Regulation of sympathetic activity in children with various congenital heart diseases

Catecholamine-Secreting Tumors in Pediatric Patients With Cyanotic Congenital Heart Disease

Catecholamine-secreting tumors are rare among the pediatric population but are increasingly being reported in children with sustained hypoxia secondary to cyanotic congenital heart disease (CCHD). With this review, we report the clinical characteristics of these tumors in children with CCHD. The articles included in the present review were identified using PubMed through February 2019. A manual search of the references retrieved from relevant articles was also performed. Pheochromocytomas and paragangliomas (PPGL) in children are commonly associated with high-risk germline or somatic mutations. There is evidently a higher risk of tumorigenesis in children with CCHD as compared with the general pediatric population, even in the absence of susceptible gene mutations. This is due to molecular mechanisms involving the aberrant activation of hypoxia-response elements, likely secondary to sustained hypoxemia, resulting in tumorigenesis. Due to overlapping symptoms with CCHD, the diagnosis of PPGL may be delayed or missed in these patients. We studied all previously reported PPGL cases in children with CCHD and reviewed phenotypic and biochemical features to assess for contributing factors in tumorigenesis. Larger studies are needed to help determine other potential predisposing factors and to establish screening guidelines in this high-risk population. A delay in diagnosis of the PPGL tumors can lead to exacerbation of cardiac failure, and therefore early diagnosis and intervention may provide better outcomes in these patients, necessitating the need for regular surveillance. We recommend routine biochemical screening in patients with sustained hypoxia secondary to CCHD.

Postnatal Cardiac Autonomic Nervous Control in Pediatric Congenital Heart Disease

Congenital heart disease is the most common congenital defect. During childhood, survival is generally good but, in adulthood, late complications are not uncommon. Abnormal autonomic control in children with congenital heart disease may contribute considerably to the pathophysiology of these long term sequelae. This narrative review of 34 studies aims to summarize current knowledge on function of the autonomic nervous system in children with a congenital heart defect. Large scale studies that measure both branches of the nervous system for prolonged periods of time in well-defined patient cohorts in various phases of childhood and adolescence are currently lacking. Pending such studies, there is not yet a good grasp on the extent and direction of sympathetic and parasympathetic autonomic function in pediatric congenital heart disease. Longitudinal studies in homogenous patient groups linking autonomic nervous system function and clinical outcome are warranted.

Pediatric Cardiac Intensive Care Society 2014 Consensus Statement: Pharmacotherapies in Cardiac Critical Care Antihypertensives

OBJECTIVE

Hypertension remains a common condition in pediatric cardiac intensive care. The physiologic effects of hypertension in this population are complex and are impacted by patient age, comorbidities, and primary cardiac disease. The objective of this study is to review current pharmacotherapies for the management of systemic hypertension in the pediatric cardiac ICU.

DATA SOURCES

Relevant literature to the treatment of systemic hypertension in children was included. Specific focus was given to literature studying the use of therapies in critically ill children and those with heart disease. Reference textbooks and drug packaging inserts were used for drug-specific pediatric guidelines.

STUDY SELECTION

A search of MEDLINE, PubMed, and the Cochrane Database was performed to find literature about the management of hypertension in children. Metaanalyses and pediatric-specific studies were primarily considered and cross-referenced. Pertinent adult studies were included.

DATA EXTRACTION

Once the studies for inclusion were finalized, priority for data extraction was given to pediatric-specific studies that focused on children with heart disease and critical illness.

CONCLUSIONS

Systemic hypertension is common, and there is significant heterogeneity in the patient population with critical heart disease. There are limited large, prospective analyses of safety and efficacy for pediatric drug antihypertensive agents. Despite patient heterogeneity, most pharmacotherapies are safe and efficacious.

Alpha blocker and angiotensin-converting enzyme inhibitor in the management of severe pulmonary valve stenosis: from bench to bedside

INTRODUCTION

Neonates with severe pulmonary valve stenosis tend to remain oxygen dependent, despite resolution of the transpulmonary gradient. Alpha 2 blockers – phentolamine – and angiotensin-converting enzyme inhibitors – captopril – were reported to improve oxygen saturation.

