Congenital heart disease (CHD) occurs in 1% of all live births. Medical and surgical advancements over time have improved the survival rates of newborns and children with CHD. Approximately 90% of children with a repaired CHD defect will survive well into adulthood. It is estimated that there are approximately 1 million children and adolescents who live with CHD in the United States (https://www.cdc.gov/ncbddd/heartdefects/data.html).
Children and adolescents with CHD often have decreased exercise capacity and muscle mass [1,2]. Decreased exercise capacity may place these patients at an increased risk of developing chronic conditions such as obesity, type 2 diabetes, depression, and anxiety. The cause of decreased exercise capacity in children with CHD is multifactorial, including external factors leading to a sedentary lifestyle as well as hemodynamic limitations caused by the CHD. For example, in complex CHD, sinus node dysfunction may affect heart rate (HR) response during exercise. Pulmonary and musculoskeletal disorders may also contribute to decreased exercise capacity in this patient population.
Regular exercise has been shown to be associated with many physiological and psychological health benefits at any age and is recommended by the American Heart Association, Center for Disease and Prevention (CDC), and European Pediatric Cardiology Association . For children aged 6–17 years, the CDC recommends participating in at least 60 min of daily moderate-to-vigorous intensity physical activity daily (Fig. 1), and clearly indicates that a greater volume of physical activity is associated with greater health benefit . This primarily includes aerobic physical activity, but also some strength training and bone strengthening activity.
In the past, clinicians have restricted physical activity for patients with CHD due to concerns that increased activity might be dangerous. However, more recently there is an understanding that promoting physical activity benefits the health and well being of children and adults with CHD. It is not clear that activity restriction reduces risk of sudden cardiac death in patients with CHD, as sudden cardiac death occurs more commonly at rest than during exercise in patients with CHD . As the benefits of regular exercise become evident, the challenge for clinicians is to tailor the exercise recommendations to each patient depending on the clinical status and type of CHD to ensure safe participation in regular physical activity.
Physical activity guidelines for children with CHD are similar to those for the general pediatric population in majority of the cases . Exercise is safe in the majority of patients with CHD and can improve exercise capacity, muscle mass and strength, prevent the development of comorbidities such as obesity, type 2 diabetes, and hypertension, and improve symptoms of anxiety or depression, and quality of life (Fig. 2) .
Despite these known benefits and the guidelines, children and adolescents with CHD often do not exercise regularly. There are several contributing factors (Fig. 3). First, these children carry the diagnosis of CHD – a heavy burden to bear from a young age on – and have most likely been asked to restrict themselves at some point during their care. As a result, they might be scared to exercise and have probably never learned how to exercise properly. Second, some parents might impose exercise restrictions on their children as they are concerned about their children's cardiac condition. Finally, a sedentary lifestyle leads to decreased exercise capacity and muscle mass and can ultimately result in obesity and hypertension, turning this in a vicious cycle. Furthermore, an inactive childhood poses a triple risk for a sedentary lifestyle in adulthood [5▪].
There is an emerging concept of using exercise as a prescription. Exercise can be used in a dose-dependent manner to positively impact health outcomes for individuals with a chronic condition. In the field of pediatric cardiology, our main clinical focus has been on exercise restrictions and determining on what type of exercise our patients should not do, rather than prescribing exercise to our patients appropriately and routinely. Some pediatric programs provide on-site cardiac rehabilitation programs in clinic; however, patients often are not able to adhere to these programs due to difficulties with transportation or missing school or work which leads to poor adherence.
The purpose of this review is to summarize the current literature on exercise in children and adolescents with CHD.
With recent advancements in the field, clinical focus in pediatric cardiology has expanded from improving mortality to improving long-term outcomes and quality of life. As part of this paradigm shift, there is emerging research to evaluate the safety, impact, and effective delivery of exercise to pediatric CHD patients with the overarching goal of promoting an active lifestyle. There is paucity of recent publications, as most of the research building on prior work is still in progress.
