Cardiac Valve Annulus Diameters in Extremely Preterm Infants: A Cross-Sectional Echocardiographic Study.

BACKGROUND: With the increasing incidence of births of very preterm very-low-birth-weight infants, there is a demand for echocardiographic reference values of cardiac dimensions. OBJECTIVES: The aim of this study was to provide reference values of cardiac valve annulus diameters in a cohort of extremely preterm very-low-birth-weight neonates and to correlate these with patient characteristics. METHODS: Valve diameters of 376 infants of < 32 weeks' gestation and with a birth weight of ≤2,000 g were measured using 2-dimensional echocardiography. Correlations between valve diameters and patient characteristics (birth length/weight, body surface area, gestational age, and sex) were assessed. Birth weight was used to establish linear regression models. Inter- and intraobserver agreement was assessed through intraclass correlation coefficient (ICC) analysis. RESULTS: Substantial variability was found (aortic valve mean [standard deviation; range]: 5.0 mm [0.6; 3.7-6.5]; pulmonic valve: 5.8 mm [0.8; 3.4-7.9]; mitral valve: 8.0 mm [1.0; 5.5-10.5]; tricuspid valve: 7.6 mm [1.2; 4.9-10.6]). There was a moderate correlation between birth weight and valve diameter (R2 aortic valve: 0.36; pulmonic valve: 0.20; mitral valve: 0.24; tricuspid valve: 0.24). Adequate intraobserver (ICC range 0.74-0.91) and interobserver agreement (ICC range 0.77-0.89) was found. CONCLUSIONS: Our study provides ready-to-use reference values for cardiac valve annulus diameters for extremely preterm infants.

Long-term results of balloon angioplasty for native coarctation of the aorta in childhood in comparison with surgery.

OBJECTIVES: Coarctation of the aorta (CoA) can be treated either surgically or with balloon angioplasty (BA). Long-term follow-up for either treatment has been limited. Our objective was to compare long-term results of BA and surgery for treatment of native CoA in childhood. METHODS: Retrospective cohort study of patients with native CoA treated with BA or surgery between 3 months and 16 years of age. Forty-eight patients filled out questionnaires and approved review of their medical records. Twenty-four patients underwent additional testing, including 24-h ambulatory blood pressure measurement, cardiopulmonary exercise testing and cardiac magnetic resonance imaging. Results were analysed cross-sectionally and longitudinally. RESULTS: Nineteen and 29 patients received BA and surgery, respectively. Prevalence of hypertension and aneurysms was similar in both groups. Fifty percent of patients were hypertensive. Two-thirds of patients demonstrating hypertension were not receiving antihypertensive medication. Aneurysm formation occurred in 1 BA (5%) and 1 surgery (3%) patient. The BA group had a significantly higher risk of recoarctation (47% vs 24%) and reintervention (hazard ratio 2.95, 95% confidence interval 1.04-8.32). Exercise capacity and global left ventricular function were preserved in both groups and not significantly different after correction for age. Quality of life was good to excellent in the majority of the patients. CONCLUSIONS: After CoA repair in childhood, most patients perform well in daily life. However, on the long term, more than half of the patients develop hypertension and many develop re-CoA, especially in those who underwent BA. Therefore, we do not recommend BA for the treatment of native CoA in children.

Computational fluid dynamics in Fontan patients to evaluate power loss during simulated exercise.

