Effect of Age on QT Variability

Heart rate variability is influenced significantly by age. Recent studies have shown the utility of QT variability to study temporal repolarization lability, and increased QT variability is reportedly associated with sudden death. Because beat-to-beat QT interval variability appears to closely follow heart rate variability, this study investigated the relationship between age and QT variability. We obtained QT variability measures in 34 adults (22–55 years of age) and 15 children (6–14 years of age) using a novel algorithm to compute beat-to-beat QT intervals. QT variability corrected for mean QT interval was significantly inversely correlated with age. Coherence in the band of 0 to 0.5 Hz and high-frequency coherence (0.15–0.5 Hz) were also significantly inversely correlated with age. QT_vi (QT variability corrected for mean QT interval over heart rate variability corrected for mean heart rate) was not significantly related to age in supine posture during spontaneous or controlled breathing, whereas there was a modest negative relationship in standing posture. These findings suggest that coherence between QT and heart rate time series appears to be modulated by cardiac vagal activity.     

Prevalence of Idiopathic Long QT Syndrome in Children with Congenital Deafness

Long QT syndrome (LQTS) is characterized by prolongation of the QT interval associated with a high risk for syncope and sudden death. Jervell and Lange-Nielsen initially described LQTS in association with congenital sensorineural deafness. We have investigated the prevalence of this syndrome in a school for deaf children, evaluating by ECG 350 congenitally deaf children with an age range of 6–19 years. The corrected QT interval (QTc) was calculated by Bazett's formula. Eight children with a QTc interval >440 ms were further studied by cardiac examination, repeat ECGs (three times), Holter monitoring, echocardiography, and exercise testing. The families were assessed for a history of syncope and deafness and underwent ECG evaluations regarding lengthened QTc interval. Among these eight children only two girls aged 14 and 15 years were diagnosed as having LQTS according to Schwartz's criteria (0.57% of the 350 deaf children; 95% confidence intervals 0, ≤p≤ 0.013). The first patient had two major criteria (QTc 483 ms and a history of syncopal attack) and one minor criteron (congenital deafness); the second also had two major criteria (QTc 613 ms and family members with LQTS) and one minor criterion (congenital deafness). Prophylactic β-blocker therapy was started in these two patients to prevent sudden death. In conclusion, this syndrome should be sought in children with syncope or a family history of it, especially those with congenital deafness.     

Oxygen consumption in infants and children during heart catheterization

Oxygen consumption was measured in infants, children, and adolescents during diagnostic heart catheterizations. A total of 825 measurements of oxygen consumption (VO₂) was performed in 504 subjects using a semiopen hood system and a paramagnetic oxygen analyzer. In 256 subjects under 3 years of age, body dimensions and heart rate were found to be significant factors for oxygen consumption. The regression equation for both sexes was: VO₂/BSA (ml/min · m²) = 3.42 · height (cm) − 7.83 · weight (kg) + 0.38 · HR − 54.1 (r ²= 0.39, SD = 38.7), where BSA is body surface area and HR is heart rate. VO₂/BSA was significantly lower in infants less than 3 months of age (133 ± 33 ml/min · m²) compared with infants of 3–12 months (171 ± 37 ml/min · m²; p < 0.01). In 272 children aged 3 years and older and adolescents, gender was a significant factor in oxygen consumption together with BSA and HR. The regression line equation for males was VO₂/BSA (ml/min · m²) = 0.79 · HR − 7.4 · BSA(m²) + 108.1 (r ²= 0.45, SD = 34.2). The regression line equation for females is VO₂/BSA (ml/min · m²) = 0.77 · HR − 5.2 · BSA(m²) + 106.8 (r ²= 0.43, SD = 34.4). Hematocrit, systemic oxygen saturation, and blood pressure were not significant factors. The predictive value of nomograms for oxygen consumption is limited because of the large interindividual variations not explained by differences in gender, body size, or simple hemodynamic variables. Preferably, oxygen consumption is measured; but if nomograms for oxygen consumption are used for hemodynamic assessment, the wide confidence intervals should be considered.     