OBJECTIVE

To describe the role of phentolamine and captopril in the treatment of these patients.

METHODS

In a retrospective cohort study, 28 neonates with severe pulmonary valve stenosis underwent balloon valvuloplasty. Among them, 20 remained oxygen or prostaglandin dependent after intervention, and were treated with phentolamine or captopril. Oxygen saturation was monitored before and after intervention and following treatment with these medications. Mean duration of hospitalisation was recorded.

RESULTS

Mean age and weight were 25.2 days and 3.1 kg, respectively. Before balloon dilation, 18/20 (90%) neonates were on prostaglandin, whereas after the procedure only 6/18 patients required it. All 20 patients required oxygen after the procedure, and nine patients (45%) were started on phentolamine. Among them, one patient with severe infundibular stenosis did not respond favourably, and 11 patients (55%) were started on captopril. After starting phentolamine or captopril treatment, prostaglandin could be discontinued after a mean time of 15.86 hours. Within <2 days, there was an increase in mean oxygen saturation from 76.6 to 93.0%.

CONCLUSION

Phentolamine and captopril seem to have therapeutic roles in neonates with severe pulmonary valve stenosis who remain oxygen dependent after balloon dilation. Both drugs led to vasodilation of the pulmonary and systemic vascularisation and facilitated inflow to the right ventricle. Right-to-left shunt across a patent foramen ovale or atrial septal defect decreased and saturation improved, leading to a significant reduction in the length of hospitalisation.

Patent ductus arteriosus in preterm infants is associated with cardiac autonomic alteration and predominant parasympathetic stimulation

BACKGROUND

Hemodynamic disorders in patent ductus arteriosus (PDA) may alter the stimulation of the autonomic nervous system.

AIM

The objective of this study was to analyze the orthosympathetic-parasympathetic balance in preterm infants with PDA.

STUDY DESIGN AND SUBJECTS

Patients were included from consecutive admissions to Amiens University Hospital from 2009 to 2011. We defined a PDA group and a Control group (echographic criteria). For each patient, three 4-minutes segments of ECG were recorded during quiet sleep and the RR chronologic series were extracted, and spectral (Fourier Transform) and time-domain analyses were performed. For each parameter of heart rate variability (HRV), average of three measures was determined and analysed.

RESULTS

Forty-four patients were included for analysis. The total HRV power, LF/HF ratio and SDNN were lower in the PDA group (n = 22, gestational age 28.2 w ± 1.9) than in the Control group (n = 22, gestational age 28.8 w ± 2). The decrease in LF power destabilized the autonomic balance in favour of parasympathetic stimulation. After adjustment for postconceptional age, PDA was still associated with parameters of autonomic neural stimulation.

CONCLUSION

These results suggest association of PDA with predominance of parasympathetic stimulation in preterm infants. The mechanisms of homeostasis in patients with PDA are very complex and involve both circulatory adaptations and control by autonomic pathway. If confirmed, our results could be interesting for future researches aiming to verify the interest of new targeted therapies for the management of PDA.

Overexpression of beta(2)AR improves contractile function and cellular survival in rabbit cardiomyocytes under chronic hypoxia

Chronic hypoxia usually evokes sustained release of endogenous neurohormones, leading to beta(2)-adrenergic receptor (beta(2)AR) desensitization and downregulation of expression, which impacts cellular contractility. We investigated whether exogenous beta(2)AR could compensate for the functional deficiency of beta(2)AR in rabbit cardiomyocytes under chronic hypoxia, and whether this led to improved contractility and cellular survival. A surgical experimental model of cyanotic heart disease was established in rabbits. Adv.hbeta(2)AR was transfected into cardiomyocytes isolated from animals subjected to 6-week systemic hypoxia. The levels of cellular contractile function, protein expression of hbeta(2)AR, p-Akt, p-Erk, and caspase-3, and cellular survival pre- and post-Adv.hbeta(2)AR delivery were determined. In the cyanotic cells, decreased shortening and lengthening of TPC and R50 were evident. Cellular diastolic functioning showed greater deterioration compared to the systolic function (P<0.05). In cyanotic cells, the positive inotropic response to isoproterenol was decreased (P<0.01), low levels of cellular survival were found, protein levels of beta(2)AR, p-Akt, and p-Erk were downregulated, and protein levels of caspase-3 were upregulated. After Adv.hbeta(2)AR delivery, enhanced contractile function was achieved (P<0.01), TPC and R50 levels recovered up to 99% and 81.7% of the normal control levels, respectively (P<0.05), and cellular survival improved (P<0.01). Our results demonstrate that overexpression of the beta(2)AR gene in cardiomyocytes exposed to chronic hypoxia provides significant catecholamine-dependent inotropic support and cellular protection.

