An estimated 64.3 million people live with heart failure worldwide [1]. In 2019, the hospitalization rate of heart failure patients in Korea was 88.4 per 100,000 patients, which was higher than that of patients with asthma [2]. The number of medical treatments such as coronary angioplasty, cardiac catheterization, or coronary artery bypass surgery due to the worsening of heart failure was 1,181 and medical costs increased to 15.7 billion won [3]. Patients with heart failure tend to report a reduction in Quality of Life (QOL) [4]. Low levels of QOL were associated with depressive and physical symptoms [5], and the longitudinal trajectories in QOL demonstrated that QOL differed significantly among patients with heart failure between survivors and non-survivors over a 12-month period [6]. Among those with heart failure, decreased physical function was one of the most common complaints [7], and notably, physical function was a strong predictor of mortality [6]. Low levels of QOL and poor physical function can be substantially improved by promoting healthy behaviors in patients with heart failure [8]. Exercise is a class I recommendation by the American College of Cardiology Foundation/American Heart Association Guideline for the Management of heart failure [9]. Exercise increases peak cardiac output, improves vascular reactivity, utilizes oxygen better through metabolic changes in the skeletal muscle, and facilitates more efficient ventilation [8]. In a previous study, heart failure patients with higher activity levels showed greater exercise capacity as measured by the 6-Minute Walk Test (6 MWT) [10]. A physically inactive lifestyle was found to correlate negatively with QOL and was identified as a significant predictor of QOL [7]. In addition, exercise training was associated with a 25.0% lower risk of all-cause hospitalization compared to usual care [8].

However, patients with heart failure engage in very limited amounts of exercise. According to a previous study [11], 42.0% of patients reported engaging in less than 60 minutes of exercise per week, and approximately two-thirds of patients had a low level of exercise [10], which corresponded to a total Physical Activity (PA) of <600 Metabolic Equivalent of Task (MET)-minutes/week according to the International Physical Activity Questionnaire (IPAQ). These results suggest that much of this population was relatively sedentary. According to a recent report [12], the rate of adherence to exercise guidelines was lower among Asians than among Caucasians. The reasons for decreased exercise among patients with heart failure included shortness of breath, exercise intolerance, and fatigue [9]. Among older adults with heart failure, poor adherence to exercise was strongly related to a lack of motivation for exercise, and the motivation and Self-Efficacy for Exercise (SEE) were significantly correlated [11]. SEE could be a mediator in the relationship between motivation and adherence to exercise [11], which implies that motivation could result in a change in SEE, which in turn could result in increased adherence to exercise. Therefore, strategies that aim to increase engagement in exercise among older adults with heart failure should address their SEE and motivation to exercise.

Motivational Interviewing (MI) is a collaborative convertsation that elicits change talk during counseling, evokes motivation, and strengthens patient commitment to the implementation of positive behavior changes [13]. Since older adults aged 60 and above value collaborative communication, MI can increase their motivation for change and enhance their responsibility for active participation and long-term adherence to an exercise program [4]. Riegel et al. conducted a study using a mixed method design and identified that MI techniques such as reflection and reframing, empathy, affirmation, and humor, and individualized problem solving contributed to improvement in self-efficacy and self-care among patients with heart failure [14]. Patients with heart failure showed an increase in PA and peak VO₂ after receiving monthly MI intervention for six months [4]. In a systematic review of the literature on the effects of MI on patients with heart failure, MI demonstrated a positive effect on self-care behaviors, including exercise, QOL, and hospital readmission [15, 16]. Significant differences in self-care management have been observed among patients with heart failure at the three-month and six-month follow-up, after one face-to-face session and three telephone contacts provided by nurses over a two-month period [17].

While there are numerous benefits of MI, it has been applied narrowly to change behaviors in patients with heart failure. In a systematic review on the effects of MI on self-care behaviors, QOL, and hospital readmission in patients with heart failure, Poudel et al. [15] researched literature published from 1990 to 2019, and only nine articles were retained at the conclusion. While nurses provided MI in five out of nine articles [15], there were few studies that conducted MI in Korean patients with heart failure. Therefore, it is necessary to establish evidence for the effects of MI by conducting a study using a strictly controlled method, such as a Randomized Controlled Trial (RCT) for heart failure patients in Korea.

