Hypoplastic left heart syndrome: Rheumatic heart disease of the fetus?

The Left Ventricular Myocardium in Hypoplastic Left Heart Syndrome

Hypoplastic left heart syndrome (HLHS) is a collective term applied to severe congenital cardiac malformations, characterised by a combination of abnormalities mainly affecting the left ventricle, associated valves, and ascending aorta. Although in clinical practice HLHS is usually sub-categorised based on the patency of the mitral and aortic (left-sided) valves, it is also possible to comprehensively categorise HLHS into defined sub-groups based on the left ventricular morphology. Here, we discuss the published human-based studies of the ventricular myocardium in HLHS, evaluating whether the available evidence is in keeping with this ventricular morphology concept. Specifically, we highlight results from histological studies, indicating that the appearance of cardiomyocytes can be different based on the sub-group of HLHS. In addition, we discuss the histological appearances of endocardial fibroelastosis (EFE), which is a common feature of one specific sub-group of HLHS. Lastly, we suggest investigations that should ideally be undertaken using HLHS myocardial tissues at early stages of HLHS development to identify biological pathways and aid the understanding of HLHS aetiology.

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.

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.

A potentially curative fetal intervention for hypoplastic left heart syndrome

Hypoplastic left heart syndrome (HLHS) encapsulates a spectrum of complex congenital cardiovascular malformations involving varying degrees of underdevelopment of the left-sided heart structures. However, despite improved survival rates since the introduction of staged surgical reconstruction, treatment options for HLHS remain palliative rather than curative. A major limiting factor in the development of definitive curative therapy for HLHS is an incomplete understanding of its pathogenesis. Currently, the aetiology HLHS is best conceptualised by the 'flow theory' of cardiogenesis, which states that normal cardiac development is reliant on the interrelationship of normal flow patterns of blood through the developing heart, and appropriate growth of the cardiac valves and myocardium. Thus, congenital cardiac malformations, such as HLHS, are thought to arise when these two processes are incorrectly coupled in utero. The rationale for the hypothesis proposed herein rests upon the flow theory of cardiogenesis. Morphological studies of HLHS indicate that, although underdeveloped, all left-sided cardiac structures are present and anatomically correct. Further, of the various structural abnormalities that can occur within the spectrum of HLHS, the presence of a ventricular septal defect (VSD) is rare. The rarity of a VSD within the morphological spectrum of HLHS suggests the syndrome may not develop in the presence of a functionally significant VSD. Presumably, the presence of a functional VSD establishes a communication between the two ventricles during cardiac development, and preserves the normal pressure-flow-dependent growth of the left ventricular (LV) myocardium, despite inflow/outflow valve defects. It is proposed that surgical creation of a VSD in utero will 'rescue' the LV of hearts with left-sided valvular deformities that render them susceptible to the development of HLHS later in gestation. In evaluating this hypothesis, potential techniques for surgical creation of a VSD in utero are offered. These techniques are based on already established catheter-based in utero interventions, and conventional postnatal percutaneous procedures for VSD creation. Further discussion is also offered on techniques to avoid, and manage, potential complications (i.e. conduction system damage) of the proposed technique(s). Finally, if VSD creation in utero is indeed practically feasible, and successfully establishes the hypothesised hemodynamic and myocardial growth normalisation within the abnormally developing LV, the clinical implications are profound. This procedure may hold a potential cure for almost every sub-type of HLHS.

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.

Maternal β-hemolytic streptococcal pharyngeal exposure and colonization in pregnancy

Objectives. To report the pharyngeal colonization rate of β-hemolytic streptococci and changes in the value of antistreptolysin O (ASO) and anti-DNase B serology titers during pregnancy. Methods. Healthy pregnant women were recruited and blood was drawn in each trimester. The upper limit of normal (ULN) values for ASO and anti-DNase B was calculated for each trimester. Throat swabs were collected for culture and positive cultures were further assessed for the identification of serogroup of the isolated β-hemolytic streptococcus. Results. Out of a total of 126 pregnant women, 34.1% had positive throat cultures. Group C and group G strains were isolated in 18.2% of throat cultures while group F was detected in 13.5% of cases. The rate of colonization with GAS was 1.6%. There was an overall drop in ASO titer during pregnancy while anti-DNase B titers remained relatively unchanged. ULN values of 164^IU, 157^IU, and 156^IU were calculated for ASO at the first, second, and third trimesters, respectively. Based on the ULN values, 28.6% of patients had recent streptococcal exposure. Conclusions. These results show that pregnant women act as a reservoir for spreading potentially immunogenic (groups C and G) and disease producing (group F) virulent strains of streptococci.

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.

Spectrum of cardiac involvement in neonatal lupus

'Neonatal' lupus erythematosus (NLE) describes a clinical spectrum of cardiac and non-cardiac abnormalities observed in neonates and foetuses whose mothers have the auto-antibodies anti-SSA/Ro (anti-Ro) and anti-SSB/La (anti-La). Of the cardiac abnormalities, congenital AVB is the most common cardiovascular abnormality found in affected foetuses and infants. Many other cardiovascular manifestations of NLE have been more recently recognized including atrial and ventricular arrhythmias and other conduction abnormalities, myocarditis, cardiomyopathy often with endocardiofibroelastosis and structural heart disease, particularly valvar lesions. In this report, the spectrum of cardiovascular manifestations observed in foetuses and infants with NLE are reviewed and the pathogenesis, diagnosis and clinical outcomes are briefly discussed.

Juvenile rheumatic mitral stenosis with multiple ventricular septal defects

Congenital heart disease is related to events occurring in the embryonal stage, while rheumatic heart disease is a sequela of immune-mediated damage following streptococcal infection. We report an unusual association of multiple ventricular septal defects and severe pulmonary arterial hypertension with rheumatic mitral stenosis in a 7-year-old girl. This case highlights the need for careful examination for coexisting rheumatic disease in late presentations of congenital heart disease.