Heart rate reduction as a marker to optimize carvedilol treatment and enhance myocardial recovery in pediatric dilated cardiomyopathy

Pediatric Chronic Heart Failure: Age-Specific Considerations of Medical Therapy

Chronic heart failure (CHF) is a rare entity in children but carries a burden of high mortality and morbidity. Medical treatment of pediatric CHF is largely based on guidelines for the adult population. In contrast to adults, evidence for the efficacy of medications in treating CHF in children is sparse. This may be due to the difficulty of conducting high-powered studies in children or to true differences in the mechanisms of CHF pathophysiology. Recent observations suggest that CHF in children differs from adults at the molecular and cellular levels. Different pathways are involved, leading to less fibrosis and hypertrophy than in adults, with potential implications for therapy. The main pathophysiological goals of medical treatment of pediatric CHF due to systemic left ventricular dysfunction are discussed in this review. These include preload and afterload optimization, diminishing cardiomyocyte apoptosis and necrosis as well as interstitial fibrosis, and optimizing myocardial oxygen consumption. The pediatric myocardium should be provided with optimal conditions to achieve its regenerative potential. The cornerstones of medical CHF therapy are angiotensin converting enzyme inhibitors (ACEI), beta blockers and mineralocorticoid receptor antagonists. There are potential benefits of tissue ACEI and ?1-selective beta blockers in children. Angiotensin receptor blockers are an alternative to ACEI and their slightly different mechanism of action may confer certain advantages and disadvantages. Diuretics are employed to achieve a euvolemic state. Digoxin is used more frequently in children than in adults. Promising new drugs already routinely used in adults include angiotensin receptor-neprilysin inhibitors and sodium-glucose contransporter 2 inhibitors. Key words: Pediatric heart failure, Heart failure with reduced ejection fraction (HFrEF), ACE inhibitor, Beta blocker, Digoxin.

Changes in adiponectin system after ventricular assist device in pediatric heart failure

Background

Ventricular assist device (VAD) implant represents a therapeutic option for pediatric patients with end-stage heart failure (HF). Heart unloading by VAD can modify several molecular pathways underlying cardiac function in HF. Among them, the potential role of microRNA (miRNAs) in response to VAD implant is emerging. This study was aimed at investigating in HF pediatric patients the effect of VAD-modified miRNAs on the adiponectin (ADPN) system, known to exert cardioprotective actions.

Methods

ADPN was measured in plasma samples obtained from HF children, before and 1 month after VAD implant, and from healthy control children. miRNA profile and molecules belonging to ADPN system were determined in cardiac biopsies collected at the time of VAD implantation (pre-VAD) and at the moment of heart transplant (post-VAD). An in vitro study using HL-1 cell line was performed to verify the regulatory role of the VAD-modified miRNA on the ADPN system.

Results

VAD implant did not affect circulating and cardiac levels of ADPN, but increased the cardiac mRNA expression of ADPN receptors, including AdipoR1, AdipoR2, and T-cad. AdipoR2 and T-cad were inversely related to the VAD-modified miRNA levels. The in vitro study confirmed the regulatory role of miR-1246 and miR-199b-5p on AdipoR2, and of miR-199b-5p on T-cad.

Conclusions

These data suggest that VAD treatment could regulate the expression of the cardioprotective ADPN system by epigenetic mediators, suggesting that miRNAs have a potential role as therapeutic targets to improve cardiac function in HF pediatric patients.

CRISPR/Cas9-mediated nexilin deficiency interferes with cardiac contractile function in zebrafish in vivo

Nexilin (NEXN) plays a crucial role in stabilizing the sarcomeric Z-disk of striated muscle fibers and, when mutated, leads to dilated cardiomyopathy in humans. Due to its early neonatal lethality in mice, the detailed impact of the constitutive homozygous NEXN knockout on heart and skeletal muscle morphology and function is insufficiently investigated. Here, we characterized a constitutive homozygous CRISPR/Cas9-mediated nexn knockout zebrafish model. We found that Nexn deficient embryos developed significantly reduced cardiac contractility and under stressed conditions also impaired skeletal muscle organization whereas skeletal muscle function seemed not to be affected. Remarkably, in contrast to nexn morphants, CRISPR/Cas9 nexn-/- knockout embryos showed a milder phenotype without the development of a pronounced pericardial edema or blood congestion. nexn-specific expression analysis as well as whole transcriptome profiling suggest some degree of compensatory mechanisms. Transcripts of numerous essential sarcomeric proteins were massively induced and may mediate a sarcomere stabilizing function in nexn-/- knockout embryos. Our findings demonstrate the successful generation and characterization of a constitutive homozygous nexn knockout line enabling the detailed investigation of the role of nexn on heart and skeletal muscle development and function as well as to assess putative compensatory mechanisms induced by the loss of Nexn.

Antiarrhythmic Drug Dosing in Children-Review of the Literature

Antiarrhythmic drugs represent a mainstay of pediatric arrhythmia treatment. However, official guidelines and consensus documents on this topic remain scarce. There are rather uniform recommendations for some medications (including adenosine, amiodarone, and esmolol), while there are only very broad dosage recommendations for others (such as sotalol or digoxin). To prevent potential uncertainties and even mistakes with regard to dosing, we summarized the published dosage recommendations for antiarrhythmic drugs in children. Because of the wide variations in availability, regulatory approval, and experience, we encourage centers to develop their own specific protocols for pediatric antiarrhythmic drug therapy.