Patterns of Electrocardiographic Abnormalities in Children with Hypertrophic Cardiomyopathy.

Hypertrophic cardiomyopathy (HCM), a common cardiomyopathy in children, is an important cause of morbidity and mortality. Early recognition and appropriate management are important. An electrocardiogram (ECG) is often used as a screening tool in children to detect heart disease. The ECG patterns in children with HCM are not well described.ECGs collected from an international cohort of children, and adolescents (≤ 21 years) with HCM were reviewed. 482 ECGs met inclusion criteria. Age ranged from 1 day to 21 years, median 13 years. Of the 482 ECGs, 57 (12%) were normal. The most common abnormalities noted were left ventricular hypertrophy (LVH) in 108/482 (22%) and biventricular hypertrophy (BVH) in 116/482 (24%) Of the patients with LVH/BVH (n = 224), 135 (60%) also had a strain pattern (LVH in 83, BVH in 52). Isolated strain pattern (in the absence of criteria for hypertrophy) was seen in 43/482 (9%). Isolated pathologic Q waves were seen in 71/482 (15%). Pediatric HCM, 88% have an abnormal ECG. The most common ECG abnormalities were LVH or BVH with or without strain. Strain pattern without hypertrophy and a pathologic Q wave were present in a significant proportion (24%) of patients. Thus, a significant number of children with HCM have ECG abnormalities that are not typical for "hypertrophy". The presence of the ECG abnormalities described above in a child should prompt further examination with an echocardiogram to rule out HCM.

Impact of Obesity on Left Ventricular Thickness in Children with Hypertrophic Cardiomyopathy.

Obesity is associated with additional left ventricular hypertrophy (LVH) in adults with hypertrophic cardiomyopathy (HCM). It is not known whether obesity can lead to further LVH in children with HCM. Echocardiographic LV dimensions were determined in 504 children with HCM. Measurements of interventricular septal thickness (IVST) and posterior wall thickness (PWT), and patients' weight and height were recorded. Obesity was defined as a body mass index (BMI) ≥ 99th percentile for age and sex. IVST data was available for 498 and PWT data for 484 patients. Patient age ranged from 2 to 20 years (mean ± SD, 12.5 ± 3.9) and 340 (68%) were males. Overall, patient BMI ranged from 7 to 50 (22.7 ± 6.1). Obesity (BMI 18-50, mean 29.1) was present in 140 children aged 2-19.6 (11.3 ± 4.1). The overall mean IVST was 20.5 ± 9.6 mm and the overall mean PWT was 11.0 ± 8.4 mm. The mean IVST in the obese patients was 21.6 ± 10.0 mm and mean PWT was 13.3 ± 14.7 mm. The mean IVST in the non-obese patients was 20.1 ± 9.5 mm and mean PWT was 10.4 ± 4.3 mm. Obesity was not significantly associated with IVST (p = 0.12), but was associated with increased PWT (0.0011). Obesity is associated with increased PWT but not IVST in children with HCM. Whether obesity and its impact on LVH influences clinical outcomes in children with HCM needs to be studied.

Risk factors for lethal arrhythmic events in children and adolescents with hypertrophic cardiomyopathy and an implantable defibrillator: An international multicenter study.

