The Pediatric Cardiomyopathy Registry: 1995–2007

Cardiomyopathy is a serious disorder of the heart muscle and, although rare, it is potentially devastating in children. Funded by the National Heart Lung and Blood Institute since 1994, the Pediatric Cardiomyopathy Registry (PCMR) was designed to describe the epidemiology and clinical course of selected CMs in patients 18 years old or younger and to promote the development of etiology-specific prevention and treatment strategies. Currently, data from more than 3000 children with cardiomyopathy have been entered in the PCMR database with annual follow-up continuing until death, heart transplant, or loss-to-follow up. Using PCMR data, the incidence of cardiomyopathy in two large regions of the United States is estimated to be 1.13 cases per 100,000 children. Only 1/3 of children had a known etiology at the time of cardiomyopathy diagnosis. Diagnosis was associated with certain patient characteristics, family history, echocardiographic findings, laboratory testing, and biopsy. Greater incidence was found in boys and infants (< 1 yr) for both dilated and hypertrophic cardiomyopathy (DCM, HCM) and black race for only DCM. In DCM, prognosis is worse in older children (> 1 yr), heart failure (HF) at diagnosis or idiopathic etiology. For HCM, worse prognosis is associated with inborn errors of metabolism or combination of HCM and another cardiomyopathy functional type. The best outcomes were observed in children presenting at age > 1 yr with idiopathic HCM. PCMR data have enabled analysis of patients with cardiomyopathy and muscular dystrophy, as well as Noonan Syndrome. Currently, collaborations with the Pediatric Heart Transplant Study group and a newly established Pediatric Cardiomyopathy Biologic Specimen Repository at Texas Children's Hospital will continue to yield important results. The PCMR is the largest and most complete multi-center prospective data resource regarding the etiology, clinical course and outcomes for children with cardiomyopathy.     

Current Practice of Exercise Stress Testing Among Pediatric Cardiology and Pulmonology Centers in the United States

The objective of this study was to characterize current practice patterns for clinical exercise stress testing (EST) in children in the United States. We conducted a survey of 109 pediatric cardiology programs and 91 pediatric pulmonology programs at children’s hospitals or university hospitals in the United States. A total of 115 programs from 88 hospitals responded (response rate, 58%). A higher percentage of cardiology programs (98.7%) have exercise laboratories compared with pulmonology programs (77.5%). Sixty-three percent of respondents have both a treadmill and a cycle ergometer. A larger proportion of respondents (76%) rely primarily or exclusively on treadmill, whereas a smaller number use cycle ergometer (24%). Sixty-seven percent of respondents reported that they include metabolic measurements in EST protocols. Respondents have varying minimum age criteria for EST, with 9% reporting ≤ 4 years, 25% reporting 5 years, 31% reporting 6 years, 16% reporting 7 years, and 20% reporting ≥8 years. Programs using cycle ergometers tend to test children at a younger age and to measure metabolic parameters. Seventy-nine percent of respondents use Bruce and modified Bruce protocols. Institutional protocols are used by 14%. Ninety percent of respondents use technicians to perform EST and 8% use nurses, but 76% require physician presence during testing. The majority of respondents (57%) perform <100 pediatric tests per year. There are wide variations in the current practice of EST among pediatric subspecialty programs in the United States. Treadmills are used more frequently than cycle ergometers, and Bruce and modified Bruce protocols are commonly used. Most survey respondents measure metabolic parameters during EST.     

Current applications and Future Needs for Biomarkers in Pediatric Cardiomyopathy and Heart Failure: Summary From The Second International Conference On Pediatric Cardiomyopathy

Biomarkers have established an important role in the diagnosis and prognosis of heart failure in adults, with early indications being that their sensitivity and specificity will be similar in the pediatric population. Since early detection of remodeling is vital to preemptive management in cardiomyopathy and in heart disease arising from congenital lesions, biomarkers may offer a means of identifying high risk patients before they develop symptoms. Although in current use, natriuretic peptides high sensitivity troponins, and C-reactive protein need to have their applications more clearly defined in pediatrics, by evidence based guidelines. Exploratory work should meanwhile continue to define the risk of disease progression in patients with dilated cardiomyopathy, and of sudden death in hypertrophic cardiomyopathy based on biomarker profiles. Further research into the interaction of the genetic basis of disease and proteomic biomarkers will be a valuable means of assessing the importance of different pathways of disease related ventricular remodeling.     

