Introduction

Cardiovascular disease is the most predominant cause of death globally, with about estimated over 17 million people who died of cardiovascular disease in 2016, representing 31% of all deaths worldwide [1], among which coronary artery disease (CAD) remains one of the top killers [2]. CAD refers to the condition of vascular lumen stenosis or occlusion and vascular spasm based on coronary artery atherosclerosis, leading to myocardial ischemia, hypoxia, or necrosis [3]. CAD has become one of the causes of high morbidity and mortality and the leading cause of severe long-term disability in developed and some develo** countries.

Percutaneous coronary intervention (PCI) is the primary way to obtain revascularization in patients with CAD [4] due to advances in PCI technology and technique [5]. After PCI, knowledge of cardiac rehabilitation (CR) and timely management of complications [6] are essential health services for patients, associated with decreasing the rate of vascular restenosis and recurrent ischemia, to improve quality of life [7]. As such, CR was recommended for secondary prevention, established by the American Heart Association and American College of Cardiology after PCI [4]. CR is a complete, full-cycle, and effective medical management strategy. However, the development of CR also faces many opportunities and challenges, such as the continuity of CR throughout the life cycle of patients [8, 9]. In the in-hospital rehabilitation period, the care team supervises the patient's daily life and motor ability to recover. But many patients do not transition to outpatient CR centers and receive recommended prescriptions in time after discharge [10]. Therefore, there are still gaps in this continuous medical behavior, which may eventually lead to unsatisfactory treatment effects and prognosis for patients. Despite the obvious evidence-based benefits, the participation rate of CR remains poor [11]. The reasons why people have low adherence to the traditional facility-based CR are multi-faceted [12], such as private insurance, the travel distance to a healthcare site and possibly affiliated CR facility, demographic and clinical factors, and existing comorbidity [13]. Therefore, it is reported that the center-based CR programs were challenged by low participant rates, insufficient attendance, and high drop-out rates. As a result, there is an urgent need for effective strategies to increase patient engagement, and home-based cardiac rehabilitation (HBCR) is one of the most potent strategies [14]. It also confirmed that the benefits of HBCR in terms of exercise capacity, control of risk factors, quality of life, and cost-effectiveness is similar to center-based CR [15, 16].But how to adequately assess the patient's situation and get timely feedback is also a major issue.

Recent advances in telecommunications technology have raised the possibility of telehealth interventions delivered by CR, which is able to overcome barriers of time and distance [17], and increase the rate of utilization mainly due to avoidance of expensive medical costs [18]. Therefore, we pay attention to the fact that home-based cardiac telerehabilitation (HBCTR) for patients in the home environment can link doctors and patients, better continue in-hospital rehabilitation, and also provide rehabilitation guarantee for out-hospital rehabilitation. Previous research has shown that the sooner CR begins in patients with CAD, the greater the benefit for patients [19]. CR for patients with CAD is divided into three stages, including stage I (in-hospital rehabilitation), stage II (out-of-hospital early rehabilitation or outpatient rehabilitation), and stage III (long-term community/family rehabilitation) [20]. Each stage of rehabilitation should follow the principle of safety. Therefore, most patients eligible for HBCTR are at low to intermediate risk, or in the transition from acute to convalescent phase and convalescent phase [14]. Telehealth can be defined as providing health management through emerging mobile devices such as mobile computing, medical sensor, and communications technologies [21]. The use of telehealth has grown tremendously and covers a wide range of content, such as digital information collection, precision medicine, virtual diagnosis, and treatment. Compared to other telehealth interventions, HBCTR focuses on the rehabilitation and prognosis of heart disease patients, and the core components of management include exercise training, risk factor control, psychological counseling, drug guidance, and nutritional prescription [22, 23]. The based model established by HBCTR is: the doctors formulate the CR prescription and send it remotely, and the patients execute the prescription, report data and conduct follow-up feedback, after that doctors make the personalized modification of the rehabilitation prescription in the standardized medical behavior. The closed-loop mechanism improves the patient's self-efficacy and enhances cardiac rehabilitation compliance. Meanwhile, HBCTR appears to be a more feasible and effective innovative rehabilitation model than conventional in-hospital CR [24]. Moreover, Stefanakis et al. showed patients received HBCTR with a low rate of adverse events after being fully evaluated before receiving the intervention [25].

It has been reported that telerehabilitation has proved beneficial effect for many patients, such as stroke survivors [26], patients with knee osteoarthritis [67], a heart rate monitor with a chest strap and a web application uploaded recorded heart rate data via the Internet were used to guide the exercise process of home telerehabilitation. However, the results showed that there was no significant difference in physical fitness between home exercise training and central exercise training guided by remote monitoring. And our systematic review has some new strengths. We investigated the participants who were restricted after PCI. Post-PCI patients urgently need self-management to improve clinical outcomes, such as reducing depression and anxiety, reducing mortality and morbidity, and improving health-related quality of life (HRQoL) [68]. Compared with a former systematic review, exercise training is a core component in previous studies, but we performed this including some multidisciplinary interventions and multifaceted care, such as physical exercise, nutritional advice, and target-driven pharmacological therapies.

Limitations

There are some limitations to this study. The first limitation is the great variability and complexity of intervention models, such as different frequency and intensity forms. Moreover, the included studies used various models of telerehabilitation (different duration, frequency, length, and intensity). For example, there were a wide of telehealth intervention models, such as smartphone-based CR platforms, remote monitoring systems, wireless monitoring, and sports band with a smartphone. Therefore, future research needs to explore which model is best for these patients. Second, some results could not be quantitatively analyzed due to the relatively small sample size of the included studies. Third, we only focused on treatment efficacy and need to pay attention to operability and cost of services, which should be included in future studies. Therefore, more extensive randomized controlled trials are required in order to confirm the current evidence.

Conclusions

This systematic review and meta-analysis have proved that HBCTR can effectively improve patients' physical function after PCI. These results justify that the home-based telehealth intervention is one of the promisingly effective CR strategies that reduce cardiovascular disease risk factors. In order to further confirm HBCTR increasing uptake and make CR available, the sample size needs to be increased, and future research needs to explore which model is best for these patients.