Cardiovascular diseases are the leading cause of death worldwide¹ and affect a significant portion of the Brazilian population: more than 4 million adults in the country have coronary artery disease and approximately 160 thousand have heart failure.² Thus, the treatment and control of these diseases are considered important public health issues.

Cardiac rehabilitation (CR) is a set of activities necessary to ensure optimal physical, mental, and social conditions for individuals with cardiovascular diseases.³ Conventional or usual cardiac rehabilitation (USUAL-CR) mainly consists of patient guidance toward healthy lifestyle habits, information about heart disease, maintenance of pharmacological treatment, and possible psychosocial interventions. Although this rehabilitation model does not include structured physical exercise, it recommends regular physical activity. Another CR model is conducted in clinical centers and is based on physical exercise (CENTER-CR). This model is strongly recommended in the treatment of cardiovascular diseases due to its greater benefits;⁴ however, even though it is an effective and low-cost intervention, a low number of patients participate in CENTER-CR programs (estimated adherence < 15%).⁵ This low adherence rate is observed worldwide, especially in low- and middle-income countries, and is mainly attributed to a lack of infrastructure (e.g., the absence of centers offering such services), low rates of medical referrals, and difficulties with behavior change.^6-8 Thus, to overcome the structural barriers that reduce adherence to CR, home-based cardiac rehabilitation (HOME-CR) has emerged as an alternative or complement model to USUAL-CR and CENTER-CR. HOME-CR is a promising tool characterized by the implementation of physical exercise programs in the home environment, with direct or indirect supervision.⁴

Although some studies have evaluated the effects of HOME-CR on various outcomes, literature lacks the systematization of findings related to the effectiveness and safety of this alternative CR model. Therefore, this study was conducted a systematic review of the literature to identify the effects of HOME-CR, focused on physical exercise, on aerobic fitness and quality of life of adult and older adult patients with coronary artery disease or heart failure. The incidence of adverse events and comparison of these outcomes between HOME-CR, USUAL-CR, and CENTER-CR were also investigated.

This systematic review was conducted through a literature search of the PubMed database. Searches were performed between February and March 2024 and included studies published up to that date.

The search strategy combined MeSH terms and keywords with filters available in the database to refine the search. A specific search was performed for each primary outcome (aerobic fitness and quality of life) and included synonyms for the outcome (aerobic fitness = aerobic capacity OR oxygen uptake OR cardiorespiratory fitness OR 6 minutes test; quality of life = quality of life) and the term "home-based CR"; the terms "anxiety", "depression", and "cancer" were excluded. The following filters were also applied: randomized controlled clinical trials, adult population, and humans.

Only studies that met the following criteria were included: randomized controlled trial (RCT) design; implementation of the HOME-CR focused on physical exercise; inclusion of adults, older adults, or both with heart failure or coronary artery disease; and assessment of at least one primary outcome (aerobic fitness or quality of life). RCTs with interventions lasting more than 1 year and those involving home-based rehabilitation alongside other non-home-based rehabilitation models were excluded.

After screening titles, abstracts, and full texts, the RCTs accepted for review were analyzed in full, and the following data were extracted: study data (author, year, and country), population (age range, sex, and clinical condition), experimental design (CR models and number of participants in each group), HOME-CR (type of supervision, monitoring, and contact with participants during the intervention), exercise protocol (intervention duration, weekly frequency, and type of training [aerobic or aerobic plus resistance]), and characteristics of aerobic training (modality, duration, and intensity). For USUAL-CR and CENTER-CR, respectively, the types of guidance provided and training protocols used were analyzed. Regarding primary outcomes, the method used to measure aerobic fitness was extracted (direct or indirect measurement of peak oxygen consumption, peak metabolic equivalent, or distance covered in the 6-minute walk test), whereas the questionnaire used to evaluate quality of life was recorded.

To evaluate the results, significant changes in the outcome between pre- and post-HOME-CR were verified in each RCT. Right after, we assessed whether this change differed significantly from that observed with USUAL-CR, CENTER-CR, or both within the same study.

Figure 1 presents the detailed flowchart of study selection.

