Hematopoietic progenitor cell deficiency in fetuses and children affected by Down's syndrome

OBJECTIVES

There is an increased risk of myeloid malignancy in individuals with Down's syndrome (DS), which is associated with a mutation in exon 2 of the transcription factor GATA-1. It is recognized that there is accelerated telomere shortening in blood cells of children with DS similar to that in conditions such as Fanconi anemia and dyskeratosis congenita. The latter conditions are associated with stem cell deficiency and clonal change, including acute myeloid leukemia. In this study we address the questions 1) whether the accelerated telomere shortening is associated with progenitor/stem cell deficiency in individuals with DS, predisposing to clonal change and 2) whether the occurrence of reduced numbers of stem/progenitor cells precede the incidence of mutations in exon 2 of GATA-1.

MATERIAL AND METHODS

Peripheral blood from fetuses (23-35 weeks gestation) and/or bone marrow from children affected by DS and age-matched hematologically healthy controls were analyzed for telomere length, content of stem/progenitor cells, and mutations in exon 2 of GATA-1.

RESULTS

We found that hematopoietic stem/progenitor cell deficiency and telomere shortening occurs in individuals with DS in fetal life. Moreover, the presence of a low number of progenitor cells was not associated with mutations in exon 2 of GATA-1.

CONCLUSIONS

We propose that stem cell deficiency may be a primary predisposing event to DS leukemia development.

Anomalous right pulmonary artery origins in association with the fetal valproate syndrome

Two cases are reported of fetal valproate syndrome in association with anomalous right pulmonary artery origin. Both diagnoses were confirmed following cardiac catheterisation as echocardiography alone was inadequate to define the anatomy. Anomalous right pulmonary artery origin is extremely rare making a chance association with fetal valproate syndrome very unlikely. We recommend that anomalous pulmonary artery origin is borne in mind in patients with valproate syndrome undergoing cardiac assessment, particularly as this may be a difficult diagnosis to make on echocardiography.

Unilateral multicystic dysplastic kidney: the case for nephrectomy

Management of unilateral multicystic dysplastic kidneys (MCDK) presents physicians and surgeons with a significant dilemma. Recent studies have indicated that the incidence of short term complications of MCDK is low and many authors have recommended conservative non-operative treatment. Surgery has been proposed by some because of the potential complications of hypertension, infection, and malignant change. Three children with hypertension secondary to MCDK seen at this institution in the past four years, one of whom had been discharged from follow up as a result of 'disappearance' of the cystic kidney on ultrasound examination, are reported. We believe that the risks of hypertension secondary to MCDK have been understated, and that based on the conclusions of these studies, many children may be receiving suboptimal follow up. We currently favour elective nephrectomy as the treatment of choice for this lesion.

Oral anticoagulation in paediatric patients: dose requirements and complications

The lack of oral anticoagulant guidelines specific to paediatric practice has led to the adoption of adult regimens, often without scientific evidence of efficacy or safety. A two year prospective study of anticoagulant control was carried out in 45 children aged 9 months to 18 years, the majority of whom were receiving primary prophylactic anticoagulation. The main indication was congenital heart disease, either with (n = 8) or without (n = 34) mechanical valve prosthesis. During a follow up period of 602 patient months the average interval between visits was three weeks. Target international normalised ratios (INRs) were achieved on 62% and 39% of visits for children with low target INR (2.0-3.0) and high target INR (3.0-4.0) respectively. However warfarin dose was altered on only 22% of visits. Warfarin doses required to achieve a stable INR of 2.0-3.0 in 33 children were strongly correlated with weight [dose (mg/d) = 0.07 x weight (kg) + 0.54] but independently influenced by age. No thrombotic complications were recorded, and haemorrhagic events were infrequent (2.1% of visits) and, with one exception, minor. Safe outpatient oral anticoagulation is feasible in children, whose warfarin requirements appear moderately predictable and whose control is no more erratic than that of adults.

Endocarditis with multiple intracardiac shunts: identification and repair

An 8-year-old boy who suffered from Hirschsprung's disease had development of tricuspid valve endocarditis that progressed to aortic root abscess formation, development of a fistulous communication between aorta and right atrium, atrial and ventricular septal defects, and a left ventricle to right atrium defect. Several surgical procedures were required. Operation consisted initially of closure of the septal defects and aortic valve repair. This was followed by homograft replacement of the aortic valve for persistent infection, and further closure of a left ventricle to right atrium fistula.

