Robbers-Visser, D.

Outcome, Hemodynamic and Genetic Assessment in Patients with Functionally Univentricular Hearts after the Fontan Operation at Young Age (Doctoral Thesis)

2012-06-14T00:00:00Z

The incidence of CHD is about 0.8%, meaning 12.5 cases per 1000 life births. Errors in the morphogenesis of a normal four-chambered heart result in congenital heart disease (CHD), the most common form of birth defects. Heart formation is a complex morphogenetic process that requires correct function of 1) various embryological developmental regions (including the heart fields and the neural crest); 2) complex looping patterns resulting from selective growth and cell death, and 3) numerous regulatory and structural genes. Disruption of these processes cumulates in various forms of CHD. In the minority of cases of CHD, there is a chromosomal or monogenetic defect. The majority of cases of CHD, however, are of multifactorial origin, meaning a complex interplay of genetic and environmental factors (i.e. a polygenic model). Up until now, several candidate genes have been identified in patients with defects of cardiac septation, conotruncal anomalies and/or underdevelopment of one of the ventricles. In patients with a so called functionally univentricular heart, all these defects can be combined in one heart. Data on the embryological development of univentricular lesions are scarce, as are candidate genes. Inheritance seems to be comparable to other types of congenital heart defect, with 2-5% of siblings affected. Hypoplastic left heart syndrome is an exception with an overrepresentation of familial congenital heart disease, with 19-33% of siblings affected.

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

2011-03-03T00:00:00Z

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.

Results of staged total cavopulmonary connection for functionally univentricular hearts; comparison of intra-atrial lateral tunnel and extracardiac conduit (Article)

2010-04-01T00:00:00Z

Objectives: This study aims to compare the outcome of the two co-existing modifications of staged total cavopulmonary connection (TCPC) - the intra-atrial lateral tunnel (ILT) and the extracardiac conduit (ECC). Methods: We included 209 patients after staged TCPC (102 ILT and 107 ECC), operated on between 1988 and 2008. Medical and surgical records were reviewed for (1) patient demographics and cardiac anatomy; (2) pre-Fontan procedures; (3) pre-Fontan haemodynamics and cardiac functional status; (4) operative details; (5) postoperative hospital course; (6) follow-up information on arrhythmias and thrombo-embolic events; (7) post-Fontan interventions; and (8) clinical status at last follow-up until June 2008. Results: Median follow-up duration was 4.3 years (interquartile range 1.5-7.4 years). At 6-year follow-up, freedom from Fontan failure (i.e., mortality or re-operations for Fontan failure) was 83% for the ILT and 79% for the ECC groups (p = 0.6); freedom from late re-operations (other than re-operations for Fontan failure) was 79% for the ILT and the ECC groups and freedom from arrhythmias was 83% for the ILT, and 92% for the ECC groups (p = 0.022). Multivariable Cox regression analysis identified intensive care unit stay and cardiopulmonary bypass time as risk factors for Fontan failure, but they were not strong predictors. Right ventricular morphology was identified as a risk factor for arrhythmias. The occurrence of thrombo-embolic events was low with no difference between the ILT and the ECC groups, and irrespective of the postoperative use of anticoagulant or anti-platelet aggregation therapy. At most recent follow-up, sinus rhythm was present in 70% of patients; in 23% of the patients, ventricular function was found to be moderately or severely impaired at echocardiography. Conclusions: Outcome after staged ILT- and ECC-type Fontan operations is good, with comparable freedom from late re-operations and freedom from Fontan failure at 6-year follow-up. The incidence of arrhythmias was significantly lower in the ECC group. Right ventricular morphology was identified as a risk factor for arrhythmias.

Intra-observer and interobserver variability of biventricular function, volumes and mass in patients with congenital heart disease measured by CMR imaging (Article)

2010-01-01T00:00:00Z

Cardiovascular magnetic resonance (CMR) imaging provides highly accurate measurements of biventricular volumes and mass and is frequently used in the follow-up of patients with acquired and congenital heart disease (CHD). Data on reproducibility are limited in patients with CHD, while measurements should be reproducible, since CMR imaging has a main contribution to decision making and timing of (re)interventions. The aim of this study was to assess intra-observer and interobserver variability of biventricular function, volumes and mass in a heterogeneous group of patients with CHD using CMR imaging. Thirty-five patients with CHD (7-62 years) were included in this study. A short axis set was acquired using a steady-state free precession pulse sequence. Intra-observer and interobserver variability was assessed for left ventricular (LV) and right ventricular (RV) volumes, function and mass by calculating the coefficient of variability. Intra-observer variability was between 2.9 and 6.8% and interobserver variability was between 3.9 and 10.2%. Overall, variations were smallest for biventricular end-diastolic volume and highest for biventricular end-systolic volume. Intra-observer and interobserver variability of biventricular parameters assessed by CMR imaging is good for a heterogeneous group of patients with CHD. CMR imaging is an accurate and reproducible method and should allow adequate assessment of changes in ventricular size and global ventricular function.

