Autonomic Changes and Heart Rate Variability in Children with Neurocardiac Syncope

This study evaluated resting autonomic function and autonomic responses to head-up tilt-table testing in children who experienced neurocardiac syncope to determine whether predictable differences existed between these patients and normal volunteers. Neurocardiac syncope is a common cause of syncope in children. The mechanism, though related to abnormalities in autonomic function, has not been fully elucidated, particularly in pediatric patients. This study evaluated resting autonomic tone using noninvasive autonomic function tests (i.e., Valsalva, handgrip, and deep breathing) and 24-hour heart rate variability (HRV). In addition, heart rate and blood pressure were evaluated during head-up tilt examination. Values from patients who experienced neurocardiac syncope were compared to those from age-matched normal volunteers. No significant differences were noted during noninvasive testing. Some time domain HRV variables demonstrated a trend toward significant difference (p < 0.10). Tilt testing data were significantly different in sinus beat to sinus beat (RR) intervals between controls and syncope patients at 2, 5, and 10 minutes after tilting. In addition, significant differences were noted in RR interval and the standard deviation of RR interval 1 or 2 minutes prior to syncope when compared to controls at 5 and 10 minutes after tilting. Children with syncope exhibited abnormalities during tilt testing indicating an increased sympathetic or decreased parasympathetic tone, particularly prior to syncope. Some measures of HRV might constitute noninvasive parameters that correlate with the positive tilt table test.     

Long-Term Outcome of Children with Complete Heart Block Diagnosed After the Newborn Period

The aims of this study were to assess morbidity, mortality, and long-term cardiac outcome of children with congenital complete heart block (CHB) diagnosed between the ages of 3 months and 15 years. The study population consists of 61 children with CHB diagnosed in five tertiary referral centers in Finland. There were two study groups: CHB diagnosed 3 months to 2 years of age (group 1; n= 29) and CHB diagnosed between the age of 2 and 15 years (group 2; n= 32). Neonatal morbidity was significantly higher in group 1 than in group 2 (p= 0.047). In the whole study population, permanent pacemaker implantation with the main indications of low ventricular rate and syncope (52%) was performed in 80% of cases, with a median age of 11.2 years. Structural heart defect not causally associated with CHB was evident in 9 of 61 patients (15%). Of 8 patients with atrial septal defect (ASD) secundum, 6 (75%) were operated on and 7 (88%) were paced. One patient had small ventricular septal defect. The incidence of dilated cardiomyopathy was 7%. The mortality with cardiomyopathy was very high (75%). Of the 61 children, 3 (5%) died due to cardiomyopathy at the ages of 2, 26, and 31 years. In the long-term follow-up of 17 years (median, range 2.9–46 years) 17% of patients who survived had cardiac problems: arrhythmias in 5, mitral valve insufficiency in 3, ASD secundum in 1, and cardiomyopathy in 1. The long-term outcome did not depend on the age at which CHB was diagnosed. In conclusion, CHB diagnosed after the newborn period carries relatively low mortality and morbidity. Pacemaker application was indicated in most children. The possibility of an associated heart defect or dilated cardiomyopathy indicates regular echocardiographic monitoring in all children and young adults with CHB.     

Non-Invasive Imaging of the Ring–Sling Complex in Children

The Ring–Sling Complex is an uncommon, congenital vascular and tracheobronchial malformation with a persistent high death rate. We report three patients in whom computed tomography (CT) and magnetic resonance imaging (MRI) were used for the preoperative diagnosis and for staging of the morphologic tracheal and vascular anomalies.     

Exercise Testing in Children with Pulmonary Valvar Stenosis

Pulmonary valvar stenosis with intact ventricular septum is a common anomaly. This lesion poses a fixed obstruction to the right ventricular outflow. The right ventricle ejects the entire cardiac output across the stenotic valve. Right ventricular systolic pressure and oxygen demand are increased at rest and more so with exercise. Exercise tolerance in children and adults with mild valvar pulmonary stenosis is nearly normal, but is diminished in those with moderate and severe stenosis, indicating impaired ability to sustain adequate cardiac output. Following relief of stenosis, cardiac performance improves in children, but remains abnormal in adults. This appears to be related to postoperative resolution of right ventricular hypertrophy in children, whereas myocardial fibrosis may explain the lack of improvement in adults.     