BACKGROUND: Predictors of risk of lethal arrhythmic events (LAE) is poorly understood and may differ from adults in children with hypertrophic cardiomyopathy (HCM). OBJECTIVE: The purpose of this study was to determine predictors of LAE in children with HCM. METHODS: A retrospective data collection was performed on 446 children and teenagers 20 years and younger (290 [65%] male; mean age 10.1 ± 5.7 years) with idiopathic HCM from 35 centers. Patients were classified as group 1 (HCM with LAE) if having a secondary prevention implantable cardioverter-defibrillator (ICD) or primary prevention ICD with appropriate interventions or group 2 (HCM without LAE) if having a primary prevention ICD without appropriate interventions. RESULTS: There were 152 children (34%) in group 1 and 294 (66%) in group 2. Risk factors for group 1 by univariate analysis were septal thickness, posterior left ventricular (LV) wall thickness, lower LV outflow gradient, and Q wave > 3 mm in inferior electrocardiographic leads. Factors not associated with LAE were family history of SCD, abnormal blood pressure response to exercise, and ventricular tachycardia on ambulatory electrocardiographic monitoring. Risk factors for SCD by multivariate analysis were age at ICD placement (hazard ratio [HR] 0.9; P = .0025), LV posterior wall thickness z score (HR 1.02; P < .005), and LV outflow gradient < 30 mm Hg (HR 2.0; P < .006). LV posterior wall thickness z score ≥ 5 was associated with LAE. CONCLUSION: Risk factors for LAE appear different in children compared to adults. Conventional adult risk factors were not significant in children. Further prospective studies are needed to improve risk stratification for LAE in children with HCM.

Electrocardiograms in Healthy North American Children in the Digital Age.

BACKGROUND: Interpretation of pediatric ECGs is limited by lack of accurate sex- and race-specific normal reference values obtained with modern technology for all ages. We sought to obtain contemporary digital ECG measurements in healthy children from North America, to evaluate the effects of sex and race, and to compare our results to commonly used published datasets. METHODS: Digital ECGs (12-lead) were retrospectively collected for children ≤18 years old with normal echocardiograms at 19 centers in the Pediatric Heart Network. Patients were classified into 36 groups: 6 age, 2 sex, and 3 race (white, black, and other/mixed) categories. Standard intervals and amplitudes were measured; mean±SD and 2nd/98th percentiles were determined by age group, sex, and race. For each parameter, multivariable analysis, stratified by age, was conducted using sex and race as predictors. Parameters were compared with 2 large pediatric ECG data sets. RESULTS: Among ECGs from 2400 children, significant differences were found by sex and race categories. The corrected QT interval in lead II was greater for girls compared with boys for age groups ≥3 years (P≤0.03) and for whites compared with blacks for age groups ≥12 years (P<0.05). The R wave amplitude in V6 was greater for boys compared with girls for age groups ≥12 years (P<0.001), for blacks compared with white or other race categories for age groups ≥3 years (P≤0.006), and greater compared with a commonly used public data set for age groups ≥12 years (P<0.0001). CONCLUSIONS: In this large, diverse cohort of healthy children, most ECG intervals and amplitudes varied by sex and race. These differences have important implications for interpreting pediatric ECGs in the modern era when used for diagnosis or screening, including thresholds for left ventricular hypertrophy.

Anomalous left pulmonary artery origin from internal carotid artery: prospective echocardiographic diagnosis of a previously unknown variant.

We present a neonate with dextrocardia, tetralogy of Fallot, right arch, and aberrant left subclavian artery with left pulmonary artery origin from the left internal carotid artery, which is previously unreported.

Temporary atrial pacing for cardiac output after pediatric cardiac surgery.

Pediatric cardiothoracic surgery is often associated with low cardiac output in the postoperative period. This study sought to determine whether increasing heart rate via temporary atrial pacing is beneficial in augmenting cardiac output. Patients younger than 18 years who underwent cardiothoracic surgery and had no perioperative arrhythmias were eligible for the study. Patients not paced postoperatively were atrial paced at a rate of 15 % above the intrinsic sinus rate (not to exceed 170 beats per minute, less for older patients) for 15 min. Patients paced for cardiac output postoperatively had their pacemakers paused for 15 min. Markers of cardiac output were measured before and after the intervention. Of the 60 patients who consented to participate, 30 completed the study. Failure to complete the study was due to tachycardia (n = 13), lack of pacing wires (n = 7), junctional rhythm (n = 4), advanced atrioventricular block (n = 3), and other cause (n = 3). Three patients were paced at baseline. There was no change in arteriovenous oxygen saturation difference, mean arterial blood pressure, central venous pressure, toe temperature, or lactate with atrial pacing. Atrial pacing was associated with a decrease in head and flank near-infrared spectroscopy (p = 0.01 and <0.01 respectively). Secondary analysis found an inverse relationship between mean arterial pressure response to pacing and bypass time. Temporary atrial pacing does not improve cardiac output after pediatric cardiac surgery and may be deleterious. Future research may identify subsets of patients who benefit from this strategy. Practitioners considering this strategy should carefully evaluate each patient's response to atrial pacing before its implementation.