Infective endocarditis in newborn infants with structurally normal hearts

Twelve infants with structurally normal hearts were demonstrated to have intracardiac vegetations on echocardiography and diagnosed as having infective endocarditis. All were found in the right side of the heart, most frequently at the junction of the superior vena cava and the right atrium and in no case involved the tricuspid or pulmonary valves. Most were diagnosed in the course of investigation of repeatedly positive blood cultures, despite appropriate antibiotic therapy. Coagulase-negative staphylococci were isolated from blood culture in nine infants, and Streptococcus sanguis and Candida albicans from one each. All infants had had intracardiac central lines inserted to facilitate venous access, either by a percutaneous technique or as a formal surgical procedure. Eight (67%) were successfully treated and made a full recovery. Cardiac murmurs were absent in all of the cases. Echocardiography should be included in the investigation of all neonates with persistently positive blood culture, particularly when intracardiac lines have been sited. Right-sided, non-valvar lesions and infection with coagulase-negative staphylococci may carry a better prognosis than previously reported.

Complications of the naevoid basal cell carcinoma syndrome: results of a population based study

There are many potential complications which have been reported in association with the naevoid basal cell carcinoma syndrome. We have been able to show the relative frequencies of these problems in a population based study of 84 cases in the north west of England. The major complications of basal cell carcinomas and jaw cysts occur in over 90% of patients by 40 years of age, but may both occur before 10 years of age. Less well described complications are ovarian calcification or fibroma (24%), medulloblastoma (5%), cardiac fibroma (3%), cleft palate (5%), and ophthalmic abnormalities such as squint or cataract (26%). This study more clearly defines the possible complications of the syndrome and gives clearer guidelines for counselling and screening affected and at risk persons.

Double-outlet right ventricle: morphologic demonstration using nuclear magnetic resonance imaging

Sixteen patients with double-outlet right ventricle, aged 1 week to 29 years (median 5 months), were studied with a 1.5 tesla nuclear magnetic resonance (NMR) imaging scanner. Two-dimensional echocardiography was performed in all patients. Thirteen patients underwent angiography, including nine who underwent subsequent surgical correction. Three patients underwent postmortem examination. Small children and infants were scanned inside a 32 cm diameter proton head coil. Multiple 5 mm thick sections separated by 0.5 mm and gated to the patient's electrocardiogram were acquired with a spin-echo sequence and an echo time of 30 ms. A combination of standard and oblique imaging planes was used. Imaging times were less than 90 min. The NMR images were technically unsuitable in one patient because of excessive motion artifact. In the remaining patients, the diagnosis of double outlet right ventricle was confirmed and correlated with surgical and postmortem findings. The NMR images were particularly valuable in demonstrating the interrelations between the great arteries and the anatomy of the outlet septum and the spatial relations between the ventricular septal defect and the great arteries. Although the atrioventricular (AV) valves were not consistently demonstrated, NMR imaging in two patients identified abnormalities of the mitral valve that were not seen with two-dimensional echocardiography. In one patient who had a superoinferior arrangement of the ventricles, NMR imaging was the most useful imaging technique for demonstrating the anatomy. In patients with double-outlet right ventricle, NMR imaging can provide clinically relevant and accurate morphologic information that may contribute to future improvement in patient management.

Morphological evaluation of atrioventricular septal defects by magnetic resonance imaging

Twelve patients aged between 2 weeks and 22 months (median 6 weeks) with atrioventricular septal defects were examined with a 1.5 T, whole body, magnetic resonance imaging system. Ten patients had a common atrioventricular orifice (complete defect) while two patients had separate right and left valve orifices (partial defect). Associated cardiac malformations included the tetralogy of Fallot in two, isomerism of the right atrial appendages and pulmonary atresia in two, and right isomerism and double outlet right ventricle in one. All had previously been examined by cross sectional echocardiography. Eight subsequently had angiography and six underwent surgical correction. There was one operative death and three other deaths. Three of these patients underwent postmortem examinations. Small children and infants were scanned inside a 32 cm diameter head coil. Multiple electrocardiographically gated sections 5 mm thick, separated by 0.5 mm, were acquired using a spin echo sequence with echo time of 30 ms. A combination of standard and oblique imaging planes was used. Magnetic resonance imaging was more accurate than echocardiography in predicting the size of the ventricular component of the defect. It was also better than either echocardiography and angiography in identifying the presence of ventricular hypoplasia. All these findings were confirmed by surgical or postmortem examinations or both. Magnetic resonance imaging is capable of providing detailed morphological information in children with atrioventricular septal defects which is likely to be of value in their management.

