Abnormalities in respiratory function are highly prevalent among patients with congenital heart disease (CHD) and are an independent predictor of all-cause mortality1 (Figure 1). Pulmonary abnormalities observed in CHD patients may involve the tracheobronchial tree, lung parenchyma, pulmonary vasculature and chest wall.2 Reduced maximum inspiratory and expiratory pressure has been reported in CHD, indicating compromised respiratory muscle strength.3 These findings are part of a larger picture of progressive heart failure, with deterioration of muscle function and detraining, especially in patients with more complex and/or palliated CHD, or those with long-standing significant residual lesions.4
Effects of resistance training on muscles and other organs.
Exercise intolerance and heart failure are multifactorial in CHD, related to a chronically low cardiac output, cyanosis, musculoskeletal anomalies, prior surgery, neurocognitive deficits et cetera, combined with an inactive lifestyle, which is common in this population.5 Detraining is often related to overprotection by parents and physicians who, in the past, and often nowadays, inappropriately advise CHD patients against exercise. This results in physical deconditioning, which has detrimental effects on exercise capacity, quality of life and outcomes. As the worldwide population of adults with CHD is expanding and becoming older, traditional cardiovascular risk factors are becoming ever more relevant, and regular physical activity becomes ever more important in optimizing long-term outcome.
In this future issue of the European Journal of Preventive Cardiology, Smith et al. present evidence of a clear association between musculoskeletal fitness and respiratory function in CHD.6 They included 538 patients aged 6–82 years, most of whom had CHD and were followed in a single tertiary centre. All patients underwent cardiopulmonary exercise testing and isometric grip strength assessment using a handgrip dynamometer. The authors demonstrated a positive association between forced expiratory volume and grip strength, which was independent of the underlying CHD diagnosis, body habitus and age. This relationship remained significant, albeit somewhat attenuated, after data were adjusted for peak oxygen consumption (peak VO2).
Until recently, major emphasis was given to aerobic fitness in patients with heart failure and/or CHD, as measured by peak VO2. As a result, the importance of musculoskeletal fitness has been less investigated and often overlooked. A recent meta-analysis demonstrated that, in patients with coronary artery disease, isolated progressive resistance training resulted in increased lower and upper body strength, and improved aerobic fitness to a similar degree as aerobic training.7 Moreover, the effects of aerobic training on fitness and strength were enhanced by progressive resistance training added to aerobic training. The association between musculoskeletal strength and respiratory function in the study by Smith et al. supports the use of exercise protocols that combine dynamic and static exercise in CHD, also targeting the respiratory muscles. Inspiratory muscle training has been shown to improve the exercise capacity and quality of life of non-CHD heart failure patients with reduced or preserved ejection fraction8,9 and is likely to be of benefit to many CHD patients.10,11 Recently, the ‘aerobic/resistance/inspiratory (ARIS) muscle training hypothesis in heart failure’ was introduced, which supports combined ARIS muscle training for maximizing the benefits of exercise in patients with heart failure.10
Respiratory function is particularly important in patients with single ventricle physiology and Fontan-type circulation, in whom systemic venous return depends, at least in part, on negative intrathoracic pressure that develops during respiration. Laohachai et al. recently demonstrated that targeted respiratory muscle training increased maximal inspiratory pressure and resting cardiac output and improved respiratory efficiency, as measured by the VE/VCO2 slope, in patients with a Fontan circulation.11 A 20-week programme of high-intensity resistance training in Fontan patients led to improved muscle strength and exercise capacity, as well as cardiac output, which was attributable to an improvement in respiratory muscle strength and muscle pump.12,13
Current adult CHD practice has shifted from cautioning patients against exercise to routinely recommending physical activity as part of daily life.14 There is urgent need to develop strategies to encourage appropriate physical activity in these patients.15,16 In this effort, patient education on the benefits of physical activity and the deleterious effects of a sedentary lifestyle is extremely important.12 Individualized exercise prescription is recommended for adults with CHD, based on cardiovascular anatomy and physiology (e.g. ventricular function, aortic dilatation, arrhythmia, pulmonary hypertension) and the results of incremental cardiopulmonary exercise testing.17 All types of exercise have a dynamic and a static (isometric) component, and patients with different cardiac conditions should be advised by CHD experts on the type and intensity of exercise that are appropriate for them. Unfortunately, there is still little evidence to support such recommendations in adults with CHD, and most guidance focuses on the eligibility for competitive sports, which is not relevant to the vast majority of individuals with CHD, in whom exercise is a means of keeping fit or part of recreation.15,16
Although the full impact of resistance training in specific CHD populations has yet to be explored, Smith et al. provide a strong rationale for future clinical studies. Such studies should ideally focus on subgroups of CHD patients with similar anatomic substrate and use individualized exercise regimens that combine static and dynamic exercise, as recommended by current expert statements, as well as respiratory muscle training.17,18
Declaration of conflicting interests
The author(s) declared no potential conflicts of interest with respect to the research, authorship and/or publication of this article.
Funding
The author(s) received no financial support for the research, authorship and/or publication of this article.
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