3.1 Significant Clinical Benefits of Exercise Rehabilitation for Older persons with CHD
PCI has become the most important means of revascularization for CHD patients, not only effectively improving patients' clinical symptoms but also significantly reducing the mortality of acute myocardial infarction and high-risk angina patients. However, for older persons, the cardiovascular risk of heart failure, arrhythmia, and sudden death remain after PCI due to the added effects of age-related physiological changes. Compared to non-CHD patients, exercise tolerance is significantly reduced in CHD patients. The decline in exercise tolerance is even more pronounced in older persons with CHD, who may also have mental issues such as depression and dementia, severely affecting their quality of life [5].
Previous studies found that increased daily physical activity was associated with a reduced mortality rate in CHD patients, particularly in those who were sedentary, as they experienced greater cardiovascular benefits [6]. Cardiac rehabilitation could promote the physical and mental health of older persons, improving their quality of life [7, 8], and offer benefits for older CHD patients, such as reduced mortality and rehospitalization rates and further revascularization [9, 10]. Many studies have reported that aerobic exercise training improves exercise capacity, frailty, and quality of life in older CHD patients [11-14]. However, the patients included in these previous studies were relatively young compared with those in the current study. In particular, in CHD patients aged 75 and older, muscle degeneration and atrophy are more severe; additionally, there is a lack of ligament toughness and elasticity and a greatly reduced capacity for stress responses in the nervous system. Consequently, the risk of exercise-related injuries may increase. Providing an appropriate exercise intensity is a crucial aspect of cardiac rehabilitation, enhancing the efficacy and safety of the treatment.
3.2 Advantages of CPET-Guided Exercise Rehabilitation
CPET is an objective and accurate method for assessing cardiopulmonary function in patients after PCI and is relatively safe [15, 16]. For older CHD patients, CPET not only reflects the level of cardiopulmonary function and disease severity but could also be used to assess patients' balance ability and quality of life [17]. By providing reasonable exercise recommendations based on the collected data, CPET could be used to prescribe exercise rehabilitation programs for older CHD patients, helping to mitigate risk during exercise training.
In the past, the maximum heart rate has often been used as the standard for designing exercise programs in cardiac rehabilitation. It is usually difficult for older persons to achieve their maximum heart rate, and there are unpredictable exercise risks. Moreover, heart rate could be affected by medications such as beta-blockers. A more ideal standard is to individually evaluate patients' exercise capacity; as exercise capacity improves, CPET could provide guidance for different stages of exercise recommendations.
3.3 Impact of CPET-Guided Exercise Rehabilitation on Exercise Capacity and Exercise Habits
In this study, the average age of the patients was 80.5 ± 4.3 years. Exercise intensity was guided based on patients' anaerobic threshold oxygen uptake during exercise tests, encouraging them to engage in regular, continuous, moderate-intensity exercise. The average follow-up period was 12 ± 2 months, after which patients' exercise habits were reassessed and CPET was repeated. The results showed a significant increase in VO2peak and other indicators in the regular exercise group, suggesting that CPET-guided exercise rehabilitation can significantly improve patients' exercise capacity.
This study found that some patients' exercise habits changed during the follow-up period after receiving cardiac rehabilitation exercise guidance. At enrolment, 7.6% of patients had exercise habits but did not maintain them during the follow-up period. In contrast, more patients (22%) without exercise habits at enrolment began to develop regular exercise habits during the follow-up period.
In previous research, cardiac rehabilitation increased exercise participation in CHD patients [18]. CPET-based exercise rehabilitation guidance may help older CHD patients gain more confidence in the safety of exercise, thus increasing their enthusiasm for physical activity. Additionally, this study found that patients with exercise habits during the follow-up period had a significantly higher exercise capacity than those without exercise habits. Patients who did not maintain exercise during the follow-up period experienced a decline in exercise capacity due to age or disease progression, which may counteract the benefits gained from their previous regular exercise.
Many medical institutions conduct exercise assessments and cardiac exercise rehabilitation for older CHD patients due to concerns about exercise-related adverse events or potential risks, which limits the development of cardiac exercise rehabilitation programs. However, this study's results suggest that even older CHD patients after PCI can safely and effectively improve their exercise capacity through CPET-guided exercise rehabilitation, with the improvement of exercise habits being a crucial aspect. Current research has also explored the use of remote medical devices to improve patients' adherence to cardiac exercise rehabilitation [19, 20]. However, due to potential barriers in using remote medical devices and the greater social and economic challenges faced by older persons, further exploration of simpler and more effective methods is needed to enhance the therapeutic effects of exercise rehabilitation in this population.
This study had certain limitations, as it was a single-centre study. The results may have limited generalizability, necessitating further validation in more medical institutions. Additionally, this study was retrospective and did not involve prospective interventional research. The older persons included in the study had few comorbidities and were able to cooperate with cardiopulmonary exercise tests and exercise rehabilitation. As such, the study's conclusions may not apply to older CHD patients with multiple comorbidities, a bedridden status, or a poor exercise capacity. Furthermore, due to a high amount of missing data regarding quality-of-life scores, such as the SF-36 questionnaire scores, these were not included in the statistical analysis.