Role of β-blocker therapy in pediatric heart failure

Heart failure is becoming an increasingly common and significant problem in the field of pediatric cardiology. The numerous types of cardiomyopathies, and more recently, long-term survival of patients with congenital heart disease, have added to a growing patient population. Over the last several decades, our knowledge base regarding mechanisms of disease and therapeutic intervention in adult patients with heart failure has drastically changed. The most recent and important breakthrough in the pharmacologic treatment of heart failure has been the particular role of β-blocker therapy. This medication has led to significant improvements in survival and symptoms in adults, with less convincing findings in limited studies in pediatrics. The ability to study the benefits of this therapy in patients has been challenging owing to the heterogeneity of the patient population and lack of large sample sizes. However, as we investigate the mechanisms behind the disease process, the differences that exist between disease conditions and ages, and the significant alterations that may exist at the molecular and genetic level, our understanding of β-blocker therapy in pediatric heart failure will improve, and ultimately may lead to patient-specific therapy.

Sympathetic overactivity in patients with pulmonary stenosis and improvement after percutaneous balloon valvuloplasty

OBJECTIVE

Percutaneous balloon valvulotomy (PBV) is the procedure of choice for the treatment of valvular pulmonary stenosis (PS) with similar results comparable to surgical valvotomy but less invasive.

METHODS AND RESULTS

Twenty-seven consecutive patients with PS being evaluated for PBV were enrolled in the study. Peak instantaneous transvalvular gradient, right ventricle (RV) diameter, mean atrial pressures, RV systolic pressure (RVSP), pro-brain natriuretic peptide (proBNP) levels significantly decreased immediately after PBV. Regarding heart rate variability (HRV) parameters, mean HR (heart rate), LF (low frequency) day and night, LF/HF day and night significantly decreased and standard deviation of all NN intervals (SDNN), root mean square of successive differences (RMSSD), P number of NN intervals that differed by more than 50 ms from adjacent interval divided by the total number of all NN intervals (PNN50), HF (High frequency) day and night significantly increased 1 day after PBV and these changes were shown to be preserved at the first month. The increase in SDNN was correlated with the decrease in right atrial pressure (RAP) (r =-0.5, P = 0.04); the increase in standard deviation of the 5-minute mean RR intervals (SDANN) was correlated with the decrease in proBNP (r =-0.4, P = 0.03).

CONCLUSIONS

Sympathetic overactivity and increased proBNP levels were associated with the symptomatic status of patients with PS. Associated with a decrease in atrial pressures and proBNP levels, PBV yielded a decrease in adrenergic overactivity in the patients with PS.

Porcine pulmonary artery and bronchial responses to endothelin-1 and norepinephrine on recovery from hypoxic pulmonary hypertension

Many infants recovering from acute lung disease and pulmonary hypertension still have evidence of reactive airways disease at one year of age, suggesting longer-term airway effects. We hypothesized that parallel changes in smooth muscle would occur in airways and pulmonary arteries from animals with pulmonary hypertension and during normoxic recovery. Thus, two-hour-old piglets were subjected to 3 d chronic hypobaric hypoxia and 3-d-old piglets were subjected to 11 d hypoxia. Some animals were allowed to recover in room air for 3 or 6 d. The amount of smooth muscle and responses of isolated paired bronchial and pulmonary artery rings to endothelin-1 (ET-1) and norepinephrine were studied at the end of hypoxic exposure, on recovery and in age-matched control animals. In all hypoxia induced pulmonary hypertensive animals, smooth muscle area and ET-1 contractile response was increased in the pulmonary arteries and bronchi. Norepinephrine-induced relaxant response was impaired significantly in both bronchi and pulmonary arteries. After 3 d recovery, pulmonary arterial smooth muscle area decreased by 65%, and ET-1-induced contractile responses were normal for age. In the airways, ET-1 contractile response only normalized after six days and bronchial smooth muscle was still increased. After 6 d recovery pulmonary arterial norepinephrine-induced relaxant response had returned to normal, but bronchial response remained impaired. Thus during pulmonary hypertension, both bronchial and pulmonary arterial smooth muscle area and contractile responses are increased. On recovery, regression of bronchial structural and functional abnormalities is slower than in pulmonary arteries.