Assessment of Ventricular Repolarization in Deaf–Mute Children

The long QT syndrome is a congenital disease with frequent familial transmission, characterized primarily by prolongation of the QT interval and by the occurrence of life-threatening arrhythmias. The syndrome may be familial, with or without congenital deafness, or it may be idiopathic. We attempted to assess ventricular repolarization and to identify patients with the Jervell and Lange–Nielsen syndrome among 132 deaf–mute school children. Five deaf–mute subjects had Jervell and Lange–Nielsen syndrome. The deaf–mute subjects were divided into two subgroups according to the length of their QT intervals: group 1 included 5 cases with the long QT interval (>440 msec), and group 2 included 127 subjects with the normal QT interval (≤440 msec). Group 3 was composed of 96 control subjects. The mean QT, QTc, JT, and JTc intervals (418 ± 70, 500 ± 38, 302 ± 65, and 389 ± 36 msec, respectively) in group 1 were significantly longer than those of group 2 (344 ± 23, 408 ± 22, 249 ± 34, and 291 ± 28 msec, respectively) and group 3 (325 ± 11, 383 ± 26, 228 ± 36, and 269 ± 46 msec, respectively). The dispersion (d) values (QT-d, QTc-d, JT-d, and JTc-d; 63 ± 10, 73 ± 8, 60 ± 8, and 62 ± 11 msec, respectively) of group 1 were significantly longer than those of group 2 (49 ± 16, 43 ± 11, 48 ± 21, and 45 ± 18 msec, respectively) and group 3 (33 ± 13, 33 ± 14, 28 ± 16, and 27 ± 14 msec, respectively) at similar mean RR intervals. Also, the mean QT, QTc, JT, and JTc intervals and the dispersion values (QT-d, QTc-d, JT-d, and JTc-d) in group 2 were significantly longer than those of group 3 at similar mean RR intervals. Consequently, in this study, we determined that the deaf–mute children who did not meet the criteria for Jervell and Lange–Nielsen syndrome still had evidence of subtle derepolarization abnormalities evidenced by intermediate prolongation of QTc, JTc, and the corresponding measures of dispersion, and we believe an electrocardiogram examination of deaf–mute subjects will reveal this potentially life-threatening syndrome.     

Normal Values for Corrected Sinus Node Recovery Time in Adolescents

Sinus node recovery times have been used to evaluate sinus node function in adults and children. Normal values for corrected sinus node recovery time (CSNRT) are generally accepted as 275 and 500–550 msec in young children and adults, respectively. However, normal CSNRT values have not been determined for adolescent patients. Therefore, we mesured CSNRT in 29 consecutive patients, ages 12–17 years, who underwent electrophysiology testing as part of radiofrequency ablation. CSNRTs were performed by rapid atrial pacing for 30 seconds. Pacing cycle lengths were then shortened in 50-msec decrements to a minimum of 300 msec CSNRTs were determined by subtracting the patients' resting sinus cycle length from the maximal SNRT measured. The mean CSNRT was 323 ± 61 msec (mean ± SD, range 186–422 msec). A significant positive correlation between CSNRT and age was found. We conclude that the CSNRT value for the upper limit of normal in adolescents lies between the normal values previously determined for children and adults and is approximately 445 msec (mean + 2 SD). Because sinus node dysfunction is a well-recognized, long-term complication following surgical repair for complex congenital heart disease, this value becomes especially relevant as more children with congenital heart disease survive into adolescence.     

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.     

X-Chromosomal (p21) Muscular Dystrophy and Left Ventricular Diastolic and Systolic Function

In order to screen for cardiac abnormalities, we prospectively studied 15 patients (age 8–25 years, mean 15.5 years) with Duchenne's (DMD) (n= 9) and Becker's (BMD) (n= 6) muscular dystrophy using the echocardiogram. Data were compared to a control group of 92 healthy individuals (age 7.9–25 years, mean 14.3 years). Left ventricular filling in diastole showed a different pattern when comparing echocardiographic Doppler results in patients and controls: Patients had lower peak velocity of early left ventricular diastolic filling (E-vmax)(P < 0.0001) and smaller time velocity integral of the E-wave (E-tvi)(P < 0.0001). In contrast, the atrial component (A-vmax, A-tvi) of diastolic filling in DMD/BMD showed no significant difference to controls. The mean area of the mitral valve orifice was significantly larger in patients (P < 0.0001) without presence of mitral regurgitation. Systolic left ventricular function was significantly impaired in the DMD/BMD group; we found lower heart rate corrected fiber shortening velocity VCFc (P < 0.001) and higher peak systolic wall stress (P < 0.001) in DMD/BMD. In 8 of 15 patients, peak systolic wall stress was above 95th percentile of controls. In 6 of 15 patients, VCFc was lower than the 5th percentile of controls. Systolic and diastolic myocardial impairment was found even in young patients and at low stages of disability—equally among patients with DMD or BMD. Diastolic left ventricular impairment predominantly affected the early diastolic filling, but atrial compensation was poor. Peak systolic wall stress measurements were particularly useful in patients with CMP, reflecting the left ventricular afterload.     

