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Pediatric cardiomyopathy (CM) represents a group of rare, severe disorders that affect the myocardium. To date, the etiology and mechanisms underlying pediatric CM are incompletely understood, hampering accurate diagnosis and individualized therapy development. Here, we identified biallelic variants in the highly conserved flightless-I (FLII) gene in 3 families with idiopathic, early-onset dilated CM. We demonstrated that patient-specific FLII variants, when brought into the zebrafish genome using CRISPR/Cas9 genome editing, resulted in the manifestation of key aspects of morphological and functional abnormalities of the heart, as observed in our patients. Importantly, using these genetic animal models, complemented with in-depth loss-of-function studies, we provided insights into the function of Flii during ventricular chamber morphogenesis in vivo, including myofibril organization and cardiomyocyte cell adhesion, as well as trabeculation. In addition, we identified Flii function to be important for the regulation of Notch and Hippo signaling, crucial pathways associated with cardiac morphogenesis and function. Taken together, our data provide experimental evidence for a role for FLII in the pathogenesis of pediatric CM and report biallelic variants as a genetic cause of pediatric CM.

Background: Plasma renin activity (PRA) has gained relevance as prognostic marker in adults with heart failure. The use of PRA as a clinically meaningful parameter in children and children with heart failure requires a thorough knowledge of the factors that influence PRA to correctly assess PRA levels. We aim to evaluate the influence of age, heart failure and angiotensin-converting enzyme inhibitor (ACEi) on PRA levels in children. Methods: We conducted a systematic literature search to identify studies on PRA levels in healthy children and in children with heart failure. In addition, we analysed PRA data measured before (n = 35, aged 25 days–2.1 years), 4 hours after (n = 34) and within the first 8 days of enalapril treatment (n = 29) in children with heart failure from the European project Labeling of Enalapril from Neonates up to Adolescents (LENA). Results: Age has a profound effect on PRA levels in healthy children, as PRA levels in the literature are up to about 7 times higher in neonates than in older children. Children with heart failure younger than 6 months showed 3–4 times higher PRA levels than healthy peers in both the literature and the LENA studies. In the LENA studies, the ACEi enalapril significantly increased median predose PRA by a factor of 4.5 in children with heart failure after 4.7 ± 1.6 days of treatment (n = 29, p < 0.01). Prior to treatment with enalapril, LENA subjects with symptomatic heart failure (Ross score ≥3) had a significantly higher PRA than LENA subjects with asymptomatic heart failure of comparable age (Ross score ≤2, p < 0.05). Conclusions: Age, heart failure and ACEi treatment have a notable influence on PRA and must be considered when assessing PRA as a clinically meaningful parameter. Clinical Trial Registration: The trials are registered on the EU Clinical Trials Register (https://www.clinicaltrialsregister.eu). Trial registration numbers: EudraCT 2015-002335-17, EudraCT 2015-002396-18.

Abstract Aims We aimed to determine whether in children with dilated cardiomyopathy repeated measurement of known risk factors for death or heart transplantation (HTx) during disease progression can identify children at the highest risk for adverse outcome. Methods and results Of 137 children we included in a prospective cohort, 36 (26%) reached the study endpoint (SE: all‐cause death or HTx), 15 (11%) died at a median of 0.09 years [inter‐quartile range (IQR) 0.03–0.7] after diagnosis, and 21 (15%) underwent HTx at a median of 2.9 years [IQR 0.8–6.1] after diagnosis. Median follow‐up was 2.1 years [IQR 0.8–4.3]. Twenty‐three children recovered at a median of 0.6 years [IQR 0.5–1.4] after diagnosis, and 78 children had ongoing disease at the end of the study. Children who reached the SE could be distinguished from those who did not, based on the temporal evolution of four risk factors: stunting of length growth (−0.42 vs. −0.02 length Z‐score per year, P 6 years at presentation (all P