The searches for aerobic fitness and quality of life identified 77 and 66 RCTs, respectively, totaling 143 RCTs. After removing duplicates, 99 RCTs studies remained. Title screening excluded 27 RCTs, and abstract screening excluded 18 RCTs that did not meet the inclusion criteria. As a result, 54 full texts were read and 31 RCTs were excluded. Therefore, the final review included 23 RCTs.

USUAL-CR consisted only of traditional care recommendations, such as regular medical appointments and counseling on lifestyle changes (e.g., smoking cessation, healthy eating, and stress self-management), and information about the heart disease of the patient, psychosocial intervention, and continuing pharmacological treatment. Six RCTs^{13,14,18,19,22,23} also encouraged participants to maintain their physical activity levels or perform exercises independently, but without a structured exercise program.

CENTER-CR followed traditional cardiovascular rehabilitation protocols, with training modalities, duration, weekly frequency, and intensity similar to those of HOME-CR. The only difference was the place where training was conducted (i.e., clinical center vs. home).

HOME-CR varied across studies. Three RCTs conducted face-to-face supervision at the home of participants,^19,25,29 while the others used only remote methods. Of those using remote delivery, eight conducted synchronous supervision during exercise sessions.^{9,16-18,26-28,30} Among them, seven monitored heart rate and ECG during the sessions,^{9,17,18,26-28,30} while one also measured arterial blood pressure.²⁷ Hwang et al.¹⁶ used synchronous video calls via an app. All RCTs included some form of contact with participants: most (n = 20) used only remote contact (phone calls or messaging apps), and three^19,21,25 used remote and in-person contact. The frequency of contacts was daily (1 RCT),²⁷ weekly (11 RCTs),^{9,11,12,17-20,23,24,26,31} or every two weeks (6 RCTs).^{10,13,14,21,25,29}

Table 2 describes the exercise protocols employed during HOME-CR. All studies included aerobic training, and walking was the most common modality (19 RCTs),^{9,10,12-15,17-20,22,24-31} followed by cycle ergometer (12 RCTs).^{9,12-15,17,21,22,24,25,30,31} Six RCTs also included strength training.^{16,19,22-24,30} Intervention duration ranged from 8 to 48 weeks, with a frequency of 2 to 6 sessions per week. Aerobic sessions lasted between 10 and 60 minutes. Intensity varied from very light to moderate in 9 RCTs^{13,16,19,20,23-25,30,31} and reached vigorous levels in 12 RCTs.^{9-12,14,17,18,21,22,26-28}

This systematic review analyzed high-quality studies (RCTs) to assess the evidence regarding the effects of HOME-CR on aerobic fitness, quality of life, and risk of adverse events, and compare these effects with those of USUAL-CR and CENTER-CR. The main findings indicate that HOME-CR improves aerobic fitness and quality of life more effectively than USUAL-CR and similarly to CENTER-CR. Additionally, its risk profile is comparable to that of USUAL-CR and CENTER-CR.

Regarding the effects of HOME-CR on aerobic fitness, nearly all studies (87%) reported improvements in measured or estimated aerobic capacity. These improvements may reflect the expected cardiovascular benefits of aerobic training, including increased peak stroke volume, cardiac output, and muscle vasodilation, resulting in greater blood flow and oxygen delivery to active muscles. Furthermore, aerobic training enhances muscle oxidative capacity, increasing the ability to extract oxygen.^32-37 Altogether, these cardiovascular and muscular adaptations support the observed increase in peak oxygen consumption.^38,39 This physiological rationale also explains the smaller improvements seen with USUAL-CR, as this CR model does not include structured aerobic training. In contrast, the improvements in aerobic fitness achieved by HOME-CR were similar to those obtained with CENTER-CR, which employed the same structured aerobic training.