Ictal electrocardiographic changes in children presenting with seizures

Background: The aim of this study was to determine electrocardiographic changes in children during seizures. Methods: We assessed heart rate changes, RR intervals and QT changes during 47 seizures in children. Consecutive QT and RR intervals were measured for 60 s before the seizures, during the seizures and 60 s after the seizures during video electroencephalography monitoring. Results: There were 47 seizures in 18 patients. Five patients had generalized seizures and 13 patients had focal seizures. Twelve patients were male. The mean age during monitoring was 10.1 years (range 4 months–19 years). Ictal tachycardia was seen in every seizure. No ictal bradycardia was noted. There was only one dropped beat in a patient. The mean ictal heart‐rate‐corrected QT (QTc) interval was significantly higher than the postictal measurements (P= 0.005). Mean ictal QTc variation tended to increase during seizures and then decreased below the pre‐ictal measurements in the postictal period. However these changes were statistically insignificant (P > 0.05). RR variance was significantly decreased during seizures compared to the postictal period and the standard deviation of the RR intervals was significantly decreased in the ictal period compared to the pre‐ictal period (P= 0.014 and P= 0.001, respectively). Conclusion: Tachycardia is the main finding in seizures in children. Ictal bradycardia and cardiac arrhythmias are very rare despite being more frequent in adults with seizures.     

Quantitation of the Global Right Ventricular Function in Children with Normal Heart and Congenital Heart Disease: A Right Ventricular Myocardial Performance Index

Although the assessment of right ventricular (RV) function is important in the clinical management of children with congenital heart disease, available imaging techniques have been limited because of the complex geometry of the right ventricle. A new Doppler index combining systolic and diastolic time intervals (the Tei index) has been reported to be useful for the assessment of global RV function in adults. However, normal values in children, age-related changes, and the clinical utility of the Tei index with regard to congenital heart disease have not been demonstrated. The purpose of this study was to prospectively assess RV function in children with normal heart and congenital heart disease using the Tei index. The subjects included 150 healthy children and 43 patients with congenital heart disease (35 patients with atrial septal defects and 8 patients who had had a Senning operation). The index was defined as the sum of isovolumetric contraction time and isovolumetric relaxation time divided by ejection time and was measured from conventional RV outflow and inflow Doppler velocity profiles. The Tei index was not affected by age in healthy children (0.24 ± 0.04). There was a significant difference in index rating between patients who had had a Senning operation (0.58 ± 0.09) and healthy children (p < 0.01), but there was no significant difference between children with atrial septal defect (0.25 ± 0.13) and healthy children. The Tei index is a feasible approach to use when assessing global RV function in children with congential heart disease.     

Exercise Tolerance and Blood Pressure Response to Exercise Testing in Children and Adolescents After Renal Transplantation

