greater part by a morphologically right ventricle. Bilateral infundibula and ventricular septal defects are highly debated criteria. This study examines the anatomic controversies surrounding double-outlet right ventricle. We show that hearts with double-outlet right ventricle can have atrioventricular-to-arterial valvular continuity. We emphasize the difference between the interventricular communication and the zone of deficient ventricular septation. METHODS: The hearts examined were from the University of Florida in Gainesville; Johns Hopkins All Children's Hospital, St Petersburg, Fla; and Lurie Children's Hospital, Chicago, Ill. Each specimen had at least 75% of both arterial roots supported by the morphologically right ventricle, with a total of 100 hearts examined. The morphologic method was used to assess anatomic features, including arterial-atrioventricular valvular continuity, subarterial infundibular musculature, and the location of the hole between the ventricles. RESULTS: Most hearts had fibrous continuity between one of the arterial valves and an atrioventricular valve, with bilateral infundibula in 23%, and intact ventricular septum in 5%. CONCLUSIONS: Bilateral infundibula are not a defining feature of double-outlet right ventricle, representing only 23% of the specimens in our sample. The interventricular communication can have a posteroinferior muscular rim or extend to become perimembranous (58%). Double-outlet right ventricle can exist with an intact ventricular septum.

The independence of the infundibular building blocks in the setting of double-outlet right ventricle.

It has long been contentious as to whether the presence of bilateral infundibulums, or conuses, is a prerequisite for the diagnosis of double-outlet right ventricle. As the use of such a criterion would abrogate the so-called "morphological method", which correctly states that one variable entity should not be defined on the basis of another entity that is itself variable, it is now accepted that double outlet can exist in the setting of fibrous continuity between the leaflets of the atrioventricular and arterial valves. Although this debate has now been resolved, there are other contentious areas still requiring clarification in the setting of hearts unified because of the presence of this particular ventriculo-arterial connection - for example, it is questionable whether the channel between the ventricles should be described as a "ventricular septal defect", whereas it is equally arguable that the mere presence of fibrous continuity between the leaflets of the arterial valves does not necessarily place the channel in a doubly committed location. In this review, we describe a series of autopsied hearts in which the anatomical features serve to illuminate these various topics. We then discuss recent findings regarding cardiac development that point to the individuality of the building blocks of the ventricular outflow tracts, specifically the outlet septum, the inner heart curvature, or ventriculo-infundibular fold, and the septomarginal trabeculation, or septal band.

Surgical planning for a complex double-outlet right ventricle using 3D printing.

Rapid prototyping may be beneficial in properly selected cases of complex congenital heart disease, providing detailed anatomical understanding that helps to guide potential surgical and cardiac catheterization interventions. We present a case of double-outlet right ventricle, where the decision to obtain a three-dimensional printed model helped for better understanding of the anatomy, with the additional advantage of surgical simulation in planning the surgical approach and type of surgical repair.

Anatomical Classifications of the Coronary Arteries in Complete Transposition of the Great Arteries and Double Outlet Right Ventricle with Subpulmonary Ventricular Septal Defect.

Objective To discuss the anatomical morphologies of the coronary arteries and frequencies of unusual coronary arteries in complete transposition of the great arteries and double outlet right ventricle (DORV) associated with a subpulmonic ventricular septal defect (VSD). Methods Between March 1999 and August 2012, 1,078 patients with complete transposition of the great arteries or DORV with subpulmonary VSD underwent arterial switch operations (ASOs) and were visually evaluated to classify their coronary artery morphology during open heart surgery. Results The coronary arteries could be classified into five patterns with several subtypes. Unusual coronary arteries were observed in 248 of the 1,078 cases, providing a frequency of 23.01%. The frequencies of the patients with transposition of the great arteries with intact ventricular septum (TGA/IVS), TGA/VSD, and DORV with subpulmonary VSD were 17.65, 23.28, and 31.84%, respectively. The most common morphologies were the right coronary artery (RCA) originating from sinus 1 and circumflex (CX) originating from sinus 2 (1R, AD; 2CX; 26.50%); the CX originating from sinus 2 (1AD; 2R, CX; 21.36%); the RCA, left anterior descending artery, and CX originating from single sinus 2 (2R, AD, CX; 13.24%). The in-hospital mortalities of the patients with or without unusual coronary arteries after ASO were 14.1 and 6.02%, respectively. Conclusion Patients with complete transposition of the great arteries or DORV with subpulmonary VSD have a high frequency of unusual coronary arteries, which might greatly impact on the mortality for ASO. Improving the preoperative diagnostic criteria for coronary artery morphology may significantly increase the success rate for ASOs.

