Long-term survival after mitral valve replacement in children aged <5 years: a multi-institutional study.

BACKGROUND: Short- and long-term outcomes after prosthetic mitral valve replacement (MVR) in children aged <5 years are ill-defined and generally perceived as poor. The experience of the Pediatric Cardiac Care Consortium (45 centers, 1982 to 1999) was reviewed. METHODS AND RESULTS: MVR was performed 176 times on 139 patients. Median follow-up was 6.2 years (range 0 to 20 years, 96% complete). Age at initial MVR was 1.9+/-1.4 years. Complications after initial MVR included heart block requiring pacemaker (16%), endocarditis (6%), thrombosis (3%), and stroke (2%). Patient survival was as follows: 1 year, 79%; 5 years, 75%; and 10 years, 74%. The majority of deaths occurred early after initial MVR, with little late attrition despite repeat MVR and chronic anticoagulation. Among survivors, the 5-year freedom from reoperation was 81%. Age-adjusted multivariable predictors of death include the presence of complete atrioventricular canal (hazard ratio 4.76, 95% CI 1.59 to 14.30), Shone's syndrome (hazard ratio 3.68, 95% CI 1.14 to 11.89), and increased ratio of prosthetic valve size to patient weight (relative risk 1.77 per mm/kg increment, 95% CI 1.06 to 2.97). Age- and diagnosis-adjusted prosthetic size/weight ratios predicted a 1-year survival of 91% for size/weight ratio 2, 79% for size/weight ratio 3, 61% for size/weight ratio 4, and 37% for size/weight ratio 5. CONCLUSIONS: Early mortality after MVR can be predicted on the basis of diagnosis and the size/weight ratio. Late mortality is low. These data can assist in choosing between MVR and alternative palliative strategies.

Is arrhythmia detection by automatic external defibrillator accurate for children?: sensitivity and specificity of an automatic external defibrillator algorithm in 696 pediatric arrhythmias.

BACKGROUND: Use of automatic external defibrillators (AEDs) in children aged <8 years is not recommended. The purpose of this study was to develop an ECG database of shockable and nonshockable rhythms from a broad age range of pediatric patients and to test the accuracy of the Agilent Heartstream FR2 Patient Analysis System for sensitivity and specificity. METHODS AND RESULTS: Children aged

A soluble neuronal factor alters contractile function of ventricular myocytes without effect on troponin T isoform expression.

OBJECTIVE: The purpose of this investigation was to establish a model system to facilitate identification of the sympathetic neuronal factor(s) that promotes improved contractility in neonatal cardiac myocytes. Conditioned medium from PC12 cells with sympathetic phenotype served as the source of the neuronal factor. METHODS: Contraction frequency, amplitude and velocity of cultured neonatal rat cardiac myocytes were measured by online video analysis. Interventions included in vitro sympathetic innervation, exposure to PC12 conditioned medium, neurotransmitters and antagonists. Metabolic activity was assayed by 2-deoxyglucose uptake. Troponin T isoform expression was analyzed by SDS-polyacrylamide gel electrophoresis. RESULTS: Medium conditioned by neuronal PC12 cells induced contractility changes similar to those induced by in vitro sympathetic innervation. These effects of PC12 conditioned medium and innervation were not suppressed by adrenergic or muscarinic antagonists nor reproduced by neuropeptide Y or somatostatin. Neuronal PC12 conditioned medium but not chromaffin PC12 conditioned medium, increased metabolic activity of the myocytes as detected by [3H]-2-deoxyglucose, indicating that the effect was specific to the neuronal PC12 cells. The in vitro switch of troponin T isoform expression was not altered by exposure to PC12 conditioned medium. CONCLUSIONS: Increased contractile function induced by sympathetic innervation is reproduced by PC12 conditioned medium, but neither is mediated by sympathetic or muscarinic neurotransmitters. Troponin T isoform expression is not related to the contractility changes. This model system will allow identification of the factor(s).

Pediatric defibrillation: current flow is improved by using "adult" electrode paddles.