OBJECTIVE: Exercise intolerance is common in total cavopulmonary connection (TCPC) patients. It has been suggested that power loss (Ploss) inside the TCPC plays a role in reduced exercise performance. Our objective is to establish the role of Ploss inside the TCPC during increased flow, simulating exercise in a patient-specific way. METHODS: Cardiac MRI (CMR) was used to obtain flow rates from the caval veins during rest and increased flow, simulating exercise with dobutamine. A 3D reconstruction of the TCPC was created using CMR data. Computational fluid dynamics (CFD) simulations were performed to calculate Ploss inside the TCPC structure for rest and stress conditions. To reflect the flow distribution during exercise, a condition where inferior caval vein (IVC) flow was increased twofold compared with rest was added. 29 TCPC patients (15 intra-atrial lateral tunnel (ILT) and 14 extracardiac conduit (ECC)) were included. RESULTS: Mean Ploss at rest was 1.36 ± 0.94 (ILT) and 3.20 ± 1.26 (ECC) mW/m(2) (p<0.001), 2.84 ±1.95 (ILT) and 8.41 ± 3.77 (ECC) mW/m(2) (p<0.001) during dobutamine and 5.21 ± 3.50 (ILT) and 15.28 ± 8.30 (ECC) mW/m(2) (p=0.001) with twofold IVC flow. The correlation between cardiac index and Ploss was exponential (ILT: R(2)=0.811, p<0.001; ECC: R(2)=0.690, p<0.001). CONCLUSIONS: Ploss inside the TCPC structure is limited but increases with simulated exercise. This relates to the anatomy of TCPC and the surgical technique used. In all flow conditions, ILT patients have lower Ploss than ECC patients. We did not find a relationship between Ploss and exercise capacity.

Ventricular response to dobutamine stress relates to the change in peak oxygen uptake during the 5-year follow-up in young patients with repaired tetralogy of Fallot.

AIMS: To evaluate the additional value of dobutamine stress testing in patients with repaired tetralogy of Fallot (TOF) by relating stress imaging parameters at baseline to relevant parameters of clinical condition and right ventricular (RV) size during a serial follow-up. METHODS AND RESULTS: We prospectively included 27 patients (14 ± 4 years at baseline), who were studied twice with a 5-year interval. Patients underwent cardiovascular magnetic resonance imaging to assess RV systolic and diastolic function at rest and during dobutamine stress. Normal response to dobutamine was defined as a decrease in RV end-systolic volume, and a increase in RV ejection fraction (EF) during stress. Exercise testing and electrocardiography were performed to determine peak oxygen uptake (peak VO2), QRS duration, and QT interval corrected for heart rate (QTc) interval. RV volumes, QRS duration, and QTc interval increased significantly from baseline to follow-up; peak VO2 tended to decrease (95 ± 20-89 ± 14%, P = 0.086). Response to dobutamine was normal in 26 of 27 patients and remained stable during the follow-up [relative increase in RVEF during stress: +25 ± 9% (baseline) vs. +27 ± 10% (follow-up)]. A smaller relative increase in RVEF during stress at baseline related to a larger relative decrease in peak VO2 during the follow-up (r = 0.59, P = 0.004). No significant associations were found with the relative increase in QRS duration, QTc interval, or RV end-diastolic volume during a 5-year follow-up. CONCLUSION: In a young TOF population, response to dobutamine stress was normal and remained stable during the 5-year follow-up. A smaller increase in RVEF during stress at baseline was predictive for a larger decrease in peak VO2 during the 5-year follow-up.

Exercise capacity in children with isolated congenital complete atrioventricular block: does pacing make a difference?

The management of patients with isolated congenital complete atrioventricular block (CCAVB) has changed during the last decades. The current policy is to pace the majority of patients based on a variety of criteria, among which is limited exercise capacity. Data regarding exercise capacity in this population stems from previous publications reporting small case series of unpaced patients. Therefore, we have investigated the exercise capacity of a group of contemporary children with CCAVB. Sixteen children (mean age 11.5 ± 4; seven boys, nine girls) with CCAVB were tested. In 13 patients, a median number of three pacemakers were implanted, whereas in three patients no pacemaker was given. All patients had an echocardiogram and completed a cardiopulmonary cycle exercise test. Exercise parameters were determined and compared with reference values obtained from healthy Dutch peers. The peak oxygen uptake/body mass was reduced to 34.4 ± 9.5 ml kg(-1) min(-1) (79 ± 24% of predicted) and the ventilatory threshold was reduced to 52 ± 17% of peak oxygen uptake (78 ± 21% of predicted), whereas the peak work load/body mass was 2.8 ± 0.6 W/kg (91 ± 24% of predicted), which was similar to controls. Importantly, 25% of the paced patients showed upper rate restriction by the pacemaker. In conclusion, children with CCAVB show a reduced peak oxygen uptake and ventilatory threshold, whereas they show normal peak work rates. This indicates that they generate more energy during exercise from anaerobic energy sources. Paced children with CCAVB do not perform better than unpaced children.

