Congenital Heart Disease versus Coronary Artery Disease

The term “heart disease” in children is a bit of a misnomer. Adult coronary heart disease is typically acquired atherosclerotic or degenerative valve disease that develops over time and is often abbreviated CHD. In contrast, congenital heart disease or congenital heart defects are anatomic malformations that occur during cardiac development in the embryo. The abbreviation is the same, CHD, which further blurs this important distinction. For the remainder of this chapter, the abbreviation CHD will be used to represent congenital heart disease or congenital heart defects by convention, although congenital heart “conditions” may be more appropriate.

Based on the 2010 Centers for Disease Control and Prevention (CDC) statistics, there are just over 2 million US infants, children, adolescents, and young adults living with congenital heart defects. CHD are the most common type of birth defect, affecting approximately 40,000 (1%) of births per year in the United States. There is a wide range of types of heart defects, and the spectrum of severity as well as unique combinations of lesions makes for a diverse patient population. It is important to note that children can develop acquired heart disease as well, yet it is less common and has a different composition than that typically seen in older adults. Acquired conditions in children include inflammatory or infectious heart disease, such as rheumatic heart disease, endocarditis, and Kawasaki’s disease. Genetic cardiomyopathies and channelopathies with delayed phenotypic expression can also occur. Last, certain severe familial hyperlipidemias may also lead to coronary artery disease in the young, but this is rare.

With the advancements in the field of CHD, survival is the expectation, and babies born with CHD today are living longer and healthier lives than in any past era. Therefore, it is essential that health care providers caring for pediatric patients with heart disease promote healthy and active lifestyles and maximize potential from early ages. The underlying pathophysiology in adult-onset heart disease is different from that of CHD in children. The goals of a structured, supervised exercise and secondary prevention program therefore are very different between the two and require specialized considerations. Also, the smaller numbers and highly specialized care required for these young patients leave a gap in regional resources and expertise and create challenges when configuring a pediatric cardiac rehabilitation program.

Physical Activity in All Youth

Physical inactivity in all youth is a major health concern in the United States, not just for those afflicted by a cardiac condition. Currently, most American children and adolescents without disease do not meet the physical activity recommendations of at least 60 minutes of moderate to vigorous physical activity per day.¹ It is also known that participation in physical activity declines as young people age, which is an alarming trend.² Unfortunately, children with CHD when compared with unaffected peers often have poorer levels of daily physical activity and are at higher risk for obesity and other cardiovascular risk factors compounded on their underlying defects.³ Therefore, CHD patients should be encouraged and motivated to participate in lifelong physical activity to prevent acquired heart disease in addition to reaping the immediate functional benefits.⁴

Research from adult cardiac rehabilitation programs has shown significant benefits in both physiological and psychosocial realms. These same benefits have been well documented for over 35 years in children and adolescents with CHD who engage in structured exercise and heart-healthy programs.⁵ Despite the clear need and benefit, pediatric cardiac rehabilitation programs for children and adolescents living with CHD are almost nonexistent in the United States compared with the adult population. There are only a handful of hospitals within the United States offering this type of program to their patients with CHD. Hence it is vital for more institutions to create, develop, and implement these programs in their own health care practices.

Sports Participation

Often one of the most difficult and controversial decisions providers are asked to make is whether to allow children with CHD to participate in sports due to concerns about safety and risk of sudden cardiac death. With the known benefits of physical activity and harsh repercussions of a sedentary lifestyle, it can sometimes be a challenge to make such a decision. It is important to emphasize that all individuals with CHD should be encouraged to be physically active. Pediatric cardiac rehabilitation programs can help improve cardiovascular function and in some cases can advance return to sport in individuals temporarily debilitated due to intercurrent surgical or interventional procedures. The decision about participation in competitive athletics is a different question than physical activity promotion and requires thoughtful and individualized assessments that are outside the scope of this chapter.

Goals

Participation in physical activity yields not only cardiovascular benefits but a multitude of social and emotional benefits as well. These benefits include cultivating friendships, increasing self-esteem, and building a sense of community and support. Ideally, a pediatric cardiac rehabilitation program will address the range of hemodynamic and developmental needs of this population. Typical adult cardiac programs seek to delay the downhill natural history of the underlying disease process and return to a former state of health and employment. In contrast, for pediatric to young-adult patients with CHD, the goal is to help them maximize their current and future potential. Other goals include the development of enhanced confidence in activity and control over an aspect of one’s own health. Furthermore, pediatric cardiac rehabilitation programs are comprehensive. Additional goals include an improved exercise capacity, a decrease in sedentary behavior, an increase in daily physical activity, better self-efficacy, development of a sense of accomplishment, and the learning of heart-healthy habits that participants can use throughout their lives.

Definition

While a multitude of published studies have cited the benefits of physical activity and structured exercise in patients with CHD, there are no data regarding optimal training regimens, intensity or pace of training, or how to best achieve behavior change and gain widespread self-confidence. Thus, the basic elements have been borrowed from the adult literature.

Our definition of cardiac rehabilitation for this population is as follows. A congenital cardiac rehabilitation and heart-health program is a medically supervised program designed to optimize a CHD patient’s cardiovascular function, self-efficacy and confidence, social functioning, nutrition, and habits for leading a heart-healthy life. This includes physician-prescribed, developmentally appropriate exercise and physical activity goals, patient and family education, school or community education, psychosocial assessment, nutrition assessment, and outcomes assessment. In our institution, we broadly mapped the adult elements to generate a blueprint for the CHD population (Table 61–1) to serve as a basis until we have developed a more formalized curriculum based on expert consensus and existing literature.

