Stefan Zink

Systematic assessment of atypical deletions reveals genotype–phenotype correlation in 22q11.2

Introduction: Clinical variability associated with the common 22q11.2 microdeletion is well known, and has led to a broad application of FISH diagnostics with probes for loci TUPLE1 or D22S75 (N25), although, rarely reported atypical deletions associated with the same phenotypic spectrum would not be discovered by these probes. As most types of 22q11.2 deletions occur between low copy repeats within the region (LCR22), we assumed that atypical deletions should be more common than has been reported. To address this question and the possibility of a deletion size related genotype-phenotype correlation, we systematically assessed the frequency of typical and atypical 22q11.2 deletions in a large cohort of patients. Methods: We used a set of 10 fluorescent in situ hybridisation (FISH) DNA probes, capable of detecting all reported and hypothetical deletions between the LCR22, and analysed 350 patients. Deletion sizes in atypical deletions were established by use of further FISH probes. Frequency of certain atypical deletions was analysed in controls by FISH and quantitative PCR. Results: Patients with conotruncal heart defects (ctCHD) and with typical VCFS phenotype showed the common 3 Mb or nested 1.5 Mb deletions (in 18.5% and 78.6%, respectively), but no atypical deletion, while 5% (3/63) of patients with a mildly suggestive, atypical phenotype showed atypical distal deletions, which were not detected in patients with mental retardation of unknown origin or in healthy controls. Discussion: These statistically significant differences demonstrate that atypical distal 22q11.2 deletions are very uncommon in patients with ctCHDs, while atypical congenital heart defects and mild dysmorphism are recognisable feature of atypical distal deletions. Further phenotype-genotype analysis disclosed association of significant developmental delay with the distal part of the common deletion region, and choanal atresia and atypical CHDs with the adjacent distal deletion region.

Comprehensive genotype–phenotype analysis in 230 patients with tetralogy of Fallot

Background Tetralogy of Fallot (ToF), the most frequent cyanotic congenital heart disease, is associated with a wide range of intra- and extracardiac phenotypes. In order to get further insight into genotype–phenotype correlation, a large cohort of 230 unselected patients with ToF was comprehensively investigated. Methods and results 230 patients with ToF were studied by karyotyping, comprehensive 22q11.2 deletion testing and sequencing of TBX1, NKX2.5 and JAG1, as well as molecular karyotyping in selected patients. Pathogenic genetic aberrations were found in 42 patients (18%), with 22q11.2 deletion as the most common diagnosis (7.4%), followed by trisomy 21 (5.2%) and other chromosomal aberrations or submicroscopic copy number changes (3%). Mutations in JAG1 were detected in three patients with Alagille syndrome (1.3%), while NKX2.5 mutations were seen in two patients with non-syndromic ToF (0.9%). One patient showed a recurrent polyalanine stretch elongation within TBX1 which represents a true mutation resulting in loss of transcriptional activity due to cytoplasmatic protein aggregation. Conclusion This study shows that 22q11.2 deletion represents the most common known cause of ToF, and that the associated cardiac phenotype is distinct for obstruction of the proximal pulmonary artery, hypoplastic central pulmonary arteries and subclavian artery anomalies. Atrioventricular septal defect associated with ToF is very suggestive of trisomy 21 and almost excludes 22q11.2 deletion. We report a further patient with a recurrent polyalanine stretch elongation within TBX1 and for the first time link TBX1 cytoplasmatic protein aggregation to congenital heart defects.

B-type natriuretic peptide levels in patients with functionally univentricular hearts after total cavopulmonary connection.

To assess plasma B‐type natriuretic peptide (BNP) levels in patients with univentricular hearts late after volume unloading by total cavopulmonary connection (TCPC).

B-Type Natriuretic Peptide in Patients with Systemic Right Ventricle

Objective: To examine the diagnostic value of B-type natriuretic peptide (BNP) in patients with systemic right ventricle. Methods: Plasma BNP levels were measured in 48 outpatients with D-transposition of the great arteries after atrial switch procedure or congenitally corrected transposition of the great arteries. Results: Plasma BNP was ≤20 pg/ml in 52% and <200 pg/ml in all patients, significantly higher in females compared to males (p = 0.004), and positively correlated with age (r = 0.3, p = 0.04). New York Heart Association class I patients had significantly lower BNP than class II patients (p = 0.03). A positive correlation was found between BNP and severity of tricuspid regurgitation (r = 0.5, p < 0.001). Plasma BNP was weakly, negatively correlated to maximum exercise capability, peak oxygen uptake, maximum heart rate during exercise testing and minimal heart rate in the 24-hour Holter monitoring. Additionally, BNP was negatively correlated with flow velocity across the pulmonary valve in patients with congenitally corrected transposition of the great arteries (r = –0.81, p = 0.03). Conclusion: Plasma BNP is normal in patients with systemic right ventricle, but increases with deterioration of clinical status and decreasing exercise capability. BNP is positively correlated with severity of tricuspid regurgitation, a prognostic factor for survival.

Decreasing ratio of plasma N-terminal pro-B-type natriuretic peptide and B-type natriuretic peptide according to age.

