Introduction
The prognosis for individuals with CHD has seen a remarkable shift in recent decades. Advances in early diagnosis, surgical techniques, and percutaneous interventions have significantly increased the survival rate of CHD patients. Reference Marelli1 As these individuals live longer, the emphasis on their comprehensive management across diverse aspects of life grows in importance. Reference van der Bom, Bouma, Meijboom, Zwinderman and Mulder2
Physical activity plays a paramount role in this context. Regular engagement in physical activity and sports not only augments exercise capacity and musculoskeletal function but also reduces the risk of cardiovascular mortality and complications. Reference Duppen, Takken and Hopman3 Acknowledging its significance, clinical guidelines for CHD management actively recommend assessing physical activity levels and advocate its promotion. Reference Tran, Maiorana and Ayer4,Reference van Deutekom and Lewandowski5
Exercise capacity, denoted by peak oxygen uptake, has gained recognition as a holistic measure of cardiopulmonary function and a vital determinant of the health status of patients with CHD. Reference Wikner, Sandström and Rinnström6–Reference Diller, Dimopoulos and Okonko8 Reduced exercise capacity is commonly observed in patients with CHD. Reference Villaseca-Rojas, Varela-Melo and Torres-Castro9 A myriad of factors, ranging from chronic low cardiac output, prior surgeries, and neurocognitive deficits, to parental overprotection leading to limited physical activity, influence exercise capacity in this population. Reference Swan and Hillis10 Notably, exercise capacity has shown a stronger association with physical activity than even with cardiac structure in patients with CHD. Reference O’Byrne, Mercer-Rosa, Ingall, McBride, Paridon and Goldmuntz11
Further broadening the perspective, health-related quality of life has emerged as a salient parameter to gauge the efficacy of therapeutic outcomes in CHD patients. Factors affecting health-related quality of life offer insights into patient perceptions and the effectiveness of disease interventions. Reference Ladak, Hasan, Gullick and Gallagher12 Though health-related quality of life’s correlations with both physical activity and sedentary behaviours in patients with CHD are documented, Reference Brudy, Meyer, Oberhoffer, Ewert and Müller13,Reference Kim, Jae and Choo14 the strength of the relationship varies. For instance, Müller, Hess, and Hager Reference Müller, Hess and Hager15 found a robust association of physical activity with exercise capacity but a weaker link with overall health-related quality of life in their study based on 147 Fontan patients (aged 7–18 years). Reference Müller, Hess and Hager15
While cross-sectional analyses have posited a positive relationship between higher physical activity and enhanced exercise capacity and health-related quality of life in patients with CHD, the influence of changing physical activity levels (increase, maintenance, decrease) over time on these parameters remains an open question. Given the natural variability in physical activity behaviours over an individual’s life, understanding how these changes impact exercise capacity and health-related quality of life could unlock potential therapeutic interventions to mitigate mortality risks and improve life quality. We therefore sought to explore the longitudinal interplay between physical activity, exercise capacity, and health-related quality of life over a 3-year span in patients with CHD.
Materials and method
Study population
This retrospective longitudinal study derives from a baseline survey conducted between November 2015 and February 2016, which initially encompassed 228 patients (127 males, 101 females). A follow-up assessment took place between February 2019 and September 2019, during which participants returned to S Hospital for routine examinations. From the primary group of 228, only 104 were informed about this subsequent study. Out of those approached, five opted out, culminating in a final sample size of 99 participants (60 males and 39 females, aged 13–18 years). It is noteworthy that the exercise capacity metrics were based on 58 participants who partook in cardiopulmonary exercise tests both at baseline (2014–2017) and during the follow-up (2017–2019) periods.