Pediatric pulmonary hypertension in the Netherlands: epidemiology and characterization during the period 1991 to 2005.

BACKGROUND: Incidence and prevalence rates for pediatric pulmonary hypertension (PH) and pulmonary arterial hypertension (PAH) are unknown. This study describes the nationwide epidemiological features of pediatric PH in the Netherlands during a 15-year period and the clinical course of pediatric PAH. METHODS AND RESULTS: Two registries were used to retrospectively identify children (0-17 years) with PH. Overall, 3263 pediatric patients were identified with PH due to left heart disease (n=160; 5%), lung disease/hypoxemia (n=253; 8%), thromboembolic disease (n=5; <1%), and transient (n=2691; 82%) and progressive (n=154; 5%) PAH. Transient PAH included persistent PH of the newborn and children with congenital heart defects (CHD) and systemic-to-pulmonary shunt, in whom PAH resolved after successful shunt correction. Progressive PAH mainly included idiopathic PAH (n=36; iPAH) and PAH associated with CHD (n=111; PAH-CHD). Pulmonary arterial hypertension associated with CHD represented highly heterogeneous subgroups. Syndromes were frequently present, especially in progressive PAH (n=60; 39%). Survival for PAH-CHD varied depending on the subgroups, some showing better and others showing worse survival than for iPAH. Survival of children with Eisenmenger syndrome appeared worse than reported in adults. For iPAH and PAH-CHD, annual incidence and point prevalence averaged, respectively, 0.7 and 4.4 (iPAH) and 2.2 and 15.6 (PAH-CHD) cases per million children. Compared to studies in adults, iPAH occurred less whereas PAH-CHD occurred more frequently. CONCLUSIONS: Pediatric PH is characterized by various age-specific diagnoses, the majority of which comprise transient forms of PAH. Incidence of pediatric iPAH is lower whereas incidence of pediatric PAH-CHD is higher than reported in adults. Pediatric PAH-CHD represents a heterogeneous group with highly variable clinical courses.

Safety and observer variability of cardiac magnetic resonance imaging combined with low-dose dobutamine stress-testing in patients with complex congenital heart disease.

BACKGROUND: In patients with complex congenital heart disease (CHD) abnormal ventricular stress responses have been reported with dobutamine stress cardiovascular magnetic resonance (DCMR). These abnormal stress responses are potential indicators of long-term outcome. However, safety and reproducibility of this technique has not been reported in a larger study. The aim of this study was to report our experiences regarding safety and intra-observer and inter-observer variability of low-dose DCMR in complex CHD. METHODS: In 91 patients, 110 low-dose DCMR studies were performed with acquisition of a short axis set at rest, and during dobutamine administration (7.5 µg/kg/min maximum). We assessed biventricular end-diastolic volumes, end-systolic volumes, stroke volumes, ejection fraction and ventricular mass. Intra- and inter-observer variability for all variables was assessed by calculating the coefficient of variation (%), i.e. the standard deviation of the difference divided by the mean of 2 measurements multiplied by 100%. RESULTS: In 3 patients minor side effects occurred (vertigo, headache, and bigeminy). Ten patients experienced an increase in heart rate of >150% from baseline, although well tolerated. For all variables, intra-observer variability was <10% at rest and during stress. At rest, inter-observer variability was 10.5% maximal. With stress-testing, only the variability of biventricular end-systolic volumes (ESV) exceeded 10%. CONCLUSIONS: In patients with complex CHD low-dose DCMR is feasible, and safe. Intra-observer variability is low for rest and stress measurements. Inter-observer variability of biventricular ESV is high with stress-testing. Whether this limits the potential usefulness of DCMR for risk assessment during follow-up has to be assessed.