Dental Bacteremia in Children

Bacteremia resulting from dental extraction is regarded as an important cause of bacterial endocarditis, and it is therefore recommended that patients undergoing tooth extraction be given prophylactic antibiotics. As dental procedures other than extractions may also cause bacteremias, we studied a variety of dental procedures routinely used in pediatric dentistry. Blood samples for cultures were obtained 30 s after each of 13 dental operative procedures in 735 anesthetized children aged 2–16 years. Four procedures used for conservative dentistry caused bacteremias significantly more often than the baseline value of 9.4%: polishing teeth 24.5%, intraligamental injection 96.6%, rubber dam placement 29.4%, and matrix band with wedge placement 32.1%. In comparison, toothbrushing alone caused a bacteremia on 38.5% of occasions. The organisms isolated were typical of odontogenic bacteremias in that 50% of the isolates were identified as varieties of viridans streptococci. These data show that a wider variety of dental procedures than was previously documented cause bacteremia.     

Cardiorespiratory Exercise Tolerance in Asymptomatic Children with Ebstein's Anomaly

The aim of the study was to evaluate cardiorespiratory exercise tolerance in asymptomatic children with Ebstein's anomaly. Eleven children with a mean age of 9.6 years were prospectively studied by spirometry, cardiopulmonary exercise testing (bicycle ergometer n= 8, treadmill test n= 3), and contrast echocardiography. A right-to-left atrial shunt was detected by contrast echocardiography in 7 children (group 1), whereas no shunt was found in 4 (group 2). VO₂ max was decreased [84.5 (SD = 16.8)] and was strongly correlated to oxygen saturation in group 1 (p < 0.0001). Oxygen saturation at peak uptake was significantly decreased compared to baseline [97.4 (SD = 2.0) vs 90% (SD = 9.5%), p= 0.02] and was significantly lower in group 1 than in group 2 [85.7 (2.2) vs 98.2% (SD = 1.2%), p= 0.03]. Oxygen desaturation was related to a right-to-left atrial shunt (p= 0.01). Decreased VO₂ max was also correlated to the small size of the left ventricle (p= 0.05). We concluded that decreased exercise tolerance in children with asymptomatic Ebstein's anomaly is related to a right-to-left atrial shunt and to a small left ventricle. In case of poor exercise tolerance, a contrast echocardiography should be performed to detect an atrial septal defect.     

Ultrasound Myocardial Tissue Characterization by Integrated Backscatter in Children Treated with Anthracyclines

The objective of our study was to evaluate integrated backscatter (IBS) measurement, an ultrasound method of myocardial tissue characterization, in children receiving cardiotoxic anthracyclines for malignancy. Myocardial injury is known to diminish the normal cyclic variation of IBS (CVIBS) during the cardiac cycle. We used a cross-sectional, case-controlled study of children receiving anthracyclines and serial, prospective observation in a subgroup of children. The study took place in a university-affiliated, tertiary referral center for pediatric cardiology and oncology. Children undergoing routine echocardiograms before, during, and after anthracycline treatment participated in this study. Children evaluated in the cardiology clinic for innocent murmurs participated as controls. There was no intervention. CVIBS was measured using specialized echocardiographic software which quantitates the intensity of backscattered echoes returning from myocardial cells within a user-defined region of interest. Standard echocardiographic measures of left ventricular function were also made. The results indicated that abnormal CVIBS was prevalent during anthracycline treatment (17%) and at late follow-up (20%). In serial studies, CVIBS decreased in all children after anthracycline treatment. Anthracycline dose and time since last dose did not predict which children would have abnormalities of left ventricular function or of CVIBS. This report provides preliminary evidence that CVIBS may be a useful supplement to the noninvasive, echocardiographic assessment of the heart during anthracycline treatment in children.     

