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

Considering the Genetic Architecture of Hypoplastic Left Heart Syndrome

Hypoplastic left heart syndrome (HLHS) is among the most severe cardiovascular malformations and understanding its causes is crucial to making progress in prevention and treatment. Genetic analysis is a broadly useful tool for dissecting complex causal mechanisms and it is playing a significant role in HLHS research. However, unlike classical Mendelian disorders where a relatively small number of genes are largely determinative of the occurrence and severity of the disease, the picture in HLHS is complex. De novo single-gene and copy number variant (CNV) disorders make an important contribution, but there is emerging evidence for causal contributions from lower penetrance and common variation. Integrating this emerging knowledge into clinical diagnostics and translating the findings into effective prevention and treatment remain challenges for the future.

Environmental Exposures and Congenital Heart Disease

Congenital heart disease (CHD) is the most common congenital abnormality worldwide, affecting 8 to 12 infants per 1000 births globally and causing >40% of prenatal deaths. However, its causes remain mainly unknown, with only up to 15% of CHD cases having a determined genetic cause. Exploring the complex relationship between genetics and environmental exposures is key in understanding the multifactorial nature of the development of CHD. Multiple population-level association studies have been conducted on maternal environmental exposures and their association with CHD, including evaluating the effect of maternal disease, medication exposure, environmental pollution, and tobacco and alcohol use on the incidence of CHD. However, these studies have been done in a siloed manner, with few examining the interplay between multiple environmental exposures. Here, we broadly and qualitatively review the current literature on maternal and paternal prenatal exposures and their association with CHD. We propose using the framework of the emerging field of the exposome, the environmental complement to the genome, to review all internal and external prenatal environmental exposures and identify potentiating or alleviating synergy between exposures. Finally, we propose mechanistic pathways through which susceptibility to development of CHD may be induced via the totality of prenatal environmental exposures, including the interplay between placental and cardiac development and the internal vasculature and placental morphology in early stages of pregnancy.

Seasonality of Hypoplastic Left Heart Syndrome and Single Ventricle Heart in Poland in the Context of Air Pollution

Hypoplastic left heart syndrome (HLHS) and single ventricle (SV) remain a significant cause of cardiac deaths occurring in the first week of life. Their pathogenesis and seasonal frequency are still unknown. Therefore, we attempt to look at the genesis of the HLHS and SV in the context of territorial distribution as well as seasonality. A total of 193 fetuses diagnosed with HLHS and 92 with SV were selected. The frequency was analyzed depending on the year, calendar month, quarter and season (fall-winter vs. spring-summer). The spatial distribution of HLHS and SV in Poland was analyzed. We observed a statistically significant overrepresentation of HLHS formation frequency in March: 27 (14.00%) in comparison to a monthly median of 15 (IQR: 13.75-16.25; p = 0.039), as well as a significantly higher frequency of HLHS in 2007-2009: 65 cases (33.68%) in comparison to the annual mean of 13.79 ± 6.36 (p < 0.001). We noted a higher frequency of SV among parous with the last menstrual period reported in the fall/winter season of 58 vs. 34 in the spring/summer season (p = 0.014). The performed analysis also revealed significant SV overrepresentation in 2008: 11 cases (12.00%) in comparison to the annual mean of 6.57 ± 2.71 (p = 0.016). Every single case of HLHS was observed when the concentration of benzo(a)pyrene and/or PM10 exceeded the acceptable/target level. Our research indicates that both the season and the level of pollution are significant factors affecting the health of parous women and their offspring. The reason why HLHS and SV develop more frequently at certain times of the year remains unclear, therefore research on this topic should be continued, as well as on the effects of PM10 and benzo(a)pyrene exposure.

Monthly variation in univentricular heart and transposition of the great arteries - 10-year national population-based cohort study

OBJECTIVE

Monthly variation in the total prevalence of the univentricular heart (UVH) and dextro-transposition of the great arteries (d-TGA) at gestational age 7 + 0 weeks was assessed to determine potential environmental factors, such as viral or bacterial infections, underlying the variation.

STUDY DESIGN

The nationwide retrospective ten-year population-based cohort consisted of 592 733 births and 2764 terminated pregnancies due to fetal anomaly. The pre- or postnatally diagnosed cases of UVH (n = 440) and simple d-TGA (n = 127) from five national registers included live births, stillbirths, and pregnancy terminations due to fetal anomaly. We evaluated the variation in the monthly total prevalence of UVH and d-TGA at gestational age 7 + 0 weeks. The monthly variation of UVH and d-TGA was also compared with monthly variation in reported viral and bacterial infections.