Lessons learned from preparticipation cardiovascular screening in a state funded program.

In 2007, the Texas legislature appropriated money for a pilot study to evaluate cardiovascular screening of student athletes to identify those who might be at risk of sudden death using a questionnaire, physical examination, electrocardiography, and limited echocardiography. We sought to determine (1) the feasibility of a state-wide cardiovascular screening program, (2) the ability to reliably identify at-risk subjects, and (3) problems in implementing screening state wide. The data were analyzed using established pediatric electrocardiographic and echocardiographic criteria. Positive results were confirmed by a blinded reviewer. In 31 venues (2,506 students), the electrocardiographic findings met the criteria for cardiovascular disease in 57 (2.3%), with 33 changes suggestive of hypertrophic cardiomyopathy, 14 with long QT syndrome, 7 with Wolff-Parkinson-White syndrome, and 3 with potential ischemic findings related to a coronary anomaly. Of the 2,051 echocardiograms, 11 had findings concerning for disease (9 with hypertrophic cardiomyopathy and 1 with dilated cardiomyopathy). In patients with electrocardiographic findings consistent with hypertrophic cardiomyopathy, the limited echocardiograms were normal in 24 of 33. Of the 33 who remained at risk of sudden death on the electrocardiogram or echocardiogram, 25 (65.8%) pursued the recommended evaluation, which confirmed long QT syndrome in 4, Wolff-Parkinson-White syndrome in 7, and dilated cardiomyopathy in 1. The interobserver agreement was 100% for electrocardiography and 79% for echocardiography. The questionnaire identified 895 (35% of the total) potentially at-risk students, with disease confirmed in 11 (1.23%). In conclusion, in this large state-funded project, electrocardiographic and echocardiographic screening identified 11 of 2,506 patients potentially at risk of cardiovascular disease. The questionnaire was of limited value and had a large number of false-positive results. Interobserver variation was significant for echocardiography and might create problems with limited echocardiographic screening. Finally, many subjects with abnormal screening results declined a follow-up evaluation.

Relation of right ventricular pacing site to left ventricular mechanical synchrony.

Transvenous pacing leads are regularly placed in the right ventricular (RV) apex. Pediatric patients can develop myopathic changes after long-term RV apical pacing. Left ventricular (LV) mechanical dyssynchrony, estimated with echocardiography, may explain the acute decrease in LV function and long-term histopathologic changes. Ts-4w is an established echocardiographic measurement of LV synchrony, using tissue Doppler imaging (TDI). The purpose of this study was to determine whether TDI could identify acute changes in LV synchrony during pacing from different RV sites. We prospectively measured Ts-4w and Doppler-derived cardiac output after 5 minutes of pacing in 19 subjects undergoing catheter ablation. Each subject underwent pacing at 4 sites in random order: high right atrium, high RV septum (septal), RV outflow tract, and RV apex. Ts-4w was measured during sinus rhythm and each pacing protocol, with a value >65 ms defining mechanical dyssynchrony. Ts-4w during high right atrial (32.6 +/- 17.6 ms) and septal (28.9 +/- 10.9 ms) pacing were not different from sinus rhythm (39.5 +/- 15.5 ms). RV apex (85.7 +/- 18.4 ms) and RV outflow tract (84.2 +/- 20.4 ms) pacing induced mechanical dyssynchrony (p <0.0001). In conclusion, TDI demonstrated significant differences in LV synchrony related to pacing site. Ts-4w may be useful to determine ideal lead placement because it correlates with acutely improved hemodynamics.