Impact of different types of exercises
Historically, the impact of aerobic rather than other types of exercise on cardiovascular health in the general population has been studied the most. Recently, however, there has been more focus on resistance training and its impact on muscle mass.
- (1) Aerobic exercise: A recent systematic review in 621 children with CHD participating in regular aerobic exercise training programs reported an average of 8% increase in VO2max, a validated measure of exercise capacity. None of the patients in these studies experienced adverse exercise-related events.
- (2) Resistance training: Low-to-moderate intensity strength training of individual muscle groups is safe in the majority of CHD patients (i.e., a high number of repetitions 10–15, with lower resistance). High-intensity strength training has not been examined in this cohort and may increase the risk of injury and could increase blood pressure, decrease cardiac output, and cause bradycardia in some patients with CHD. High-intensity strength training should be avoided in this group until further research is available.
- (3) Flexibility and mobility training: Dynamic stretching exercises have been included as a component of numerous exercise intervention studies (such as warm-up prior to aerobic or resistance training). This type of low-intensity movement prepares the body for exercise therefore children with CHD can likely safely participate in flexibility training.
Duration and frequency of exercise
A review of exercise training programs in pediatric CHD patients has reported the duration of the interventions to be an average of 12-weeks, with exercise sessions held 3×/week and training intensity set at a percentage of the patients’ peak HR. While systematic review data largely showed a positive change in the main outcome measure after the training period (72% of studies) and no negative findings reported (0/31 studies), the long-term outcomes data (e.g., adherence and health outcomes) are limited and further investigation is needed [6▪▪].
Delivery mode of exercise
To achieve results, an effective mode of delivery of the exercise program is vital. Patients and parents often are not able to attend on-site clinic exercise programs as they face difficulties with transportation or missing school or work.
Recently, McKillop et al. published a compelling article on the impact of motivational interviewing to improve moderate-to-vigorous physical activity in adolescents with CHD. The participants randomized to the intervention received one-on-one phone-based adapted motivational interview sessions over 3 months. The interviews were feasible, however, there were no significant differences found in their outcomes which were acceptability, change mechanisms (stage of change and self-efficacy), and limited efficacy (physical activity, fitness, and quality of life). Participants accumulated 47.24 ± 16.36 min of moderate-to-vigorous physical activity per day and had comparable outcomes with peers without heart disease (except for functional capacity).
Recently, our team has demonstrated that a live-video-supervised exercise and diet intervention is feasible in pediatric heart transplant recipients. The 12–16-week intervention phase included live-video-supervised exercise (3×/week) and nutrition (1×/week) sessions. The 12–16-week maintenance phase included 1×/week live-video-supervised exercise and nutrition sessions and 2×/week self-directed exercise sessions. Our results demonstrated excellent adherence with significant improvements in cardiovascular and functional health [8▪▪]. Fourteen patients (median age, 15.2) at a median of 3.3 years after heart transplant completed the intervention. Patients attended 89.6 ± 11% of exercise and 88.4 ± 10% of nutrition sessions during the intervention and 93.4 ± 11% of exercise and 92.3 ± 11% of nutrition sessions during maintenance. After intervention, BMI percentile (median, −27%; P = 0.02), endothelial function (median, +0.29; P = 0.04), maximum oxygen consumption (median, +2 ml/kg/min; P = 0.002). Functional Movement Screening total score (median, +2.5; P = 0.002) and daily consumption of saturated fat (median, −6 g; P = 0.02) improved significantly. After maintenance, improvements in maximum oxygen consumption (median, +3.2 ml/kg/min; P = 0.02) and Functional Movement Screening total score (median, +5; P = 0.002) were sustained.
