Initial Counseling Prior to Palliation for Hypoplastic Left Heart Syndrome: 2021 vs 2011

We sought to examine current practices and changes in practice regarding initial counseling for families of patients with hypoplastic left heart syndrome (HLHS) given the evolution of options and outcomes over time. Counseling (Norwood with Blalock-Taussig-Thomas shunt (NW-BTT), NW with right ventricle to pulmonary artery conduit (NW-RVPA), hybrid palliation, heart transplantation, or non-intervention/hospice (NI)) for patients with HLHS were queried via questionnaire of pediatric care professionals in 2021 and compared to identical questionnaire from 2011. Of 322 respondents in 2021 (39% female), 299 respondents were cardiologists (92.9%), 17cardiothoracic surgeons (5.3%), and 6 were nurse practitioners (1.9%). Respondents were largely from North America (96.9%). In 2021, NW-RVPA procedure was the preferred palliation for standard risk HLHS patient (61%) and was preferred across all US regions (p < 0.001). NI was offered as an option by 71.4% of respondents for standard risk patients and was the predominant strategy for patients with end-organ dysfunction, chromosomal abnormality, and prematurity (52%, 44%, and 45%, respectively). The hybrid procedure was preferred for low birth-weight infants (51%). In comparison to the identical 2011 questionnaire (n = 200), the NW-RVPA was endorsed more in 2021 (61% vs 52%, p = 0.04). For low birth-weight infants, hybrid procedure was more recommended than in 2011 (51% vs 21%, p < 0.001). The NW-RVPA operation is the most recommended strategy throughout the US for infants with HLHS. The hybrid procedure for low birth-weight infants is increasingly recommended. NI continues to be offered even in standard risk patients with HLHS.

Nomenclature for Pediatric and Congenital Cardiac Care: Unification of Clinical and Administrative Nomenclature - The 2021 International Paediatric and Congenital Cardiac Code (IPCCC) and the Eleventh Revision of the International Classification of Diseases (ICD-11)

Substantial progress has been made in the standardization of nomenclature for paediatric and congenital cardiac care. In 1936, Maude Abbott published her Atlas of Congenital Cardiac Disease, which was the first formal attempt to classify congenital heart disease. The International Paediatric and Congenital Cardiac Code (IPCCC) is now utilized worldwide and has most recently become the paediatric and congenital cardiac component of the Eleventh Revision of the International Classification of Diseases (ICD-11). The most recent publication of the IPCCC was in 2017. This manuscript provides an updated 2021 version of the IPCCC. The International Society for Nomenclature of Paediatric and Congenital Heart Disease (ISNPCHD), in collaboration with the World Health Organization (WHO), developed the paediatric and congenital cardiac nomenclature that is now within the eleventh version of the International Classification of Diseases (ICD-11). This unification of IPCCC and ICD-11 is the IPCCC ICD-11 Nomenclature and is the first time that the clinical nomenclature for paediatric and congenital cardiac care and the administrative nomenclature for paediatric and congenital cardiac care are harmonized. The resultant congenital cardiac component of ICD-11 was increased from 29 congenital cardiac codes in ICD-9 and 73 congenital cardiac codes in ICD-10 to 318 codes submitted by ISNPCHD through 2018 for incorporation into ICD-11. After these 318 terms were incorporated into ICD-11 in 2018, the WHO ICD-11 team added an additional 49 terms, some of which are acceptable legacy terms from ICD-10, while others provide greater granularity than the ISNPCHD thought was originally acceptable. Thus, the total number of paediatric and congenital cardiac terms in ICD-11 is 367. In this manuscript, we describe and review the terminology, hierarchy, and definitions of the IPCCC ICD-11 Nomenclature. This article, therefore, presents a global system of nomenclature for paediatric and congenital cardiac care that unifies clinical and administrative nomenclature.The members of ISNPCHD realize that the nomenclature published in this manuscript will continue to evolve. The version of the IPCCC that was published in 2017 has evolved and changed, and it is now replaced by this 2021 version. In the future, ISNPCHD will again publish updated versions of IPCCC, as IPCCC continues to evolve.

Model of magnetically guided fetal cardiac intervention: potential to avoid direct cardiac puncture

OBJECTIVE

Fetal cardiac interventions are performed via direct cardiac puncture and are associated with significant fetal morbidity. The feasibility of utilizing magnetic navigation to maneuver a guide wire and balloon across a fetal aortic valve without direct cardiac puncture is tested.