OBJECTIVE: Current flow, the major determinant of defibrillation success, depends on delivered energy and transthoracic impedance. Previous experimental data suggest that transthoracic impedance is higher using "pediatric" electrode paddles compared to the larger "adult" electrode paddles. There are few data from actual shocks to support the experimental studies. The purpose of this study was to measure transthoracic impedance during actual shock delivery and to determine the optimal electrode paddle size for pediatric defibrillation and cardioversion. METHODS: We prospectively evaluated all shocks of < or = 20 joules given to pediatric patients at the University of Iowa from 1988 to 1992. Data collected included energy selected by the operator, energy delivered by the defibrillator, peak current flow and transthoracic impedance. Data were analyzed by unpaired t test and linear regression. RESULTS: Fifty-five shocks were delivered to 20 patients, age newborn to 8 years. Thirty-seven shocks were given with "pediatric" electrode paddles (surface area 21 cm2) and 18 with "adult" electrode paddles (surface area 83 cm2). Selected energy correlated well with delivered energy (r = .98, P < .0001). Delivered energy using "pediatric" electrodes did not differ from that delivered with "adult" electrodes (8.0 +/- 0.9 joules vs 10.5 +/- 1.2 joules P > .1). However transthoracic impedance was significantly higher with "pediatric" electrodes (78.1 +/- 4.4 ohms vs 54.6 +/- 2.7 ohms P < .0008), resulting in lower peak current flow through "pediatric" electrode paddles (6.2 +/- 0.5 amps vs 8.7 +/- 0.5 amps P < .002). There was no correlation between joules/kg and peak current flow (r = .26, P > .05). CONCLUSION: Use of "pediatric" electrode paddles results in higher transthoracic impedance and thus lower peak current flow. In pediatric defibrillation, larger "adult" electrode paddles should be used as soon as chest size permits (approximately 10 kg). Lower transthoracic impedance results in higher current flow that facilitates cardioversion and defibrillation.

Accurate recognition and effective treatment of ventricular fibrillation by automated external defibrillators in adolescents.

OBJECTIVES: To evaluate the accuracy and efficacy of automated external defibrillators (AEDs) in patients <16 years old. BACKGROUND: AEDs are standard therapy in out-of-hospital resuscitation of adults and have led to higher success rates. Their use in children and adolescents has never been evaluated, despite recommendations from the American Heart Association that they be used in children >8 years of age. METHODS: This was a retrospective cohort study of children <16 years old who underwent out-of-hospital cardiac resuscitation and on whom an AED was used during the resuscitation. The setting was rural and urban prehospital emergency medical systems. Patients were identified by review of a database of cardiac arrests maintained by a large surveillance program of these services. RESULTS: AEDs were used to assess cardiac rhythm in 18 patients with a mean age of 12.1 +/- 3.7 years. The cardiac rhythms were analyzed 67 times and included ventricular fibrillation (25), asystole/pulseless electrical activity (32), sinus bradycardia (6), and sinus tachycardia (4). The AEDs recognized all nonshockable rhythms accurately and advised no shock. Ventricular fibrillation was recognized accurately in 22 (88%) of 25 episodes and advised or administered a shock 22 times. Sensitivity and specificity for accurate rhythm analysis were 88% and 100%, respectively. One patient with a nonshockable rhythm survived, whereas 3 of 9 patients with ventricular fibrillation survived. CONCLUSIONS: These data furnish evidence that AEDs provide accurate rhythm detection and shock delivery to children and young adolescents. AED use is potentially as effective for children as it is for adults.

Pediatric defibrillation: importance of paddle size in determining transthoracic impedance.

Transthoracic impedance is a major determinant of successful defibrillation or cardioversion, but no data are available concerning the range and determinants of transthoracic impedance in children. Transthoracic impedance was measured in ten ambulatory infants, 6 weeks to 9 months of age, and 37 children, 1.5 to 15 years of age, using a previously validated "test pulse" technique that measures transthoracic impedance without actually delivering a shock. We used hand-held "pediatric" (21 cm2) and "adult" (83 cm2) electrode paddles coated with either Redux paste or Redux creme. Transthoracic impedance in children was 108 +/- 24 omega (range 61 to 212 omega) using pediatric paddles. Using adult paddles lowered the transthoracic resistance by 47% to 57 +/- 11 omega (range 29 to 101 omega), P less than .05. In infants, transthoracic impedance (measured only with pediatric paddles) was 94 +/- 17 omega (range 74 to 124 omega). Using Redux paste as the coupling agent reduced transthoracic impedance by 13% (P less than .05). Transthoracic impedance was significantly but poorly related to body weight and body surface areas, but the correlations were not sufficiently high to be clinically useful. These data indicate that the larger adult electrode paddles will minimize transthoracic impedance and should be used when the child's thorax is large enough to permit electrode to chest contact over the entire paddle surface. This transition occurred at an approximate weight of 10 kg.

Correlation between directly measured and indirectly estimated sinoatrial conduction time in children.

The indirectly estimated sinoatrial conduction time has been widely used in children to assess sinus node (SN) function, but has never been validated in pediatric patients. Using a standard quadripolar catheter with high amplification and low-pass filters, SN electrograms were recorded in 11 of 26 (42%) pediatric cardiac patients (age range 10 months to 18 years) with normal SN function. The sinoatrial conduction time was measured directly from the SN electrogram and estimated indirectly by the premature stimulation and continuous pacing methods. The direct sinoatrial conduction time (15 to 91 ms) in these 11 patients (ages 1 to 18 years) correlated well with that estimated by the premature stimulation method (r = 0.81, n = 9, p less than 0.01). There was a poor correlation between the direct and continuous pacing methods (r = 0.53, n = 8, p = 0.17). It was concluded that SN electrograms can be recorded in children and that there is a good correlation between the directly measured sinoatrial conduction time and the indirectly estimated sinoatrial conduction time by the premature stimulation method.