Juxtaductal coarctation of both pulmonary arteries in a cat.

A 4-year-old, male, neutered cat was referred because of recurrent episodes of dyspnea. Physical examination revealed a harsh systolic murmur, with the point of maximal intensity in the left heart base, with an intensity of 4 out of 6. Echocardiographic diagnosis was severe supravalvular pulmonary artery stenosis. A selective right ventricular angiocardiogram showed an absence of arterial blood flow to the left lung lobes. A balloon dilatation of the localized stenosis of the right pulmonary artery was attempted with cardiac catheterization. However, when the catheter was passed through the stenosis, the blood flow to the lungs temporarily completely ceased, which led to death. Postmortem examination revealed a circumscribed stenosis of both pulmonary arteries at the site of the bifurcation, where the ligamentum arteriosum was attached. Histopathology showed that the localized ridge-like stenosis at the pulmonary artery bifurcation was caused by connective tissue. The suspected cause of this congenital anomaly is the presence of ectopic ductal tissue in the wall of the pulmonary artery. When the ductus arteriosus closes at birth, pulmonary artery stenosis developed because of constriction of the ectopic ductal tissue.

Outcome of pediatric patients with pulmonary arterial hypertension in the era of new medical therapies.

Little is known about the effects of "second-generation drugs" (prostanoids, endothelin receptor antagonists, 5-phosphodiesterase inhibitors) in children with pulmonary arterial hypertension (PAH). This study describes the outcome of a national cohort of children with PAH in an era when these drugs became available. From 1993 to 2008, 52 consecutive children with idiopathic PAH (n = 29) or systemic-to-pulmonary shunt-associated PAH (n = 23) underwent baseline and follow-up assessments. Treatment was initiated depending on functional class, acute pulmonary vasoreactivity response, and drug availability. Observed survival was evaluated depending on time of diagnosis in relation to second-generation drug availability and subsequently compared to calculated predicted survival. Children for whom second-generation drugs were available had improved survival compared to their predicted survival (1-, 3-, and 5-year survival rates 93%, 83%, and 66% vs 79%, 61%, and 50%, respectively). However, this improved survival was observed only in patients for whom second-generation drugs became available during their disease course. No improved survival was observed in patients for whom drugs were available already at diagnosis. Baseline variables associated with decreased survival included higher functional class, higher pulmonary-to-systemic arterial pressure ratio, lower cardiac index, and higher serum levels of N-terminal pro-brain natriuretic peptide and uric acid. After start of second-generation drugs, functional class, 6-minute walking distance, and N-terminal pro-brain natriuretic peptide improved but gradually decreased after longer follow-up. In conclusion, survival of pediatric PAH seemed improved since the introduction of second-generation drugs only in selected patients for whom these drugs became available during their disease course. Start of second-generation drugs initially induced clinical improvements, but these effects decreased after longer follow-up.

A multicenter, long-term study on arrhythmias in children with Ebstein anomaly.

To assess the prevalence, history, and treatment of arrhythmias, in particular preexcitation and Wolff-Parkinson-White (WPW) syndrome, in patients with Ebstein anomaly (EA) during childhood and adolescence, we performed a multicenter retrospective study of all consecutive live-born patients with EA, diagnosed, and followed by pediatric cardiologists between 1980 and 2005 in The Netherlands. During a follow-up after EA diagnosis of 13 years 3 months (range: 6 days to 28 years 2 months), 16 (17%) of the 93 pediatric EA patients exhibited rhythm disturbances. Nine patients showed arrhythmic events starting as of the neonatal period. Supraventricular tachycardia was noted in 11 patients. One patient died in the neonatal period due to intractable supraventricular tachycardia resulting in heart failure and one patient died at 5 weeks of age most probably due to an arrhythmic event. The 14 surviving patients all show preexcitation, albeit 4 of them intermittently, and all have a right-sided accessory pathway location. Nine patients underwent catheter ablation of an accessory pathway. Only four patients are currently on antiarrhythmic drugs. The 17% prevalence of rhythm disturbances in pediatric EA patients, most commonly supraventricular arrhythmias, is significantly lower than in adult EA patients. Life-threatening rhythm disturbances are not frequent early in life. Symptomatic patients are well treated with radiofrequency catheter ablation.