METHODS

A fetal heart model was manufactured and placed in a catheterization laboratory equipped with magnetic navigation. Magnetically steerable guide wires along with commercially available coronary balloons were inserted into the model at a site mimicking a hepatic vein.

RESULTS

Passage of the wire and balloon was achieved on every attempt. The model was suitable for testing although the structural characteristics of the model made wire passage from the right to the left atrium the most challenging aspect. Once the wire was positioned in the left ventricle, it was easily maneuvered 180 degrees towards the left ventricular outflow tract and then the descending aorta. Advancement of a coronary balloon over this wire was uncomplicated.

CONCLUSION

In a fetal heart model, it is feasible to deliver a wire and balloon from abdominal venous access antegrade across the aortic valve. Progression to fetal lamb models is planned and may advance fetal cardiac interventions by reduction of fetal morbidity.

Abstract 520: Elastic Fiber Fragmentation and Aberrant Angiogenesis Precede Inflammation in Early-Onset Aortic Valve Disease

Introduction

Elastic fiber fragmentation (EFF) is a hallmark of aortic valve disease (AVD), and both inflammation and neovascularization have been identified as late findings, presumably due to atherosclerosis through a wound healing like response. However, EFF independently stimulates angiogenesis, suggesting an alternative mechanism for neovascularization in AVD.

Hypothesis

We hypothesized that aberrant angiogenesis would be an early AVD finding, preceding inflammation, due to EFF.

Methods

To examine disease progression, valve tissue was examined using histochemistry and immunohistochemistry from early (<40yo) and late (≥40yo) onset AVD specimens, as well as age-matched autopsy control aortic valves. Angiogenesis (VEGF-A, CD-31, SMA and chondromodulin), EFF (elastin, fibrillin-1, emilin-1, fibulin-5), progenitor valve interstitial cell phenotype (CD-34, CD-45) and inflammation (CD-68, LRP-5) were assessed.

Results

Bicuspid aortic valve was more common in early-onset AVD (n=21), and cardiovascular comorbidities were more common in late-onset AVD (n=11). Early-onset AVD specimens demonstrated angiogenesis without inflammation or atherosclerosis. A distinct pattern of EFF and elastic fiber components surrounded early-onset AVD neovessels, which were not present in control valves, including increased emilin and decreased fibulin-5, and the elastase/anti-elastase ratio and localization were altered in both early and late-onset AVD, suggesting a dynamic disease progression. Interestingly, progenitor VICs were present in control valves at both stages and were unchanged in age-matched AVD specimens.

Conclusions

Aberrant angiogenesis is an early mechanism in AVD pathogenesis preceding inflammation, implicating EFF as an inciting factor. Elucidation of the underlying mechanisms may inform the development of new pharmacologic therapeutics and durable bioprostheses.

A prospective phase II trial of vinblastine and methotrexate in multivessel intraluminal pulmonary vein stenosis in infants and children

OBJECTIVE

To determine the safety and efficacy of the chemotherapeutic agents vinblastine and methotrexate in the treatment of children with progressive multivessel intraluminal pulmonary vein stenosis (PVS).

METHODS

Children received weekly vinblastine and methotrexate for a period of 1 year. Outcomes (for patients receiving ≥1 month of chemotherapy) were classified separately for patients with isolated PVS and PVS with congenital heart disease (CHD). Primary efficacy outcome was "response to treatment" categorized by echocardiographic criteria of response. Survival to 1 year was also evaluated. All adverse events were classified according to Cancer Therapy Evaluation Program, Common Terminology Criteria version 3.0. Events were further classified as related to chemotherapy, cardiac, or other causes.

RESULTS

Among 29 patients enrolled, 28 received at least one dose of chemotherapy and were evaluable for toxicity, while 23 were evaluable for response (21 CHD, 2 isolated). Both patients in the isolated group had progressive disease and died. Overall, 33% (7/21) of patients with PVS and CHD had stable disease; 1-year survival of 38%; and four patients continue in remission (93, 96, 124, and 125 months after treatment initiation). While both cardiac-related (19%) and chemotherapy-related (53%) toxicities were common, most were asymptomatic laboratory changes. Grade 3 (13%) and grade 4 (4%) toxicities were reversible, and no treatment-related grade 5 toxicities were observed.

