Cardiomyocyte maturation alters molecular stress response capacities and determines cell survival upon mitochondrial dysfunction.

Cardiomyocyte maturation during pre- and postnatal development requires multiple intertwined processes, including a switch in energy generation from glucose utilization in the embryonic heart towards fatty acid oxidation after birth. This is accompanied by a boost in mitochondrial mass to increase capacities for oxidative phosphorylation and ATP generation required for efficient contraction. Whether cardiomyocyte differentiation is paralleled by augmented capacities to deal with reactive oxygen species (ROS), physiological byproducts of the mitochondrial electron transport chain (ETC), is less clear. Here we show that expression of genes and proteins involved in redox homeostasis and protein quality control within mitochondria increases after birth in the mouse and human heart. Using primary embryonic, neonatal and adult mouse cardiomyocytes in vitro we investigated how excessive ROS production induced by mitochondrial dysfunction affects cell survival and stress response at different stages of maturation. Embryonic and neonatal cardiomyocytes largely tolerate inhibition of ETC complex III by antimycin A (AMA) as well as ATP synthase (complex V) by oligomycin but are susceptible to complex I inhibition by rotenone. All three inhibitors alter the intracellular distribution and ultrastructure of mitochondria in neonatal cardiomyocytes. In contrast, adult cardiomyocytes treated with AMA undergo rapid morphological changes and cellular disintegration. At the molecular level embryonic cardiomyocytes activate antioxidative defense mechanisms, the integrated stress response (ISR) and ER stress but not the mitochondrial unfolded protein response upon complex III inhibition. In contrast, adult cardiomyocytes fail to activate the ISR and antioxidative proteins following AMA treatment. In conclusion, our results identified fundamental differences in cell survival and stress response in differentiated compared to immature cardiomyocytes subjected to mitochondrial dysfunction. The high stress tolerance of immature cardiomyocytes might allow outlasting unfavorable intrauterine conditions thereby preventing fetal or perinatal heart disease and may contribute to the regenerative capacity of the embryonic and neonatal mammalian heart.

Heart transplantation surgery in children and young adults with congenital heart disease.

BACKGROUND: Pediatric cardiac transplantation remains a surgical challenge as a variety of cardiac and vessel malformation are present in patients with congenital heart disease (CHD). Despite limited availability and acceptability of donor hearts, the number of heart transplantations remains on a stable level with improved survival and quality of life. OBSERVATION: As treatment options for CHD continue to improve and the chances of survival increase, more adult CHD patients are listed for transplantation. This review focuses on the clinical challenges and modified techniques of pediatric heart transplantations. CONCLUSION: Not only knowledge of the exact anatomy, but above all careful planning, interdisciplinary cooperation and surgical experience are prerequisites for surgical success.

Inhibition of mitochondrial respiration has fundamentally different effects on proliferation, cell survival and stress response in immature versus differentiated cardiomyocyte cell lines.

Myocardial tissue homeostasis is critically important for heart development, growth and function throughout the life course. The loss of cardiomyocytes under pathological conditions ultimately leads to cardiovascular disease due to the limited regenerative capacity of the postnatal mammalian heart. Inhibition of electron transport along the mitochondrial respiratory chain causes cellular stress characterized by ATP depletion as well as excessive generation of reactive oxygen species. Adult cardiomyocytes are highly susceptible to mitochondrial dysfunction whereas embryonic cardiomyocytes in the mouse heart have been shown to be resistant towards mitochondrial complex III inhibition. To functionally characterize the molecular mechanisms mediating this stress tolerance, we used H9c2 cells as an in vitro model for immature cardiomyoblasts and treated them with various inhibitors of mitochondrial respiration. The complex I inhibitor rotenone rapidly induced cell cycle arrest and apoptosis whereas the complex III inhibitor antimycin A (AMA) had no effect on proliferation and only mildly increased cell death. HL-1 cells, a differentiated and contractile cardiomyocyte cell line from mouse atrium, were highly susceptible to AMA treatment evident by cell cycle arrest and death. AMA induced various stress response mechanisms in H9c2 cells, such as the mitochondrial unfolded protein response (UPRmt), integrated stress response (ISR), heat shock response (HSR) and antioxidative defense. Inhibition of the UPR, ISR and HSR by siRNA mediated knock down of key components does not impair growth of H9c2 cells upon AMA treatment. In contrast, knock down of NRF2, an important transcriptional regulator of genes involved in detoxification of reactive oxygen species, reduces growth of H9c2 cells upon AMA treatment. Various approaches to activate cell protective mechanisms and alleviate oxidative stress in HL-1 cells failed to rescue them from AMA induced growth arrest and death. In summary, these data show that the site of electron transport interruption along the mitochondrial respiratory chain determines cell fate in immature cardiomyoblasts. The study furthermore points to fundamental differences in stress tolerance and cell survival between immature and differentiated cardiomyocytes which may underlie the growth plasticity of embryonic cardiomyocytes during heart development but also highlight the obstacles of cardioprotective therapies in the adult heart.