Clinical outcome 5 to 18 years after the Fontan operation performed on children younger than 5 years.

OBJECTIVE: This study assessed clinical condition at midterm follow-up after total cavopulmonary connection for a functionally univentricular heart performed on children younger than 5 years. METHODS: Thirty-four Fontan patients (median age 10.4 years, range 6.8-20.7 years, 22 boys, median follow-up 7.8 years, 5.0-17.8 years) underwent electrocardiography, Holter monitoring, bicycle exercise testing, cardiac magnetic resonance imaging, and N-terminal prohormone brain natriuretic peptide (NT-pro-BNP) analysis. RESULTS: Twenty-three patients (68%) were in sinus rhythm. Holter monitoring demonstrated normal mean heart rate, low maximal heart rate, and no clinically significant arrhythmias or sinus node dysfunction. With maximal bicycle ergometry (n = 19), maximum workload (60% of normal), maximum heart rate (90% of normal), and maximal oxygen uptake (69% of normal) were all significantly lower in the Fontan group than in a control group (P < .001). Variables of submaximal exercise indicated less efficient oxygen uptake during exercise in all Fontan patients. Ejection fraction was lower than in control subjects (59% +/- 13% vs 69% +/- 5%, P < .001). Mean end-diastolic and end-systolic volumes and ventricular mass were higher than in control subjects (P < .001). Mean NT-pro-BNP levels were increased relative to reference values, but only 8 patients had levels above the upper reference limit. CONCLUSION: At midterm follow-up, Fontan patients were in acceptable clinical condition, with preserved global ventricular function, moderately decreased exercise capacity, and NT-pro-BNP levels within reference range. Systemic ventricular mass was elevated, however, suggesting contractility-afterload mismatch. Long-term consequences for ventricular function merit further investigation.

Clinical characterization of pediatric pulmonary hypertension: complex presentation and diagnosis.

OBJECTIVES: To describe the clinical presentation of pediatric pulmonary arterial hypertension (PAH) and the intricacies of how to classify pediatric PAH according to the Venice classification. STUDY DESIGN: Children (n = 63) seen at a national referral center for pediatric PAH underwent a diagnostic work-up for diagnosis of pulmonary hypertension (PH) and associated conditions and for assessment of the explanatory role of associated conditions for the PH. Subsequently, PH was classified. RESULTS: In 18 patients (29%), no associated conditions were identified; they were classified as having idiopathic PAH. In 45 patients (71%), > or = 1 associated conditions were detected: congenital heart defects (CHD, n = 40), connective tissue disease (CTD, n = 2), disorders of respiratory system and/or hypoxemia (RSH, n = 17), and chronic thromboembolic disease (CTE, n = 1). Patients were classified according to the condition judged to be primarily explanatory for the PH. In 11 of 45 patients with associated conditions, the PH was not sufficiently explained by these conditions; these patients were classified as having idiopathic-like PAH. In 17 of 40 cases of CHD and 9 of 17 cases of RSH, these conditions were not sufficiently explanatory for the PH. Syndromal abnormalities were frequent (43%). Ultimately, classification revealed idiopathic (-like) PAH (n = 29; 46%), PAH-CHD (n = 23; 37%), PAH-CTD (n = 2; 3%), PH-RSH (n = 8; 12%), and CTE-PH (n = 1; 2%). CONCLUSION: Pediatric PH frequently presents with associated conditions and syndromal abnormalities. However, detailed evaluation of this complex presentation reveals that associated conditions are not always explanatory for the PH.

