Hypoplastic left heart syndrome: it is all in the genes

Prenatal Genetic Diagnosis in Three Fetuses With Left Heart Hypoplasia (LHH) From Three Unrelated Families

Background: Congenital heart defects (CHDs) are the most common birth defects, and left heart hypoplasia (LHH) is a severe form of CHD and responsible for more than 20% cardiac deaths during the first week of life, however, its genetic causes remain largely elusive.

Methods: Three families with fetal LHH were recruited. Genomic DNA from amniotic fluid or peripheral blood, and trio whole exome sequencing (trio-WES) and copy number variation sequencing (CNV-seq) were performed.

Results: All the three couples had no family history, and mid-gestation ultrasound revealed LHH and other variable cardiovascular defects in the fetuses. Trio-WES revealed de novo pathogenic variations in KMT2D (p.Gly3465Aspfs^*37) (NM_003482) and WDFY3 (p.Ser117Xfs^*) (NM_014991), and CNV-seq identified a deletion of 150 kb encompassing NOTCH1. KMT2D and NOTCH1 previously have been reported to be associated with CHDs, however, WDFY3 is reported for the first time to be possibly related to CHD in human.

Conclusion: Our study suggested that genetic component is an important risk factor for the development of LHH, and next generation sequencing is a powerful tool for genetic diagnosis in fetuses with CHDs and genetic counseling, however, more studies and data are need to establish the correlation of fetal phenotypes and genotypes.

A Novel Technique for the Administration of Sub-Ambient Oxygen in the Operating Room

Hypoplastic left heart syndrome (HLHS) is a common form of congenital heart disease with abnormal development of left-sided structures of the heart. As excessive pulmonary blood flow is common prior to palliative surgical procedures, therapeutic maneuvers may be required to decrease pulmonary blood flow and augment systemic cardiac output. Respiratory manipulations to optimize the ratio of pulmonary to systemic blood flow may include techniques to induce hypercarbia or the delivery of sub-ambient concentrations of oxygen (FiO₂ less than 0.21). We present a neonate with HLHS who required intraoperative care during a stage I hybrid procedure. Options for the intraoperative administration of a sub-ambient concentration of oxygen are presented.

The myocardial and coronary histopathology and pathogenesis of hypoplastic left heart syndrome

Hypoplastic left heart syndrome has the greatest mortality rate among all CHDs and without palliation is uniformly fatal. Despite noble efforts, the aetiology of this syndrome is unknown and a cure remains elusive. The genetic and anatomic heterogeneity of hypoplastic left heart syndrome supports a rethinking of old hypotheses and warrants further investigation into the histological and vascular variations recognised with this syndrome. In an effort to elucidate the pathogenesis of hypoplastic left heart syndrome, this review will focus on its unique myocardial and coronary pathology as well as evaluate the association of hypoplastic left heart syndrome with the endocardial fibroelastosis reaction.

Congenital heart disease linked to maternal autoimmunity against cardiac myosin

Structural congenital heart disease (CHD) has not previously been linked to autoimmunity. In our study, we developed an autoimmune model of structural CHD that resembles hypoplastic left heart syndrome (HLHS), a life-threatening CHD primarily affecting the left ventricle. Because cardiac myosin (CM) is a dominant autoantigen in autoimmune heart disease, we hypothesized that immunization with CM might lead to transplacental passage of maternal autoantibodies and a prenatal HLHS phenotype in exposed fetuses. Elevated anti-CM autoantibodies in maternal and fetal sera, as well as IgG reactivity in fetal myocardium, were correlated with structural CHD that included diminished left ventricular cavity dimensions in the affected progeny. Further, fetuses that developed a marked HLHS phenotype had elevated serum titers of anti-β-adrenergic receptor Abs, as well as increased protein kinase A activity, suggesting a potential mechanism for the observed pathological changes. Our maternal-fetal model presents a new concept linking autoimmunity against CM and cardiomyocyte proliferation with cardinal features of HLHS. To our knowledge, this report shows the first evidence in support of a novel immune-mediated mechanism for pathogenesis of structural CHD that may have implications in its future diagnosis and treatment.

Seasonality of hypoplastic left heart syndrome in the United States: a 10-year time-series analysis

OBJECTIVE

Hypoplastic left heart syndrome is a major congenital heart defect and is associated with significant morbidity and mortality. Its etiology remains unknown although genetic studies imply complex inheritance. Anecdotal reports of cluster presentations suggest the possible involvement of an environmental component, although previous epidemiologic studies have been of limited scope. The objective of this study was to examine seasonal and temporal patterns of hypoplastic left heart syndrome births compared with other left-sided heart defects in the United States.

METHODS

We conducted a retrospective analysis of the Pediatric Health Information System inpatient database from pediatric hospitals across the country from 1996 to 2006. Population and index case patterns were analyzed for each diagnostic category. An epidemiologic survey was performed through time-series analyses using Fisher's Kappa test and the Bartlett Kolmogorov-Smirnov test. The existence and strength of seasonality for the left-sided heart defects was quantified by the autoregression R2.

RESULTS

A seasonal occurrence was found in hypoplastic left heart syndrome but not other left-sided heart diseases. Significant seasonal differences occurred each year, with peaks in summer months and troughs in winter months. The seasonality inversely correlated with the incidence of chromosomal and extracardiac anomalies; such anomalies were highest in interrupted aortic arch, which had a random pattern of presentation.

CONCLUSIONS

There is a significant seasonal pattern in the presentation of hypoplastic left heart syndrome, with preponderance in summer months, in contrast to the random pattern in other left-sided heart diseases. Further studies are warranted to identify the influence of potential environmental factor(s) in hypoplastic left heart syndrome, as seen in diseases with seasonal patterns.