CONCLUSION

We report on the first prospective trial of chemotherapy for infants and children targeting the presence of myofibroblastic cells within the lesions of PVS based on myofibroblastic proliferation associated with desmoid tumors of infancy. The toxicity profile resulted in numerous treatment delays and interruptions that, combined with limited information on the natural history of PVS in this patient population, hampered our ability to determine the true efficacy of this approach. These results will be important as a baseline for clinical trials in this patient population.

Common aortic arch anomalies: diagnosis and management

Vascular rings are a rare form of congenital malformation that completely encircle the trachea and esophagus with vascular structures. The two most common forms are double aortic arch and right aortic arch with an aberrant left subclavian artery and a left-sided ligamentum arteriosum. Patients may present with symptoms of airway or esophageal impingement, including "noisy breathing," stridor, respiratory distress, difficulty feeding, or dysphagia. Typically, the more severe the airway or esophageal compression, the earlier the age at presentation. Diagnosis was traditionally made by posterior compression of the esophagus demonstrated by barium swallow; in the current era, CT angiography or magnetic resonance angiography is used. Although helpful to delineate intracardiac anatomy and associated structural heart defects, echocardiography is less useful for imaging vascular structures when atretic segments comprise part of the vascular ring. Management includes surgical division of the structures contributing to the vascular ring. Some centers also perform surgical remodeling of Kommerell's diverticulum because this structure may contribute to continuing tracheal or esophageal compression even after the ring has been released. Patients with associated tracheomalacia may continue to have symptoms that can last for months, but ultimately resolve with time. Long-term results are generally excellent with minimal morbidity and mortality.

Atrial remodeling after the Fontan operation

The hemodynamics after Fontan surgery are notable for hypertension and dilation of the right atrium (RA). The effect of this stress on atrial cytoarchitecture has not been systematically studied and might be relevant to arrhythmias and their treatment. Morphologic and histopathologic analyses were performed on tissue from the RA and left atrium (LA) from autopsy specimens of Fontan hearts (n = 47). The findings were compared to those from control samples from young patients with normal atrial hemodynamics (n = 15). Most Fontan specimens were from young patients who died after a relatively short duration of Fontan physiology. The tissues were analyzed for wall thickness, fibrosis content, and fibrosis pattern. The mean wall thickness for the RA (3.0 +/- 1.0 mm) and LA (2.3 +/- 0.6 mm) in the Fontan hearts was significantly greater than that in the control hearts (RA, 1.8 +/- 0.4 mm; LA, 1.8 +/- 0.5 mm; p <0.001 and p = 0.024, respectively). The predictors for thickening of the RA included (1) older age at Fontan surgery, (2) older age at death, and (3) longer duration of Fontan circulation. The Fontan hearts and control hearts exhibited nearly identical fibrosis patterns in the RA and LA. Neither wall thickness nor fibrosis varied with the underlying heart defect or style of Fontan connection. In conclusion, atrial remodeling after Fontan surgery for univentricular heart physiology involves increased wall thickness in both the RA and LA. Interstitial fibrosis was also observed in the Fontan atria; however, because a similar pattern was present in the control tissue, this likely represented normal fibroelastic atrial structure, rather than a specific response to Fontan hemodynamics. The degree of wall thickening observed in the Fontan atria was not so excessive as to preclude transmural lesions during catheter or surgical ablation of reentrant arrhythmias.

Echocardiographic Diagnosis and Management of Bilateral Coronary Ostial Atresia in a Patient with Pulmonary Atresia and Intact Ventricular Septum

Bilateral atresia of the coronary artery ostia in patients with pulmonary atresia and intact ventricular septum is a rare condition with no reported survivors beyond early infancy. We report the first case of diagnosis by echocardiography followed by successful cardiac transplantation.

Pulmonary vein stenosis: expression of receptor tyrosine kinases by lesional cells

BACKGROUND

Primary pulmonary vein stenosis (PVS) is a progressive disorder of infants. Although catheter based intervention and chemotherapy are used to manage the disorder, the benefit of these approaches is reduced considerably by restenosis. The nature of the intimal cells causing the occlusive lesions in PVS is poorly understood.