Cerebral Oxygenation in Children with Syncope During Head-Upright Tilt Test

The pathophysiology of neurocardiogenic syncope remains incompletely known. In this entity, besides abnormal systemic hemodynamic regulation, potential cerebral circulatory abnormalities have been reported. In this setting, cerebral saturation assessment could detect cerebral blood flow changes and estimate the sufficiency of brain oxygenation during the event. A head-upright tilt test was performed in 25 children aged between 6 and 16 years. In addition to the standard protocol, cerebral oxygen saturation was determined noninvasively by means of a near-infrared spectrophotometry device. In the 19 children with a positive tilt test, significant impairment of cerebral saturation was detected both at the start of the patient's complaints (without hemodynamic modifications) and during syncope. Our results support the hypothesis of the presence of abnormal cerebral hemodynamic autoregulation in children with neurocardiogenic syncope.     

Iodixanol Pharmacokinetics in Children

The objective of this report was to study the elimination pharmacokinetics of iodixanol in children. Iodixanol (Visipaque, Nycomed Inc., Wayne, PA, USA) is a new iso-osmolar iodinated radiocontrast agent. We hypothesized that elimination of this agent would be dependent on age-related differences in renal clearance. Seven centers enrolled 43 patients. Cardiac catheterization was performed in 41 patients and cranial computed tomography in 2. Patients were entered into 5 age groups: newborn to <2 months, 2 to <6 months, 6 months to <1 year, 1 to <3 years, and 3 to 6 months of age that is comparable to normal adults. Prolonged elimination in children <6 months of age is related to renal immaturity.     

CT and MRI Findings in a Child with Constrictive Pericarditis

Constrictive pericarditis is rare in children. We report computed tomography (CT) and magnetic resonance imaging (MRI) findings in a 3-year-old girl. She had a swollen abdomen that increased in two months. CT and MRI showed a thickened pericardium (5.2 mm) without calcification. Both atria were enlarged and ventricles were relatively small. The engorged inferior vena cava had 2.8× the diameter of the descending aorta at the same level. Symptoms were dramatically improved after pericardiectomy. The histopathological features confirmed chronic pericarditis.     

Increased Arterial Stiffness in Children with a Parental History of Hypertension

The vascular dynamics of children with a parental history of hypertension has not been defined. The purpose of the current study was to determine whether or not these children have different arterial stiffness compared to the offspring of normotensive parents. One hundred healthy, nonobese subjects (ages 10–21 years) were divided into two groups of 50. Group A included the offspring of hypertensive patients and group B the offspring of normotensive parents. The variables studied were body surface area, blood pressure, and systolic and diastolic diameters of the aortic and carotid arteries as well as maximum velocity flow of these vessels. Carotid and aortic stiffness were calculated. Children and adolescents with a parental history of hypertension had higher carotid stiffness and smaller carotid diameters. These differences continued to be significant when correcting for body surface area. A higher blood pressure and a greater body surface area were also found.     

The Range of Normal Values of Cardiovascular Structures in Infants, Children, and Adolescents Measured by Magnetic Resonance Imaging

Magnetic resonance imaging (MRI) is a powerful diagnostic technique and research tool for assessment of congenital heart disease due to its ability to accurately assess anatomy, function, and flow in any orientation in the thorax. However, little data exist on normative reference values for cardiac structures, except in small study populations, and even fewer data exist for pediatric populations. In this review, MRI acquisition and analysis methods for assessment of aortic size, pulmonary artery size, and right and left ventricular function, volume, and mass are presented along with reference data obtained in pediatric populations by MRI. Where MRI data are not available, reference data obtained by echocardiography or angiography are included.     

Abnormalities in lymphocyte populations in infants with neural crest cardiovascular defects

The DiGeorge syndrome has been associated with various immune deficits. Embryologically, defects of the neural crest are associated with conotruncal and aortic arch abnormalities. The objective of this study was to determine if children with neural crest congenital heart defects can have subtle but significant immunodeficiencies. Complete blood counts with differential counts and a standard lymphocyte immunophenotyping panel of selected monoclonal antibodies were performed on peripheral blood from 20 children with neural crest cardiac disease and 34 normal newborns. The children with cardiac disease were grouped as survivors and nonsurvivors. The mean total white blood cell count was similar for all groups, but the percent lymphocytes was significantly less in the nonsurvivors than in the survivors and normal newborns (p < 0.02). The lymphocyte subsets affected were CD2, CD3, and CD4. When the cardiac patients were compared to the normal newborns, again differences in lymphocyte subsets CD2, CD3, and CD4 were seen. When comparing nonsurvivors with survivors, the mean percentages of the CD2, CD3, and CD4 T lymphocyte markers, as well as the mean lymphocyte, B cell (CD20), and natural killer cell (CD16) percentages were all lower in the nonsurvivors. It was concluded that abnormalities in specific lymphocyte populations and their subsets may be predictors of infants at greatest risk for immunodeficiency complications. Therefore children with neural crest cardiac defects should have evaluations of lymphocyte subsets at birth and be treated as if potentially immunodeficient.     