The aim of the study was to assess exercise tolerance and blood pressure (BP) response to treadmill exercise in children after renal transplantation. Forty-five children were selected (29 males and 16 females) whose mean age was 14.3 ± 4.2 years. All children had Hb ≥ 10 g/dl and creatinine clearance ≥40 ml/min/1.73 m². They were at least 6 months posttransplantation and were on triple immunosuppressive therapy. Twenty-seven were also on various antihypertensive medications. Each underwent clinical examination and measurement of BP, both at rest and during exercise testing on treadmill. The test was stopped on muscular fatigue or exhaustion. The patients were divided into two groups: those off (A) or on (B) antihypertensive therapy. When compared to a population of healthy children the patients had reduced exercise tolerance (10.1 ± 2.1 vs 15.1 ± 1.7 min, p < 0.001) (67 ± 16%), increased heart rate (174 ± 19 vs 161 ± 19 beats/min, p < 0.001) (109 ± 15%), and increased maximum systolic BP (150 ± 26 vs 134 ± 13 mmHg, p < 0.001) (113 ± 19%) at comparable workloads. Within the two patient groups, significant differences were observed during exercise testing for maximum heart rate, which was lower in group B (p= 0.03), and maximum systolic BP, which was higher in group A (p= 0.04). Our study confirms that children and adolescents on immunosuppressive therapy after renal transplantation have a hypertensive response during exercise, probably related to medication-induced peripheral vascular tone.     

Congenital Heart Disease Among 815,569 Children Born Between 1980 and 1990 and Their 15-Year Survival: A Prospective Bohemia Survival Study

The objective of this study was to ascertain the prevalence and survival rate of children born with a heart defect. A total of 816,569 children live-born between 1980 and 1990 in Bohemia (52,478 km², population 6.314 million, western Czech Republic) were followed up and those with suspected heart disease referred to a center. Echocardiography was done in all of them. All dead children were autopsied. Congenital heart disease was found in 5030 of 816,569 children (6.16 per 1000 live births). The most frequent conditions were ventricular septal defect (41.59%), atrial septal defect (8.67%), aortic (7.77%) and pulmonary (5.81%) stenoses, transposition of the great arteries (5.39%), coarctation of the aorta (5.29%) and persistent ductus arteriosus (5.07%). The first week was survived by 92.46%, the first month by 89.14%, 6 months by 82.42%, and the first year of life by 80.02%, and 77.11% (95% CI 75.91–78.31%) survived to age 15 years. The best prognosis was found in pulmonary stenosis (15-year survival 95.55%), atrial septal defect (92.04%), persistent ductus arteriosus (90.59%), ventricular septal defect (89.37%) and aortic stenosis (88.39%). The worst results were attained in hypoplastic left heart, truncus arteriosus and pulmonary atresia with intact ventricular septum. In conclusion, the prevalence of congenital heart disease was 6.16 per 1000 live births; 77.11% of patients survived to age 15 years.     

Responses of Plasma Norepinephrine and Heart Rate During Exercise in Patients After Fontan Operation and Patients with Residual Right Ventricular Outflow Tract Obstruction After Definitive Reconstruction

To determine the exercise responses of patients with congenital heart disease, 20 patients—5 who had undergone a right ventricular outflow tract reconstruction (group R; age, 15 ± 2 years), eight who had undergone a Fontan operation (group F; age, 13 ± 2 years), and seven who had a history of Kawasaki disease (group C; age, 15 ± 1 years)—performed a treadmill exercise test. Patients of group R had a significant residual right ventricular outflow obstruction. Oxygen uptake (VO₂), heart rate (HR), and plasma norepinephrine (NE) concentrations were measured at rest, during warm-up, at ventilatory threshold (VT), and at peak exercise. Exercise capacity was determined as a percentage of the predicted normal peak VO₂ (%pVO₂). The %pVO₂ for groups R and F was 65 ± 10 and 56 ± 11, respectively. Peak HR for groups R and F was 171 ± 4 and 155 ± 5, which were lower than the HR for group C (p < 0.001). Although NE concentrations at rest, during warm-up, and at VT were significantly greater in groups R and F (p < 0.05), there were no significant differences in the NE concentrations at peak exercise. Peak HR correlated with %pVO₂ (p < 0.001). The ratio of the increase in HR to NE from rest to VT was significantly lower in groups R and F than in group C (p < 0.001) and correlated with %pVO₂ (r= 0.80; p < 0.001). These data suggest that sympathetic nervous activity in groups R and F is increased at rest and during mild to moderate exercises, and reduced sinus node sensitivity to NE may be partly responsible for the abnormal HR response during exercise of patients with uncorrected congenital heart disease.     

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.     