Stress imaging in congenital cardiac disease (Article)

2009-10-01T00:00:00Z

In patients with coronary arterial disease, stress imaging is able to demonstrate abnormalities in the motion of the ventricular walls, and abnormalities in coronary arterial perfusion not apparent at rest. It can also provide information on prognostic factors. In patients with congenitally malformed hearts, stress imaging is used to determine contractile reserve, abnormalities of mural motion, and global systolic function, but also to assess diastolic and vascular function. In most of these patients, stress is usually induced using pharmacological agents, mainly dobutamine given in varying doses. The clinical usefulness of abnormal responses to the stress induced in such patients has to be addressed in follow-up studies. The abnormal stress might serve as surrogate endpoints, predicting primary endpoints at an early stage, which are useful for stratification of risk in this population of growing patients. We review here the stress imaging studies performed to date in patients with congenitally malformed hearts, with a special emphasis on echocardiography and cardiac magnetic resonance imaging.

Clinical outcome 5 to 18 years after the Fontan operation performed on children younger than 5 years (Article)

2009-07-01T00:00:00Z

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.

Normal biventricular function, volumes, and mass in children aged 8 to 17 Years (Article)

2009-03-01T00:00:00Z

Purpose: To assess normal values for biventricular function, volumes, and mass with current cardiovascular magnetic resonance (CMR) imaging sequences in children. Materials and Methods: Included in the study were 60 healthy children aged 8-17 years. A short axis set of contiguous slices was acquired with CMR imaging employing steady-state free precession. Biventricular end-diastolic volume (EDV), end-systolic volume (ESV), ejection fraction (EF), and mass were determined. Uni- and multivariate linear regression analyses were performed to study the interrelation of age, gender, and body surface area (BSA) on biventricular volumes and mass. The coefficient of variation was calculated for intra- and interobserver variability. Results: EF did not differ between boys and girls (mean LV-EF 69 ± (SD) 5%, mean RV-EF 65 ± 5%). BSA had good (EDV, mass) and modest (ESV) correlation with biventricular measurements. Gender appeared a significant modifier of these relations, whereas age had no independent contribution. The intra- and interobserver coefficient of variation was in the range 2.1%-13.9°/o for biventricular EDV, ESV,and mass. Conclusion: This study reveals gender-specific normative data for biventricular function, volumes, and mass in children age 8-17 years that can be used as reference data in the follow-up of pediatric cardiac patients.

Pulmonary artery size and function after fontan operation at a young age (Article)

2008-11-01T00:00:00Z

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 μg/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.

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 (Article)

2008-06-01T00:00:00Z

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 μg/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 β-adrenergic stimulation. However, as a result of impaired preload with stress, cardiac output can be increased only by increasing heart rate.

Large variations in absolute wall shear stress levels within one species and between species (Article)

2007-12-01T00:00:00Z

Wall shear stress (WSS), the frictional force between blood and endothelium, is an important determinant of vascular function. It is generally assumed that WSS remains constant at a reference value of 15 dyn/cm2. In a study of small rodents, we realized that this assumption could not be valid. This review presents an overview of recent studies in large and small animals where shear stress was measured, derived from velocity measurements or otherwise, in large vessels. The data show that large variations exist within a single species (human: variation of 2-16 N/m2). Moreover, when we compared different species at the same location within the arterial tree, an inverse relationship between animal size and wall shear stress was noted. When we related WSS to diameter, a unique relationship was derived for all species studied. This relationship could not be described by the well-known r3law of Murray, but by the r2law introduced by Zamir et al. in 1972. In summary, by comparing data from the literature, we have shown that: (i) the assumption of a physiological WSS level of ∼15 dyn/cm2for all straight vessels in the arterial tree is incorrect; (ii) WSS is not constant throughout the vascular tree; (iii) WSS varies between species; (iv) WSS is inversely related to the vessel diameter. These data support an "r2law" rather than Murray's r3law for the larger vessels in the arterial tree.