Incidence of Femoral Vein Occlusion After Catheter Ablation in Children: Evaluation with Magnetic Resonance Angiography

Catheter ablation in children requires placement of multiple large femoral venous sheaths and catheters. Magnetic resonance angiography (MRA) was used to evaluate the effect of indwelling lines on femoral venous blood flow. Between October 1993 and February 1994 a total of 17 patients scheduled for catheter ablation underwent venous MRA. Two-dimensional time-of-flight MRA was performed 12–70 hours after catheterization on all patients. All patients received intravenous heparin during the procedure and had aspirin therapy instituted after ablation. Eighteen catheter ablations and MRA studies were performed on the 17 patients (one patient underwent repeat ablation). There were 7 females and 10 males, with a mean age of 14.8 ± 4.2 years (range 8–21 years). Patients had three venous sheaths inserted in the left femoral vein (5F, 6F, and 7F with external diameters measuring 1.7, 2.0, and 2.3 mm, respectively) and one sheath in the right femoral vein (7F). Four patients (22%) had altered venous flow (two complete obstructions and two partial obstructions) following catheterization. None of these patients experienced symptoms or complications. It was concluded that there is an increased incidence (22%) of venous obstruction following catheter ablation, but there are no related complications. Venous MRA provides a rapid, noninvasive method for evaluating venous flow abnormalities and possibly detects patients at risk for complications.     

Trends of Childhood Infective Endocarditis in Israel with Emphasis on Children Under 2 Years of Age

This study retrospectively analyzed the characteristics of infective endocarditis (IE) in children in light of recent advances in pediatric cardiology. We evaluated 25 consecutive patients with IE from 1980 to 1991 at a tertiary Children's Medical Center in Israel. The incidence of IE increased significantly over the second half of the study period, owing mainly to an increase in the number of patients less than 2 years old. Concomitantly, the causative microorganisms changed considerably, with a decrease in viridans streptococci, an increase in staphylococci and other uncommon causes of IE, and increased antibiotic resistance. Children under the age of 2 years, previously considered uncommon IE patients, accounted for 47% of the IE cases during the second half of the study period. The infection often (78%) appeared in children with complex congenital heart diseases, commonly after early palliative or definitive cardiac surgery. Infants who underwent systemic-to-pulmonary shunting, especially with implantation of foreign materials, were at highest risks. IE was more often hospital-acquired (56% versus 6%) and acute (56% versus 44%) in the younger children than in the older ones and often lacked the typical clinical presentation of the disease. In addition, uncommon causative organisms were noted more frequently (67% versus 13%; p= 0.009) in the younger group. The study shows a significant increase in IE in infants and young children with distinctive underlying conditions, clinical presentation, and microbiologic findings, all of which should be considered currently for the diagnosis and treatment of pediatric IE.     

Hemodynamic Abnormalities in Fetuses with Congenital Heart Disease

The purpose of this investigation was to assess left and right ventricular function, volume ejection fraction, combined stroke volume, and combined ventricular output in the human fetus with congenital heart disease compared to the normal healthy fetus. Seventy-two fetuses with a variety of in utero diagnosed congenital cardiac defects were compared with a control group of fetuses with structurally normal hearts matched for race, maternal age, and gestational age. We demonstrated significant hemodynamic changes in the fetus with congenital heart disease. There was a significant (p < 0.0001) decrease in the volume ejection fractions, biventricular stroke volume, and cardiac output in the congenital heart disease group compared to matched controls. Our findings suggest that hemodynamic abnormalities in the fetus with congenital heart disease are present before birth and we speculate that myocardial reserve may not be adequate to respond to hemodynamic stressors such as birth or heart surgery.     