Magnetic resonance imaging of the great arteries in infants

Sixty infants, aged 1-48 (median 8) weeks, with suspected congenital heart disease underwent a morphological evaluation of the great arteries using magnetic resonance imaging at 1.5 Tesla. Cross-sectional echocardiography was performed in all infants, angiography in 33 and surgery in 44. Multiple sections, 5 mm thick and gated to the patients' electrocardiogram were acquired in standard and oblique imaging planes. Ventriculo-arterial connexions were correctly identified in 54 infants (6 did not have intracardiac imaging performed) and an accurate description of the relationships of the great arteries was made in all. Magnetic resonance imaging clearly demonstrated normal and hypoplastic pulmonary arteries to the level of the first hilar branches and was better than echocardiography at confirming the presence or absence of central intrapericardial pulmonary arteries in 4 infants with pulmonary atresia. All parts of the thoracic aorta were accurately demonstrated and, in 23 infants with clinical suspicion of aortic coarctation, magnetic resonance images provided more information than echocardiography. Magnetic resonance imaging accurately demonstrates great arteries non-invasively supplementing echocardiographic and angiographic findings. In many cases, it replaces the need for invasive investigations.

Balloon dilatation of critical stenosis of the pulmonary valve in neonates

Percutaneous balloon dilatation was attempted in 15 consecutive neonates (mean age 7.3 (range 1-27) days and weight 3.2 (range 2.5-4.1) kg) with critical stenosis of the pulmonary valve. Dilatation was successful in 11 (73%) patients. The mean balloon to annulus ratio was 1.1 (range 0.6-1.77). The ratio of right ventricle to femoral artery systolic pressure decreased from a mean (1 SD) of 1.4 (0.32) before to 0.8 (0.24) after dilatation and the transvalvar gradient decreased from 81 (29.7) mm Hg before to 33 (27.7) mm Hg after dilatation. All four (27%) patients in whom dilatation was unsuccessful underwent surgical valvotomy. Complications of balloon dilatation occurred in three (20%) patients; these included retroperitoneal haematoma (one) and iliofemoral venous occlusion (two). In one (7%) patient severe hypoxia and hypotension developed when the valve was crossed with a guide wire and balloon catheter. Despite successful dilatation he died 7 days after the procedure. During a mean (1 SD) follow up of 2 (1.7) years, seven (64%) of the 11 patients remained free of important restenosis. One patient required repeat dilatation three weeks after the initial procedure. In three (27%) patients restenosis developed 4-9 months after dilatation and all three had surgical valvotomy. Of the four patients initially referred for surgery three required a second operation and one required balloon dilatation. Percutaneous balloon dilatation gave effective relief of critical pulmonary stenosis in most neonates but complications and restenosis requiring surgery were common.

Doppler evaluation of superior caval venous pathways after Mustard and Senning operations

Doppler waveforms from the superior caval vein were analysed to evaluate the patency of superior caval venous pathways following venous redirection (Mustard and Senning) operations for complete transposition. The group consisted of 26 unselected survivors of Mustard (9 patients) and Senning operations (17 patients). Patients were examined a mean of 5.9 (range 0.1-15.3) years following operation and their age at study ranged from 0.4-25.3 years, mean 7.3 years. Doppler waveforms were correlated with digital subtraction angiograms, which were performed in every patient within 24 hours of the Doppler study. Totally occluded superior caval venous pathways were identified in 3 patients with digital subtraction angiography. The remaining patients had angiographically patent pathways. In the 23 patients with patent pathways, Doppler waveforms demonstrated an initial systolic peak smaller than a second diastolic peak. In the 3 patients with totally occluded pathways, the pattern of the waveform was reversed, with the systolic larger than the diastolic peak. Doppler examination of the superior caval vein is a quick and simple bedside method of accurately determining patency of superior caval venous pathways after atrial redirection procedures for complete transposition.

Magnetic resonance imaging at a high field strength of ventricular septal defects in infants

Magnetic resonance imaging at a high field strength has potential benefits for the study of the heart in infants, which is when most congenital heart disease presents. Seventeen infants with various anatomical types of ventricular septal defect were studied by this technique. Good quality, high resolution, images were obtained in every case. There were no major practical problems. The morphology of the defects in all 17 hearts was displayed in great detail. In some instances, the interpretation of the images resembled that of equivalent images from cross sectional echocardiography. But this new technique allowed imaging in planes that cannot be obtained by echocardiography. One particularly valuable plane gave a face on view of the inlet and trabecular components of the septum. This allowed very precise localisation of defects in these areas. The relation between the defects and the atrioventricular and arterial valves was exceptionally well shown in various different imaging planes. One patient in the series had multiple trabecular defects that were clearly shown. Magnetic resonance imaging gives detailed morphological information about ventricular septal defects.

Dilatation with progressively larger balloons for severe stenosis of the pulmonary valve presenting in the late neonatal period and early infancy

Balloon dilatation in infants with severe pulmonary valve stenosis may not be a straightforward procedure once the arterial duct has closed. Balloon dilatation was attempted in three neonates and infants. In an 11 week old infant hypotension and bradycardia developed shortly after a 5 French end hole catheter was passed through the severely stenosed pulmonary valve. An emergency Waterston shunt was subsequently performed, but he died three days later. After this experience the technique was modified so that progressively larger balloons were used for dilatation in two infants, aged one and three weeks, with severe pulmonary valve stenosis in whom the arterial duct had closed. It was successful in both.