Rewiring the heart: stem cell therapy to restore normal cardiac excitability and conduction.

The regenerative capacity of the mammalian heart is insufficient to recover from myocardial infarction. Stem cells are currently considered as a promising and valuable tool to replace the, often large, loss of contractile tissue. One of the bottlenecks hampering fast clinical application is the large amount of cells required to replace a single damaged region combined with an appropriate strategy to succeed in homogeneous repair. A second class of major cardiac disorders for which stem cell therapy might be fruitful and would require less cells for repair, are chronic rhythm disorders. In this area, most research has been focused on stem-cell based biological pacemakers, but increasing amounts of data on AV nodal repair appear in literature. Both therapies, in principle, could eventually replace current instrumentation with electronic pacemakers. Finally, an emerging field of interest explores transplantation of stem cells expressing specific ion channels aiming at suppression of focal arrhythmias, providing an alternative strategy for surgical and catheter-mediated ablation. Since in this second class of applications the number of transplanted cells required may be relatively low, effective clinical therapy may be within close range. Here, we will review recent achievements in the fields of stem-cell based biological pacemakers, AV nodal repair and biological ablation.

Assessment of biventricular functional reserve and NT-proBNP levels in patients with RV volume overload after repair of tetralogy of Fallot at young age.

PURPOSE: To assess biventricular functional reserve (FR), NT-proBNP levels and exercise performance, in relation to right ventricular volume in patients with pulmonary regurgitation (PR) after repair of tetralogy of Fallot (TOF) at young age. METHODS: In 53 TOF patients (maximum age at repair 2.0 years, interval since repair 15 (5) years) without residual lesions except PR, biventricular FR (derived from magnetic resonance imaging with dobutamine stress), NT-proBNP levels, maximal workload, and peak oxygen uptake were assessed. RESULTS: Mean right ventricular end-diastolic volume was 140(38) ml/m(2). Median pulmonary regurgitant fraction was 37% (range 0-57%). Biventricular systolic stress response was normal: mean (SD) ESV decreased (DeltaRVESV -17(8) ml/m(2), DeltaLVESV -11(5)), SV increased (DeltaRVSV +12(9) ml/m(2), DeltaLVSV +9(6)), FR was positive in all (RV-FR +11(5)%, LV-FR +13(6)). No serious adverse effects to dobutamine were encountered. NT-proBNP was increased in 2 patients. Median level was 10 pmol/L (range 2-42). NT-proBNP correlated with PR-percentage but not with right ventricular size. High-risk levels of NT-proBNP indicated a smaller RV-FR and a smaller decrease of biventricular ESV. Mean (SEM) VO2(max) was 96(3)%, mean Workload(max) 89(2)% of predicted. CONCLUSION: At mid to long term follow-up overall NT-proBNP levels are normal and biventricular functional reserve and exercise tolerance are well preserved in TOF repaired at young age, irrespective of RV volume. This questions the validity of isolated PR or RV volume criteria for pulmonary valve replacement in this group. Low-dose dobutamine stress testing is well tolerated and may be a useful additional tool for clinical decision making.

Pulmonary artery size and function after Fontan operation at a young age.

PURPOSE: To assess pulmonary artery (PA) size, flow variables, and wall shear stress (WSS) in patients after Fontan operation at a young age. MATERIALS AND METHODS: Flow in the branch PA was obtained with phase contrast velocity-encoded cardiovascular magnetic resonance imaging in 14 patients before and after low-dose dobutamine stress (7.5 microg/kg/min) and in 17 healthy controls at rest. RESULTS: At rest, stroke index, total flow, average, and peak flow rate were all statistically significantly lower in patients than in controls (P<0.001). With stress-testing, all variables increased in patients (P<0.001), apart from stroke index, which did not change. At rest, branch PA area did not differ between patients and controls. Distensibility was lower in patients than in controls (P<0.001). With stress-testing, area and distensibility did not change. At rest, WSS was lower in patients than in controls (P<0.001). WSS increased with stress-testing (P<0.001), but not to the same levels as during resting conditions of the control group. CONCLUSION: PA size is normal long-term after Fontan operation at a young age. Flow variables, distensibility, and WSS are significantly lower compared to healthy controls, and do not show adequate reactions with stress-testing, which is suggestive of pulmonary artery endothelial and/or vascular dysfunction.