Background: Catheter ablation (CA) is the first-choice treatment for tachyarrhythmia in children. Currently available CA techniques differ in mechanism of catheter navigation and energy sources. There are no large studies comparing long-term outcomes between available CA techniques in a pediatric population with atrioventricular reentry tachycardia (AVRT) or atrioventricular nodal reentry tachycardia (AVNRT) mechanisms. Objective: This study aimed to compare procedural and long-term outcomes of remote magnetic navigation-guided radiofrequency (RF) ablation (RMN), manual-guided RF ablation (MAN) and manual-guided cryoablation (CRYO). Methods: This single-center, retrospective study included all first consecutive CA procedures for AVRT or AVNRT performed in children without structural heart disease from 2008 to 2019. Three study groups were defined by the ablation technique used: RMN, MAN or CRYO. Primary outcome was long-term recurrence of tachyarrhythmia. Results: In total, we included 223 patients, aged 14 (IQR 12–16) years; weighting 56 (IQR 47–65) kilograms. In total, 108 procedures were performed using RMN, 76 using MAN and 39 using CRYO. RMN had significantly lower recurrence rates compared to MAN and CRYO at mean follow-up of 5.5 ± 2.9 years (AVRT: 4.3% versus 15.6% versus 54.5%, P

Background: Pediatric trials to add missing data for evidence-based pharmacotherapy are still scarce. A tailored training concept appears to be a promising tool to cope with critical and complex situations before enrolling the very first patient and subsequently to ensure high-quality study conduct. The aim was to facilitate study success by optimizing the preparedness of the study staff shift.Method: An interdisciplinary faculty developed a simulation training focusing on the communication within the informed consent procedure and the conduct of the complex pharmacokinetic/pharmacodynamic (PK/PD) sampling within a simulation facility. Scenarios were video-debriefed by an audio-video system and manikins with artificial blood simulating patients were used. The training was evaluated by participants' self-assessment before and during trial recruitment.Results: The simulation training identified different optimization potentials for improved informed consent process and study conduct. It facilitated the reduction of avoidable errors, especially in the early phase of a clinical study. The knowledge gained through the intervention was used to train the study teams, improve the team composition and optimize the on-ward setting for the FP-7 funded “LENA” project (grant agreement no. 602295). Self-perceived ability to communicate core elements of the trial as well as its correct performance of sample preparation increased significantly (mean, 95% CI, p ≤ 0.0001) from 3 (2.5–3.5) to four points (4.0–4.5), and from 2 (1.5–2.5) to five points (4.0–5.0).Conclusion: An innovative training concept to optimize the informed consent process and study conduct was successfully developed and enabled high-quality conduct of the pediatric trials as of the very first patient visit.

Angiotensin-converting enzyme inhibitors (ACEI), such as enalapril, are a cornerstone of treatment for pediatric heart failure which is still used off-label. Using a novel age-appropriate formulation of enalapril orodispersible minitablets (ODMTs), phase II/III open-label, multicenter pharmacokinetic (PK) bridging studies were performed in pediatric patients with heart failure due to dilated cardiomyopathy (DCM) and congenital heart disease (CHD) in five participating European countries. Children were treated for 8 weeks with ODMTs according to an age-appropriate dosing schedule. The primary objective was to describe PK parameters (area under the curve (AUC), maximal concentration (Cmax), time to reach maximal concentration (t-max)) of enalapril and its active metabolite enalaprilat. Of 102 patients, 89 patients (n = 26, DCM; n = 63 CHD) were included in the primary PK endpoint analysis. Rate and extent of enalapril and its active metabolite enalaprilat were described and etiology and age could be identified as potential PK modifying factors. The dosing schedule appeared to be tolerated well and did not result in any significant drug-related serious adverse events. The PK analysis and the lack of severe safety events supports the applied age-appropriate dosing schedule for the enalapril ODMTs.

