Beta-adrenoceptor density on mononuclear leukocytes and right atrial myocardium in infants and children with congenital heart disease

Resuscitation and perioperative management of the high-risk single ventricle patient: first-stage palliation

Infants born with hypoplastic left heart syndrome or other lesions resulting in a single right ventricle face the highest risk of mortality among all forms of congenital heart disease. Before the modern era of surgical palliation, these conditions were universally lethal; recent refinements in surgical technique and perioperative management have translated into dramatic improvements in survival. Nonetheless, these infants remain at a high risk of morbidity and mortality, and an appreciation of single ventricle physiology is fundamental to the care of these high-risk patients. Herein, resuscitation and perioperative management of infants with hypoplastic left heart syndrome are reviewed. Basic neonatal and pediatric life support recommendations are summarized, and perioperative first-stage clinical management strategies are reviewed.

Cardiovascular catecholamine receptors in children: their significance in cardiac disease

Adrenoceptors and dopamine receptors are grouped together under the name 'catecholamine receptors.' Catecholamines and catecholaminergic drugs act on catecholamine receptors located on or near the cardiovascular system. The physiological effects of catecholamine receptor stimulation are only partly understood. The catecholaminergic drugs used in critical care medicine today are not selective, or are, at best, in part selective for the various catecholamine receptor subtypes. Many patients, however, depend on them. A variety of animal models has been developed to unravel catecholamine distribution and function. However, the identification of species heterogeneity makes it imperative to determine catecholamine receptor distribution and function in humans. In addition, age-related alterations in catecholamine receptor distribution and function have been identified in human adults. This might have implications for our understanding of the effect of catecholamines in pediatric patients. This article will focus on the pediatric population and will review currently available in vitro data on the distribution and the function of catecholamine receptors in the cardiovascular system of fetuses and children. Also discussed are relevant young animal models and in vivo hemodynamic effects of cardiotonic drugs acting on the catecholamine receptor in children requiring major cardiac surgery. A better understanding of these topics might provide clues for new, receptor subtype-selective, therapeutic approaches in newborns and children with cardiac disease.

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.

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.

Distribution of myocardial beta-adrenoceptor subtypes and coupling to the adenylate cyclase in children with congenital heart disease and implications for treatment

In congestive heart failure, down-regulation of myocardial beta-adrenoceptors (beta-AR) due to an elevated sympathetic tone is well known. In infancy and childhood, heart failure is usually related to congenital heart disease (CHD). Therefore, 71 samples of right atrial tissue of infants and children with CHD undergoing cardiac surgery were studied for beta-adrenoceptor density and distribution of the beta 1-/beta 2-AR subtypes. In 49 cases, the coupling of the beta-AR to the adenylate cyclase (AC) was examined. In a further study of 19 myocardial samples, AC was selectively stimulated with beta 1- or beta 2-AR whereas the other subtype was blocked by an antagonist. The following results were obtained: (1) Infants and children with severe acyanotic or cyanotic CHD had severely reduced beta-AR densities. (2) In most of the cases, the beta-AR down regulation is beta 1-subtype selective, but in critically ill newborns with congenital aortic valve stenosis or transposition of the great arteries, there is additional significant beta 2-AR down-regulation. In Fallot patients treated with the beta-antagonist propranolol, a significant increased beta-AR number compared with untreated Fallot patients was found. (3) beta-Adrenoceptor reduction in CHD is correlated with elevated noradrenaline plasma levels, thus proving a sympathetic dysregulation. (4) In CHD with moderate hemodynamic load, beta 2-AR coupling to AC was markedly more efficient than beta 1-AR coupling. The small number of myocardial beta 2-AR produced most of the cyclic adenosine monophosphate. (5) In severe acyanotic and cyanotic CHD, a partial decoupling of the beta 2-AR to the AC occurred.(ABSTRACT TRUNCATED AT 250 WORDS)