The Influence of Exercise Training on Quality of Life and Psychosocial Functioning in Children with Congenital Heart Disease: A Review of Intervention Studies

Children and adolescents operated upon for congenital heart disease may show reduced exercise capacity and physical activity, associated with lowered quality of life. This review presents intervention studies on the influence of an exercise program on quality of life and psychosocial functioning in children with severe congenital heart disease. Participation in an exercise program among young people with complex congenital heart disease seemed to have positive effects on quality of life and passive leisure time spent. However, more effects of the exercise programs may have been expected. For future research it is important to critically evaluate the content of the exercise programs.


Introduction
Over the last decades, improvements in diagnostic techniques and pre-, peri-, and post-operative care have resulted in better cardiac outcomes in children with congenital heart disease. In the initial treatment era, more than 80% of children with congenital heart disease died, whereas nowadays more than 90% reach adulthood [1].
Children with mild congenital heart disease usually have few physical problems during daily activity. However, children with complex congenital heart disease may experience long-term morbidity, which may be unavoidable even after their heart surgery [2,3]. Compared with healthy peers, these children may have a reduced exercise capacity, which has been associated with a reduced health-related quality of life (HRQoL) [4]. In a recent study, sports participation, especially competitive sports, was related to better self-reported physical quality of life, and, to a lesser extent, to better psychosocial quality of life in children and young adults with congenital heart disease [5].
Being less physically active in adolescence may be associated with an increased risk of cardiovascular disease in adulthood [6]. In general, adolescents who are less physically active will be less physically active in adulthood [7]. Therefore, it is important to stimulate children and adolescents with congenital heart disease to participate in exercise to make sure they will remain physically active in the long term. Two systematic reviews [8,9] on the effects of exercise training on physical functioning and exercise capacity have shown that exercise training can be considered an effective method of improving exercise capacity. However, until now, a review specifically focusing on the effects of an In total, eight studies were eligible for this review, shown in Table 1. Two of the studies used a randomized, controlled design [10,11], two studies used a prospective, non-randomized design with controls [12,13] and four studies used a prospective design without control groups [14][15][16][17], two of which were pilot studies [16,17]. Most studies included children with severe congenital heart disease, e.g., tetralogy of Fallot, Fontan circulation, transposition of the great arteries [10,[13][14][15][16]. Two studies included various diagnoses (both mild and severe) [11,12] and one study included children with pulmonary arterial hypertension [17]. The age range in the all studies was eight to 17 years.
Five studies used a standardized exercise program that combined aerobic exercise training with light static, resistance exercises [10,12,13,16,17], shown in Table 2. Three studies had a set training intensity based on heart rate and were supervised by a physiotherapist [10,12,13]. Two studies used a sports camp in which children could choose in which dynamic sports they would participate [14,15]. One study encouraged children to participate in as much high-intensity short-term activities in daily life as possible [11].

The Effect of an Exercise Program on Quality of Life
A total of seven studies assessed quality of life as an outcome of exercise training [10,11,[13][14][15][16][17]. In one of the two randomized, controlled trials [10], participation in a 12-week standardized aerobic exercise program, under the supervision of a child physiotherapist near their home, improved self-reported cognitive functioning in children with severe congenital heart disease between 10 and 15 years old. They reported to experience less trouble with concentration and learning at school. Their parents reported that their children improved in regards to social functioning; for example, their children played with other children more frequently. Children and adolescents in the intervention group with low quality of life at baseline before exercise training improved in cognitive functioning, motor functioning and pain and physical symptoms, whereas control children with low baseline quality of life, who only received medical care as usual, did not. As to young people between 16 and 25 years old, the exercise program had no effect on their quality of life [10].
These short-term improvements of a relatively short-run exercise program are in contrast with the results of a second randomized, controlled trial in a group of children with various diagnoses between 13 and 16 years old [11]. A 52-week eHealth intervention had no effect on self-reported generic and disease-specific quality of life or in influencing daily physical activity in the long term. However, the intervention did not comprise a standardized exercise program but a mobile e-health application to promote physical activity in which adolescents could register their short-term, high-intensity activities of at least 10 min. This may also explain the contrast in results, since in a standardized exercise program [10] the children had to exercise in a gym under the supervision of a physiotherapist and wearing a heart rate monitor to help them perform their exercises within the predetermined submaximal heart rate range. This guaranteed treatment integrity whereas in the eHealth intervention, children had to register their own activities without subjective monitoring or supervision of integrity. The adherence in the standardized exercise program [10,20] was 89%, which means that, on average, four training sessions in 12 weeks were missed. Besides, three participants (3%) dropped out. In the eHealth intervention [11], 35 randomized participants (43%) did not adhere to the eHealth application; 10% of the randomized participants were active users.
The remaining five non-randomized studies used small samples. Besides, one had a voluntary control group that did not want to participate in the exercise program [13] and four of them did not have any control group [14][15][16][17]. The exercise programs in these five non-randomized studies were very diverse and it was not always clear whether they were standardized; they either used a three-day sports camp without a predetermined training intensity [14,15], a 12-week rehabilitation program in a satellite clinic of a larger hospital or in a center near the child's home [13], or a 16-week exercise program at home [16]. All studies found promising results regarding quality of life; however, no unambiguous picture can be given.