BACKGROUND B-type natriuretic peptide (BNP) and the N-terminal fragment of proBNP (NT-proBNP) seem to be useful diagnostic tools also in children with cardiac disease. Recent data suggest that plasma levels of both peptides show different patterns from infancy to adolescence. AIM To investigate the relationship of BNP and NT-proBNP in children and adolescents according to age. SUBJECTS AND METHODS In 46 individuals without cardiac disease (22 males, 24 females, aged 0.4-17.5 years) and 30 patients with congenital heart disease (17 males, 13 females, aged 0.2-18.4 years), plasma levels of BNP and NT-proBNP were measured in the same sample (triage BNP assay, Biosite and Elecsys NT-proBNP assay, Roche Diagnostics). RESULTS The range of BNP plasma levels was 5-32 pg/ml in individuals without heart disease and 5-1300 pg/ml in the patient group, the range of NT-proBNP was 10-298 pg/ml and 30-18,966 pg/ml, respectively. In both groups, the ratio NT-proBNP/BNP decreased with increasing age (P<0.001). CONCLUSION Although proBNP is cleaved into the two fragments NT-proBNP and BNP, there is a decreasing ratio of NT-proBNP/BNP with increasing age caused probably by age-dependent differences in the metabolic clearance of both peptides. This has to be considered in comparison studies on BNP and NT-proBNP regarding their benefit to paediatric cardiology.

Plasma levels of B-type natriuretic peptide in patients with tetralogy of Fallot after surgical repair

OBJECTIVE To evaluate the utility of plasma BNP measurement in the long term follow-up of patients with surgically repaired tetralogy of Fallot (TOF). METHODS From 2002 to 2008, plasma BNP concentration was measured in 130 patients with TOF at the age of mean 16.1+/-7.1 years and mean 13.0+/-6.5 years after surgically repair. BNP levels were compared to age and gender-specific normal values, results of exercise testing, clinical, electrocardiographic, and echocardiographic data. RESULTS BNP was <200 pg/ml in all and elevated in 60% of patients. Higher values were found in females (p=0.001), in patients waiting for pulmonary valve replacement (p<0.001), and in NYHA class II compared to NYHA I patients (p=0.012) with an inverse correlation between BNP and exercise time (r=-0.59, p<0.001). BNP was correlated with right ventricular dilatation (r=0.29, p=0.005) and severity of both tricuspid (r=0.22, p=0.015) and pulmonary regurgitation (r=0.20, p=0.029). Longitudinal data revealed increasing BNP levels before (p=0.04) and a BNP decrease after pulmonary valve replacement (p=0.03), but no change in patients without surgery. CONCLUSIONS In patients with surgically repaired TOF, plasma BNP is significantly correlated with right ventricular volume load. In clinical practice a considerable overlap limits the estimation of right ventricular volume load by BNP, but longitudinal evaluation helps to appoint the appropriate timing of pulmonary valve replacement.

Plasma levels of B-type natriuretic peptide in children and adolescents with high degree atrioventricular block

B-type natriuretic peptide (BNP) was measured in 43 children and adolescents with high-grade second degree or complete atrioventricular conduction block. BNP plasma level was significantly higher (p<0.01) in patients without pacemaker (n=21) than in patients with permanent pacemaker (n=26). In all four patients with measurement of BNP both before and after placement of a permanent pacemaker, individual plasma BNP decreased. Additionally, patients with dual-chamber pacing had significantly lower BNP values compared to those with single chamber ventricular pacing (p<0.05). Conclusively, high degree atrioventricular block can induce elevated plasma BNP levels and the loss of atrioventricular synchrony induce a further increase of plasma BNP.

Isolated left pulmonary artery: Interventional stenting of a persistent fifth aortic arch

A few cases of isolated pulmonary artery have been successfully palliated by stenting the arterial duct using coronary stents. However, progressive luminal narrowing within the stent due to neointimal proliferation and peal formation is a considerable problem. We report the successful interventional palliation in a 7‐week‐old infant with isolated left pulmonary artery using sirolimus‐eluting stents. In this unusual case, the isolated pulmonary artery was supplied by a duct‐like remnant of a persistent fifth aortic arch, whereby the distal part of this vessel showed severe constriction. Implantation of two sirolimus‐eluting coronary stents re‐established good perfusion of the left pulmonary artery. Seven months after the procedure, echocardiography revealed that perfusion of the stented vessel and the left pulmonary artery was still very good. Stents eluting antimitotic agents also help to preserve the patency of small vessels in infants, and may be useful for ductal stenting.

Decreasing ratio of plasma N-terminal pro-B-type natriuretic peptide and B-type natriuretic peptide according to age: NT-proBNP/BNP-ratio according to age

Background: B‐type natriuretic peptide (BNP) and the N‐terminal fragment of proBNP (NT‐proBNP) seem to be useful diagnostic tools also in children with cardiac disease. Recent data suggest that plasma levels of both peptides show different patterns from infancy to adolescence. Aim: To investigate the relationship of BNP and NT‐proBNP in children and adolescents according to age. Subjects and methods: In 46 individuals without cardiac disease (22 males, 24 females, aged 0.4–17.5 years) and 30 patients with congenital heart disease (17 males, 13 females, aged 0.2–18.4 years), plasma levels of BNP and NT‐proBNP were measured in the same sample (triage BNP assay, Biosite® and Elecsys NT‐proBNP assay, Roche Diagnostics®). Results: The range of BNP plasma levels was 5–32 pg/ml in individuals without heart disease and 5–1300 pg/ml in the patient group, the range of NT‐proBNP was 10–298 pg/ml and 30–18966 pg/ml, respectively. In both groups, the ratio NT‐proBNP/BNP decreased with increasing age (P<0.001).
Conclusion: Although proBNP is cleaved into the two fragments NT‐proBNP and BNP, there is a decreasing ratio of NT‐proBNP/BNP with increasing age caused probably by age‐dependent differences in the metabolic clearance of both peptides. This has to be considered in comparison studies on BNP and NT‐proBNP regarding their benefit to paediatric cardiology.