Nurse-led MI may improve patient outcomes in diverse areas such as medical-surgical units, intensive care units, oncology units, and home healthcare when used effectively [18]. We predicted that MI would play an important role in promoting engagement in exercise and maintaining exercise involvement among patients with heart failure by improving their SEE. Given this evidence, MI could be a promising target for regular exercise and exercise capacity alongside QOL in patients with heart failure in Korea. Furthermore, according to Katherine Letourneau, an Adult-Gerontology Nurse Practitioner, and Janice H. Goodman, a psychiatric and mental health clinical nurse specialist, MI alleviates the burden of healthcare providers who persuade patients to change their behaviors [19]. The purpose of this study was to examine the effects of nurse-led MI on SEE, regular exercise, exercise capacity, and QOL, and the sustainability of the effects over three months.

In this study, we used MI to evoke participants’ intrinsic motivation to make positive behavioral changes [13]. Specifically, patients with heart failure were encouraged to motivate themselves to engage in health-related behaviors. The present study revealed that the intervention was effective in increasing engagement in regular exercise and QOL. This observation is consistent with previously reported effects of similar interventions that have been provided to patients with heart failure [4, 16] and other patient populations, such as those with physical disabilities [28] and older patients who underwent coronary artery bypass surgery [29].

Our study showed no significant improvements in SEE after nurse-led MI in patients with heart failure. This finding is inconsistent with the results of Vellone et al.’s study, which found a beneficial and significant effect of MI on self-care self-efficacy in patients with heart failure at six- and nine-month follow-ups [17]. Our findings may be explained by the significant group differences at baseline and the small sample size due to the high dropout rate. Baseline SEE scores were significantly higher in the intervention group, and because of the high dropout rate, only 24 of 66 patients were included in the repeated measures ANOVA for the SEE analysis. If the sample size was larger and MI techniques were further strengthened self-efficacy by emphasizing reflection, empathy, affirmation, and humor [14], the improvement in SEE would have been verified.

In the study by Audsley et al. [30], interventions delivered on a monthly or quarterly basis over six months to two years consistently showed significant effects on exercise maintenance. Intervention time periods and contact frequency appeared to influence intervention effectiveness. Therefore, it may be necessary to implement a long-term intervention or include additional contact, such as a booster session or follow-up prompts, in future research. Moreover, in this study, participants kept an exercise diary during the intervention period to increase compliance for intervention and elicit their motivation to exercise. However, they did not monitor their exercise for two months after the first month of intervention. We suggest a varying additional approach to eliciting the motivation of heart failure patients to exercise. Specifically, utilizing an activity diary for a longer time may be helpful in motivating participants to exercise [4, 31]. Alternatively, increased family engagement may play a crucial role in patients with an Asian cultural background [29].

In Arkkukangas et al.’s study, participants in the intervention group showed intervention adherence of 55.0% and adherence of an adequate amount of exercise (22.0%) among all participants [32]. Intervention adherence of older adults was influenced by weather conditions and life events such as death among close family members, in addition to behavioral and cognitive factors such as activity level, self-efficacy, and motivation [32]. Since there was no significant improvement in SEE in this study, it is thought that the increased exercise was not maintained until three months. Considering the older age of the participants in this study, recurring life events and coping strategies for these life events could have played a critical role in the compliance of healthy behaviors. Therefore, guiding participants through MI intervention across various topics can be an essential approach for older adults with chronic health problems to improve healthy behaviors.

Our study showed no significant improvement in exercise capacity. Similarly, Schertz et al. found no significant change in performance on the 6 MWT between baseline and the six-month follow-up in either intervention or control group participants [4]. Patients with heart failure in Korea should be motivated to consistently increase their level of exercise to improve their exercise to a greater extent, particularly as patients with heart failure in other countries reported a higher walking distance [4, 12] than the value that emerged in this study. There were many missing values of the 6 MWT because data collection was conducted by mail to participants who were unable to visit the hospital on the follow-up day. Moreover, some participants refused to participate in the 6 MWT after answering the questionnaire. Nevertheless, the 6 MWT is an easy-to-use, low-cost test that objectively evaluates the degree of functional limitation and prognosis of heart failure [26], and it is recommended that the 6 MWT be measured on a patient’s regular hospital visit.

