Cardiovascular diseases (CVD) remain the leading contributor to global premature mortality and morbidity. In Europe, more than 4 million people die from CVD every year, with more than 1.4 million dying before the age of 75 years [1]. Today, secondary prevention of CVD, including coronary artery disease (CAD), by means of cardiac rehabilitation (CR) is considered a class IA recommendation by the European Society of Cardiology, American Heart Association, and American College of Cardiology [2]. CR is now recognized as an essential part of contemporary CAD management that has significantly contributed to the observed reduction in cardiovascular mortality and disability by facilitating the adoption of and adherence to healthy behaviors and promoting an active lifestyle [3]. However, the majority of patients fail to achieve secondary prevention targets in the long term [4]. Many patients receiving center-based CR adopt healthier lifestyles but relapse into old habits when returning to everyday life. After completion of a structured, supervised, exercise-based CR program without any extended support or follow-up, the assumption, of both the participant and CR staff, is that the patient will be able to self-maintain these appropriate health behaviors and optimal CVD risk profile. Unfortunately, studies have shown that patients exiting center-based CR have difficulty retaining the positive benefits derived from their participation [5]. Moreover, previous reports indicate decreased exercise adherence and increased body weight and serum lipid levels as early as 6 months after CR [4,6].

Consequently, there is a need for innovative CR methods to increase long-term adherence to a physically active lifestyle that will result in more sustained effects on health-related physical fitness and cardiovascular health, thus, reducing morbidity and mortality [7]. One attractive strategy is the use of home-based exercise training in combination with telemonitoring guidance. Home-based programs may overcome barriers associated with participation in a center-based exercise program, and they have been shown to provide comparable long-term effects on mortality, recurrent coronary event risk, and cardiovascular risk factors in patients with CVD [8]. This has been attributed partly to the fact that home-based interventions focus more on the development of self-regulatory techniques that create empowerment and perceived control, resulting in longer lasting effects on physical activity improvements [9]. That is, individuals who develop their own physical activity plans are more likely to adhere to these plans than those who have a structured exercise plan imposed on them [9]. The use of information and communication technology to augment home-based programs also enables the provision of additional feedback, education, and counseling [8].

A recent meta-analysis by Buckingham et al [10] found no significant differences in the short-term (<12 months) or long-term (>12 months) patient outcomes including exercise capacity, modifiable risk factors (blood pressure, blood lipid concentrations, and smoking), health-related quality of life (HRQoL), and cardiac events (mortality, coronary revascularization, and hospital readmissions) among patients participating in home-based or center-based phase II CR. However, there is little evidence about the added benefits of a home-based exercise program for patients being discharged from center-based CR compared with advice only.

In this paper, we report on the secondary objective of the TeleRehabilitation in Coronary Heart disease (TRiCH) study. We aimed to investigate the short-term effect of an HR CR program with telemonitoring guidance on physical fitness and other secondary outcomes in CHD patients following completion of a center-based CR program. We also aimed to compare the effectiveness of this program with that of a prolonged center-based CR program by means of a randomized controlled trial (NCT02047942). The longer-term results of the TRiCH study will be published in a second report.

A total of 90 CAD patients agreed to participate and were randomized to home-based group (n=30), center-based group (n=30), and control group group (n=30). Figure 1 shows the flow of patients throughout the study. Six patients, (4 men: control group, n=4; home-based, n=2) dropped out during the 3-month intervention period. Reasons for dropout included loss of interest (control group, n=2; home-based, n=2) and a new cardiac intervention (ie, percutaneous coronary intervention) (control group, n=2). No serious adverse events related to exercise occurred in any of the groups.

The basic characteristics of the study population are described in Table 1. The mean age of the participants was 61.4 (SD 7.3) years (range: 42-73 years). A total of 10 (11.1%) women participated in the study, and patients were on average slightly overweight, 27.5 (SD 3.4 kg/m²). Overall, exercise capacity was normal, 101.1% (SD 21.1) compared with reference values [18]. Baseline characteristics were comparable between the groups regarding physical characteristics, reason for referral, and pharmacological therapy.

The significant finding of our randomized controlled study is that a 3-month home-based rehabilitative intervention with telemonitoring guidance results in further improvement of exercise capacity (VO₂ P) in CAD patients who had recently completed a phase II ambulatory program, and a home-based program is as effective as a prolonged center-based CR. The observed improvements of 1.30 mL·kg⁻¹·min⁻¹and 1.10 mL·kg⁻¹·min⁻¹in VO₂ P of center-based and home-based groups, respectively, are likely to be clinically relevant. It has been shown in earlier studies that a 1 mL·kg⁻¹·min⁻¹increase in exercise capacity is associated with a 10% reduction in cardiovascular mortality [20]. Thus, our results support the added value of a structured continued rehabilitation program.

There are only few studies in the literature that have investigated the effectiveness of a home-based, telemonitored, phase III CR program starting immediately after completion of a phase II center-based CR program. A small proof-of-concept study by Brubaker et al [5] randomly assigned 31 patients to home-based, center-based, or standard care. In line with our results, they found that the home-based program was as effective as the center-based program at improving and maintaining oxygen consumption among patients 9 months after exiting a CR program. In the Telerehab III trial [21], 140 patients were randomized to a telerehabilitation program in addition to conventional CR or conventional CR alone. This study also reported that a 6-month patient-specific comprehensive telerehabilitation program initiated 6 weeks after the start of ambulatory rehabilitation leads to a bigger improvement in VO₂ P and confirmed our results of lack of an additional weight loss, blood pressure reduction, lipid profile improvement, and glycemic control.