Cardiovascular follow-up at school age after perinatal glucocorticoid exposure in prematurely born children: perinatal glucocorticoid therapy and cardiovascular follow-up.

OBJECTIVE: To study whether antenatal or neonatal glucocorticoid therapy to reduce the incidence and severity of chronic lung disease in preterm infants is associated with long-term adverse cardiac effects and hypertension. DESIGN: Retrospective matched-cohort study. SETTING: Outpatient clinic of a tertiary care hospital. PARTICIPANTS: One hundred ninety-three children aged 7 to 10 years who had been born prematurely between December 2, 1993, and September 15, 1997. Main Exposure Neonatal treatment with dexamethasone disodium phosphate(n = 48) or the clinically equally effective glucocorticoid hydrocortisone (n = 51), or only antenatal treatment with betamethasone disodium phosphate and betamethasone acetate (n = 51). These 3 groups were compared with a reference group of prematurely born children who had not been exposed to perinatal glucocorticoid therapy (n = 43). MAIN OUTCOME MEASURES: General hemodynamic data (heart rate and blood pressure), cardiovascular function as assessed at echocardiography, intima-media thickness of the carotid arteries, and cardiac biochemical features as early markers of expansion and volume overload of the cardiac left ventricle (B-type natriuretic peptide and N-terminal pro-B-type natriuretic peptide). RESULTS: No significant group differences were found for heart rate, blood pressure, biochemical features, intima-media thickness, or systolic or diastolic left ventricular function. CONCLUSIONS: Although no differences were found in blood pressure and cardiovascular function at school age in children antenatally or neonatally treated with glucocorticoids, further cardiovascular follow-up may be advisable because cardiovascular dysfunction may become apparent only later in life.

Usefulness of cardiac magnetic resonance imaging combined with low-dose dobutamine stress to detect an abnormal ventricular stress response in children and young adults after fontan operation at young age.

After Fontan operation, patients are limited in increasing cardiac output and in exercise capacity. This has been related to impaired preload or other factors leading to decreased global ventricular performance with stress. To study these factors, the stress responses of functionally univentricular hearts were assessed at rest and during low-dose dobutamine stress using cardiovascular magnetic resonance imaging. Thirty-two patients after Fontan completion at young age were included (27 with total cavopulmonary connection, 5 with atriopulmonary connection; mean age 13.3 years, range 7.5 to 22.2; 23 male patients; median follow-up after Fontan operation 8.1 years, range 5.2 to 17.8). A multiphase short-axis stack of 10 to 12 contiguous slices of the systemic ventricle was obtained at rest and during low-dose dobutamine stress cardiovascular magnetic resonance imaging (maximum 7.5 microg/kg/min). With stress-testing, heart rate, ejection fraction, and cardiac index increased adequately (p <0.001). There was an abnormal decrease in end-diastolic volume and an adequate decrease in end-systolic volume (p <0.001). Stroke volume did not change with stress testing (p = 0.15). At rest, dominant left ventricles had higher ejection fractions than dominant right ventricles (p = 0.01), but this difference disappeared with stress testing. In conclusion, a functionally univentricular heart after Fontan completion at young age has an adequate increase in ejection fraction with beta-adrenergic stimulation. However, as a result of impaired preload with stress, cardiac output can be increased only by increasing heart rate.

Down syndrome: a novel risk factor for respiratory syncytial virus bronchiolitis--a prospective birth-cohort study.