RESULTS

In the UVH and d-TGA, we observed significant monthly variation in total prevalence. However, we observed no correlations in the studied viral or bacterial infections and the number of cases.

CONCLUSIONS

Assessing monthly variation in total prevalence at early pregnancy, including pregnancy terminations and stillbirths, and using first-trimester timing provides the most accurate information on the variation. The reasons for monthly variation remain unclear, but we observed no associations with specific viral or bacterial infections.

Detection screening and seasonality evaluation of hypoplastic left heart syndrome in the polish national registry for fetal cardiac anomalies from the years 2004 to 2016

OBJECTIVES

To evaluate the incidence of hypoplastic left heart syndrome (HLHS) and the efficiency of the screening program using data from the Polish National Registry for Fetal Cardiac Anomalies. To investigate whether HLHS incident rates in Poland are seasonally variable.

METHODS

Data on 791 cases of HLHS from the Registry collected between 2004 and 2016 was analyzed.

RESULTS

The median gestational age for the 734 cases of HLHS detected was 23 weeks. Comparing the age at time of HLHS detection between 2004 and 2016, a decrease from 26 to 20.8 weeks was observed. We noted a rapid increase in HLHS incidence during the initial years of the Registry data, the annual percentage change during that period was 22.0% and this trend lasted until 2010. In the following years, the Registry became representative of the general population which has an estimated incidence of HLHS of 20.93 cases per 100 000 live births. We observed no clear seasonal patterns of HLHS incidence in our population.

CONCLUSION

The Registry reached a plateau state in terms of diagnosing new cases of HLHS. No evidence of seasonality has been noted. The average gestational age of patients identified as having HLHS decreased significantly during the study period.

Familial Screening for Left-Sided Congenital Heart Disease: What Is the Evidence? What Is the Cost?

Since the American Heart Association’s recommendation for familial screening of adults with congenital heart disease for bicuspid aortic valve, similar recommendations for other left-sided heart defects, such as hypoplastic left heart syndrome (HLHS), have been proposed. However, defining at-risk populations for these heart defects based on genetics is less straightforward due to the wide variability of inheritance patterns and non-genetic influences such as environmental and lifestyle factors. We discuss whether there is sufficient evidence to standardize echocardiographic screening for first-degree relatives of children diagnosed with HLHS. Due to variations in the inclusion of cardiac anomalies linked to HLHS and the identification of asymptomatic individuals with cardiac malformations, published studies are open to interpretation. We conclude that familial aggregation of obstructive left-sided congenital heart lesions in families with history of HLHS is not supported and recommend that additional screening should adopt a more conservative definition of what truly constitutes this heart defect. More thorough consideration is needed before embracing familial screening recommendations of families of patients with HLHS, since this could inflict serious costs on healthcare infrastructure and further burden affected families both emotionally and financially.

Resource and cost considerations in treating hypoplastic left heart syndrome

Hypoplastic left heart syndrome (HLHS) was a uniformly fatal diagnosis before 1983, when surgical treatment was first undertaken with the Norwood I operation as the first of 3-staged operations. Since then, operative survival rate of stage I has risen from 53% to over 90% in the current era, not only thanks to technical advances in surgery but also through prenatal diagnosis and imaging, enhanced cardiopulmonary bypass technology, better perioperative intensive care, and closer interstage monitoring. The improvements in patient outcomes achieved through rigorous multidisciplinary teamwork have come at a tremendous cost in manpower and resources, making HLHS still a challenge to all congenital heart programs, established or emerging. We review the various surgical steps to treat HLHS and their current expected outcomes, and put into perspective cost considerations compared to other more “simple” congenital heart defects.

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.

A Method of Trigonometric Modelling of Seasonal Variation Demonstrated with Multiple Sclerosis Relapse Data

This report describes a novel Stata-based application of trigonometric regression modelling to 55 years of multiple sclerosis relapse data from 46 clinical centers across 20 countries located in both hemispheres. Central to the success of this method was the strategic use of plot analysis to guide and corroborate the statistical regression modelling. Initial plot analysis was necessary for establishing realistic hypotheses regarding the presence and structural form of seasonal and latitudinal influences on relapse probability and then testing the performance of the resultant models. Trigonometric regression was then necessary to quantify these relationships, adjust for important confounders and provide a measure of certainty as to how plausible these associations were. Synchronization of graphing techniques with regression modelling permitted a systematic refinement of models until best-fit convergence was achieved, enabling novel inferences to be made regarding the independent influence of both season and latitude in predicting relapse onset timing in MS. These methods have the potential for application across other complex disease and epidemiological phenomena suspected or known to vary systematically with season and/or geographic location.

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.