METHODS

Seven PVS cases were studied with antibodies for smooth muscle actin (SMA), muscle-specific actin (MSA), monoclonal desmin, S100 protein, CD31, CD34, CD45RO, CD68, CD99, Ki-67 (MIB-I), and with antibodies directed against several receptor tyrosine kinases (RTK), including platelet-derived growth factor alpha and beta receptor (PDGFR-alpha and -beta), epidermal growth factor receptor (EGFR), fibroblast growth factor receptor (FGFR), vascular endothelial growth factor 1 and 2 receptor (VEGFR), and stem cell factor receptor (c-kit).

RESULTS

Lesional cells stained strongly and diffusely with SMA and MSA, but not for macrophage, lymphocyte, endothelial markers, or for Ki-67. RTK expression was strong and diffuse for PDGFR-alpha and -beta, FGFR, and VEGFR-2. Lesional cells stained for VEGF and PDGF beta receptor was phosphorylated.

CONCLUSIONS

The histologic appearance, and the strong diffuse immunoreactivity for smooth muscle markers, indicates that the intimal lesional cells are myofibroblast-like. Expression of various receptor tyrosine kinases and some ligands suggests an autocrine or paracrine role of these proteins in the pathogenesis of the intimal occlusive lesion in PVS.

Isolated left-sided scimitar vein connecting all left pulmonary veins to the right inferior vena cava

When the common pulmonary vein fails to develop, the embryonic connections of the pulmonary veins to one or more of the systemic veins almost always persist. Anomalous pulmonary venous connections to the inferior vena cava (IVC) are typically characterized by hypoplasia of the involved pulmonary veins and pulmonary artery, as well as abnormal parenchyma of the involved lung. Such cases have been described as "scimitar syndrome." We report the case of a young female patient in whom all the left pulmonary veins converged into a common vessel that drained into the IVC but who had a normal left pulmonary artery and left lung. Surgical intervention was successful, and our patient is still alive.

Morphogenesis of the right ventricle requires myocardial expression of Gata4

Mutations in developmental regulatory genes have been found to be responsible for some cases of congenital heart defects. One such regulatory gene is Gata4, a zinc finger transcription factor. In order to circumvent the early embryonic lethality of Gata4-null embryos and to investigate the role of myocardial Gata4 expression in cardiac development, we used Cre/loxP technology to conditionally delete Gata4 in the myocardium of mice at an early and a late time point in cardiac morphogenesis. Early deletion of Gata4 by Nkx2-5Cre resulted in hearts with striking myocardial thinning, absence of mesenchymal cells within the endocardial cushions, and selective hypoplasia of the RV. RV hypoplasia was associated with downregulation of Hand2, a transcription factor previously shown to regulate formation of the RV. Cardiomyocyte proliferation was reduced, with a greater degree of reduction in the RV than in the LV. Late deletion of Gata4 by Cre recombinase driven by the alpha myosin heavy chain promoter did not selectively affect RV development or generation of endocardial cushion mesenchyme but did result in marked myocardial thinning with decreased cardiomyocyte proliferation, as well as double-outlet RV. Our results demonstrate a general role of myocardial Gata4 in regulating cardiomyocyte proliferation and a specific, stage-dependent role in regulating the morphogenesis of the RV and the atrioventricular canal.

GATA4 is a dosage-sensitive regulator of cardiac morphogenesis

Normal heart development is orchestrated by a set of highly conserved transcription factors that includes GATA4, Nkx2-5, and Tbx5. Heterozygous mutation of each of these genes causes congenital heart disease in humans. In mouse models, haploinsufficiency for Nkx2-5 or Tbx5 resulted in an increased incidence of structural heart disease, confirming that normal heart development is sensitive to small changes in expression levels of Nkx2-5 and Tbx5. However, mice haploinsufficient for GATA4 have not been reported to have cardiac abnormalities. We generated two new GATA4 alleles, GATA4(H) and GATA4(flox). GATA4(flox/flox) embryos expressed 50% less GATA4 protein in the heart and survived normally. In contrast, GATA4(H/H) embryos expressed 70% less GATA4 protein in the heart and died between days 13.5 and 16.5 of gestation. These embryos had common atrioventricular canal (CAVC), double outlet right ventricle (DORV), hypoplastic ventricular myocardium, and normal coronary vasculature. Myocardial hypoplasia was associated with diminished cardiomyocyte proliferation. Hemodynamic measurements demonstrated that these embryos had normal systolic function, severe diastolic dysfunction, and atrioventricular regurgitation. Surprisingly, expression levels of the putative GATA4 target genes ANF, BNP, MEF2C, Nkx2-5, cyclin D2, and BMP4 were unchanged in mutant hearts, suggesting that GATA4 is not a dose-limiting regulator of the expression of these genes during later stages of embryonic cardiac development. These data demonstrate that multiple aspects of embryonic cardiac morphogenesis and function are exquisitely sensitive to small changes in GATA4 expression levels.