Cardiomyopathy in propionic acidaemia

Following the death of a patient with propionic acidaemia with a cardiomyopathy we reviewed 19 patients with the same disorder for evidence of cardiomyopathy. Six patients were found to meet the diagnostic criteria. Three patients died and in the other three the cardiac diease resolved completely. All patients were treated with standard therapy and some receivedl-carnitine but this did not seem to influence the eventual outcome. Cardiomyopathy is an important complication of propionic acidaemia and may be rapidly fatal.     

Cardiac Rehabilitation Improves Heart Rate Recovery Following Peak Exercise in Children with Repaired Congenital Heart Disease

We assessed heart rate (HR) recovery following peak exercise before and after a 12-week cardiac rehabilitation program in 14 children, 12.1 ± 1.8 years of age, with repaired complex congenital heart disease (CHD; 11 with Fontan surgery) and impaired exercise performance. Exercise testing using bicycle ergometry was performed at baseline, after completion of the rehab program and 1.0 ± 0.2 years after the baseline test. These data were compared to HR recovery in 15 controls (age, 12.7 ± 2.4 years) with CHD (13 with Fontan surgery) with two serial exercise tests at an interval of 1.1± 0.3 years. There was no change in peak HR between the two serial tests in either group. Peak VO₂ improved in the rehab group (26.3 ± 9.6 ml/kg/min at baseline vs 30.9 ± 9.6 ml/kg/min after rehab, p = 0.01) but remained unchanged in controls on serial testing. One-minute HR recovery (in beats per minute) improved significantly following completion of the rehab program (27 ± 15 at baseline vs 40 ± 23 after rehab, p = 0.01). Partial improvement in 1-minute HR recovery in the rehab group persisted 1 year later (1-minute HR recovery, 35 ± 19; p = 0.1 compared to baseline). There was no change in 1-minute HR recovery over time in the control group (37 ± 16 vs 40 ± 13, p = not significant). In conclusion, HR recovery following peak exercise improves in children with CHD after participation in a cardiac rehab program.     

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.     

Persistent Atrial Standstill in Noncompaction Cardiomyopathy

Atrial standstill is a rare form of bradyarrhythmia and consists of a transitory or permanent loss of the electrical and mechanical activity of the atria. It has been described in a few cases of long-standing valvular disease, amyloidosis, myocarditis, and muscular dystrophy. We report on a young female with noncompaction cardiomyopathy that progressed to congestive heart failure. Electrocardiogram showed persistence atrial standstill that was confirmed clinically and by electrocardiomyopathy, Doppler two-dimensional echocardiogram, and tissue Doppler imaging. We assume that worsening of asymptomatic noncompaction and progression to the congestive form of cardiomyopathy could be presaged by the presence of persistent atrial standstill. Thus, persistence of atrail standstill in asymptomatic cardiomyopathy is a sign of poor prognosis.     

Exercise Testing in Children with Primary Pulmonary Hypertension

Cardiopulmonary exercise testing is a useful noninvasive tool to assess physiological changes associated with exercise. Developing noninvasive methods to assess the severity of cardiopulmonary disorders, as well as the response to therapeutic interventions, is useful in conditions, such as primary pulmonary hypertension, in which invasive procedures carry significant risks. The 6-minute walk test is a simple measure of exercise endurance. Exercise studies that measure both hemodynamic and ventilatory responses provide additional information regarding the interaction of the circulatory and pulmonary systems. Subtle changes in exercise capacity may suggest deterioration prior to clinical manifestations. This may lead to an earlier reevaluation, including repeat cardiac catheterization, and subsequently changes in medical and/or surgical therapy.     