Background: Disconnected unilateral pulmonary arteries are frequently misdiagnosed as “absent”. They typically arise from the base of the innominate artery and are fed by an aberrant arterial duct. If diagnosed early enough, they can be reconnected with catheter techniques even after closure of this aberrant duct. Consecutive surgical anatomical correction at a later stage is possible. Methods: Four cases illustrate the anatomical findings on computed tomography and angiography, all show an outpouching at the base of the brachiocephalic artery. Results: The therapeutic approach consisted of stenting of the aberrant ductus and consecutive surgery. In the oldest patient, 13 years, such an approach was impossible. Conclusion: If identified early in life, disconnected pulmonary arteries can be recruited with catheter techniques, and reconnected surgically at a later stage. It is not yet known if this approach prevents pulmonary damage, which is frequently seen in older untreated patients.

Objective To characterise heart failure (HF) maintenance pharmacotherapy for children across Europe and investigate how angiotensin-converting enzyme inhibitors (ACE-I) are used in this setting.Methods A Europe-wide web-based survey was conducted between January and May 2015 among European paediatricians dedicated to cardiology.Results Out of 200-eligible, 100 physicians representing 100 hospitals in 27 European countries participated. All participants reported prescribing ACE-I to treat dilated cardiomyopathy-related HF and 97% in the context of congenital heart defects; 87% for single ventricle physiology. Twenty-six per cent avoid ACE-I in newborns. Captopril was most frequently selected as first-choice for newborns (73%) and infants and toddlers (66%) and enalapril for children (56%) and adolescents (58%). Reported starting and maintenance doses varied widely. Up to 72% of participants follow formal creatinine increase limits for decision-making when up-titrating; however, heterogeneity in the cut-off points selected existed. ACE-I formulations prescribed by 47% of participants are obtained from more than a single source. Regarding symptomatic HF maintenance therapy, 25 different initial drug combinations were reported, although 79% select a regimen that includes ACE-I and diuretic (thiazide and/or loop), 61% ACE-I and aldosterone antagonist; 44% start with beta-blocker, 52% use beta-blockers as an add-on drug. Of the 89 participants that prescribe pharmacotherapy to asymptomatic patients, 40% do not use ACE-I monotherapy or ACE-I-beta-blocker two-drug only combination.Conclusions Despite some reluctance to use them in newborns, ACE-I seem key in paediatric HF treatment strategies. Use in single ventricle patients seems frequent, in apparent contradiction with current paediatric evidence. Disparate dosage criteria and potential formulation-induced variability suggest significant differences may exist in the risk-benefit profile children are exposed to. No uniformity seems to exist in the drug regimens in use. The information collected provides relevant insight into real-life clinical practice and may facilitate research to identify the best therapeutic options for HF children.

Introduction: Treatment of paediatric heart failure is based on paradigms extensively tested in the adult population assuming similar underlying pathophysiological mechanisms. Angiotensin converting enzyme inhibitors (ACEI) like enalapril are one of the cornerstones of treatment and commonly used off-label in children. Dose recommendations have been extrapolated from adult experience, but the relationship between dose and pharmacokinetics (PK) in (young) children is insufficiently studied. Furthermore, appropriate paediatric formulations are lacking. Within the European collaborative project LENA, a novel formulation of enalapril orodispersible minitablets (ODMT), suitable for paediatric administration, will be tested in (young) children with heart failure due to either dilated cardiomyopathy or congenital heart disease in two pharmacokinetic bridging studies. Paediatric PK data of enalapril and its active metabolite enalaprilat will be obtained. In a follow-up study, the safety of enalapril ODMTs will be demonstrated in patients on long-term treatment of up to 10 months. Furthermore, additional information about pharmacodynamics (PD) and ODMT acceptability will be collected in all three studies. Methods and Analysis: Phase II/III, open-label, multicentre study. Children with dilated cardiomyopathy (DCM) (n = 25; 1 month to less than 12 years) or congenital heart disease (CHD) (n = 60; 0 to less than 6 years) requiring or already on ACEI will be included. Exclusion criteria include severe heart failure precluding ACEI use, hypotension, renal impairment, hypersensitivity to ACEI. For those naïve to ACEI up-titration to an optimal dose will be performed, those already on ACEI will be switched to an expected equivalent dose of enalapril ODMT and optimised. In the first 8 weeks of treatment, a PK profile will be obtained at the first dose (ACEI naïve patients) or when an optimal dose is reached. Furthermore, population PK will be done with concentrations detected over the whole treatment period. PD and safety data will be obtained at least at 2-weeks intervals. Subsequently, an intended number of 85 patients will be followed-up up to 10 months to demonstrate long-term safety, based on the occurrence of (severe) adverse events and monitoring of vital signs and renal function. Ethics and dissemination: Clinical Trial Authorisation and a favourable ethics committee opinion were obtained in all five participating countries. Results of the studies will be submitted for publication in a peer-reviewed journal. Trial registration numbers: EudraCT 2015-002335-17, EudraCT 2015-002396-18, EudraCT 2015-002397-21. Keywords: Clinical pharmacology, Paediatric cardiology, Heart failure, Dilated cardiomyopathy, Congenital heart disease