Ventricular assist devices in paediatric cardiomyopathy and congenital heart disease: An analysis of the German National Register for Congenital Heart Defects.

BACKGROUND: Ventricular assist devices (VAD) are increasingly used in patients with end-stage heart failure due to acquired heart disease. Limited data exists on the use and outcome of this technology in children. METHODS: All children (<18 years of age) with VAD support included in the German National Register for Congenital Heart Defects were identified and data on demographics, underlying cardiac defect, previous surgery, associated conditions, type of procedure, complications and outcome were collected. RESULTS: Overall, 64 patients (median age 2.1 years; 45.3% female) receiving a VAD between 1999 and 2015 at 8 German centres were included in the analysis. The underlying diagnosis was congenital heart disease (CHD) in 25 and cardiomyopathy in 39 children. The number of reported VAD implantations increased from 13 in the time period 2000-2004 to 27 implantations in the time period 2010-2014. During a median duration of VAD support of 54 days, 28.1% of patients experienced bleeding complications (6.3% intracerebral bleeding), 14.1% thrombotic (10.9% VAD thrombosis) and 23.4% thromboembolic complications (including cerebral infarction in 18.8% of patients). Children with cardiomyopathy were more likely to receive a cardiac transplantation (79.5% vs. 28.0%) compared to CHD patients. Survival of cardiomyopathy patients was significantly better compared to the CHD cohort (p < 0.0001). Multivariate Cox-proportional analysis revealed a diagnosis of CHD (hazard ratio [HR] 4.04, p = 0.001), age at VAD implantation (HR 1.09/year, p = 0.04) and the need for pre-VAD extracorporeal membrane oxygenation (ECMO) support (HR 3.23, p = 0.03) as independent predictors of mortality. CONCLUSIONS: The uptake of VAD therapy in children is increasing. Morbidity and mortality remain high, especially in patients with congenital heart disease and those requiring ECMO before VAD implantation.

Against all odds-late repair of multiple shunt lesions in a patient with Down syndrome: a case report.

BACKGROUND: Children with congenital heart defects (CHD) usually undergo elective surgical repair of haemodynamically relevant shunt lesions within the first year of life. Due to susceptibility for pulmonary arterial hypertension (PAH) in patients with Down syndrome, repair is usually aimed for no later than 6 months of life. However, with rising immigration from developing countries to Europe, more patients with unrepaired CHD are diagnosed at a later age. Anatomical repair may be precluded, when advanced pulmonary vascular disease has been established. CASE SUMMARY: We report a 39-month-old male patient with Down syndrome with a large non-restrictive perimembranous ventricular septal defect, a large patent ductus arteriosus, and a secundum-type atrial septal defect with a prominent left-to-right shunting. Haemodynamic assessment revealed only a mild increase of pulmonary artery pressures (mPAP) with low pulmonary vascular resistance index (PVRi). Vasodilator testing led to a further increase of the left-to-right shunt and decrease of PVRi, suggesting operability. After careful consideration, the patient underwent complete surgical repair with a good post-operative clinical outcome. Cardiac catheterization 6 months after corrective repair showed a normal mPAP. No signs of PAH have been detected in the medium-term follow-up. DISCUSSION: Expertise, increased physician awareness, and a thorough pre-operative multidisciplinary evaluation are paramount to determine the best treatment approach for patients, who may present late with multiple shunts, and-in our case-underlying Down syndrome. Long-term close post-surgical follow-up in an expert centre is warranted to promptly diagnose and treat a possible late presentation of PAH appropriately.