Principles of Training

To improve fitness, the American College of Sports Medicine has published guidelines for training to follow the “FITT principle,” or identifying frequency, intensity, time, and type of exercise. For the first three, the CDC recommends at least 60 minutes of moderate- or vigorous-intensity aerobic physical activity daily, with at least 3 days per week including play at a vigorous intensity such as bike riding, brisk walking or running, dancing, or playing active games such as tag or basketball. As part of those 60 minutes, on at least 3 days per week, there should be muscle-strengthening activities such as playing on a jungle gym or climbing for younger children and gymnastics or supervised strength training for older children and teenagers. Last, on at least 3 days per week, some of the 60 minutes should include weight-bearing activities that strengthen bones, such as skipping, jumping, running, or, for appropriate ages, push-ups, pull-ups, or body-weight exercises. Given the developmental levels of various children, variety and fun should be woven into all activities for compliance.

Within these guidelines, there are two main types of exercise training that can yield improved cardiovascular function: moderate continuous training (MCT) and high-intensity interval training (HIIT). MCT is the mainstay of adult cardiac rehabilitation programs, with demonstrated safety and efficacy. HIIT programming works at near-maximal intensity for brief sports and has the advantage of time efficiency and appeal to children and teens. In essence, HIIT programming mimics their play (such as games of tag) on the playground. Both programs have their place in a formal supervised exercise program and, in the adult literature, have probably equal benefit. Specific patient characteristics, interest, time/space constraints, and the presence of any comorbidities such as orthopedic abnormalities may dictate optimal programming at the individual patient level.

Cardiopulmonary Exercise Testing in Children

Exercise testing is a common noninvasive test used in the pediatric cardiac patient population and can be beneficial for diagnostic and therapeutic purposes. One of the primary goals for performing exercise testing in this population is to provide health care professionals with an opportunity to gain valuable, objective insights into clinically important aspects of a patient’s cardiopulmonary function. The purpose of pediatric exercise testing is to

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  Identify mechanisms that limit exercise capacity from cardiac and other comorbidities

  
  
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  Evaluate symptoms with exercise

  
  
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  Detect for exertional arrhythmias

  
  
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  Assess arterial oxygen saturation with exercise

  
  
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  Assess for pulmonary limitations with exercise

  
  
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  Use as a sequential functional assessment for patients with CHD

  
  
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  Determine appropriate guidelines for an individualized exercise prescription

What can be most challenging when it comes to exercise testing is determining the appropriate test protocol and equipment modality. The exercise test protocol should be driven by the clinical question and data that are needed from the test. There are various types of exercise tests, and there are advantages and disadvantages to all of them. The most commonly used exercise tests are cardiopulmonary exercise tests (CPETs; also known as a “metabolic study” or “met cart”) and standard exercise treadmill tests such as the Bruce protocol. In all types of exercise tests, the patient’s heart rate, electrocardiogram (ECG), and blood pressure are continuously monitored. Oxygen saturation and pre-/postexercise spirometry can also be measured when appropriate. Manual exercise test protocols can also be helpful in attempting to elicit exercise-induced symptoms and may be appropriate in special clinical conditions.

Safety of Testing

For children with CHD, cardiopulmonary exercise testing is extremely low risk.⁶ As for any procedure, the benefits and information derived from the test need to be weighed against potential risks. The majority of events are low-severity neurally mediated syncope and clinically insignificant nonsustained arrhythmias. While there are different models of supervision, we have used a model in which all cases are directly supervised by a trained exercise physiologist and performed within a cardiology clinic. The nursing and physician staff in the clinic serves as the immediate resource for any event. Preidentified higher-risk studies, which may represent about 10% of studies, have direct physician supervision. There are some guidelines that would place these patients into a higher-risk category.⁷ Despite the guidelines, individual institutions may craft their own policies because local care patterns will appropriately reflect the precise resources immediately available to the laboratory. Table 61–2 shows a list developed in the exercise laboratory at Boston Children’s Hospital for children with diagnoses who meet high-risk criteria requiring careful assessment of risk versus benefit and physician supervision to proceed with testing.

In a recent retrospective review of exercise tests performed at Boston Children’s Hospital between 2013 and 2015, the authors noted that “dangerous arrhythmias are rare during exercise testing in a high volume pediatric cardiology program. Pre-defined high risk criteria identify all patients with the most serious events. The absence of any criteria predicts a very low risk for arrhythmias requiring test termination.”⁸

Congenital Heart Disease

There is a distinctive and marked difference between cardiac rehabilitation programs designed to address coronary artery disease with a goal of secondary prevention and programs targeted to meet the hemodynamic and developmental needs of pediatric patients with CHD. Rather than “rehabilitation,” the main thrust for patients with CHD is optimization of hemodynamics and promoting confidence to be physically active at each stage of life. Moreover, to avoid compounding the risk from their CHD with later atherosclerotic disease, it is important to set lifelong heart-healthy habits at an early age. Indeed, in addition to the burden from their structural heart defects, children with CHD tend to be more sedentary than their peers and have higher rates of obesity.⁶ There has been a national call to promote physical activity in children, teens, and young adults with CHD.⁹ Despite the need, very few programs are available, as well as limited information regarding optimal frequency, intensity, time, and type of activities to promote health and mitigate risk. Additionally, there are no known best practices that motivate these patients to become more active, promote pediatric cardiovascular health education, and engage families in setting optimal heart-healthy habits.