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

Vasoactive-ventilation-renal score: a reliable prognostic index for perioperative outcomes following congenital heart surgery in adults

INTRODUCTION

The number of adults requiring surgeries for CHD is increasing. We sought to evaluate the utility of the vasoactive-ventilation-renal (VVR) score as a predictor of prolonged length of stay in adults following CHD surgery.

METHODS

This is a retrospective review of 158 adult patients who underwent CHD surgery involving cardiopulmonary bypass. VVR score was calculated upon arrival to ICU and every 6 hours for the first 48 hours post-operatively. Our primary outcome was prolonged length of stay defined as hospital length of stay greater than 75th percentile for the cohort (≥8 days).

RESULTS

The study cohort had a median age of 25.6 years (18-60 years), and 83 (52.5%) were male. The groups with and without prolonged length of stay were comparable in age, gender, race, and surgical severity score. VVR score was significantly higher at all time points in the group with prolonged length of stay. The first post-operative day peak VVR score ≥13 had a sensitivity of 81% and specificity of 75% for predicting prolonged length of stay (p = 0.0001). On regression analysis, peak VVR score during the first day was independently associated with prolonged length of stay.

CONCLUSIONS

Peak VVR score during the first post-operative day was a strong predictor of prolonged length of stay in adults following CHD surgery.

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.

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.

Heart failure in the adult patient with congenital heart disease

BACKGROUND

Adult survival is now the rule for most congenital heart defects. However, despite surgical "repair," heart failure remains a common long-term complication of congenital heart disease. Heart failure specialists are seeing an increasing number of patients with congenital defects as the underlying etiology of their heart failure.

METHODS AND RESULTS

Familiarity with the anatomy, physiology, and long-term sequelae of surgical correction are essential for providing care to this complex group of patients.

CONCLUSION

This review discusses the diagnosis, pathophysiology, and management of the adult congenital heart patient with concomitant heart failure.

Metoprolol and coronary artery bypass grafting surgery: does intraoperative metoprolol attenuate acute beta-adrenergic receptor desensitization during cardiac surgery?

Cardiac surgery results in significant impairment of beta-adrenergic receptor (beta AR) function and is a cause of depressed myocardial function after surgery. We previously demonstrated that acute administration of beta AR blocker during cardiopulmonary bypass (CPB) in an animal model of coronary artery bypass grafting (CABG) surgery attenuates beta AR desensitization, whereas chronic oral beta-blockade therapy in patients undergoing CABG surgery does not prevent it. Therefore we hypothesized that acute administration of metoprolol during CABG surgery would prevent acute myocardial beta AR desensitization. A placebo-controlled initial phase (n = 72) was performed whereby patients were randomized to either metoprolol 10 mg or placebo immediately before CPB. Then a second dose-finding study was performed where patients received 20 mg (n = 20) or 30 mg (n = 20) of metoprolol. Hemodynamic monitoring, atrial membrane adenylyl cyclase activity, atrial beta AR density, and postoperative outcomes were measured. All groups showed similar decreases in isoproterenol-stimulated adenylyl cyclase activity (13%-24%). Cardiac output remained similar in all 4 groups throughout the intraoperative and postoperative period. In addition, patients receiving metoprolol 20 or 30 mg had less supraventricular arrhythmias 24 h postoperatively compared with patients receiving metoprolol 10 mg or placebo. Therefore, unlike our previous animal model of CABG surgery, metoprolol did not attenuate myocardial beta AR desensitization.

IMPLICATIONS

We investigated whether IV metoprolol given during cardiac surgery attenuates myocardial beta-adrenergic receptor (beta AR) desensitization. Although metoprolol did not reduce beta AR desensitization, the incidence of supraventricular arrhythmias was reduced by 75% in patients receiving 20 mg or 30 mg metoprolol.

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.

Beta-adrenoceptors: three-dimensional structures and binding sites for ligands

Recent progress in analyzing the structures and functions of G-protein coupled receptors (GPCRs) including beta-adrenoceptors (beta-ARs) has been made by pharmacological, physiological and molecular biological techniques. The three-dimensional (3D) structures, interaction sites with ligands and conformational changes of these receptor subtypes due to ligand binding are now better understood by the simulation of these receptors using computer-aided molecular modeling. Based on these techniques, numbers and conformations of amino acid sequences of each subtype (beta1-, beta2- and beta3-ARs) were defined and also interaction sites or modes of interaction between ligands and beta-ARs could be analyzed three-dimensionally. In addition, simulation of 3D structures of beta-ARs by molecular modeling could clearly determine the limited size, space or pocket for fitting with ligands. These studies will give some clues for the clarification of other GPCRs. Thus, this review summarizes current findings on chemical structures of ligands, amino acid sequences, 3D structures and important amino acids of beta-AR subtypes for interacting with ligands obtained from mutagenesis, chimeric studies and molecular modeling techniques.