Operative mortality and frequency of coexistent anomalies in interruption of the aortic arch.

Operative mortality for 262 infants with interruption of the aortic arch repaired from 1982 to June 1993 has remained constant at about 35%. Major coexistent cardiac malformations, type B interruption, or staged repair are risk factors for mortality.

Complete heart block in association with graft-versus-host disease.

An infant who received haploidentical BM for severe combined immunodeficiency (SCID) developed acute, reversible complete heart block in association with an exacerbation of GVHD. Respiratory distress and myocardial dysfunction were also seen with this and previous GVHD exacerbations. The patient had not received chemotherapy or radiation prior to BMT. The complete heart block resolved after 1 week of intensive immunosuppression. The association of complete heart block with GVHD is important because the heart block is potentially reversible with prompt, aggressive control of the GVHD.

A multimodal approach to functional dysphagia.

Functional dysphagia in children has historically been treated using a cognitive behavioral approach. The case of a 7-year-old boy treated using a successful multimodal approach, including behavioral, family, and play therapy with alprazolam augmentation, is reported. The patient showed minimal response to early interventions but rapidly improved with the prescription of alprazolam before meals.

Chronotropic responsiveness of developing sinoatrial and ventricular rat myocytes to autonomic agonists following adrenergic and cholinergic innervation in vitro.

The chronotropic responses of isolated sinoatrial node and ventricular muscle cells to neurotransmitters were compared in vitro with and without selective adrenergic and cholinergic innervation. Explants of either thoracolumbar sympathetic ganglion or sacrococcygeal spinal cord were added to cultures of newborn rat sinus node regions or ventricular apexes harvested before the onset of autonomic innervation in vivo. Catecholamine synthesis was detected by glyoxylic acid histofluorescence. Acetylcholine synthesis was indicated by monoclonal antibody labeling of choline acetyltransferase. After electrical or pharmacological stimulation of neurons, the chronotropic response of individual myocardial cells confirmed the presence of neuroeffector transmission; the nature of the myocyte response identified the stimulated neuron as either adrenergic or cholinergic. Chronotropic responses of all myocardial cells to norepinephrine or acetylcholine were transcribed on a recorder coupled to a video photoconductive cell monitor. Isolated sinoatrial node cells were supersensitive to norepinephrine and acetylcholine; thresholds were 3 x 10(-16) M and 6 x 10(-15) M, respectively. These sinoatrial node cells remained sensitive to both norepinephrine and acetylcholine after the development of innervation in vitro. Ventricular cells also were sensitive with thresholds of 3 x 10(-11) M and 6 x 10(-14) M to norepinephrine and acetylcholine, respectively. However, following in vitro innervation, ventricular cells were significantly less sensitive to norepinephrine and acetylcholine (thresholds 3 x 10(-9) M and 6 x 10(-11) M). These data are the first to demonstrate that neurotrophic modulation is not homogeneous throughout the myocardium and that it may be dependent on the specific myocardial cell innervated.

Common cardiovascular problems in the young: Part II. Hypertension, hypercholesterolemia and preparticipation screening of athletes.

Blood pressure should be measured during health maintenance visits in all children three years of age and older. Cholesterol levels should be obtained in children with a family history of hypercholesterolemia or premature coronary artery disease and in children with other risk factors, such as hypertension, smoking or obesity. Preparticipation screening for sports participation should include a detailed questionnaire regarding the athlete's personal or family history of syncope, sudden death or arrhythmia, as well as measurement of blood pressure, auscultation of the heart and evaluation of upper and lower extremity pulses.

Foramen ovale/atrial septum area ratio: a marker of transatrial blood flow.

We examined 51 cardiac specimens to test the hypothesis that the size of the foramen ovale is directly proportional to the relative volume of transatrial blood flow during cardiac morphogenesis. Included in the study were 18 normal specimens, five with tricuspid atresia, four with pulmonary atresia and intact ventricular septum, nine with secundum atrial septal defect, eight with simple coarctation of the aorta and seven with aortic stenosis. The areas of the foramen ovale and atrial septum were measured and the ratio of foramen ovale to atrial septum was calculated. The area of the atrial septum did not differ significantly among the six groups. Normal specimens had a ratio of 0.19 +/- 0.07. Specimens with tricuspid atresia and pulmonary atresia had ratios of 0.43 +/- 0.01 and 0.38 +/- 0.10, respectively (p less than 0.05). The ratio in specimens with coarctation of the aorta was 0.15 +/- 0.07 (NS). Specimens with aortic stenosis had a ratio of 0.11 +/- 0.06 (p less than 0.05). Specimens with secundum atrial septal defects had a ratio of 0.37 +/- 0.08 (p less than 0.05). These data indicate that the foramen ovale is a marker of transatrial blood flow in utero. Secundum atrial septal defects may be a consequence of increased transatrial blood flow.