Assessment of demographic and disease-related characteristics
Demographic data for patients with CHD were ascertained through self-reported questionnaires covering age, gender, height, weight, body mass index, occupation, smoking and alcohol consumption habits, as well as the NYHA functional classification. Disease-specific details were collected from medical records, encompassing past interventions, surgical procedures, hospitalisations within the preceding 3 years, current medication regimen, ejection fraction, occurrence of arrhythmias, use of pacemakers, and diagnostic data. Disease type was classified according to the ACC/AHA 2008 guidelines. Reference Warnes, Williams and Bashore16
Physical activity assessment
For the assessment of physical activity, we utilised the Global Physical Activity Questionnaire, a tool that is widely used. The Korean adaptation of the Global Physical Activity Questionnaire incorporates 15 items, partitioned into domains: work-related activities (6 items), leisure-time sports activities (6 items), and transportation-related activities (3 items). An additional item addresses sedentary behaviour. Vigorous physical activity refers to intense activities that cause heavy breathing or a significant increase in heart rate. Moderate physical activity refers to activities of moderate intensity that cause slightly increased breathing or heart rate. Sedentary time refers to all time spent sitting or lying down, excluding sleeping hours. To compute the total physical activity level, metabolic equivalent values were attributed based on the activity’s intensity. Vigorous activities were denoted as eight metabolic equivalents, while both moderate and transport-related activities were set at four metabolic equivalents. 17 Physical activity was calculated as change values at two different time points and categorised into increasing quartiles (Decreased, Little decreased, Little increased, Increased). Additionally, participants were stratified into four groups according to achieved (active) or not-achieved (inactive) recommended levels of physical activity (>150 minutes/week) at both baseline and follow-up time points: Active-active, active-inactive, inactive-active, and inactive-inactive groups. 17
Exercise capacity assessment
Exercise capacity was determined through the quantification of peak oxygen uptake during a cardiopulmonary exercise test. Peak oxygen uptake and ventilatory equivalent for carbon dioxide were evaluated using data collected during exercise, while haemodynamic variables, including heart rate and blood pressure, were assessed at rest, during exercise, and during recovery phases of the cardiopulmonary exercise test. The cardiopulmonary exercise test in this study was performed using a Q-Stress TM55 treadmill (Quinton Cardiology Systems, Inc. USA) and a gas analyser (True One 2400 Parvo Medics, Salt Lake City, UT, USA). The modified Bruce protocol was employed for the test. Criteria for determining maximum exercise capacity were set at a rating of perceived exertion Borg scale of 17 or higher and a respiratory exchange ratio of 1.10 or higher. Only data meeting these criteria were included in the analysis.
Health-related quality of life assessment
Health-related quality of life was assessed using the validated Korean version of the PedsQL 4.0 Generic Core Scales, which has been shown to have reliability and validity for patients with CHD. Reference Varni, Seid, Knight, Uzark and Szer18 The assessment scale consists of a 5-point scale, with responses ranging from “Never a problem (1 point)” to “Almost always a problem (5 points).” Each item score was transformed into a scale ranging from 0 to 100, with scores closer to 100 indicating better health-related quality of life. Health-related quality of life is composed of four subscales: Physical function, Emotional function, Social function, and School function. Cronbach’s alpha coefficient for the health-related quality of life questionnaire in this study was 0.86. To assess health-related quality of life, both at baseline and follow-up, the same researchers administered the questionnaire to each participant in a one-on-one setting. Completed questionnaires were collected immediately after completion, and any missing responses were reviewed and addressed before data aggregation.
Data analysis
The Kolmogorov-Smirnov test was utilised to confirm the normality of data distribution. Variables that did not follow a normal distribution were evaluated using non-parametric statistical analysis. Continuous variables were presented as mean ± standard deviation or median [interquartile range], and categorical variables were presented as counts (%). To examine differences over time in non-normally distributed changes in physical activity, Wilcoxon’s signed-rank test was used. Changes in exercise capacity and health-related quality of life were evaluated using paired t-tests. Correlation analysis (Supplementary Table S1) was conducted to assess the associations between changes in moderate to vigorous physical activity, exercise capacity, and health-related quality of life. Multiple regression analysis (Supplementary Table S2) was performed to independently ascertain relationships among moderate to vigorous physical activity, exercise capacity and health-related quality of life. To examine associations between changes in physical activity levels (“Decreased,” “Little decreased,” “Little increased,” “Increased”) and changes in exercise capacity and health-related quality of life, one-way analysis of variance was performed, followed by Scheffe post hoc analysis. Additionally, changes in exercise capacity and health-related quality of life based on adherence to recommended levels of physical activity were assessed using one-way analysis of variance and paired t-tests. All statistical analyses were performed using SPSS-PC version 25.0 (SPSS Inc., Chicago, IL, USA), with a significance level (p) set at <0.05.