Both beta(2)- and beta(1)-adrenergic receptors mediate hastened relaxation and phosphorylation of phospholamban and troponin I in ventricular myocardium of Fallot infants, consistent with selective coupling of beta(2)-adrenergic receptors to G(s)-protein

BACKGROUND

In adult human heart, both beta(1)- and beta(2)-adrenergic receptors mediate hastening of relaxation; however, it is unknown whether this also occurs in infant heart. We compared the effects of stimulation of beta(1)- and beta(2)-adrenergic receptors on relaxation and phosphorylation of phospholamban and troponin I in ventricle obtained from infants with tetralogy of Fallot.

METHODS AND RESULTS

Myocardium dissected from the right ventricular outflow tract of 27 infants (age range 21/2 to 35 months) with tetralogy of Fallot was set up to contract 60 times per minute. Selective stimulation of beta(1)-adrenergic receptors with (-)-norepinephrine (NE) and beta(2)-adrenergic receptors with (-)-epinephrine (EPI) evoked phosphorylation of phospholamban (at serine-16 and threonine-17) and troponin I and caused concentration-dependent increases in contractile force (-log EC(50) [mol/L] NE 5.5+/-0.1, n=12; EPI 5.6+/-0.1, n=13 patients), hastening of the time to reach peak force (-log EC(50) [mol/L] NE 5.8+/-0.2; EPI 5.8+/-0.2) and 50% relaxation (-log EC(50) [mol/L] NE 5.7+/-0.2; EPI 5.8+/-0.1). Ventricular membranes from Fallot infants, labeled with (-)-[(125)I]-cyanopindolol, revealed a greater percentage of beta(1)- (71%) than beta(2)-adrenergic receptors (29%). Binding of (-)-epinephrine to beta(2)-receptors underwent greater GTP shifts than binding of (-)-norepinephrine to beta(1)-receptors.

CONCLUSIONS

Despite their low density, beta(2)-adrenergic receptors are nearly as effective as beta(1)-adrenergic receptors of infant Fallot ventricle in enhancing contraction, relaxation, and phosphorylation of phospholamban and troponin I, consistent with selective coupling to G(s)-protein.

Amrinone versus dopamine and nitroglycerin in neonates after arterial switch operation for transposition of the great arteries

OBJECTIVE

To compare the efficacy and safety of amrinone and a combination of dopamine and nitroglycerin in neonates after reconstructive surgery for transposition of the great arteries.

DESIGN

A prospective, randomized, double-blind study.

SETTING

Pediatric intensive care unit in a university hospital.

PARTICIPANTS

Thirty-five neonates with transposition of the great arteries.

INTERVENTIONS

A loading dose of amrinone, 2 mg/kg, followed by a maintenance infusion of 7.5 microg/kg/min, were administered to 16 neonates before separation from cardiopulmonary bypass. The remaining 19 patients were administered a combination of dopamine, 5 microg/kg/min, and nitroglycerin, 1 microg/kg/min. An open-label epinephrine infusion was administered in both groups as required.

MEASUREMENTS AND MAIN RESULTS

The circulatory state of the patients was evaluated from 4 to 18 hours after cardiopulmonary bypass. The systemic blood flow index, calculated using the Fick principle, was higher in the amrinone group (1.7+/-0.5 L/min/m2 [mean +/- SD]) compared with the dopamine-nitroglycerin group (1.4+/-0.4 L/min/m2; p < 0.04). The systemic vascular resistance in the amrinone group was lower (26+/-8 Wood units x m2) than in the dopamine-nitroglycerin group (35+/-12 Wood units x m2; p < 0.02). The oxygen extraction ratio was higher in the dopamine-nitroglycerin group (0.34+/-0.08) compared with the amrinone group (0.28+/-0.06; p < 0.02). Lower platelet counts were observed in the amrinone group, but no difference in hemorrhagic complications was seen between the groups.

CONCLUSION

With the dosage regimen used, supplemented with epinephrine, amrinone provides a higher cardiac output and more favorable oxygen dynamics than a combination of dopamine and nitroglycerin.

L-type calcium current in human ventricular myocytes at a physiological temperature from children with tetralogy of Fallot

OBJECTIVE

The aim was to investigate the electrophysiological properties of the L-type calcium current (ICa,L) in ventricular myocytes at a physiological temperature (36-37 degrees C) isolated from children undergoing surgical repair of tetralogy of Fallot.

METHODS

ICa,L was recorded with the patch-clamp technique in the single electrode whose-cell mode at a physiological calcium concentration (1.8 mmol/l) at 36-37 degrees C.

