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MTRR 66A>G polymorphism in relation to congenital heart defects.

BACKGROUND: Evidence is accumulating that periconceptional folic acid supplementation may prevent congenital heart defects (CHD). The methionine synthase reductase (MTRR) enzyme restores methionine synthase (MTR) enzyme activity and therefore plays an essential role in the folate- and vitamin B(12)-dependent remethylation of homocysteine to methionine. We studied the influence of the MTRR 66A>G polymorphism on CHD risk. In addition, possible interaction between this variant and plasma methylmalonic acid (MMA) concentrations, as an indicator of intracellular vitamin B(12) status, was investigated. METHODS: Case-control and case-parental studies were conducted to explore this association. In total, 169 CHD patients and 213 child controls, and 159 mothers with a CHD-affected child and 245 female controls were included. RESULTS: The maternal MTRR 66AG and GG vs. AA genotypes revealed an odds ratio (OR) of 1.3 (95% CI 0.72-2.20) and 1.3 (0.71-2.37), respectively. Family-based transmission disequilibrium analysis did not reveal a significant association of the foetal 66G allele with the development of a heart defect in children (chi(2)=2.94, p=0.086). Maternal 66GG genotype in combination with high MMA concentration (above the 80th percentile) was associated with a three-fold (OR 3.3, 95% CI 0.86-12.50) increased risk for all types of CHD in offspring. CONCLUSIONS: These data indicate that maternal MTRR 66A>G polymorphism is not a risk factor for CHD. Maternal MTRR 66GG genotype with compromised vitamin B(12) status may possibly result in increased CHD risk. In addition to folate, vitamin B(12) supplementation may contribute to the prevention of CHD.

Adolescent↗

Alterations of myocardial contraction associated with a structural heart defect in embryonic chicks.

Ablation of cardiac neural crest at stages 8-10 produces a structural heart defect (persistent truncus arteriosus, PTA) in embryonic chicks. PTA is associated with decreased myocardial contractility, as indicated by decreased left ventricular ejection fraction. We compared the force of small ventricular strips from normal and defective chick hearts. In intact muscle, ablation of the neural crest leads to a 30-50% decrease in twitch force at any level of extracellular Ca2+ (0.45-20 mM) at embryonic days (ED) 7 and 15, relative to sham-operated controls. These differences could reflect defects at the level of the contractile apparatus and/or in the excitation-contraction coupling process. To distinguish changes of the contractile apparatus, we used detergent skinned preparations. The maximal Ca(2+)-activated force (Fmax) at ED15 was not significantly different between control and experimental embryos. At ED 7, however, Fmax was reduced by 36% in experimental preparations. Electron-micrographs showed that the organization and orientation of the myofibrils was similar in experimental and control ventricles. At ED 14, however, the average myofibrillar diameter was significantly increased in experimental ventricles. The content of the major myofibrillar proteins (myosin heavy chain, actin, and tropomyosin), determined from polyacrylamide gel electrophoresis and Coomassie Blue staining, normalized to total protein, was not statistically different in experimental and control ventricles at ED7. At ED15, however, content of these proteins was doubled in experimental ventricles. These data suggest a possible defect of the contractile apparatus at both ED 7 and 15, since the ratio of Fmax/myosin is reduced in the experimental hearts.

Animals↗

Genetic counseling for young adults who have a congenital heart defect.

Early individual guidance is needed for all adolescents and young adults with congenital heart defects. This should include not only a personal interest in the individual but also an attempt to identify concerns about sex education, smoking, drugs and the risks of pregnancy and possible inheritance. In a prospective study of 252 women with various cardiac malformations, the incidence of congenital heart defects in their progeny was 15.7% (13% exclusive of genetic syndromes and those with a positive family history). In those with a positive family history or a genetic syndrome the incidence was 56% in the offspring. Genetic syndromes with cardiac components are increasingly apparent. The role of teratogens such as medications, illicit drugs, and environmental exposure play a not yet clearly defined role. Careful discussion with potential parents, giving facts but with a positive approach, is an obligation of every physician.

Adolescent↗

Familial recurrence of heart defects in subjects with congenitally corrected transposition of the great arteries.

Familial recurrence of congenitally corrected transposition of the great arteries (CCTGA) is considered uncommon. Most of the previous familial studies involved a small number of patients and referred to all situs and looping anomalies including single ventricle, heterotaxia, and other cardiac defects different from CCTGA. We performed a large, consecutive clinical case series study in order to detect the recurrence of congenital heart defects in families of children with the classic form of CCTGA. From January 1997 through December 2004, 102 consecutive patients with CCTGA were evaluated in four institutions. There were 59 male (57.8%) and 43 female (42.2%). Mean age was 8.6 +/- 7.8 years. Eighty-eight patients (86.3%) had situs solitus of the atria, 14 (13.7%) situs inversus. The cardiac and extracardiac anomalies among relatives and the patterns of familial recurrence were investigated. Relatives with congenital heart defects were found in 16/102 families (15.7%). Transposition of the great arteries (TGA) was the most common recurrent defect (6/102 families). Consanguinity was identified in the parents of three probands. Six probands had an unaffected twin-sib. Recurrence risks for congenital heart defects were calculated at 5.2% (6/116) for siblings. In conclusion, CCTGA is not always sporadic in families. The pattern of inheritance, the presence of consanguinity among parents and the recurrence of situs inversus could suggest, in some families, an autosomal recessive mechanism with similarities with that occurring in some pedigrees with heterotaxia. The recurrence of TGA and CCTGA in the same family suggests a pathogenetic link between these two anatomically different malformations.