Managed ventricular pacing in pediatric patients and patients with congenital heart disease.

Ventricular dyssynchrony induced by ventricular pacing (VP) may predispose patients to congestive heart failure. The detrimental effects of VP are directly related to the cumulative percentage of VP (Cum%VP). Managed VP (MVP) is a novel pacing algorithm developed to minimize unnecessary VP by uncoupling atrial pacing from VP. This retrospective analysis assessed the feasibility of using MVP in pediatric patients and patients with congenital heart disease (CHD). A multicenter review evaluated all pediatric patients <22 years old and older patients with CHD that had an implanted device using a MVP algorithm. Primary outcome variables were Cum%VP and adverse events. A subgroup analysis evaluated patients that had a DDD(R) pacemaker before a MVP device and compared Cum%VP before and after initiation of MVP. From 6 centers 62 patients (mean age 21.5 +/- 9.6 years) were included; 64% had CHD. With a MVP device, mean Cum%VP was 4.3 +/- 14.6% (range 0 to 83.7): Eleven patients were eligible for subgroup analysis. Compared with DDD(R), Cum%VP significantly decreased with MVP (67.1 +/- 29.4% vs 9.2 +/- 24.8%, p = 0.002). One MVP-related adverse event occurred; a patient with intermittent atrioventricular block had symptoms with frequent nonconducted atrial depolarizations and was reprogrammed to DDD. In conclusion, MVP can be used safely and can significantly reduce unnecessary VP in pediatric patients and patients with CHD.

Genetic factors are important determinants of neurodevelopmental outcome after repair of tetralogy of Fallot.

OBJECTIVE: Adverse neurodevelopmental sequelae are common in children with congenital heart defects. Tetralogy of Fallot is part of the clinical phenotype of many genetic syndromes. We evaluated the determinants of neurodevelopmental outcome in patients with tetralogy of Fallot. METHODS: We performed a subgroup analysis of children with tetralogy of Fallot undergoing complete repair before 6 months of age who were enrolled in a trial assessing apolipoprotein E genotype as a predictor of neurodevelopmental outcome. Assessment included genetic evaluation, neurologic examination, and the Bayley Scales of Infant Development-II, yielding the Mental Developmental Index and Psychomotor Developmental Index. RESULTS: Sixty children were tested at 1 year of age. A confirmed or suspected genetic syndrome was identified in 18.3%. The mean Mental Developmental Index was 89 +/- 13, and the mean Psychomotor Developmental Index was 81 +/- 17. Scores for the Mental Developmental Index (76 +/- 13 vs 92 +/- 11) and Psychomotor Developmental Index (63 +/- 13 vs 85 +/- 15) were significantly lower for patients with genetic syndromes. The presence of a genetic syndrome was a predictor of lower Mental Developmental Index and Psychomotor Developmental Index (P = .002 and P = .001). The presence of tetralogy of Fallot with pulmonary atresia and the apolipoprotein E epsilon2 allele were predictive of a lower Mental Developmental Index (P = .001 and P = .035). No other preoperative or operative variables were predictive of worse neurodevelopmental outcome. CONCLUSIONS: At 1 year of age after repair of tetralogy of Fallot, most patients had neurodevelopmental scores within the normal range. Genetic syndromes and the apolipoprotein E epsilon2 allele were important risk factors for neurodevelopmental dysfunction and accounted for some interindividual differences in outcome.

Substrate characterization of ventricular tachycardia in a porcine model of tetralogy of Fallot using noncontact mapping.