RESULTS

Under these conditions, maximum current density averaged -5.80 +/- 0.45 pA/pF. ICa,L showed a bell-shaped current-voltage relationship: the current activated at -37.7 +/- 1.36 mV, peaked at +9.41 +/- 1.60 mV and reversed at +57.7 +/- 2.12 mV (n = 17). At +10 mV, time to peak of ICa,L was 5.23 +/- 0.46 ms. Membrane potentials for half-maximal steady-state activation and inactivation of ICa,L were -6.02 and -20.4 mV, respectively, the slope factors were 7.16 mV for steady-state activation and 6.49 mV for steady-state inactivation. ICa,L did not completely inactivate and showed a big window current between -45 and +40 mV. The inactivation of ICa,L showed a biexponential time course with a fast time constant ranging from 9.11 to 12.9 ms and a slow time constant ranging from 60.9 to 220 ms between -30 and +30 mV. Only the slow time constant showed a pronounced voltage dependency. The recovery from inactivation of ICa,L was biphasic with a fast time constant of 60.7 ms and a slow time constant of 619 ms. beta-Adrenergic stimulation with isoprenaline (1 mumol/l) increased the ICa,L density from -5.71 +/- 1.55 to -13.8 +/- 1.96 pA/pF (142%; P < 0.05) at +10 mV.

CONCLUSIONS

The present study demonstrates that most of the electrophysiological properties of ICa,L in ventricular myocytes isolated from children with tetralogy of Fallot resemble those of adult ventricular cells. The existence of a big calcium window current could be involved in the occurrence of early afterdepolarizations which could lead to the high incidence of arrhythmias after surgical repair of tetralogy of Fallot.

Stress response and mode of ventilation in preterm infants

AIM

To assess the change in stress response in preterm babies changed from patient triggered ventilation (PTV) to conventional mandatory ventilation (CMV) and vice versa; to determine outcome in relation to stress hormone concentrations.

METHODS

A randomised controlled study was conducted in two district general hospital neonatal intensive care units. Thirty babies, treated initially with CMV, were randomly assigned to remain on CMV or to change to PTV. A second group of 29 babies, treated initially with PTV, were randomly assigned to remain on PTV or to change to CMV. The babies were less than 32 weeks of gestation, ventilated within 72 hours of birth, with clinical and radiological features compatible with respiratory distress syndrome (RDS). Stress hormone concentrations and clinical distress score were measured before and 20 minutes after allocation of mode of ventilation.

RESULTS

Babies changed from CMV to PTV had significantly reduced adrenaline concentrations (median change -0.4 nmol/l) compared with those who remained on CMV. There was no increase in adrenaline in babies changed from PTV to CMV. There were no significant changes in noradrenaline concentrations or clinical distress score. Babies who died had significantly higher adrenaline and noradrenaline concentrations than those who survived.

CONCLUSION

A change in mode of ventilation significantly reduces adrenaline concentrations. Raised catecholamine values are associated with a poor outcome.

Amrinone versus dopamine-nitroglycerin after reconstructive surgery for complete atrioventricular septal defect

OBJECTIVES

To compare the effectiveness and safety of amrinone and a combination of dopamine and nitroglycerin in infants after reconstructive surgery for congenital heart disease.

DESIGN

A prospective, randomized, double-blind study.

SETTING

Pediatric intensive care unit in a university hospital.

PARTICIPANTS

Thirty-two infants with complete atrioventricular septal defect.

INTERVENTIONS

Amrinone loading dose, 2 mg/kg, followed by a maintenance infusion, 7.5 micrograms/kg/min, was given to 17 infants before separation from cardiopulmonary bypass. The remaining 15 patients received a combination of dopamine, 5 micrograms/kg/min, and nitroglycerin, 1 microgram/kg/min.

MEASUREMENTS AND MAIN RESULTS

The circulatory state of the patients was evaluated from 4 to 18 hours after cardiopulmonary bypass. The systemic blood flow index, calculated using the Fick principle, was higher in the amrinone group (2.5 +/- 0.7 L/min/m2) compared with the dopamine-nitroglycerin group (2.0 +/- 0.6 L/min/m2, mean +/- SD). The pulmonary blood flow index in the amrinone group was higher (2.9 +/- 0.6 L/min/m2) than in the dopamine-nitroglycerin group (2.2 +/- 0.6 L/min/m2); no significant difference was noted in the mean pulmonary artery pressure. The oxygen extraction ratio was higher in the dopamine-nitroglycerin group (0.41 +/- 0.07) compared with the amrinone group (0.34 +/- 0.08). Despite lower platelet counts in the amrinone group, no hemorrhagic complications were seen in any patient.

CONCLUSIONS

With this dosage regimen, amrinone provides a higher cardiac output, more favorable oxygen dynamics, and lower pulmonary vascular resistance than dopamine and nitroglycerin.