Cardiac CT in the Preoperative Diagnostics of Neonates with Congenital Heart Disease: Radiation Dose Optimization by Omitting Test Bolus or Bolus Tracking.

RATIONALE AND OBJECTIVES: Congenital heart diseases (CHD) belong to the leading causes of infant mortality worldwide. Prognostic improvements result from multimodal therapy strategies leading to an increased demand for noninvasive imaging. The aim of the study was to further optimize cardiac CT radiation dose by omitting the test bolus or bolus tracking scan, which can have a relevant share of radiation exposure, especially in neonates. MATERIALS AND METHODS: This retrospective study included 25 neonates with CHD who received a CT angiography (CTA) from 2009 to 2018. The examinations were performed as a high-pitch CTA (pitch 3.4, 80 kV) with manual contrast administration (1.5 ml/kg body weight) and fixed scan delay depending on the respective heart defect. Diagnosis, adverse events, radiation dose parameters, objective (contrast-to-noise ratio) and subjective (4-point Likert scale) image quality as well as diagnostic accuracy compared to intraoperative findings was assessed. RESULTS: All examinations were diagnostically evaluable without adverse events. The median CT dose index volume (CTDIvol) was 0.50 mGy (range, 0.15-0.94), the median dose-length product was 8 mGy × cm (range, 3-17). The estimation of the effective dose by Monte Carlo simulation revealed lower median dose levels 0.66 mSv (range, 0.25-1.40 mSv) than previously published in comparable groups. All examinations achieved a very good mean image quality score of 1.2 ± 0.4 with only minimal image noise and mean contrast-to-noise ratio of 16.1 ± 7.0. Diagnostic accuracy was 100 % as cardiac anatomy revealed no new diagnoses or significant differences in the subsequent cardiac surgery. CONCLUSION: Cardiac high-pitch CTA of neonates with CHD can be performed safely and dose-reducing without additional test bolus or bolus tracking scan. With very good image quality, it provides a detailed insight into the cardiac anatomy and thus enables a differentiated, noninvasive therapy planning.

Valve-Sparing Aortic Root Replacement in an 8-Month-Old Infant With Loeys-Dietz Syndrome.

The clinical experience with Loeys-Dietz syndrome (LDS) reveals fateful natural history with intracerebral incidents and aortic dissections. A newborn child was referred to our hospital with significantly dilated aortic root and clinical signs of LDS phenotype later genetically confirmed as LDS type I. A therapy with antihypertensive medicines was initiated to postpone the surgery. Despite that, aortic root dilatation progressed to 33 mm (z-score +9.3). To avoid aortic rupture, a valve sparing aortic root replacement was performed at patient age of 8 months. The purpose of this report is to share our dilemmas and experience in the treatment of this child.

Extubation in the Operating Room After Fontan Procedure: Does It Make a Difference?

Early extubation appears to have beneficial effects on the Fontan circulation. The goal of this study was to assess the impact of extubation on the operating table in comparison with extubation during the first hours after Fontan operation (FO) on the early postoperative course. Between 2013 and 2016, 114 children with a single ventricle heart malformations (mean age, 3.8 ± 2.3 years) underwent FO: 60 patients were extubated in the operating room (ORE) and 54 in the intensive care unit (ICUE) in the median time of 195 min (range 30-515 min) after procedure. Pre-, peri-, and postoperative records were retrospectively analyzed. The hospital survival rate was 100%. One patient from the ORE group needed an immediate reintubation because of laryngospasm. The ORE group showed lower heart rate (106.5 vs. 120.3 bpm; p < 0.001) and lower central venous pressure (10.4 vs. 11.4 mmHg; p = 0.001) than patients in the ICUE group within the first 24 h after FO, as well as higher systolic blood pressure within 7 h after operation (88.6 ± 2.5 vs. 85.6 ± 2.6 mmHg; p = 0.036). The ORE children manifested significantly less pleural effusions during 48 h after FO (38.0 vs. 49.5 ml/kg; p = 0.004), received less intravenous fluid administration within 24 h after FO (54.1 vs. 73.8 ml/kg; p = 0.019), less inotropic support (9.8 vs. 12.8 h of dopamine; p = 0.033), and less antibiotics (4.7 vs. 5.8 days; p = 0.037). ICUE children manifested metabolic acidosis more frequently than the ORE group 3-4 h after FO (p < 0.05). Immediate extubation after FO in comparison with extubation in the ICU appears to be associated with improved hemodynamics and reduced application of therapeutic interventions in the postoperative course.