Results
The demographic and disease-related characteristics of the study participants are presented in Table 1. Although there was a general increase in physical activity, exercise capacity, and health-related quality of life over the 3-year period, the changes were not statistically significant (all p > 0.05). No significant differences were observed in the classification based on physical activity guidelines over time (p = 0.441). Additionally, there was no statistically significant difference in relative peak exercise capacity (32.5 ± 7.9 ml/kg/minute versus 31.9 ± 7.1 ml/kg/minute, p = 0.452), and health-related quality of life (78.7 ± 15.1 versus 79.8 ± 15.6, p = 0.386), and similar patterns were observed in all subdomain scores over time (Table 2).
Table 1. Demographic characteristics of patients with CHD.
*Current smoking status = No means that “have never smoked cigarette before” or “past smoker,” Yes means that “current smoker,”; #Alcohol consumption = No means that “have never drunk alcohol before” or “less than one glass of alcohol consumed in a month in a recent year,” Yes mean that “more than one glass of alcohol a month in a recent year”
Table 2. Changes in physical activity, exercise capacity, and health-related quality of life over time.
Data = median [interquartile range], mean ± standard deviation or n (%); *Mann-Whitney.
PA = physical activity; MVPA = moderate to vigorous physical activity; HR = heart rate; SBP = systolic blood pressure; DBP = diastolic blood pressure; MET = metabolic equivalent of task; CPET = cardiopulmonary exercise test; SpO2 = saturation of percutaneous oxygen; RPE = rating of perceived exertion; RER = respiratory exchange ratio; VE/VCO2 = minute ventilation/minute carbon dioxide production; peak VO2 = peak oxygen uptake; HRQoL = health-related quality of life.
The changes in moderate to vigorous physical activity positively correlated with changes in exercise capacity and health-related quality of life (Supplementary Table S1), while the change in moderate to vigorous physical activity was positively associated with the changes in exercise capacity (ß = 0.250, p = 0.040) and health-related quality of life (ß = 0.380, p < 0.001) (Supplementary Table S2 and S3). Changes in exercise capacity were significantly lower in the Decreased physical activity and Little decreased physical activity groups (Q1, Q2), compared to the Little increased physical activity and Increased physical activity groups (Q3, Q4) (Fig 1). The group with the greatest increase in physical activity (the Increased group, Q4), showed an exercise capacity change that was approximately 9.7 ml/kg/minute higher than that of the group with the greatest decrease in physical activity (the Decreased group, Q1) (−7.0 ± 4.4 versus 2.7 ± 5.3 ml/kg/minute, p < 0.001) (Table 3).
Figure 1. Changes in exercise capacity (EC) and health-related quality of life (HRQoL) by group of changes in physical activity. *p < 0.05 versus little increased group, increased group; #p < 0.05 versus decreased group, little decreased group, little increased group. Decreased = change in physical activity <−560.0 (METs-minutes/week); little decreased = change in physical activity −560.0 to 200.0 (METs-minutes/week); Little increased = change in physical activity 200.0–880.0 (METs-minutes/week); Increased = change in physical activity >880.0 (METs-minutes/week).
Table 3. Comparison of follow-up variables between four groups classified by change in physical activity.
Data = mean ± standard deviation.
BMI = body mass index; LVEF = left ventricular ejection fraction; EC = exercise capacity; HRQoL = health-related quality of life; Decreased group (Q1) = change in physical activity <−560.0 METs-minutes/week; Little decreased (Q2) = change in physical activity −560.0 to 200.0 METs-minutes/week; Little increased (Q3) = change in physical activity 200.0–880.0 METs-minutes/week; Increased (Q4) = change in physical activity >880 METs-minutes/week; Δ = change in value (follow-up – baseline).
Changes in health-related quality of life were significantly higher in the Increased physical activity group (Q4), compared to the Decreased physical activity and Little decreased physical activity groups (Q1, Q2) (Fig 1). The group with the greatest increase in physical activity (the Increased group, Q4) exhibited a 13.5-point higher improvement in health-related quality of life, compared to the group with the greatest decrease in physical activity (the Decreased group, Q1) (9.7 ± 9.9 versus −3.8 ± 10.3, p < 0.001) (Table 3).