Family Health↗

Neurodevelopmental outcomes after biventricular repair of congenital heart defects.

OBJECTIVE: This study was undertaken to assess neurodevelopment of children after biventricular repair of congenital heart defects. METHODS: Full-scale, performance, and verbal IQs of 69 patients who had undergone biventricular repair were assessed at 5 years of age with the Wechsler Preschool and Primary Scales of Intelligence-Revised. The Wide Range Assessment of Visual-Motor Abilities was used to measure visual-motor skills. Regression analyses adjusting for parental IQ and socioeconomic status were used to evaluate outcome predictors. RESULTS: Median age at repair was 91 days (range 1-1558 days). Hypothermic circulatory arrest was used in 35 cases (mean duration of hypothermic circulatory arrest 33 +/- 17 minutes). Mean full-scale, performance, and verbal IQs for the entire study population were within the reference range (full-scale 96.9 +/- 15.9, performance 96.6 +/- 16.8, verbal 97.7 +/- 15.2). Anatomic diagnosis, age at operation, and use of hypothermic circulatory arrest did not influence full-scale IQ (P =.66, P =.14, and P =.46, respectively), performance IQ (P =.64, P =.36, and P =.73, respectively), or verbal IQ (P =.74, P =.08, and P =.39, respectively). Among patients subjected to hypothermic circulatory arrest, duration of arrest was evaluated as a predictor of outcome. After adjustment for parental IQ, full-scale (P =.12), performance (P =.07), and verbal (P =.22) IQ scores of patients with more than 39 minutes of hypothermic circulatory arrest were not different from those of patients who had arrest periods of 39 minutes or less. After adjustment for socioeconomic status, however, full-scale (P =.05) and performance (P =.03) IQ scores were lower among patients who had more than 39 minutes of hypothermic circulatory arrest. After adjustment for either parental IQ or socioeconomic status, patients with more than 39 minutes of arrest had lower scores on Wide Range Assessment of Visual-Motor Abilities subtests of visual-motor and fine motor abilities and on several performance IQ subtests. CONCLUSIONS: IQs of patients who had undergone biventricular repair of congenital heart defects were within the reference range. However, hypothermic circulatory arrest for longer than 39 minutes was associated with deficits in visual-motor and fine motor skills and possibly in full-scale IQ.

Boston↗

Search for somatic 22q11.2 deletions in patients with conotruncal heart defects.

A wide range of clinical variability in patients with 22q11.2 deletions has been demonstrated in numerous studies. Nevertheless, it is still an open question if major genetic factors contribute to clinical expression. Therefore one aim of this study was to investigate, if patients with 22q11.2 deletion and conotruncal heart defects show a "second hit" somatic 22q11.2 deletion in tissue from the conotruncus, heart vessels or thymus. The second aim was to analyse patients with conotruncal heart defects without 22q11.2 deletion in blood cells for somatic deletion mosaicism. We were able to study tissue samples from heart surgery from 23 patients, 9 of whom had 22q11 deletions by FISH analysis on metaphase spreads from peripheral lymphocytes. Analysis of 18 polymorphic markers from the 22q11.2 region in DNA prepared from thymus and/or heart vessels and/or conotruncus tissue and peripheral lymphocytes in each patient did not show any allelic loss. Thus somatic 22q11.2 deletions apparently do not play a major role in conotruncal heart defects in patients with or without germ line 22q11.2 deletion.

Child↗

Prenatal detection of heart defects as an indication for chromosome analysis.

Chromosome investigations were carried out in 588 fetuses with prenatally diagnosed growth retardation and/or congenital malformations. Out of these cases 116 (19.7%) revealed a chromosome disorder. Among the prenatally diagnosed malformations heart defects were detected in 102 fetuses (17.3%) and were therefore one of the most common abnormalities. Within this group of prenatally diagnosed heart defects 41 fetuses (40.2%) had a chromosome disorder, with trisomy 18 and 21 as the most common syndromes. The results of our study demonstrate that heart defects which can be recognized prenatally by ultrasound are caused in about 40% of the cases by a chromosome aberration and that they are therefore always an indication for fetal karyotyping.

Abnormalities, Multiple↗

Severity and recurrence risk of congenital heart defects exemplified by atrial septal defect secundum.