A post-receptor defect of adenylyl cyclase in severely failing myocardium from children with congenital heart disease

The aim of this study was to determine whether a defect at the post-receptor level of adenylyl cyclase may also contribute to the decreased effectiveness of cAMP-increasing agents in severely failing patients with congenital heart disease. The severity of congestive heart failure in 31 patients with congenital heart disease was graded by a scoring system which included a description of historical and clinical variables. Patients were divided into a group with no or mild heart failure (score < or = 6) and a group with severe heart failure (score > 6). beta-Adrenoceptor-stimulated adenylyl cyclase activity was significantly decreased by 65% in patients with severe heart failure in comparison to the group of patients with no or mild heart failure. In addition, receptor-independent adenylyl cyclase stimulation by forskolin was reduced by 52% in patients with score > 6 compared to patients with score < or = 6. This post-receptor defect of adenylyl cyclase was apparently due to a decrease in the activity of catalytic subunit of adenylyl cyclase as adenylyl cyclase stimulation by forskolin in the presence of Mn2+ which uncouples catalytic subunit from the G proteins, G(s) and G(i), was also significantly diminished in the patients with severe heart failure. In contrast, the level of inhibitory G protein alpha-subunits was apparently not different in the two groups. In summary, the data indicate that a defect at the catalytic subunit of adenylyl cyclase apparently contributes to the decreased effectiveness of cAMP-increasing agents in severely failing patients with congenital heart disease.

Differences in response to activation of adenylyl cyclase by various stimulants in human myocardium

The response of adenylyl cyclase complex in human atrial tissue removed at corrective surgery of normoxemic and hypoxemic congenital heart defects in children to various stimulants was evaluated and related to the oxygenation state of the myocardium. When comparing response to stimulation in normoxemic and hypoxemic atria a higher basal as well as stimulated adenylyl cyclase activity was found in hypoxemic atria; an insignificant stimulatory effect of isoprenaline in normoxemic hearts became significant in the atria of hypoxemic patients. Hypoxemic samples also showed two times higher activity when the total catalytic activity was evaluated by the stimulation with forskolin. Higher stimulatory effect of Gpp/NH/p was also observed in hypoxemic than in normoxemic state. Increased adenylyl cyclase activity might represent one of adaptive mechanisms to hypoxemia in patients with congenital heart defects.

Circulating noradrenaline and beta-adrenergic receptors in children with congestive heart failure

This study was designed to investigate changes in plasma catecholamine concentrations and the number of beta-adrenoceptors (beta-AR) of circulating lymphocyte in 94 noncyanotic congenital heart patients. In 43 patients with congestive heart failure, beta-AR density was significantly lower (p < 0.001) and plasma noradrenergic levels were significantly higher (p < 0.001) compared with corresponding values in 51 patients without heart failure. A significant negative correlation between lymphocyte beta-AR density and plasma noradrenergic levels was observed (r = -0.61, p < 0.001). The degree of left-to-right shunt and pulmonary pressure was correlated directly with noradrenaline level and inversely with lymphocyte beta-AR density. Both plasma noradrenaline level and lymphocyte beta-AR density return to normal in children with heart failure after surgical repair. Our results support the idea that changes in noradrenaline level and lymphocyte beta-adrenoceptor density occur concurrently with the presence and severity of heart failure in children.

Reduction in lymphocyte beta-adrenergic receptor density in infants and children with heart failure secondary to congenital heart disease

To identify changes in catecholamine levels and beta-adrenergic receptor density in children with varying degrees of congestive heart failure, we measured plasma norepinephrine (NE), epinephrine, and beta-adrenergic receptor levels in 91 noncyanotic patients using high-performance liquid chromatography and a radioligand binding assay. Plasma NE levels in 41 patients with heart failure (694 +/- 236 pg/ml) were significantly higher than those in 50 patients without it (274 +/- 68 pg/ml, p < 0.001). In addition, beta-adrenergic receptor density was significantly lower in patients with heart failure (0.81 +/- 0.48 fmol/10(6) cells) than in those without it (2.43 +/- 1.09 fmol/10(6) cells, p < 0.001), but epinephrine levels were not significantly different between the 2 groups. The receptor reduction in heart failure correlated well with elevated plasma NE levels (r = -0.60, p < 0.001). The degree of left to right shunt flow and pulmonary systolic pressure correlated directly with plasma NE levels and inversely with beta-adrenergic receptor density. From the best compromise between sensitivity and specificity, the optimal cutoff point for heart failure was > 390 ng/ml for NE and < 1.30 fmol/10(6) cells for beta-adrenergic receptor density, respectively. A follow-up study in 15 of 30 patients with heart failure after surgery showed a significant decrease in plasma NE and an increase in beta-adrenergic receptor density. Changes in plasma NE levels and beta-adrenergic receptor density occur concurrently with clinical symptoms of heart failure and may be used as indexes for assessing the presence and severity of heart failure in infants and children.