The Inactive-Inactive (II) group, which did not meet the recommended physical activity levels, showed notable differences in NYHA functional classification and number of medications (p = 0.007, p = 0.003), compared to the Active-Active and Active-Inactive groups. Furthermore, based on the disease type, marked differences were identified between the Active-Active and Inactive-Active groups (p < 0.001) (Table 4). Of particular interest, the Active-Inactive group showed a marked decline in exercise capacity changes, while the Inactive-Active group exhibited a significant increase in health-related quality of life (Fig 2).
Figure 2. Comparison of baseline and follow-up between classified groups by change of physical activity recommendation (150 minutes/week). *p < 0.05 baseline versus follow-up. Active-Active = baseline MVPA & follow-up MVPA ≥ 150 minutes/week; Active-Inactive = baseline MVPA ≥ 150 minutes/week & follow-up MVPA < 150 minutes/week; Inactive-Active = baseline MVPA < 150 minutes/week & follow-up MVPA ≥ 150 minutes/week; Inactive-Inactive = baseline MVPA & follow-up MVPA < 150 minutes/week.
Table 4. Comparison of follow-up variables between groups classified by change in physical activity recommendation (150 minutes/week).
Data = mean ± standard deviation.
Active (A) = MVPA ≥ 150 minutes/week; Inactive (I) = MVPA < 150 minutes/week; BMI = body mass index; LVEF = left ventricular ejection fraction; EC = exercise capacity; HRQoL = health-related quality of life; Δ = change in value (follow-up – baseline).
Discussion
In our study, we noted upward trends in physical activity, exercise capacity, and health-related quality of life over a span of 3 years, though these variations lacked statistical significance. Nonetheless, we found that changes in physical activity over time were independently associated with changes in exercise capacity and health-related quality of life. Furthermore, a decrease in adherence to recommended levels of physical activity was associated with reduced exercise capacity, while an increase in adherence to recommended levels of physical activity was linked to improvements in health-related quality of life.
Generally, levels of physical activity, exercise capacity, and health-related quality of life are factors that can change over time. For patients with CHD, these metrics often rise post-surgery due to symptomatic relief but can wane as they approach adulthood. Reference Fredriksen, Veldtman and Hechter19–Reference Moons and Luyckx21 Notably, the transition from teenage years to early adulthood represents a crucial phase where individuals shift from parental dependence to preparing for self-reliance. Reference Lenz22 This shift is especially distinct for CHD patients who, from early childhood or even infancy, have lived under the intense protective gaze of their parents due to their critical cardiac conditions. Reference Moons, Bratt and De Backer23 As a result, during this transformative phase, some CHD patients might grapple with anxiety. Compounded by the psychological stress of their chronic and potentially fatal conditions, they might drift into social isolation and reduced activity participation, subsequently impacting their quality of life. Reference Apers, Luyckx and Moons24 On the contrary, our study’s observations showed that as participants navigated from adolescence to early adulthood, there was not a significant decline in physical activity, exercise capacity, and health-related quality of life. This hints that, in a Korean context, CHD patients might experience only subtle fluctuations in these parameters during this transitional phase. Nevertheless, it is important to note that this study’s limited sample size and the relatively short 3-year follow-up period may hinder the generalisability of these findings. Further studies with larger sample sizes and longer follow-up durations would be necessary to support and validate these results.
It is commonly understood that exercise capacity in CHD patients typically decreases post-adolescence, notably in those who have had Fontan surgery, with reported yearly declines varying between 0.8% and 2.6%. Reference Jenkins, Chinnock and Jenkins20,Reference Atz, Zak and Mahony25 Surprisingly, our study did not observe any significant shifts in exercise capacity over time, a finding that diverges from prior research by Atz, Zak, Mahony et al Reference Atz, Zak and Mahony25 and Jenkins, Chinnock, Jenkins et al. Reference Jenkins, Chinnock and Jenkins20 The variations in outcomes between our study and earlier research might be attributed to the heterogeneous cardiac conditions represented in our participant pool. Moreover, an important factor to consider is that the CHD patients in our study displayed consistently high levels of physical activity from the outset and throughout the follow-up period. It is conceivable that maintaining such active physical activity levels might have countered potential decreases in exercise capacity over the span of the study.