The improvements in quality of life observed with HOME-CR can be attributed to multiple physical and psychosocial mechanisms modulated by exercise training. Aerobic exercise positively affects various physiological systems, including the cardiovascular, musculoskeletal, and endocrine,^37,39 which enhances overall physical function and, consequently, the physical domain of quality of life. In parallel, aerobic training contributes to psycho-emotional improvements (e.g., enhanced mood and reduced anxiety and stress);^37,40,41 thus, improving the emotional dimension of quality of life. In addition, improved aerobic fitness may reduce fatigue, increase vitality, and enhance self-awareness, self-confidence, and self-efficacy,^37,42,43 contributing to overall quality of life. The fact that CENTER-CR also included aerobic training may explain the similar improvements in quality of life found in HOME-CR and CENTER-CR. Conversely, the absence of structured aerobic exercise in USUAL-CR may account for the more limited impact, while the emphasis on healthy lifestyle counseling and behavior change may explain the moderate improvements observed in this group.⁴⁴

An important concern regarding HOME-CR is its potential risk, particularly the possibility of severe acute cardiac events occurring away from immediate medical support. However, this review found a low incidence of adverse events (36% of RCTs evaluating this outcome reported no events). In the remaining studies, the incidence was low and similar to, or even lower than, that observed in USUAL-CR, despite the lack of structured exercise in the latter. These findings may reflect the careful planning and execution of HOME-CR programs, which were in line with the current recommendations for this intervention and included appropriate exercise prescription, monitoring, and regular contact with participants even when conducted remotely.^4,32,33

It is interesting to highlight that all HOME-CR programs incorporated aerobic training, which is the primary type of exercise recommended for CR^4,32,33 due to its well-documented benefits for cardiovascular function and cardiovascular risk reduction.³⁴ Nevertheless, while various aerobic training modalities were employed, walking was the most commonly used, which aligns with its known cardiovascular benefits, low risk, ease of implementation, and high potential for adherence,^35,36 especially in remotely supervised settings. Considering the training load, most HOME-CR programs employed a frequency of 3 to 5 sessions per week of light to moderate intensity (30 to 60 minutes per session). In most studies (65%), the total weekly training volume reached at least 150 minutes, consistent with international recommendations for CR.^4,32,33 Moreover, some HOME-CR programs included strength and aerobic training, as recommended for global health maintenance.³⁴ Therefore, exercise protocols recommended in CR guidelines can be safely and effectively applied in the home setting, yield clear benefits, and have a low risk. Supervision can also be conducted remotely, as observed in most of the included studies, via synchronous or asynchronous interactions every one to two weeks, as recommended.^4,32,33

Despite the clinical relevance of CR and the practical advantages of home-based implementation, this review identified only 23 high-quality studies in one of the main health science databases, underscoring the need for further investigation. Moreover, most studies were recent (published within the last 10 years), possibly due to recent technological advances that have enabled more precise and safe remote supervision and monitoring of exercise programs.⁴⁵ Although nearly all RCTs were conducted in Europe and Asia (i.e., high-income countries), cardiovascular diseases affect the global population and are even more prevalent and lethal in low- and middle-income countries^6,7 in which cost-effective strategies are essential. The study by Turk-Adawi et al.⁵ found that exercise-based CR offered a better cost-effectiveness ratio than other treatments, such as coronary artery bypass grafting, percutaneous coronary intervention, or pharmacotherapy. Furthermore, the costs of HOME-CR are lower than CENTER-CR.⁴⁶ Therefore, there is an urgent need to develop, implement, and study HOME-CR in low- and middle-income countries, including Brazil.

This review has limitations that must be acknowledged. First, the study design has intrinsic limitations: as a narrative systematic review, it is constrained by the available literature and does not provide quantitative pooled estimates. However, this format allowed for a broader contextual discussion of the heterogeneous findings. Specific methodological limitations also included the following: the search was conducted in a single database that is the leading database for health-related research; inclusion was restricted to studies with a maximum duration of one year because longer studies are scarce and long-term interventions may reduce adherence; and studies involving other cardiovascular conditions were excluded because the included diseases (coronary artery disease and heart failure) are the most prevalent. Regarding outcomes, this review was limited to aerobic fitness and quality of life, and future studies should explore additional outcomes.

The Central Figure summarizes the main findings of this study. In conclusion, exercise-based CR performed in home settings improves aerobic fitness and quality of life in adults and older adults with coronary artery disease or heart failure. Furthermore, its effects are superior to USUAL-CR and comparable to CENTER-CR. Importantly, this intervention had a lower incidence of severe adverse events than USUAL-CR and CENTER-CR. The benefits of HOME-CR identified in this review can be achieved after three to six months of CR programs primarily based on aerobic training, conducted in accordance with CR guidelines, and remotely supervised every one to two weeks.