Pathologic Lung Function in Children and Adolescents with Congenital Heart Defects

Lung function tests (i.e., spirometry, flow volume, and body plethysmography) were performed in 213 patients (age 6–21 years, mean 11.3 years) with hemodynamically significant congenital heart defects: atrial septal defect, ventricular septal defect (VSD), tetralogy of Fallot, aortic stenosis and coarctation of the aorta. We measured lung vital capacity, total lung capacity (TLC), residual volume (RV), the percentage ratio of the latter two measurements (%RV/TLC), maximal expiratory flow rates at 25% and 50% of vital capacity, and specific airway conductance. Pulmonary restriction dominated in patients with tetralogy of Fallot; pulmonary hyperinflation was more frequent in patients with VSD and coarctation of the aorta; and obstruction of the airways was observed most frequently in patients with tetralogy of Fallot. In conclusion, we found a range of pathologic lung function parameters in patients with hemodynamically significant congenital heart defects.     

Cardiac Functions in Children with Vitamin D Deficiency Rickets

Nutritional deficiency of vitamin D is common in developing countries as a result of both inadequate diet and exposure to ultraviolet light. The most striking biochemical finding in this illness is hypocalcemia. Reduction in serum calcium level may affect ventricular contraction. The purpose of this study was to evaluate prospectively left ventricular function in a group of 27 infants diagnosed as having rickets. Electrocardiograms and echocardiographic studies were undertaken in all patients. A group of ten healthy infants was used as a control for the echocardiographic examinations. Patients were divided into three groups according to the biochemical classification of rickets. There were eight patients in group I, nine in group II, and ten in group III. Abnormal electrocardiographic findings were noted in four infants in group I, three in group II, and six in group III before treatment of the rickets. These changes resolved following treatment. Echocardiographic studies revealed left ventricular dysfunction in the pretreatment stage. The most striking echocardiographic finding is the increase in the ratio of interventricular septal thickness to left ventricular posterior wall thickness in eight patients from group III. This returned to normal after treatment of the rickets. This study has demonstrated echocardiographic evidence of left ventricular dysfunction in children with rickets. These abnormalities were not, however, sufficiently severe to be associated with clinical signs of cardiac failure. Cardiomyopathy may develop in rickets, especially in the third stage of the disease, and this finding may return to normal following adequate treatment of the rickets.     

Amiodarone Used Alone or in Combination with Propranolol: A Very Effective Therapy for Tachyarrhythmias in Infants and Children

The aim of the study was to evaluate the efficacy of amiodarone used alone or in combination with propranolol in infants and children affected by life-threatening or drug-resistant tachyarrhythmias. The study included 27 children (median age 3 months), affected by life-threatening and/or drug-resistant supraventricular or ventricular tachyarrhythmias. The loading dose of amiodarone was 10–20 mg/kg/day and the maintenance dose ranged between 3 and 20 mg/kg/day. When amiodarone was ineffective, propranolol was added at a dosage of 2–4 mg/kg/day. The study population was divided into two groups: group A was composed of patients <1 year and group B of patients >1 year. The effectiveness of the therapy was assessed by clinical evaluation, Holter monitoring, exercise testing, and, in patients with reentry tachycardias, electrophysiological testing. Amiodarone used alone was effective or partially effective in 4/14 (28%) patients in group A and in 11/13 (85%) patients in group B (p < 0.006). Among amiodarone-resistant patients, the combined therapy with propranolol was effective in 8/10 patients in group A and 2/2 patients in group B. Therefore, amiodarone used alone or in combination with propranolol was effective in 25/27 (93%) patients. During the follow-up (20.5 ± 13 months) there were no arrhythmic effects but side effects were noted in 5/27 (18.5%) patients. Amiodarone seems to be an effective drug in the control of the life-threatening and/or drug-resistant supraventricular and ventricular tachyarrhythmias in children. The addition of propranolol can significantly enhance the success rate of this class III drug, especially in the treatment of reentry tachycardias due to accessory pathways.