The Influence of an Exercise Program on Psychosocial Functioning
Two studies reported psychosocial functioning as an outcome after an exercise program. Both studies had comparable sample sizes in both the intervention and the control group. However, the first study [12] did not have a randomized, controlled design, and the control group consisted of volunteer control children with congenital heart disease. The other study [18] used a randomized, controlled trial design. The exercise programs differed between the two studies. The first study, with a 30% drop-out rate, used two different interventions in which children participated two times a week: either in a two-week program at a rehabilitation center or in a five-month program in a facility near the child's home. The second study, with a 3% drop-out rate, used a 12-week program in which the children participated three times a week in aerobic dynamic training in a facility near their home.
In both studies, the exercise program had no effect on self-reported general anxiety or depressive symptoms. Fredriksen et al. [12] reported a decrease in parent-reported internalizing problems in the intervention group only. Adolescents within the exercise group in the second study [18] reported a decrease in anxiety regarding exercise after the program, whereas those within the control group did not. Remarkably, in this study both adolescents and their parents in the control group reported an improvement regarding internalizing problems, such as anxiety and depression. Possibly, the two comprehensive medical and psychological assessments may have given them a feeling of safety and reassurance. These assessments, combined with the knowledge that they did not have to exercise three times a week, may have been a relief for them, and therefore may have caused the decrease in anxiety and depressive feelings.
In this last study, the exercise program had an effect on self-reported passive leisure time spent [19]. After the program, adolescents spent less time on using the computer. However, this time was not filled with active leisure activities such as walking, cycling or sports activities. This finding could be related to the finding that the exercise program had no effect on sports enjoyment in adolescents in the exercise group.

The Influence of Parental Variables on the Effects of an Exercise Program
Since parental variables may influence the well-being of children with congenital heart disease, it is important to identify these parental moderators, especially since parental anxiety and overprotection may hamper the participation of children with congenital heart disease in physical activities [21,22]. One study reported the influence of parental variables on the effects of the exercise training [23]. In that study, adolescents between 10 and 15 years old, whose parents reported anxiety or depressive symptoms, reported a decrease in their social functioning after the exercise program. They indicated that they could play or talk less comfortably with other children. Alternately, they indicated that they felt less at ease with other children.

Discussion and Conclusion
Although the design and results of the included studies were very diverse, participation in an exercise program among young people with complex congenital heart disease seemed to have positive effects on quality of life and passive leisure time spent. Unfortunately there is no strong evidence emerging from the included studies as to which exercise program had the most effective content to influence quality of life and psychosocial functioning. The only randomized, controlled trial performed until now, with a standardized 12-week exercise program in which children participated three times a week (with 89% adherence) in aerobic dynamic exercise training, reported improvements in quality of life. However, more effects of the exercise programs might have been expected. For future research, it is therefore important to critically evaluate the content of the exercise programs. Most included studies used aerobic exercise training with light static resistance exercises; however, the effects of high-intensity resistance training are unknown. Besides, the programs should be attuned to the individual needs of these young people with complex congenital heart disease to make them more attractive for them and to improve adherence. The use of technological interventions such as virtual reality might motivate children and adolescents to participate in physical activity. A contemporary example is the popularity of Pokémon Go and its effect on physical activity in children and adolescents [24]. Although the relationship between physical activity and quality of life in children with congenital heart disease is not clear [4], such an intervention might improve their quality of life.
Adding a psychosocial component to the exercise programs could have had a greater impact on quality of life and psychosocial functioning. Morrison et al. designed an exercise program for adolescents with congenital heart disease with psychological methods such as a motivational interview and monthly contact moments to check on the progress of their exercise plan [25]. This intervention improved moderate-to-vigorous physical activity in the intervention group. In addition, although not mentioned, such an intervention could have had an impact on quality of life and psychosocial outcomes. On the other hand, Klausen et al. found that a 52-week Internet-, mobile app-, and SMS-based eHealth program to encourage physical activity improved daily physical activity [11]. However, they found no improvements in generic or disease-specific HRQoL in children compared with control children. The influence of an eHealth motivational program in combination with an aerobic exercise program (monitored on integrity and adherence) on quality of life in children and adolescents with congenital heart disease has, to our knowledge, never been studied in children and adolescents with congenital heart disease.

Clinical Implications
Comparable to the well-known guidelines for young people in the general population, young people with congenital heart disease should also be encouraged to participate in 60 min of daily physical activity [26]. It is important to especially encourage those children and adolescents with a low quality of life, since they benefit the most from a standardized exercise program. As for the recommendation for clinical practice, in order to identify these children with low quality of life, semi-structured questions regarding sports participation, anxiety towards sports, and depressive symptoms in both children and their parents could be integrated in outpatient visits. This review reported contrasting outcomes as to which exercise (programs) children with congenital heart disease may benefit the most from. For future research, it is recommended to assess the effects of different kinds of exercise programs (e.g., high-intensity resistance training, augmented virtual reality, or adding a psychological, motivational component) in systematically tested, large, multicenter trials to enhance generalizability. Besides, children and adolescents should be involved in designing an exercise program in order to improve their quality of life.