Differential growth of neonatal WKY and SHR ventricular myocytes within sympathetic co-cultures.

Sympathetic innervation is known to increase heart size in the immature animal, yet the mechanism for this growth remains to be established. This comparative study stereologically quantified the volume of cultured neonatal ventricular myocytes with and without in vitro sympathetic innervation to isolate the mechanisms regulating cardiac growth. Since ventricular myocyte size at birth differs between the spontaneously hypertensive rat (SHR) and the normotensive Wistar-Kyoto (WKY), we questioned whether SHR myocytes respond differently than WKY myocytes to innervation. Four groups of ventricular myocytes from each strain were compared: myocytes grown alone, myocytes innervated by cultured sympathetic neurons, innervated myocytes exposed to adrenoceptor blockade, and non-innervated myocytes in co-culture dishes. Volumes for the myocyte, nucleus, cytoplasm, mitochondria, sarcomeres and other cellular organelles were assessed within each population and between populations. Relative volumes were determined for the mitochondria, sarcomeres, and other cellular components within the cytoplasm. Innervated WKY myocytes were 38% larger than control myocytes (P < 0.0004). This growth was not blocked by adrenoceptor blockade (P = 0.89 vs. innervated) and was present in the non-innervated myocytes distant from the neurons in the co-cultures (P = 0.39 vs. innervated). SHR myocytes were 36% larger than WKY myocytes (P < 0.009) but did not increase with innervation (P = 0.48). SHR myocyte size was also unaffected by adrenoceptor blockade (P = 0.39) or presence of the neurons in the culture dish (P = 0.53). Neonatal WKY ventricular myocyte growth can be provoked in vitro by sympathetic innervation via regulatory mechanisms independent of neuroeffector transmission or anatomic contact, whereas volume of neonatal SHR myocytes is unaltered by sympathetic coculture. These findings are significant for understanding normal as well as aberrant cardiomyocyte growth.

Concealed atrial parasystole following the Senning operation.

A patient with sick sinus syndrome following the Senning operation was also found to have concealed atrial parasystole during intracardiac electrophysiological study. This atrial parasystolic pattern could be converted to atrial bigeminy by changing the atrial drive rate.

Cine computed tomography for diagnosis of superior vena cava obstruction following the Mustard operation.

Superior vena caval obstruction is a well described complication following Mustard's repair for transposition of the great arteries. We report a case of a 6-year-old child with superior vena cava obstruction correctly diagnosed by Cine-CT. The advantages of imaging with Cine-CT for this complication are discussed.

Application of stereological analysis of cell volume to isolated myocytes in culture with and without adrenergic innervation.

A three-dimensional analysis to evaluate structural changes in cultured cardiac myocytes following adrenergic innervation was performed using stereological techniques formerly limited to cells in tissue and organs. Cell volumes were calculated for two groups of cells at 96 hours in culture: isolated myocytes and myocytes innervated with adrenergic neurons. Relative and absolute volumes of the nucleus, cytoplasm, and cell were quantified by systematically sampling sections throughout the cell and by point count sampling techniques. Volumetric estimates were similarly determined for the mitochondria, sarcomeres, and other cellular components in the cytoplasm. Data were analyzed with ANOVA and randomized block design to control for variation among the cultures. Adrenergic innervation produced a 44% increase in cell volume, X +/- SEM, (3,344 +/- 196 microns3 to 4,816 +/- 400 microns3, P = 0.007). The absolute volume of mitochondria significantly increased after innervation (521 +/- 42 microns3 to 744 +/- 54 microns3, P less than 0.01). Absolute sarcomere volume did not change significantly (750 +/- 92 microns3 to 642 +/- 1061 microns3, P = 0.14). Other cellular components, defined as all cytoplasmic components except mitochondria and sarcomeres, significantly increased with innervation (1,739 +/- 166 microns3 to 3,097 +/- 338 microns3, P = 0.02). The relative volume of the nucleus and the cytoplasm in the cell remained unchanged following innervation. However, the relative volume of mitochondria decreased by 6%, the percent of the cytoplasm occupied by the sarcomeres decreased by 44%, and the volume occupied by the other cellular components increased by 22%. These findings support the use of stereological analysis as a means to quantify cell volumes of cultured myocytes.(ABSTRACT TRUNCATED AT 250 WORDS)