Furthermore, there is currently a cluster randomized controlled trial starting in Canada to implement an evidence-based, multifaceted physical activity intervention in pediatric CHD patients. This trial aims to determine whether providing resources and protocols enables clinicians to counsel about physical activity as part of every pediatric cardiology appointment. Intervention patients will be counseled with five key physical activity messages, have questions about physical activity answered, and have access to a custom web site with personalized activity suggestions and support from a Registered Kinesiologist. The primary outcome is daily physical activity (number of steps, minutes of moderate-to-vigorous activity) assessed via pedometer 1 week/month for 6-months.
Practical applications for prescribing exercise in pediatric congenital heart disease patients
Exercise interventions are generally safe, feasible, and beneficial in children with CHD. With a team approach and careful assessment, each CHD patient can be prescribed an individualized exercise regimen safely (Fig. 4).
Regular clinical assessment of maximal exercise capacity in patients with CHD may be useful to monitor disease progression and evaluate safety guidelines for participation. A maximal cardiopulmonary exercise test may have prognostic value and may also be used to determine if any impairment in peak exercise performance exists or if an abnormal heart rhythm develops during exercise stress. These clinical tests can be used to provide exercise clearance for children and adolescents with CHD.
As recommended by the European Pediatric Cardiology Association, most children with CHD should participate in 60 min/day of moderate-to-vigorous physical activity (40–85% of VO2peak) (Fig. 1) [6▪▪]. This primarily includes aerobic physical activity, but also some strength training and bone strengthening activity. Progression in exercise duration (e.g., shorter exercise bouts of physical activity, while slowly and consistently working toward 60 min of endurance type exercise) is recommended. As the safety and effectiveness of higher intensity interval exercise (HIIT) has not been determined in CHD cohorts, HIIT should be avoided until further evidence is reported.
In patients with ventricular dysfunction, elevated pulmonary artery pressure, right or left ventricular outflow tract obstruction, and/or dilation of the aorta, the intensity of daily physical activity should be reduced to a moderate or low level depending on the severity of the abnormal cardiac condition (Fig. 1).
In patients with hypoxia, the intensity of activity should be determined by a walk test with concurrent oxygen saturation monitoring. CHD patients on anticoagulant therapy or with an implanted device (e.g., pacemaker) should avoid contact sports.
Patients with history of exertional syncope should be counseled to avoid activities that would endanger themselves or others should an event occur (e.g., horseback riding, scuba diving, rock climbing, and gymnastics).
Exercise recommendations in cardiomyopathy, long QT syndrome, and other congenital channelopathies, some arrhythmias, and congenital coronary artery anomalies should be discussed and determined with the electrophysiology and cardiomyopathy team.
Follow-up clinic visits
During follow-up visits, clinicians should assess the daily physical activity of their patient and adjust their recommendations based on activity history and the patient's clinical status. Patients should be asked about any physical activity experience that raised concerns. In patients with activity restrictions, cardiorespiratory assessment of physical activity including exercise testing is suggested every 3–5 years, or more often if there are concerns about a change in the risk of physical activity .
There remains a large gap in the literature regarding exercise suggestions and recommendations in children with CHD. This area of research should be a continued priority globally as exercise is a powerful tool to improve health.
Exercise interventions are generally safe, feasible, and beneficial in children with CHD. There is growing evidence demonstrating the benefits and utility of exercise as a prescription rather than restriction in patients with CHD. With a team approach and careful assessment, each CHD patient can be prescribed an individualized exercise regimen safely. Novel approaches and use of new technology are needed for effective delivery of exercise in this vulnerable population. Further studies are warranted for assessment of long-term benefits of exercise in pediatric CHD patients.
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Conflicts of interest
There are no conflicts of interest.
REFERENCES AND RECOMMENDED READING
Papers of particular interest, published within the annual period of review, have been highlighted as:
▪ of special interest
▪▪ of outstanding interest
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8▪▪. Chen AC, Ramirez FD, Rosenthal DN, et al. Healthy hearts via live videoconferencing: an exercise and diet intervention in pediatric heart transplant recipients. J Am Heart Assoc 2020; 9:e013816.