In the last decade, several meta-analyses have been published demonstrating the effectiveness of home-based programs for CAD patients implemented as a phase II CR program [22-24]. Although the increase in VO₂ P of 4%-5% in our phase III center-based and home-based groups is less than what has been seen in previous phase II programs, this is still of clinical relevance, as the purpose of phase III (maintenance phase) CR is to preserve, or if possible, enhance the health benefits gained in phase II. Our results further show that although patients in the home-based group exercised only 75 min per week at the prescribed intensity and the average intensity was below the recommended thresholds, patients were still able to further increase their exercise capacity compared with those in the control group who receive only advice on how to maintain a physically active lifestyle. This is in line with meta-analytic results of Swain and Franklin [25], demonstrating that in healthy individuals with a mean baseline VO_2max<40 mL·kg⁻¹·min⁻¹, there is no clear minimal intensity threshold to increase their aerobic capacity and that patients already show improvements when exercising at an intensity of 40% of HRR. Yet, there is abundant evidence that larger effects on health and fitness are established when individuals exercise at higher intensities and larger duration [26].

Regarding physical activity, Ayabe et al [27], reported that 6500-8500 steps/day should be considered as the minimal and optimal goal of physical activity for secondary prevention of CVD. With the number of steps ranging between 7612 (home-based) and 7700 (center-based), the patients in the home-based and center-based groups were within this target zone, whereas those in the control group (5566) did not seem to reach this goal. However, we were not able to promote an additional increase in the number of daily steps. These results are in line with previous studies that have demonstrated how exercise interventions focused on physical fitness improvement in cardiac patients do not influence the improvement of physical activity [21,28,29].

We observed, however, a small but significant increase in sedentary time in the center-based group. Evidence suggests that those participating in exercise-focused interventions are not likely to reduce their sedentary time by a meaningful amount [30]. King et al [31] explained this behavior as a compensatory effect for exercise. That is, the simple fact of enrolling in a supervised exercise program might reduce physical activity levels throughout the rest of the day. This compensatory effect acts in different ways by promoting adjustments in energy expenditure in order to save energy or recover from the exercise training, consequently, increasing the sedentary time [32]. Growing evidence suggest that prolonged sedentary behavior can affect cardiovascular and all-cause mortality risk independent of physical activity [33]. Probably, recommendations on sedentary behavior can be included in CR programs, given the current state of the evidence [30].

Small improvements in weight reduction and body composition as well as in blood pressure were observed post-intervention, although this did not reach significance. This is consistent with the findings in the Telerehab III trial [21]. According to Frederix et al, digital health interventions seem to be able to improve cardiovascular risk factors in primary prevention, but not in secondary prevention, programs [21]. Furthermore, we hypothesize that when the pharmacological management of the groups is close to optimal, like in our patients, the incremental benefit of secondary prevention programs over usual care is very small [34].

One of the main objectives of CR is to optimize patients’ physical functionality as a means to improve quality of life. In our study, no effects of our interventions on different HRQoL domains could be found. Contrary to our results, Smith et al [35] found clinically significant improvements in HRQoL in their home-based group compared with their hospital-based group after a 6-month intervention. The authors considered that 6 months of CR, regardless of location, was associated with improvements in physical HRQoL. Thus, it is possible that with a longer intervention for both the groups, some differences could have been obtained in our study.

One area that is not commonly considered with CR is the functional status or abilities of the patient. The typical patient in CR is over the age of 60 and presents with multiple cardiovascular risk factors, such as inactivity and obesity, and is recovering from a recent cardiac event. All these factors can lead to deficits in balance, mobility, and function. Sumide et al, found that musculoskeletal fitness and flexibility, measured by SRT, was a significant predictor of mortality in 51- to 80-year-old participants [36]. In this study, no significant difference was seen in SRT between the groups (P=.36). Our results are in line with those of Oerkild et al [37]. Regarding components of muscular fitness, Mroszcwyk et al [38] and Thomaes et al [39] found increased HG strength in patients following 3 months of a (predominantly aerobic exercise training) CR program. In our study, however, no changes were observed after 12 weeks of intervention. It is possible that the largest gains in HG strength appear during phase II of CR, while our intervention targeted phase III patients. In addition, we found no significant difference in knee extension strength or resistance after 3 months of home-based or center-based training, which may be explained by the focus on aerobic training during the intervention. These results are also consistent with those of previous studies [40,41]. Conraads et al collected muscle strength data in 75 CAD patients before and after 12 weeks of an aerobic interval training or continuous training CR program, finding that muscle strength did not improve. The authors considered as a possible cause the use of statins that has been associated with negative side effects on the muscles. In our study, 94% (79/84) of the patients are treated with statins, although insufficient evidence exists to prove that statins really affect muscle strength [42]. Currently, there is very limited evidence regarding the effects of telerehabilitation on muscle strength, and more research is needed [43].

Finally, while short-term changes are of interest, it is important to establish whether the benefits are maintained over time; thus, further research should focus on the long-term effects of home-based CR with telemonitoring guidance.