Long-term single-center experience of defibrillator therapy in children and adolescents.

BACKGROUND: Implantable cardioverter-defibrillator (ICD) systems are established therapy for prevention of sudden cardiac death. Long-term data on ICD systems in children and adolescents is rare. The present study displays a long-term single-center follow-up of children and adolescents with ICD systems. METHODS AND RESULTS: The present study represents a single-center experience of patients younger than 18 years who received an ICD (n = 58). Follow-up data included in-house follow-up as well as examinations of collaborating specialists. Mean age at implantation was 14.0 ±â€¯3.3 years and 33 patients (56.9%) were male. A transvenous ICD system was implanted in 54 patients (93.1%). In 33 patients (56.9%) electrical heart disease or idiopathic ventricular fibrillation represented the underlying condition of ICD implantation. Median follow-up duration was 70 months (45; 94). 3 patients (5.2%) died during the observation period. None of these deaths was associated with ICD failure. Appropriate shocks occurred in 32 patients (55.2%). Inappropriate shock delivery was recorded in 17 patients (29.3%). Supraventricular tachycardia represented the most frequent cause of inappropriate shock delivery (9 patients, 52.9%). T-wave oversensing led to inappropriate shock delivery in 3 patients (17.6%). In 5 patients (29.4%), lead failure caused inappropriate shock delivery. Of note, during follow-up lead failure was reported in 15 patients (25.9%) leading to surgical revision. CONCLUSION: ICD therapy in children and adolescents is effective for prevention of sudden cardiac death. The rate of appropriate shock deliveries was significantly higher as compared with large ICD trials. Inappropriate therapies occurred frequently. In particular supraventricular tachycardia, T-wave oversensing and lead failures were responsible for these episodes.

Single Ostium of the Right and Left Coronary Artery From the Right Pulmonary Artery.

We describe a newborn with single-ventricle malformation and anomalous origin of both coronary arteries from single ostium in the middle portion of the right pulmonary artery whose coronary anatomy was discovered during the operation and who underwent successful staged operative management. This report presents a unique anatomic association, proposes a means of management, and highlights the importance of intraoperative analysis.

Stenting of Native Right Ventricular Outflow Tract Obstructions in Symptomatic Infants.

OBJECTIVE: To assess feasibility, safety and effectiveness of right ventricular outflow tract (RVOT) stenting in symptomatic young infants. METHODS: Multicentre evaluation of 35 patients intended to undergo RVOT stenting in 11 pediatric cardiac centres from 2009 to August 2011. RESULTS: Median age and weight at the time of first stent implantation were 8 weeks and 3.3 kg, with 40% of patients <3 kg. A total of 19 patients had suffered from hypoxemic spells, 8 patients were ventilated, 6 on inotropic support and 5 on prostaglandin infusion. Severe concomitant malformations were present in 11 patients, and acute infections in 2. Stenting of the RVOT was successfully performed in 33 patients, improving oxygen saturation from a median of 77 to 90% 2 days after intervention. Besides the 2 patients in whom RVOT stenting was not successful for technical reasons, there were no procedural complications. In 17 of 33 patients, 1-3 reinterventions were performed during follow-up, less than half of those were reinterventions in the RVOT. A total of 27 patients have undergone successful surgical repair 4-162 (median 19.5) weeks after initial RVOT stent implantation, 2 patients are still waiting. There were no perioperative deaths. CONCLUSIONS: Stenting of the RVOT provides a safe and effective management strategy for initial palliation in symptomatic young infants, including those patients not suitable or at higher risk for surgical therapy.