Dilated cardiomyopathy amongst children (pediatric cardiomyopathy, pediatric CM) is associated with a high morbidity and mortality. Because little is known about the pathophysiology of pediatric CM, treatment is largely based on adult heart failure therapy. The reason for high morbidity and mortality is largely unknown as well as data on cellular pathomechanisms is limited. Here, we assessed cardiomyocyte contractility and protein expression to define cellular pathomechanisms in pediatric CM. Explanted heart tissue of 11 pediatric CM patients and 18 controls was studied. Contractility was measured in single membrane-permeabilized cardiomyocytes and protein expression was assessed with gel electrophoresis and western blot analysis. We observed increased Ca2+-sensitivity of myofilaments which was due to hypophosphorylation of cardiac troponin I, a feature commonly observed in adult DCM. We also found a significantly reduced maximal force generating capacity of pediatric CM cardiomyocytes, as well as a reduced passive force development over a range of sarcomere lengths. Myofibril density was reduced in pediatric CM compared to controls. Correction of maximal force and passive force for myofibril density normalized forces in pediatric CM cardiomyocytes to control values. This implies that the hypocontractility was caused by the reduction in myofibril density. Unlike in adult DCM we did not find an increase in compliant titin isoform expression in end-stage pediatric CM. The limited ability of pediatric CM patients to maintain myofibril density might have contributed to their early disease onset and severity.

The key components to the molecular understanding of the pathophysiology of various forms of heart failure involve global and/or large-scale identifications of proteins, their patterns of expression, posttranslational modifications, and functional characterization. Particularly, proteins involved in the induction of cardiac (mal)adaptive hypertrophic growth, interstitial fibrosis, and contractile dysfunction are of interest. In general, with the accumulation of vast amounts of DNA sequences in databases, researchers have become aware that merely having complete sequences of genomes and transcriptional changes for thousands of genes simultaneously will not be sufficient to elucidate, in molecular terms, the etiology and pathophysiology of cardiovascular disease. In the last decade, a new technology called proteomics has become available that allows biological and (patho)physiological questions to be approached exclusively from the protein perspective. Proteomics may enable us to map the entire complement of proteins expressed by the heart at any time and condition. This approach creates the unique possibility to identify, by differential analysis, protein alterations associated with the etiology of heart disease and its progression, outcome, and response to therapy. To illustrate the true power of proteomics, most of the currently available methodologies are first reviewed, including their limitations. This review also deals with the current status and the perspectives of proteomics applications in research on heart failure in general. Furthermore, examples of our recent data on global protein profiling of the pressure-overloaded rat right ventricle and of endothelin-1-stimulated cultures of neonatal rat cardiac myocytes are provided. The last section is devoted to the continuous advances in proteomic technologies, including protein separation methods, mass spectrometric instrumentation, computational analysis, and bioinformatic tools, together with integrative databases. [ABSTRACT FROM AUTHOR]