It has been reported that the frequency of congenital heart defects (CHD) in children of an affected parent is now three to five times what it was 20 years ago. One conceivable cause of this is that patients with CHD of a severity that would have precluded parenthood before the advent of treatment are now able to (and consequently do) have children once the defect has been corrected. The mean severity of CHD among parents who have it would have thereby increased and this might, in turn, have increased the frequency of CHD in their children. But the latter would occur only if severely affected parents confer a greater risk on their children than parents who are mildly affected. To determine whether this is the case, we investigated 83 probands, each of whom had had an atrial septal defect secundum whose dimensions had been recorded at the time of operation. Of their 166 children, 17 had CHD. The defects of probands with affected children were not found to be significantly different in size from the defects in probands whose children were all normal. Analysis of the hemodynamic data available yielded a similar result. Our findings decisively exclude surgical correction as a significant explanation for the increased recurrence of atrial septal defect.

Canada↗

Pulmonary blood flow regulates plasma tissue plasminogen activator concentrations in patients with congenital heart defects.

OBJECTIVE: The wall shear stress generated by blood flow regulates the expression of fibrinolytic proteins by endothelial cells in vitro. In the present study, the effects of pulmonary blood flow on fibrinolytic activity were studied in patients with congenital heart defects and pulmonary hypertension. METHODS: Twenty-seven patients who underwent cardiac operation because of congenital heart defects were divided into four groups according to the severity of pulmonary hypertension. Group I consisted of seven patients with normal pulmonary artery pressure, group II consisted of nine patients with pulmonary hypertension caused by increased pulmonary blood flow, group III consisted of six patients with pulmonary hypertension caused by increased pulmonary vascular resistance, and group IV consisted of five patients with tetralogy of Fallot. Plasma concentrations of tissue plasminogen activator, plasmin, and thrombin were assayed as the inhibitor-bound forms. RESULTS: The preoperative concentration of tissue plasminogen activator was higher in group II than in all other groups (p = 0.0003). However, the postoperative concentration decreased only in patients in group II when compared with the preoperative value (p = 0.01). By Pearson's correlation analysis, pulmonary blood flow was found to correlate with the preoperative concentration of tissue plasminogen activator (95% confidence interval = 3.99 to 10.58, p = 0.0001). No definite conclusion was found for the relationship between tissue plasminogen activator and plasmin concentration. Further, the preoperative thrombin concentration was similar in all groups. CONCLUSIONS: These findings suggest that pulmonary blood flow may regulate the plasma concentration of tissue plasminogen activator in patients with congenital heart defects.

Child, Preschool↗

Comparative roles of intraoperative epicardial and early postoperative transthoracic echocardiography in the assessment of surgical repair of congenital heart defects.

In 94 consecutive patients undergoing surgical repair of congenital heart defects the results of intraoperative (after cardiopulmonary bypass) epicardial two-dimensional and Doppler color flow imaging were compared with those of sequential transthoracic echocardiography performed within 24 h of surgery and again before hospital discharge to define the precise role of intraoperative imaging. In 6 of 7 patients with a residual defect requiring immediate surgical revision, intraoperative imaging correctly identified the defect; spectral Doppler imaging underestimated or did not identify a residual outflow tract gradient in 17 patients. Left atrioventricular (AV) valve regurgitation after repair of complete AV septal defect was underestimated in three patients. Although intraoperative documentation of good ventricular function was usually associated with a good outcome, in three patients poor systemic ventricular function after cardiopulmonary bypass was not associated with early mortality. A minor degree of shunting around the patch was a common finding on epicardial and early postoperative imaging and persisted at the time of hospital discharge in 17 of 46 patients who had undergone patch closure of a ventricular septal defect as part of the surgical procedure. Additional trabecular septal defects were missed on color flow imaging after cardiopulmonary bypass in three patients, one of whom required subsequent reoperation. Although intraoperative two-dimensional and color flow imaging permitted the recognition of the majority of residual defects requiring immediate revision, residual outflow obstruction or AV valve regurgitation was usually underestimated.

Child↗

Familial deafness, congenital heart defects, and posterior embryotoxon caused by cysteine substitution in the first epidermal-growth-factor-like domain of jagged 1.

In the present study, we report a kindred with hearing loss, congenital heart defects, and posterior embryotoxon, segregating as autosomal dominant traits. Six of seven available affected patients manifested mild-to-severe combined hearing loss, predominantly affecting middle frequencies. Two patients were diagnosed with vestibular pathology. All patients had congenital heart defects, including tetralogy of Fallot, ventricular septal defect, or isolated peripheral pulmonic stenosis. No individual in this family met diagnostic criteria for any previously described clinical syndrome. A candidate-gene approach was undertaken and culminated in the identification of a novel Jagged 1 (JAG1) missense mutation (C234Y) in the first cysteine of the first epidermal-growth-factor-like repeat domain of the protein. JAG1 is a cell-surface ligand in the Notch signaling pathway. Mutations in JAG1 have been identified in patients with Alagille syndrome. Our findings revealed a unique phenotype with highly penetrant deafness, posterior embryotoxon, and congenital heart defects but with variable expressivity in a large kindred, which demonstrates that mutation in JAG1 can cause hearing loss.

Abnormalities, Multiple↗