A specific IFIH1 gain-of-function mutation causes Singleton-Merten syndrome.

Singleton-Merten syndrome (SMS) is an infrequently described autosomal-dominant disorder characterized by early and extreme aortic and valvular calcification, dental anomalies (early-onset periodontitis and root resorption), osteopenia, and acro-osteolysis. To determine the molecular etiology of this disease, we performed whole-exome sequencing and targeted Sanger sequencing. We identified a common missense mutation, c.2465G>A (p.Arg822Gln), in interferon induced with helicase C domain 1 (IFIH1, encoding melanoma differentiation-associated protein 5 [MDA5]) in four SMS subjects from two families and a simplex case. IFIH1 has been linked to a number of autoimmune disorders, including Aicardi-Goutières syndrome. Immunohistochemistry demonstrated the localization of MDA5 in all affected target tissues. In vitro functional analysis revealed that the IFIH1 c.2465G>A mutation enhanced MDA5 function in interferon beta induction. Interferon signature genes were upregulated in SMS individuals' blood and dental cells. Our data identify a gain-of-function IFIH1 mutation as causing SMS and leading to early arterial calcification and dental inflammation and resorption.

Singleton-Merten syndrome: an autosomal dominant disorder with variable expression.

In 1973, Singleton and Merten described two females with abnormal dentition, unique radiographic changes especially of the hands, and severe calcification and intimal weakening of the aortic arch and valve. Since then three additional cases with similar features have been reported and the diagnosis was suggested in another three individuals. We present an update of one case and the detailed clinical phenotype of six other cases with Singleton-Merten syndrome. The occurrence of the disorder in six members of two families and vertical male-to-male transmission indicate an autosomal dominant pattern of inheritance. Variability in phenotype, also within a single family, is significant. Core manifestations are marked aortic calcification, dental anomalies (delayed eruption and immature root formation of primarily the anterior permanent teeth, and early loss of permanent teeth due to short roots, acute root resorption, high caries, and aggressive alveolar bone loss), osteopenia and acro-osteolysis, and to a lesser extend also glaucoma, psoriasis, muscle weakness, and joint laxity. Additional clinical characteristics described here include particular facial characteristics (high anterior hairline, broad forehead, smooth philtrum, thin upper vermillion) and abnormal joint and muscle ligaments. The cause and pathogenesis of this syndrome remain unknown. © 2013 Wiley Periodicals, Inc.

Do the age of patients with tetralogy of fallot at the time of surgery and the applied surgical technique influence the reoperation rate? a single-center experience.

BACKGROUND AND PURPOSE: Primary repair of tetralogy of Fallot (TOF) has been favored in many centers for years now and results and advantages of this management seem to verify this procedure. The authors wanted to know, if the age at the time of surgery and the surgical techniques had an influence on the long-term results. PATIENTS AND METHODS: Between 1992 and 2003, 124 patients underwent complete repair of TOF at the University Hospital Münster, Germany. Patients were subdivided into two groups based on their age (< 1 year and > 1 year of age). Patients in whom a transannular patch (TAP) was used were compared with those without (NTAP), or in whom a conduit was used. RESULTS: Overall mortality was 8%, with an average age of death of 9.53 years (range 0.06-19.77 years). The patients' age at the time of surgery affected their survival as only two cases of death were reported among the group of children < 1 year of age (3.2%) whereas eight patients were older (12.9%; p = 0.0483). Six patients died within the first 30 days post surgery. Reoperation had to be performed in 21 cases, 13 (61.9%) of these patients were < 1 year of age at the time of surgery, eight were older (38.1%). A TAP, NTAP or conduit treatment did not show significant differences in long-term survival or freedom from reoperation. CONCLUSION: Early repair of TOF within the 1st year of life can be recommended, because mortality is lower than in patients treated at a higher age. There seems no significant difference in the reintervention rate between patients treated within the 1st year of life or later.

Multiple giant cell lesions in patients with Noonan syndrome and cardio-facio-cutaneous syndrome.