Until now, studies examining the relationship between physical activity, exercise capacity, and health-related quality of life in CHD patients have mostly employed cross-sectional designs or have been based on physical activity interventions. Reference Duppen, Takken and Hopman3,Reference Kim, Jae and Choo14,Reference Williams, Wadey, Pieles, Stuart, Taylor and Long26
Only a longitudinal study has demonstrated that CHD patients engaging in physical activity more than twice a week led to significantly greater improvements in exercise capacity, compared to those engaging less frequently (▵peak VO2 = 1.63 ± 2.67 versus 0.06 ± 2.1 ml/kg/minute) after 2 years. Reference Dulfer, Helbing, Duppen and Utens27 However, this study presented exercise capacity changes based on a specific physical activity frequency (twice a week), which may limit a comprehensive understanding of actual physical activity changes and their direct relationship with exercise capacity. In the present study, a longitudinal design was employed to investigate variations in daily-life physical activity, revealing that changes in physical activity play a crucial role in modifying exercise capacity. Furthermore, a positive correlation between changes in moderate to vigorous physical activity and exercise capacity was demonstrated, even after adjusting for several potential confounders. Therefore, this study extends the previous findings by emphasising the impact of longitudinal physical activity changes on exercise capacity alterations.
Health-related quality of life serves as a pivotal metric when gauging treatment outcomes from the patient’s vantage point. Reference Ladak, Hasan, Gullick and Gallagher12 With the increasing longevity of CHD patients, attention has shifted from merely surgical treatments to also encompassing functional health aspects. This has amplified the importance of assessing how non-surgical measures, like lifestyle modifications, impact health-related quality of life. A systematic review by Williams, Wadey, Pieles, Stuart, Taylor and Long Reference Williams, Wadey, Pieles, Stuart, Taylor and Long26 reviewed 15 randomised controlled trials involving 924 CHD patients and posited that physical activity interventions moderately increased health-related quality of life. Reference Williams, Wadey, Pieles, Stuart, Taylor and Long26 However, there’s a notable paucity of studies exploring the effects of daily-life physical activity changes, as opposed to structured physical activity programmes, on health-related quality of life alterations. Addressing this knowledge gap, our research underscores that shifts in moderate to vigorous physical activity bear a direct correlation with health-related quality of life changes, indicating the potential of everyday physical activity adjustments to influence health-related quality of life.
This study comes with several limitations. To begin with, the study did not factor in seasonal variations when analysing shifts in physical activity from the baseline to the follow-up. Additionally, the scope of the study did not capture the full spectrum of fluctuations in physical activity, exercise capacity, and health-related quality of life between these two points. Moreover, not all potential influencing variables for alterations in physical activity, exercise capacity, and health-related quality of life were taken into account. Furthermore, even though both adolescents and adults were part of the study, there is an inherent limitation in utilising adult benchmarks for recommended physical activity levels. Notwithstanding these constraints, this investigation stands out as the first effort to evaluate the longitudinal relationship between physical activity alterations and shifts in exercise capacity and health-related quality of life in the context of Korean CHD patients.
Conclusions
Over 3 years, increased physical activity was consistently linked to increases in exercise capacity and health-related quality of life in patients with CHD. These findings underscore the potential of increased physical activity as a key intervention to improve the exercise capacity and health-related quality of life in patients with CHD.
Supplementary material
The supplementary material for this article can be found at https://doi.org/10.1017/S1047951123004031.
Acknowledgements
None.
Financial support
This work was supported by the Ministry of Education of the Republic of Korea and the National Research Foundation of Korea (NRF-2021S1A5B5A17049636) and Woochon Cardio-Neuro-Vascular Research Foundation of Korea (2018). SKK is funded by the National Institute for Health and Care Research (NIHR) Applied Research Collaboration East Midlands (ARC EM) and Leicester NIHR Biomedical Research Centre. The views expressed are those of the author and not necessarily those of the NIHR or the Department of Health and Social Care.
Competing interests
None.