Postnatal Changes in Response to Norepinephrine in the Normal and Pulmonary Hypertensive Lung

The effect of norepinephrine administration on pulmonary blood flow during the neonatal period is unclear. Therefore, norepinephrine responses were studied in isolated pulmonary arteries, pulmonary veins, and femoral arteries taken from normal pigs from birth to adulthood and from pigs subjected to chronic hypoxia either from birth for 3 days or from 3 to 14 days of age. Normally, the contractile response of pulmonary arteries and veins to norepinephrine decreased after birth (p < 0.01), and alpha2-adrenoceptor-mediated relaxation increased in pulmonary arteries and veins and in femoral arteries. Hypoxic exposure from birth prevented the normal postnatal reduction in pulmonary arterial contractile response, nor was there a postnatal increase in pulmonary arterial adrenoceptor-mediated relaxation. When hypoxic exposure followed a period of normal adaptation, the pulmonary arterial contractile response was not enhanced, but relaxation was significantly impaired. The response of pulmonary veins and femoral arteries was not affected by hypoxic exposure. The contractile effect of norepinephrine was 15- to 60-fold greater in isolated systemic arteries than in pulmonary arteries taken from both normal and pulmonary hypertensive piglets at all ages. This suggests that use of norepinephrine to manage systemic hypotension in infants and children will not compromise the pulmonary vasculature.

Beta-receptor downregulation in congenital heart disease: a risk factor for complications after surgical repair?

BACKGROUND

Neurohormonal activation in children with heart failure due to congenital heart disease leads to downregulation of myocardial beta-receptors that may influence the postoperative course after cardiothoracic surgery.

METHODS

Myocardial biopsies of 26 children (aged 14+/-4 months) were obtained from the right atrium during cardiac surgery. Patients were allocated to either of two groups based on the duration of their intensive care unit stay: group 1 comprised those who stayed less than 7 days (n = 17), whereas group 2 comprised those who stayed more than 7 days, plus 3 infants who died during the early postoperative course (n = 9). For beta1- and beta2-mRNA quantitation, real-time polymerase chain reaction with fluorescence-labeled products was used.

RESULTS

Values for myocardial beta1-receptor gene expression were twice as high in group 1 children compared with group 2 (beta1-receptor 0.12+/-0.07 versus 0.06+/-0.03, p = 0.0016; beta2-receptor 0.12+/-0.07 versus 0.06+/-0.03, p = 0.0071). Beta-receptor gene expression in 16 children who received standard treatment for heart failure averaged lower than in the 10 children who received additional propranolol.

CONCLUSIONS

Beta-receptor downregulation due to congestive heart failure has an impact on the postoperative course in children with congenital disease and depends on heart failure therapy.

Glucose metabolism and insulin secretion in children with cyanotic congenital heart disease

The aim of the study was to reveal differences in carbohydrate metabolism in children with cyanotic congenital heart diseases (CHD). Thirteen children with diseases of these kinds were investigated with regard to glucose tolerance and insulin secretion and comparisons were made with healthy controls of the same age. Investigations included an intravenous glucose tolerance test, insulin response to the glucose load in plasma and insulin secretion rate. The results reveal lower fasting glucose levels and signs of a higher insulin secretion rate in the relatively few patients in the CHD group where C-peptide measurements were performed, but no differences in glucose tolerance. The reasons for the differences are unclear, but the chronic increases in circulating catecholamines in combination with the impaired nutritional status of these children with CHD are probably the most important factors. We conclude that these divergences in carbohydrate metabolism should be emphasized in the care of children with CHD.