Noonan syndrome (NS) and cardio-facio-cutaneous syndrome (CFCS) are related developmental disorders caused by mutations in genes encoding various components of the RAS-MAPK signaling cascade. NS is associated with mutations in the genes PTPN11, SOS1, RAF1, or KRAS, whereas CFCS can be caused by mutations in BRAF, MEK1, MEK2, or KRAS. The NS phenotype is rarely accompanied by multiple giant cell lesions (MGCL) of the jaw (Noonan-like/MGCL syndrome (NL/MGCLS)). PTPN11 mutations are the only genetic abnormalities reported so far in some patients with NL/MGCLS and in one individual with LEOPARD syndrome and MGCL. In a cohort of 75 NS patients previously tested negative for mutations in PTPN11 and KRAS, we detected SOS1 mutations in 11 individuals, four of whom had MGCL. To explore further the relevance of aberrant RAS-MAPK signaling in syndromic MGCL, we analyzed the established genes causing CFCS in three subjects with MGCL associated with a phenotype fitting CFCS. Mutations in BRAF or MEK1 were identified in these patients. All mutations detected in these seven patients with syndromic MGCL had previously been described in NS or CFCS without apparent MGCL. This study demonstrates that MGCL may occur in NS and CFCS with various underlying genetic alterations and no obvious genotype-phenotype correlation. This suggests that dysregulation of the RAS-MAPK pathway represents the common and basic molecular event predisposing to giant cell lesion formation in patients with NS and CFCS rather than specific mutation effects.

A defect in dolichol phosphate biosynthesis causes a new inherited disorder with death in early infancy.

The following study describes the discovery of a new inherited metabolic disorder, dolichol kinase (DK1) deficiency. DK1 is responsible for the final step of the de novo biosynthesis of dolichol phosphate. Dolichol phosphate is involved in several glycosylation reactions, such as N-glycosylation, glycosylphosphatidylinositol (GPI)-anchor biosynthesis, and C- and O-mannosylation. We identified four patients who were homozygous for one of two mutations (c.295T-->A [99Cys-->Ser] or c.1322A-->C [441Tyr-->Ser]) in the corresponding hDK1 gene. The residual activity of mutant DK1 was 2%-4% when compared with control cells. The mutated alleles failed to complement the temperature-sensitive phenotype of DK1-deficient yeast cells, whereas the wild-type allele restored the normal growth phenotype. Affected patients present with a very severe clinical phenotype, with death in early infancy. Two of the patients died from dilative cardiomyopathy.

Cardiomyopathy in congenital disorders of glycosylation.

Congenital disorders of glycosylation are a group of inherited metabolic multisystem disorders characterized by defects in the glycosylation of proteins and lipids. In most cases, neuromuscular disease is present. The purpose of this study was to characterize the cardiological aspects in this disorder. From the literature, we identified six children with congenital disorders of glycosylation associated with cardiac disease. We then screened for cardiovascular manifestations 20 patients diagnosed with congenital disorders of glycosylation at our own institution. Of the 6 patients identified in the literature, 4 had hypertrophic cardiomyopathy, while in the other 2 the cardiac diagnosis was unclear. The mean age at cardiac diagnosis was 5 months, with a range from 34 weeks to 24 months. Of the patients, five had died at a mean age of 3.5 months, with a range from 1.5 to 6 months, with one documented cardiac death. Three of our 20 patients (15%) had coexistent cardiomyopathy, and in three additional patients presenting with cardiomyopathy we made the diagnosis of a congenital disorder of glycosylation. In our cohort, dilated cardiomyopathy was found in two-thirds of the patients, with hypertrophic cardiomyopathy in the other third. The mean age at cardiac diagnosis was 19 months, with a range from 0.5 to 84 months. Of these patients, two died in infancy at a mean age of 4 months, specifically at 1.5 and 7 months, due to cardiac disease, with one dying suddenly. The remaining four patients are alive with minor to severe cardiac dysfunction. We conclude that congenital disorders of glycosylation have to be considered in the differential diagnosis of children presenting with cardiomyopathy, and that all patients with congenital disorders of glycosylation should be screened for an associated cardiomyopathy. Cardiac involvement contributes significantly to morbidity and mortality, and probably to sudden cardiac death in this disorder.