Balloon dilatation of a stenosed modified (polytetrafluoroethylene) Blalock-Taussig shunt

A 17 month old girl with tricuspid atresia, ventricular septal defect, subvalvar and valvar pulmonary stenosis, and increasing cyanosis had angiographic evidence of proximal stenosis of a right modified (5 mm diameter) Blalock-Taussig shunt. She underwent palliative balloon angioplasty with a 6 mm Schneider balloon catheter. Successful dilatation was achieved without complication. Four months later there was subjective clinical improvement with a rise in systemic arterial saturation. Repeat angiography showed patency of the shunt without restenosis or formation of an aneurysm.

Magnetic resonance imaging of coarctation of the aorta in infants: use of a high field strength

Nineteen infants with suspected coarctation of the aorta were studied with electrocardiographically gated magnetic resonance imaging on a 1.5 T whole body imaging system. In all cases imaging was successful and produced diagnostic images of high resolution. Coarctation was shown in 12 cases. The position and shape of the coarctation were well displayed by the magnetic resonance images. In addition, they clearly showed the relation of the coarctation to arteries arising from the aortic arch and to the length and diameter of the aortic isthmus and the distal aortic arch. The anatomy was confirmed at operation in all 12 patients, except for two with a small ductus arteriosus (arterial duct), which was not seen in the magnetic resonance images. In the seven remaining patients, coarctation was excluded. Magnetic resonance imaging produced high quality images that showed the anatomy better than other non-invasive methods. It provided all the anatomical information required for surgical correction.

Growth of the pulmonary artery after neonatal balloon dilatation of the right ventricular outflow tract in an infant with the tetralogy of Fallot and atrioventricular septal defect

A two week old girl with tetralogy of Fallot and atrioventricular septal defect underwent palliation, for severe hypoxaemia, by balloon dilatation to the right ventricular outflow tract. This procedure was repeated once over the next eight months without complications. Serial right ventricular angiograms showed growth of the hypoplastic pulmonary ring ("annulus"), trunk, and arteries. Balloon dilatation is an alternative palliative procedure for patients with the tetralogy of Fallot which may promote growth of the pulmonary ring, trunk, and arteries.

Recurrence of aortic coarctation following repair by re-implantation of the subclavian artery

Four patients mean age six months, range 11 days to 2 years, underwent repair of aortic coarctation by the technique of reimplantation of the subclavian artery (Mendonca repair). All developed re-coarctation within six months of an initially successful repair.

Severe haemolysis after percutaneous closure of a ductus arteriosus (arterial duct)

Severe mechanical haemolysis occurred after transcatheter occlusion of a ductus arteriosus (arterial duct) by a Rashkind double umbrella prosthesis. Surgical removal of the device and ligation of the duct were required before haemolysis was abolished.

Experience with flecainide for the treatment of cardiac arrhythmias in children

We treated 22 children, aged 3 days to 16 years 6 months (median 11 years 1 month), with flecainide for a variety of arrhythmias where a Class I agent was indicated. In 16, conventional antiarrhythmic treatment had failed. Structural heart disease was present in nine. The arrhythmia was paroxysmal re-entry atrioventricular tachycardia in nine; paroxysmal atrial tachycardia, flutter or fibrillation in five; paroxysmal ventricular tachycardia in five and frequent ventricular extrasystoles (with couplets) in three. Sinus rhythm was achieved in all four children who received flecainide during tachycardia (three received intravenous flecainide, one oral). During follow-up of 3-24 months (median 12 months), arrhythmia control was obtained in 13 children (59%). Combination therapy was used in seven of these; with digoxin in four and a beta blocker in three. Flecainide doses used in this study ranged from 1-11 mg kg-1 day-1 (median 4 mg kg-1 day-1), 25-297 mg m-2 day-1 (median 113 mg m-2 day-1). The median, pre-dose flecainide concentration in those responding to therapy was 225 micrograms l-1 and in those failing to respond was 417 micrograms l-1. An arrhythmogenic effect occurred in one child.

Fatal multisystemic toxicity associated with prophylaxis with pyrimethamine and sulfadoxine (Fansidar)

Images

Lacunar infarcts in polycythaemia with raised packed cell volumes

Lacunar (small deep cerebral infarcts) infarction is described in association with raised packed cell volumes. Two patients had polycythaemia vera, one stress polycythaemia. They presented with transient ischaemic episodes and were shown by computed tomography to have lacunes deep in the basal ganglia and internal capsule. Such lesions may be caused by small vessel occlusions related to increased viscosity and impaired oxygen consumption by adjacent tissues. Finding a raised packed cell volume in patients with lacunes and transient ischaemic attacks offers a further possibility of treatment.