Mouse models for cardiac conduction system development

The mouse is the animal of choice for the study of molecular mechanisms involved in the regulation of cardiovascular morphogenesis and function. Recently, a series of genetically engineered mouse models have been reported (e.g. cGATA6/lacZ, MinK/lacZ knock-in/knock-out, engrailed2/lacZ, Cardiac troponin I/lacZ) that provide new and exciting information on the development of the atrioventricular conduction system (AVCS). On the basis of these and ongoing studies, concepts for the formation of the AVCS are continuously being adjusted. A proper understanding of the normal developmental mechanisms underlying the cardiac remodelling leading to the formation of the AVCS is imperative for the interpretation of cardiac abnormalities, including conduction disturbances, as observed in some genetically perturbed (knockout) mice. In this paper information on murine AVCS development will be integrated with published and unpublished results from studies in other vertebrates, including human and rabbit. We will illustrate that although many pieces of the puzzle still remain to be gathered, the outline of a very complex and critical event in cardiac morphogenesis is slowly emerging. Specifically, we will re-evaluate the concept of the 'primary ring' in the context of the new insights in the development of the AV junction as provided by the respective mouse models described above.

Transcriptional regulation in the mouse atrioventricular conduction system

We identified a GATA6 gene enhancer that selectively marks the developing atrioventricular conduction system (AVCS) in transgenic mice. This enhancer reads anterior/posterior and medial/lateral positional information early in the cardiogenic programme and remains active in progressively more restricted subsets of heart cells leading up to AVCS formation. Additional experiments will be required to determine if the potential to be recruited into the AVCS is similarly restricted to a subset of myocardial cells early in the cardiogenic programme or if this enhancer can also be activated de novo in cells that initially reside outside this field. We are using several strategies to identify factors that regulate this and other AVCS enhancers and hence govern AVCS function. We are also using this enhancer to make transgenic mice that express Cre, or an inducible form of Cre, to track lineages and to delete floxed genes in the developing or mature AVCS. This Cre/lox approach provides a means to deconstruct complex congenital heart phenotypes that involve the conduction system and to test whether genes are required to form the AVCS or to maintain AVCS function. Lastly, we are exploring strategies to isolate and analyse AVCS cells from normal and affected hearts.

Echocardiographic diagnosis of partial obstruction of Blalock-Taussig shunts

While echocardiography has previously been used to differentiate between patency and complete occlusion of aortopulmonary shunts, the echocardiographic diagnosis of partial obstruction of a shunt has not been reported. We describe a unique color flow Doppler finding that quickly and accurately diagnosed three cases of partial distal obstruction of aortopulmonary shunts.

A GATA-6 gene heart-region-specific enhancer provides a novel means to mark and probe a discrete component of the mouse cardiac conduction system

The transcriptional programs that specify the distinct components of the cardiac conduction system are poorly understood, in part due to a paucity of definitive molecular markers. In the present study we show that a cGATA-6 gene enhancer can be used to selectively express transgenes in the atrioventricular (AV) conduction system as it becomes manifest in the developing multichambered mouse heart. Furthermore, our analysis of staged cGATA-6/lacZ embryos revealed that the activity of this heart-region-specific enhancer can be traced back essentially to the outset of the cardiogenic program. We provide evidence that this enhancer reads medial/lateral and anterior/posterior positional information before the heart tube forms and we show that the activity of this enhancer becomes restricted at the heart looping stage to AV myocardial cells that induce endocardial cushion formation. We infer that a deeply-rooted heart-region-specific transcriptional program serves to coordinate AV valve placement and AV conduction system formation. Lastly, we show that cGATA-6/Cre mice can be used to delete floxed genes in the respective subsets of specialized heart cells.