Distribution of Symptomatic Congenital Heart Disease in Hong Kong

Racial group studies have identified differences in the occurrence of congenital heart disease (CHD) among ethnic populations. The aim of this study was to characterize the proportionate frequency and clinical profile of children with symptomatic cardiac abnormalities in Hong Kong. The hospital records of 666, mainly Southern Chinese children with symptomatic CHD, who were 4 years of age or younger and who were admitted to Grantham Hospital, Hong Kong, in 1994 and 1995 were analyzed retrospectively. Left-to-right shunting (45.0%) and pulmonary outflow obstruction (34.4%) were the most frequently diagnosed categories, followed by left ventricular outflow obstruction (8.3%), transposition of the great arteries (4.2%), conditions with intracardiac mixing (3.9%), and other cardiac lesions (4.2%). Compared with Western studies, pulmonary outflow obstruction (p < 0.0001), particularly tetralogy of Fallot and critical pulmonary stenosis, were more frequent in Chinese children. In contrast with previous reports, coarctation of the aorta (5%) does not seem to be uncommon in Chinese patients. Conversely, aortic stenosis and hypoplastic left ventricle may be rare in these children (1% vs 3% and 3–7%). Other cardiac lesions showed no consistent racial difference in the frequency of occurrence. Chinese patients with Down's syndrome had ventricular septal defect (38%) as the predominant lesion followed by atrioventricular septal defect (25%). Western studies usually report a reverse pattern for these two lesions. The mortality rate for the total cohort was 7.5%. However, of those with conditions with intracardiac mixing and left ventricular outflow tract obstruction many did not survive childhood (20% and 21%, respectively).     

Effect of Age on Diurnal Changes of 24-Hour QT Interval Variability

QT interval on the surface electrocardiogram (ECG) reflects the time for repolarization of myocardium and prolongation of QTc is strongly associated with sudden cardiac death. Studies using novel techniques on beat-to-beat QT interval variability (QTV) have shown that it is influenced by the autonomic nervous system and is a predictor of sudden cardiac death. In this study, we examined the awake and sleep changes in QTV in 39 normal adults (mean age, 35 years) and 10 children (mean age, 11 years) using 24-hour ECG records. We obtained eight 5-minute segments of ECG sampled at 1000 Hz from the 24-hour records. Our results show that there is a diurnal variation of QT_vm, detrended QT interval variance corrected for mean QT, and QT_vi, an index of QT_vm divided by heart rate variability corrected for mean heart rate. There was a significant increase in mean QT during sleep, whereas there was a significant decrease in QT_vm and QT_vi. QT_vi significantly increased during the early morning hours. There were significant but modest correlations between the average 24-hour and awake QT_vi and age (p < 0.01). There were also decreased low-frequency and high-frequency powers of QT during sleep. Coherence between heart rate and QT interval fluctuations in the range of 0–0.5 Hz, and especially in the high-frequency range (0.15–0.5 Hz), was significantly lower in adults than in children (p < 0.0002). These findings demonstrate diurnal fluctuations in ventricular repolarization lability. We speculate that these effects may relate to changes in cardiac autonomic function and may contribute to the well-known diurnal variation in the incidence of ventricular arrhythmias.     

Electrocardiographic and Echocardiographic Features That Distinguish Anomalous Origin of the Left Coronary Artery from Pulmonary Artery from Idiopathic Dilated Cardiomyopathy

Many authors have reported noninvasive means of diagnosing anomalous left coronary artery from pulmonary artery (ALCAPA) and differentiating ALCAPA from idiopathic dilated cardiomyopathy (DCM). Systematic evaluation using these noninvasive diagnostic modalities is not available. To distinguish between ALCAPA and DCM using a systematic approach, we examined 23 patients with ALCAPA (age 1 month to 23 years, median 7 months) and 23 patients with DCM (age 5 days to 16 years, median 6.6 months). Standard 12-lead electrocardiograms (ECG) and 2-dimensional (2-D) and color Doppler echocardiograms were performed. A logistic regression model was applied using ALCAPA diagnosis as the dependent variable and ECG and echocardiographic findings as independent variables. A scoring system was created to establish the ALCAPA diagnosis based on results from the logistic regression. On the logistic regression, the ECG feature of QT pattern in aVL (Q wave ≥ 3 mm deep with an inverted T wave) and echocardiographic features of right coronary artery diameter to aortic annulus ratio ≥ 0.14, increased papillary muscle echogenicity, and Doppler color flow of LCA from aorta or pulmonary artery were the most significant differentiating features between the ALCAPA and DCM groups. A scoring system was developed using the previous five variables and assigning a score of 1 to each variable (−1 to Doppler color flow of LCA from aorta). The scoring system had sensitivity of 100% and specificity of 91% for ALCAPA diagnosis. Compared with previous reported diagnostic features in differentiating ALCAPA and DCM, the scoring system had a much higher specificity and positive predictive value. In conclusion, we selected the most useful ECG and echocardiographic features to differentiate between ALCAPA and DCM and created a scoring system to aid clinical diagnosis. This scoring system may be useful in evaluating children with acute congestive heart failure.     