BACKGROUND: Ventricular tachycardia (VT) in patients following tetralogy of Fallot (TOF) repair is challenging to map because of the presence of scar, patch material, and hemodynamic residua of surgery. This study investigates whether noncontact mapping can identify the arrhythmia substrate in a porcine model that involves a right ventricular outflow tract (RVOT) patch and either chronic volume or pressure load on the right ventricle. METHODS: Nine infant pigs (3-5 kg) underwent surgery involving an RVOT patch and creation of pulmonary insufficiency (PI, n = 4) or pulmonary stenosis (PS, n = 5). After a mean of 4.2 months, pigs underwent invasive electrophysiology studies (EPS) with noncontact mapping (Ensite, St. Jude Medical, St. Paul, MN USA) of the right ventricle. Automated, unipolar voltage maps (VM) were constructed during sinus rhythm. Threshold for substrate was set at -0.5 mV and incrementally adjusted to higher values until a contiguous region of low voltage was delineated. Programmed stimulation was performed to induce VT. VT activation was correlated to location of VM defined substrate. Three control pigs underwent EPS and VM. RESULTS: Free-wall RVOT substrate was identified in each of the model animals, correlating to location of the patch. The mean voltage threshold was -1.1 mV. VT was induced in 6/9 animals. Diastolic activation approximated the inferior or lateral border of the substrate in all animals. No RVOT substrate was identified in the control pigs. CONCLUSION: Automated voltage mapping of sinus beats identifies substrate for VT in a porcine model of TOF. Consistent diastolic activation of the substrate border was found during VT. Targeting this area may be useful in the ablation of VT after repair of TOF.

The roles of chronic pressure and volume overload states in induction of arrhythmias: an animal model of physiologic sequelae after repair of tetralogy of Fallot.

OBJECTIVE: Sudden death occurs in as many as 8% of patients after repair of tetralogy of Fallot and has been attributed to arrhythmias. The purpose of this study was to establish an animal model to evaluate the individual contribution of different physiologic sequelae after tetralogy of Fallot repair in the development of late-onset arrhythmias. METHODS: Forty-nine piglets were divided into 5 groups: (1) pulmonary artery band; (2) pulmonary valvotomy; (3) pulmonary artery band plus pulmonary valvotomy; (4) infundibular scar; and (5) age-matched control animals. Baseline and follow-up electrocardiograms were obtained and recorded, as well as changes in QRS duration. A total of 45 animals underwent hemodynamic evaluation and programmed electrical stimulation at 5.6 months postoperatively. RESULTS: Sustained ventricular tachyarrhythmias (ventricular tachycardia/ventricular fibrillation) were induced in 31.1%, and atrial arrhythmias were induced in 33.3%. The pulmonary valvotomy group was 30 times more likely to evidence arrhythmias than control animals for sustained ventricular tachycardia/ventricular fibrillation, as well as atrial arrhythmias (P = .01). The pulmonary artery band group was 15 times more likely to evidence atrial arrhythmias than control animals (P = .02). Prolonged QRS duration was predictive of inducibility of both atrial arrhythmias (P < .01) and sustained ventricular tachycardia/ventricular fibrillation (P = .01). Mean right atrial (P = .01) and capillary wedge (P = .01) pressures predicted atrial arrhythmia inducibility. Right ventricular end-diastolic pressure predicted atrial arrhythmia (P= .01) and sustained ventricular tachycardia/ventricular fibrillation inducibility (P = .05). Right ventricular systolic pressure did not predict inducibility of either atrial arrhythmias (P = .10) or sustained ventricular tachycardia/ventricular fibrillation (P = .94). CONCLUSIONS: Chronic right ventricular volume overload resulted in an increased incidence of inducible ventricular and atrial arrhythmias.

Impact of re-coarctation following the Norwood operation on survival in the balloon angioplasty era.