OBJECTIVES: Respiratory syncytial virus is the single-most important cause of lower respiratory tract infections in children. Preterm birth and congenital heart disease are known risk factors for severe respiratory syncytial virus infections. Although Down syndrome is associated with a high risk of respiratory tract infections, little is known about the incidence of respiratory syncytial virus infections in this group. The aim of our study was to determine the incidence of respiratory syncytial virus lower respiratory tract infection-associated hospitalization among children with Down syndrome. PATIENTS AND METHODS: We performed a retrospective observational study and a prospective nationwide birth-cohort study of children with Down syndrome. The retrospective cohort comprised 176 children with Down syndrome. A birth cohort of 219 children with Down syndrome was prospectively followed until 2 years of age. All 276 siblings of the birth cohort were used as controls. RESULTS: Of the 395 patients with Down syndrome, 180 (45.6%) had a known risk factor for severe respiratory syncytial virus infections; 39 (9.9%) of these were hospitalized for respiratory syncytial virus lower respiratory tract infections. Two control children (0.7%) versus 9 term children with Down syndrome without congenital heart disease (7.6%) were hospitalized for respiratory syncytial virus lower respiratory tract infections. The median duration of hospitalization was 10 days; mechanical ventilation was required for 5 children (12.8%). CONCLUSIONS: This is the first study, to our knowledge, to demonstrate that Down syndrome is a novel independent risk factor for severe respiratory syncytial virus lower respiratory tract infections. These findings should prompt studies to investigate possible mechanisms that underlie severe respiratory syncytial virus lower respiratory tract infections in children with Down syndrome. The effect of respiratory syncytial virus prophylaxis in this specific population needs to be established.

Ebstein's anomaly: factors associated with death in childhood and adolescence: a multi-centre, long-term study.

AIMS: The objective of this study is to establish factors associated with death after diagnosis of Ebstein's anomaly (EA) during childhood and adolescence. METHODS AND RESULTS: This study is a retrospective chart review. All paediatric patients were diagnosed with EA and followed in tertiary-care university hospitals between 1980 and 2005. Factors associated with death were obtained using the Cox regression and log-rank tests. Of the 93 patients with EA, 18 (19%) died and 75 (81%) survived. The median age at EA diagnosis and follow-up was 0 (range 0-162) and 86 months (range 0-216), respectively. After 35 months of diagnosis, the Kaplan-Meier survival probability remains stable at 80%. Young age at presentation (< or =12 months), hepatomegaly, the need for medication (diuretics and Prostin) and mechanical ventilation at presentation, pulmonary valve defects (defined as moderate-to-severe pulmonary stenosis and pulmonary atresia), patent arterial duct, and ventricular septal defect were significantly associated with death. CONCLUSION: The overall survival of patients with EA during childhood and adolescence has dramatically improved when compared with earlier reports.

Exercise limitation in patients with Fontan circulation: a review.

The aim of the current literature study was to perform a literature review of the factors contributing to exercise limitation and physiological response to exercise in patients with Fontan circulation. In patients with Fontan circulation, peak oxygen uptake ranged from about 14.4 to 32.3 ml/min/kg, and showed a slowed acceleration in the kinetics of oxygen uptake at the onset of exercise. Peak heart rate during exercise was decreased to an average of 153 +/- 10 bpm and arterial oxygen saturation was also decreased at peak exercise, with an average of 89.5 +/- 1.94%. Cardiac output was subnormal, owing to reduced stroke volume, heart rate response and affected pulmonary venous return. Ventilatory anaerobic threshold was below normal values. Moreover, the ventilatory equivalent for carbon dioxide was found to be higher. Patients with Fontan circulation possess a unique physiological response to exercise. Although there is a wide range in exercise capacity among patients, all patients have reduced tolerance to exercise. Cardiac, pulmonary, and muscular factors might play a role in reduced exercise capacity and this distinct response to exercise.