Procainamide for Rate Control of Postsurgical Junctional Tachycardia

This study was conducted to determine the efficacy of procainamide therapy for rapid rate control of postoperative junctional tachycardia (JT). Postoperative JT is one of the most difficult forms of tachycardia to manage. Reported success with a variety of treatments of JT in infants and children has been inconsistent and limited. Rate control using procainamide was achieved in 17 children having rapid JT (heart rate >200 beats/min) between 1986 and 1997. In the first 5 patients (protocol A), following a loading dose of 3 mg/kg over 20 minutes, a continuous procainamide infusion was initiated at a rate of 20 μg/kg/min. The infusion dose was increased in 10 μg/kg steps every 30 minutes to 40–120 μg/kg/min until the heart rate decreased below the target rate of 180 beats/min. In the other 12 patients (protocol B), after a higher loading dose of 10 mg/kg the infusion rate was increased every 10–15 minutes until the heart rate decreased below the target rate of 180 beats/min. Procainamide decreased JT rates in all patients but the response was significantly faster in protocol B. In the patients treated with protocol A, pretreatment JT rates ranged from 203 to 240 (213 ± 17) beats/min and decreased to 195 ± 10 beats/min at 2 hours (p= ns), 186 ± 8.8 at 4 hours (p < 0.02), and 179 ± 8 at 6 hour postinitiation of PA. In protocol B, pretreatment JT rates ranged from 201 to 240 (218 ± 17) beats/min and decreased to 183 ± 20 beats/min at 2 hours (p < 0.001) and 171 ± 12 at 4 hours after starting the procainamide therapy. The mean duration to decrease JT rates below the target rate of 180 beats/min was 3.2 ± 1.1 hours in protocol B compared to 6.4 ± 3.8 hours in protocol A (p < 0.02). Eight of 12 patients in protocol B achieved rate control below the target rate of 180 beats/min within 4 hours despite remaining on significant inotropic support. The procainamide infusion rates to maintain heart rates below 180 beats/min were 40–120 (68.4 ± 22.1) μg/kg/min. No proarrhythmia, bradycardia, or significant hypotension was observed. In this series procainamide provided safe, effective, and rapid rate control of JT occurring in the immediate postoperative period.     

Evidence of α-Adrenoceptor-Mediated Chronotropic Action in Children

We investigated α-adrenoceptor-mediated positive chronotropic action in children using a pharmacological autonomic function test. Under cardiac vagal and sympathetic blockade, chronotropic responses to intravenous infusion of an α-agonist, phenylephrine, were determined in 129 patients with suspected autonomic dysfunction. Heart rate changes to phenylephrine infusion (0.4 μg/kg/min) for 5 minutes ranged from −2 to 50 beats/min (mean ± SD, 13.8 ± 9.7 beats/min). α-Adrenoceptor-mediated chronotropic (APC) action more than 5 beats/min was observed in 88 (68%) subjects. APC was negatively correlated with age. Multivariate analysis showed that APC was correlated negatively with β-sympathetic tone and positively correlated with intrinsic heart rate. These results suggest that the α-adrenoceptor-mediated chronotropic action is a developmental phenomenon and may play an important role in controlling heart rate in response to cardiac sympathetic activation.     