The concept of double inlet-double outlet right ventricle: a distinct congenital heart disease.

The aim of this study was to estimate the incidence and to analyze the anatomy of double inlet-double outlet right ventricle complex and its associated cardiac anomalies in our autopsy series. Among the 1640 hearts with congenital heart disease of our Anatomical Collection, we reviewed the specimens with double inlet-double outlet right ventricle, according to the sequential-segmental analysis, identifying associated cardiac anomalies and examining lung histology to assess the presence of pulmonary vascular disease. We identified 14 hearts with double inlet-double outlet right ventricle (0.85%). Right atrial isomerism was observed in 10 hearts, situs solitus in 3 and left atrial isomerism in one. Regarding the mode of atrioventricular connection, all hearts but one had a common atrioventricular valve. Systemic or pulmonary venous abnormalities were noted in all patients with atrial isomerism. In nine patients a valvular or subvalvular pulmonary stenosis was present. Among the functionally "univentricular hearts", double inlet- double outlet right ventricle represents a peculiar entity, mostly in association with right atrial isomerism. Multiple cardiac anomalies are associated and may complicate surgical repair.

Use of a Three Dimensional Printed Cardiac Model to Assess Suitability for Biventricular Repair.

Three dimensional (3D) printing is rapidly gaining interest in the medical field for use in presurgical planning. We present the case of a seven-year-old boy with double outlet right ventricle who underwent a bidirectional Glenn anastomosis. We used a 3D cardiac model to assess his suitability for a biventricular repair. He underwent a left ventricle-to-aorta baffle with a right ventricle-to-pulmonary artery conduit placement. He did well postoperatively and was discharged home with no evidence of baffle obstruction and good biventricular function. A 3D printed model can provide invaluable intracardiac spatial information in these complex patients.

The finding of an undiagnosed long segment tracheal stenosis in a cyanotic child undergoing an arterial switch operation and VSD closure.

This report details the case of a 2-month-old baby boy with known cyanotic congenital heart disease (double outlet right ventricle with subpulmonary ventricular septal defect, VSD) in whom tracheal stenosis was undetected, being found later on failed intubation while undergoing anaesthesia for an arterial switch operation and VSD closure. As a result, the cardiac surgery was postponed. Such an association between congenital heart disease and tracheal stenosis has been reported but remains exceptionally rare. The baby subsequently underwent a slide tracheoplasty the next day and had major cardiac surgery a few days later. He was discharged approximately 3 weeks later after spending 8 days on the cardiac intensive care unit.

Triple outlet right ventricle: a previously unknown cardiac malformation.

We present the case of an infant with three distinct outflow tracts from the right ventricle. Three outlets from the heart have been previously named the "Tritruncal Heart". We review the two previously reported cases of tritruncal hearts and describe the anatomy, diagnosis, surgical management, and outcome of our case. Embryologic implications are also discussed.

Perioperative management of pulmonary hypertension during lung transplantation (a lesson for other anaesthesia settings) / Manejo perioperatorio de la hipertension pulmonar durante el trasplante pulmonar (Una lección para otros escenarios anestésicos)

Patients with pulmonary hypertension are some of the most challenging for an anaesthesiologist to manage. Pulmonary hypertension in patients undergoing surgical procedures is associated with high morbidity and mortality due to right ventricular failure, arrhythmias and ischaemia leading to haemodynamic instability. Lung transplantation is the only therapeutic option for end-stage lung disease. Patients undergoing lung transplantation present a variety of challenges for anaesthesia team, but pulmonary hypertension remains the most important. The purpose of this article is to review the anaesthetic management of pulmonary hypertension during lung transplantation, with particular emphasis on the choice of anaesthesia, pulmonary vasodilator therapy, inotropic and vasopressor therapy, and the most recent intraoperative monitoring recommendations to optimize patient care (AU)

La presencia de hipertensión pulmonar en el paciente quirúrgico constituye un reto para el anestesiólogo, dado que se asocia con una elevada morbilidad y mortalidad debido a lo frecuente del fallo del ventrículo derecho y colapso circulatorio. El trasplante pulmonar es la última opción terapéutica en los pacientes con insuficiencia respiratoria terminal. Estos pacientes representan un reto para el anestesiólogo siendo la hipertensión pulmonar el más importante. El propósito de esta artículo es la revisión del manejo anestésico de la hipertensión pulmonar durante el trasplante de pulmón, con especial énfasis en la elección del tipo de anestesia, uso de vasodilatadores pulmonares, soporte inotrópico y vasopresor, y monitorización intraoperatoria (AU)

On the role of the gap junction protein Cx43 (GJA1) in human cardiac malformations with Fallot-pathology. a study on paediatric cardiac specimen.