Solution-Focused Coaching in Pediatric Rehabilitation: An Integrated Model for Practice

ABSTRACT

This article describes the conceptual basis and key elements of a transdisciplinary model for solution-focused coaching in pediatric rehabilitation (SFC-peds). The model exemplifies a strengths-based, relational, and goal-oriented approach to clinical practice. It provides a distinct shift from a problem-oriented, therapist-directed approach to a possibilities-oriented approach where client empowerment takes precedence. The model facilitates client change through a method of working with client strengths and resources that involves the use of strategic questions to co-construct therapy intervention. Through client–therapist collaboration, therapy goals and plans are developed that align with client hopes, priorities, and readiness for change. SFC supports client self-determination and capacity for change through customized therapy goals and plans that are meaningful for the child and family. Implications for therapists include the need for relational expertise, practical coaching skills, and expertise in facilitating change. The need for research on the effectiveness of this approach in pediatric rehabilitation is discussed.     

Nutrition in Pediatric Cardiomyopathy

Pediatric cardiomyopathies are heterogeneous groups of serious disorders of the heart muscle and are responsible for significant morbidity and mortality among children who have the disease. While enormous improvements have been made in the treatment and survival of children with congenital heart disease, parallel strides have not been made in the outcomes for cardiomyopathies. Thus, ancillary therapies, such as nutrition and nutritional interventions, that may not cure but may potentially improve cardiac function and quality of life, are imperative to consider in children with all types of cardiomyopathy. Growth failure is one of the most significant clinical problems of children with cardiomyopathy with nearly one-third of children with this disorder manifesting some degree of growth failure during the course of their illness. Optimal intake of macronutrients can help improve cardiac function. In addition, several specific nutrients have been shown to correct myocardial abnormalities that often occur with cardiomyopathy and heart failure. In particular, antioxidants that can protect against free radical damage that often occurs in heart failure and nutrients that augment myocardial energy production are important therapies that have been explored more in adults with cardiomyopathy than in the pediatric population. Future research directions should pay particular attention to the effect of overall nutrition and specific nutritional therapies on clinical outcomes and quality of life in children with pediatric cardiomyopathy.     

Ventricular Arrhythmia in the X-linked Cardiomyopathy Barth Syndrome

Barth syndrome is an X-linked disorder characterized by dilated cardiomyopathy, cyclic neutropenia, skeletal myopathy, abnormal mitochondria, and growth deficiency. The primary defect is a mutation in the TAZ gene on the X chromosome at Xq28, resulting in abnormal phospholipid biosynthesis and cardiolipin deficiency. To date, there has been no systematic evaluation of the cardiac phenotype. We report five cases of cardiac arrest and/or placement of an internal cardiac defibrillator with documented ventricular arrhythmia. We suggest that ventricular arrhythmia is part of the primary phenotype of the disorder and that patients should be screened accordingly.     

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.     

New Paradigms in Hypertrophic Cardiomyopathy: Insights from Genetics

Understanding the genetic basis of hypertrophic cardiomyopathy (HCM) provides a remarkable opportunity to predict and prevent disease. HCM is caused by mutations in sarcomere genes and is the most common monogenic cardiovascular disorder. Although unexplained left ventricular hypertrophy (LVH) is considered diagnostic, LVH is not always present. LV wall thickness is often normal until adolescence or later, even in individuals known to carry pathogenic sarcomere mutations. In contrast, genetic testing can identify both individuals who carry pathogenic sarcomere mutations and have a clinical diagnosis of HCM, as well as mutation carriers who have not yet manifest LVH but are at very likely to develop disease. Studying this important new patient subset, designated early or preclinical HCM, allows characterization of the initial consequences of sarcomere mutations, prior to the onset of overt hypertrophic remodeling. Such study has defined novel early phenotypes, including impaired left ventricular relaxation, myocardial energetic deficiencies, and altered collagen metabolism, in mutation carriers with apparently normal cardiac morphology. These results indicate that sarcomere mutations have substantial impact on myocardial function and biochemistry before the onset of frank hypertrophy. Furthermore, animal models of preclinical HCM have identified promising new treatment strategies that may diminish the emergence of overt disease. We can now begin to reshape the paradigm for treating genetic disorders. With improved mechanistic insight and the capability for early diagnosis, genetic advances can lead to new approaches for disease modification and prevention.     