Percutaneous Transluminal Angioplasty for Stenosis of the Aorta Due to Aortic Arteritis in Children

Percutaneous transluminal balloon angioplasty for stenosis of the aorta due to aortic arteritis was attempted on 45 lesions in 41 children (age range, 4–14 years; mean, 9.9±4.2 years) presenting with symptoms of hypertension, severe congestive heart failure, and lower limb claudication. Balloon dilatation was technically successful in 38 (92.7%) patients for 41 stenotic lesions (91.1%). The mean peak systolic pressure gradient (PSG) decreased from 71.7 ± 23.9 mmHg to 23.2 ± 17.5 mmHg (p < 0.001) and the diameter of the stenosed segment increased from 3.3 ± 1.1 mm to 7.5 ± 2.2 mm (p < 0.001) immediately after angioplasty. Patients with short-segment (<3 cm) stenosis had a lower residual gradient (17.9 ± 11.1 mmHg vs 30.5 ± 22.6 mmHg; p < 0.05) and a wider diameter of the aorta (8.8 ± 1.1 mm vs 7.5 ± 2.2 mm; p < 0.02) compared to patients with long-segment (≥3 cm) stenosis. Four patients required stent implantation; 2 for flow-limiting dissection, 1 for failure to reduce PSG by >50%, and 1 for recurrent restenosis. There was marked hemodynamic and angiographic improvement in these 4 patients. Hemodynamic and angiographic restudy in 21 of the 41 patients at mean follow-up period of 6.2 ± 4.2 months (range, 3–24 months) showed restenosis in 4 (19%) patients. Restenosis was more common in patients with long-segment stenosis than those with short-segment stenosis (30% vs 9.1%). Late restudy in 8 patients, done at 3–7 years after first restudy, showed no recurrence of aortic narrowing. On clinical follow-up of 38 patients for a mean of 58.8 ± 36.0 months (range, 8–146 months) there was marked improvement in symptoms. Hypertension was cured in 11 (29%), improved in 24 (63%), and persisted in 3 (8%). Six patients with associated severe renal artery stenosis showed further improvement in hypertension after successful renal angioplasty. Severe congestive heart failure improved in 21 (95.4%) of 22 patients. Mean left ventricular ejection fraction improved from 0.32 ± 0.08 to 0.48 ± 0.10 (p < 0.001) at a mean follow-up of 28.7 ± 8.4 months in these patients. Hemodynamic restudy in 10 of these patients showed improvements in left ventricular end-diastolic pressure from a mean 37 ± 9 mmHg (range, 25–55 mmHg) to 16.4 ± 6.2 mmHg (range, 6–25 mmHg) (p < 0.001). Lower limb claudication improved in all 4 patients. Our results suggest that percutaneous transluminal balloon angioplasty in children is safe and highly effective in relieving stenosis of the aorta due to aortic arteritis, with marked clinical improvement, and should be the treatment of choice particularly for discrete stenosis.     

On-Line Automated Border Detection for Echocardiographic Quantification of Right Ventricular Size and Function in Children

Rapid, accurate assessment of right ventricular (RV) size is important for the management of children with congenital heart disease. The usefulness of the Acoustic Quantification system of automated border detection (ABD) and on-line quantification (AQ) for assessment of RV size was tested in 36 children. AQ data were compared to ``corrected AQ' measurements (after correction for cavity areas erroneously included in the region of interest) required for AQ. Furthermore, the influence of necessary changes to gain settings was tested in ``lateral gain control' (LGC) images obtained by removal of ABD overlays. All results were compared to conventional echocardiography (echo), and agreement with magnetic resonance imaging (MRI) RV areas was assessed. Systematic differences (±) limits of agreement with MRI (transverse plane) for conventional echo and AQ (apical four-chamber view) were as follows: end-diastolic −0.8 ± 3.8 (conventional echo) versus −1.7 ± 4.6 (AQ) cm²/m² (p < 0.001); end-systolic −1.3 ± 3.2 versus −4.9 ± 5.8 (AQ) cm²/m² (p < 0.001); fractional area change 7.8 ± 17.0% versus 26.9 ± 31.4% (AQ) (p < 0.001). Differences between conventional echo, LGC, and corrected AQ areas were not statistically significant. The best agreement between MRI and echocardiography was with conventional echo. We conclude that automated border detection of the RV can be performed successfully with the AQ system at a fixed point in the cardiac cycle. For adequate assessment of RV function manual corrections of online AQ results are still required, which results in an important reduction of the time gain of on-line quantification.