OBJECTIVES: The objective of this study was to determine the efficacy of balloon angioplasty (BA) by comparing the immediate and long-term outcomes of patients with and without re-coarctation after a Norwood procedure. BACKGROUND: Although BA has become the standard means for treating recurrent coarctation following a Norwood operation, it has been suggested that re-coarctation remains a significant cause of morbidity and mortality. METHODS: Patients who survived a Norwood operation from December 1986 through June 2001 were studied. Differences between groups were evaluated by t test and logistic regression. Survival differences were tested by log-rank tests using Kaplan-Meier survival curves. RESULTS: Fifty-eight of 633 patients underwent treatment for re-coarctation (9.2%). Thirty-five patients underwent BA (before 1988, 23 had surgery). Median age at catheterization was 6.6 months (1.9 to 35.6 months). Balloon angioplasty was successful (gradient <10 mm Hg) in 32 of 35 patients (92%). There were no BA-related deaths or neurologic complications. Recurrent obstruction after BA occurred in seven patients (20%); five underwent re-dilation. Kaplan-Meier estimates of freedom from recurrent obstruction after initial BA were 97% at one month, 79% at one year, and 79% at five years. There were no differences in survival between patients with re-coarctation treated by BA and patients who did not undergo treatment for re-coarctation. CONCLUSIONS: We found that 9.2% of patients underwent treatment for re-coarctation following a Norwood operation. Balloon angioplasty is effective, with low morbidity, no early mortality, and no difference in long-term survival when compared with patients who did not have re-coarctation. Recurrent coarctation following BA occurred in 17% of patients, usually within the first year after BA.

Postpericardiotomy syndrome after permanent pacemaker implantation in children and young adults.

BACKGROUND: Postpericardiotomy syndrome (PPS) occurs in 10% to 50% of pediatric patients after cardiac surgery. The incidence and outcome of PPS after permanent pacemaker implantation in children is not described. METHODS: A retrospective analysis was performed of all pediatric patients who underwent isolated placement of a pacemaker between January 1984 and December 2002. Patients who underwent congenital heart surgery at the time of pacemaker implantation were excluded. PPS was diagnosed on the basis of clinical symptoms with echocardiographic confirmation of a pericardial effusion. RESULTS: Four hundred and forty-three pacemakers (237 epicardial, 206 transvenous) were implanted in 370 patients (median age 10 years, range 2 months to 24 years). Eight (2%) episodes of PPS (6 epicardial, 2 transvenous) occurred in 7 patients. The median time from implantation to PPS was 12.5 days (range 8 to 22 days). Six (75%) episodes followed primary pacemaker implantation, two occurred after subsequent lead revision. Three patients were initially treated with medical therapy (1 nonsteroidal agents, 2 steroids), and 1 required subsequent pericardiocentesis. Five patients underwent initial pericardiocentesis followed by medication. One patient had echocardiographic recurrence of a pericardial effusion 3 weeks after a nonsteroidal taper, with resolution after nonsteroidal agents were reinitiated. One patient required a pericardial window for a persistent effusion. No pacemaker was explanted. CONCLUSIONS: PPS occurred in 2% of children undergoing isolated pacemaker implantation of both epicardial and transvenous systems. PPS is usually managed successfully with medical therapy. Patients with medical treatment failure were successfully treated with pericardiocentesis or the surgical creation of a pericardial window.

Midaortic syndrome in the fetus and premature newborn: a new etiology of nonimmune hydrops fetalis and reversible fetal cardiomyopathy.

Nonimmune hydrops fetalis is the final common pathway of many conditions that ultimately result in fetal anasarca. Even after extensive evaluation, the etiology of a small percentage of cases of hydrops remains unknown. We present a case of midaortic syndrome, also known as abdominal coarctation syndrome, in a fetus with hydrops and a severe cardiomyopathy. The clinical manifestations of midaortic syndrome in this fetus and premature newborn, including malignant hypertension and reversible cardiomyopathy, are detailed. The fetal pathophysiology of midaortic syndrome remains speculative, but likely includes fetal hypertension as the cause of cardiac dysfunction. To our knowledge, this is the first report of midaortic syndrome as an etiology for nonimmune hydrops fetalis.