Echocardiographic assessment of cardiac function and morphology in patients with generalised lipodystrophy

Because cardiomegaly has been observed in lipodystrophic patients we studied cardiac morphology and function with one- and two-dimensional echocardiography in addition to general cardiologic examination in a series of seven patients. Muscular hypertrophy with increased chamber size and myocardial indentations were found. Two patients had asymmetrical septal hypertrophy (ASH), and two patients demonstrated systolic anterior movement (SAM) of the mitral valve. Wall motion analysis showed anomalities in four patients during contraction, in three during the early relaxation phase. Since pathological findings, probably increasing with age, were made in the majority of the patients, these findings add an additional unfavourable aspect to the syndrome.Abbreviations ASH asymmetrical septal hypertrophy - SAM systolic anterior movement - CGL congenital generalised lipodystrophy - ATL acquired total lipoatrophy - LA/Ao left atrial/aortic ratio - NRDD normalised rate of diameter decrease - NRID reduced rate of increased diameter - HOCM hypertrophic obstructive cardiomyopathy - VCF velocity of circumferencial fiber shortening     

Factors Affecting the Exercise Capacity of Pediatric Patients with Aortic Regurgitation

Although exercise testing is commonly employed to identify adult aortic regurgitation (AR) patients with early left ventricular (LV) dysfunction, the role and value of exercise testing in the management of pediatric AR patients have not been established. The purposes of this study were to evaluate the cardiorespiratory response to exercise of pediatric patients with chronic AR, examine the relation between exercise function and baseline echocardiographic measurements, and identify factors related to diminished exercise capacity (EC). The study group consisted of 26 patients aged 8 to 21 years (mean 14.4 ± 3.7) with moderate or severe AR referred for exercise physiology testing. All patients underwent a baseline echocardiographic study and a symptom-limited, progressive cycle ergometer exercise test. LV diastolic dimension averaged 120 ± 12% predicted, systolic dimension 112 ± 20% predicted, shortening fraction 0.41 ± 0.07, end-systolic wall stress 65 ± 23 g/cm², and regurgitant fraction 38 ± 16%. The average EC was 88 ± 28% (56–143) predicted. No statistically significant correlation was found between EC and any of the echocardiographic parameters studied. Nine patients had EC < 75% predicted. These individuals did not differ from patients with higher EC with regard to any of the echocardiographic parameters or with regard to peak heart rate, blood pressure, respiratory exchange ratio, and incidence of ectopy or ST depression. However, the oxygen pulse at peak exercise (an index proportional to forward stroke volume at peak exercise) was significantly depressed among patients with EC < 75% predicted (77 ± 6 vs. 106 ± 16% predicted, p < .0001). In conclusion, most pediatric patients with moderate or severe AR compensate well for their valve disease, maintain normal forward stroke volume during exercise, and have normal EC. However, a subset of AR patients have diminished EC secondary to an inability to augment forward stroke volume appropriately. These patients cannot be identified on the basis of resting echocardiographic studies. Timely identification of these patients, through formal exercise physiology testing, may have important clinical implications.     

Measurement Practices in Pediatric Rehabilitation

We investigated measurement practices in pediatric rehabilitation. We conducted a survey of 63 physical, 72 occupational, and 74 speech-language therapists working in one of 16 children's rehabilitation programs in Ontario, Canada. Therapists were surveyed about their measurement practices, and their confidence, beliefs, and attitudes about measurement. Results showed that standardized clinical measures were used frequently, but were often modified. Clinicians rated themselves as least comfortable with statistical concepts related to the uncertainty in test scores, and rated factors related to finding appropriate measures as the most important influences on their measurement practices. Some variance in measurement attitudes and practices was associated with treatment centre of practice, suggesting that there may be organizational or peer influences on measurement behaviour. The results have implications for continuing education, measurement development, and interventions designed to facilitate sound measurement practices.