INTRODUCTION: Gap junction channels are involved in growth and differentiation. Therefore, we wanted to elucidate if the main cardiac gap junction protein connexin43 (GJA1) is altered in patients with Tetralogy of Fallot or double-outlet right ventricle of Fallot-type (62 patients referred to as Fallot) compared to other cardiac anomalies (21 patients referred to as non-Fallot). Patients were divided into three age groups: 0-2years, 2-12years and >12years. Myocardial tissue samples were collected during corrective surgery and analysis of cell morphology, GJA1- and N-cadherin (CDH2)-distribution, as well as GJA1 protein- and mRNA-expression was carried out. Moreover, GJA1-gene analysis of 16 patients and 20 healthy subjects was performed. RESULTS: Myocardial cell length and width were significantly increased in the oldest age group compared to the younger ones. GJA1 distribution changed significantly during maturation with the ratio of polar/lateral GJA1 increasing from 2.93±0.68 to 8.52±1.41. While in 0-2years old patients ∼6% of the lateral GJA1 was co-localised with CDH2 this decreased with age. Furthermore, the changes in cell morphology and GJA1-distribution were not due to the heart defect itself but were significantly dependent on age. Total GJA1 protein expression decreased during growing-up, whereas GJA1-mRNA remained unchanged. Sequencing of the GJA1-gene revealed only few heterozygous single nucleotide polymorphisms within the Fallot and the healthy control group. CONCLUSION: During maturation significant changes in gap junction remodelling occur which might be necessary for the growing and developing heart. In our study point mutations within the Cx43-gene could not be identified as a cause of the development of TOF.

The trabecula septomarginalis (Leonardo's cord) in abnormal ventriculo-arterial connections: anatomic and morphogenetic implications.

BACKGROUND: The abnormal ventriculo-arterial connections in atrio-ventricular concordance and situs solitus with two well developed ventricles include the range from tetralogy of Fallot throughout the different forms of double outlet right ventricle to transposition of great arteries.The infundibular septum and the trabecula septomarginalis are the fundamental anatomical landmarks for the segmental analysis.In these abnormalities there is a pathological progressive counter-clockwise rotation of the infundibular septum which divorces from the antero-superior limb of the trabecula septomarginalis and achieves his identity. Is there any anatomical evidence of a simultaneous abnormal counter-clockwise rotation of the trabecula septomarginalis? METHODS: Malposition of great arteries is a generic term since all relationships have to be expected.We present specimens with anatomical evidence of a progressive counter-clockwise rotation from 0° to about 180°of the plane passing throughout the trabecula septomarginalis's limbs. RESULTS: We can observe sequentially:1. Malformations in which the posterior limb of the trabecula septomarginalis is committed to the ventriculo infundibular fold: (tetralogy of Fallot, double outlet right ventricle with sub-aortic ventricular septal defect, truncus arteriosus and doubly committed ventricular septal defect);2. Malformations in which the posterior limb of the trabecula septomarginalis is committed to the infundibular septum (double outlet right ventricle with sub-pulmonary ventricular septal defect, transposition of great arteries). CONCLUSIONS: 1. The sequential-segmental analysis identify all the morphologies.2. The trabecula septomarginalis plane presents a progressive counter-clockwise twist on the long axis.3. Since the trabeculated portions of the ventricles are the oldest developmental components, our observations support the hypothesis that the abnormal ventriculo-arterial connections could be in relation with a pathological myocardial process during early cardio-genesis.We are promoting new studies to investigate our anatomical observations.

Perioperative Management of DORV.

The diagnosis of double-outlet right ventricle (DORV) characterizes a complex heterogeneous group of congenital cardiac malformations for which multiple classification schemes have been used. A clear understanding of the anatomy is critical to understanding the physiologic consequences of the specific type of DORV. Perioperative considerations include the medical management of the patient during the preoperative period, anesthetic and surgical management, and postoperative care. Both anesthetic and surgical management strategies are very different depending on the type of DORV. Key principles for anesthetic management include balancing the systemic and pulmonary circulations, optimizing systemic cardiac output, and closely monitoring for impaired oxygen delivery to the tissues. Depending on the specific anatomy the patient is usually placed on a 1- or 2-ventricle pathway, and initial palliation may involve placement of a systemic arterial to pulmonary artery shunt or pulmonary artery banding. In some cases the child may undergo a complete repair during the first few months of life. Surgical outcomes, both short and long-term, are dependent on the type of DORV and surgical procedure done. These patients require long-term follow up and may present for surgical or catheter-based interventions as adults.