A significant group-by-time effect on QOL was observed following nurse-led MI in patients with heart failure. Similarly, other published studies reported positive results regarding the impact of MI on QOL at 3~4 months among patients with heart failure [15]. The QOL of patients with heart failure may decrease over a three-month period due to the deterioration of the disease. However, the QOL of participants in the intervention group in this study remained almost the same throughout the study period, and the QOL of the control group decreased over time. This is thought to be the result of increased exercise in the intervention group at one month.

In this study, it was very difficult to induce participation in the study because many participants were elderly and in debilitating health conditions. Among the participants assigned to the intervention group, 22 participants (44.0%) declined to participate even before the intervention started, and 12 of 28 members of the intervention group (42.9%) and 23 of 38 members of the control group (60.5%) dropped out at the three-month follow-up. Among the reasons for dropout of the intervention group, "difficult to answer all the questionnaire" was the most common response for three cases, and "not interested", "questionnaire not returned by mail", and "failed to contact" were given as reasons in two cases each. Therefore, it is crucial to develop a data collection strategy to induce heart failure patients to participate in future studies.

There were many cases of not answering or refusing phone calls and feeling burdened by inducing behavioral changes during the intervention period. Participants were asked questions according to the prepared protocol, but a very limited number of participants responded adequately. When answering a call on a cellular phone, there was a tendency for people to be disturbed or to lose concentration on the content of the conversation because they answered the call wherever they were. It was thought that these participants would have had difficulty obtaining sufficient MI effects. In the case of participants who were reluctant to change, a differentiated approach and intervention with sufficient time, frequency, and interval adjustment to induce behavioral change are required according to their readiness for behavior change. In the case of the participants of this study, in order to minimize the inconvenience of additional visits to medical institutions, MI was provided by phone. Since MI depends on collaboration and elicits active thinking about health behaviors in patients, it may be delivered less effectively [16, 33] and may increase dropout rates when offered primarily over the telephone as opposed to face-to-face sessions. Methods such as face-to-face interviews or video calls are thought to further enhance the effectiveness of the interview, by eliciting an appropriate response from the participant to questions and inducing smooth communication, which should be considered in future research.

In the control group, "not interested" was the most common reason given for dropout with ten cases, and "failed to contact" followed with six cases (Figure 1). Heart failure patients in Korea had a prejudice against participation in the study, making it very difficult to invite patients with heart failure to take part in the study. Several patients who wanted to receive the intervention dropped out after being randomly assigned to the control group. High dropout rates have been observed in lifestyle modification interventions [20]. Patients with heart failure in Korea seem to rely on medication rather than lifestyle changes to manage their disease. It needs to be strongly emphasized that study participation could improve health by establishing a lifestyle that reduces symptoms of exacerbations in patients with heart failure. In addition, increasing rewards for participating in research may be a solution to reduce dropout rates. Recently, Wade et al. explored predictors of dropout within an exercise program using MI [34]. It found that people who were categorized as engaging in health-enhancing PA were less likely to drop out [34]. Therefore, special attention is needed to ensure that those engaging in low exercise do not drop out.

This study had several strengths. First, the study investigated the effects of MI on SEE, exercise, exercise capacity, and QOL in patients with heart failure and the sustainability of the effects after the intervention was terminated (i.e., at the three-month follow-up). Second, exercise capacity was measured using an objective test rather than a self-report measure. Third, to improve the quality of the study, an RCT was conducted. However, this study also had some limitations that must be considered when interpreting the results. A large percentage of participants were men (81.8%) and had NYHA class I heart failure (63.6%). This limits the generalizability of our findings to a larger population of patients with heart failure in Korea. Future studies should aim to recruit a larger and more diverse sample. Second, a high dropout rate can reduce the statistical power. Furthermore, since higher numbers of dropout patients had comorbidities than those who remained until the end of the study, this may have impacted the results favorably toward intervention groups with regard to outcomes measured. Third, data on all medications used were not investigated in this study. Medication use may be a covariate affecting outcome variables and should be thoroughly investigated in future studies. Finally, these results may differ from the current clinical environment because the data was collected between 2012 and 2013.

Despite these limitations, MI is a clinical communication skill that nurses can develop to elicit patients’ personal motivations for changing behavior to promote health that has been utilized in the past and at present [17, 18]. As nurses are health care providers who interact most closely with patients, nurse-led MI needs to be widely applied. With MI, nurses can explore patients’ understanding, motivation, confidence, and barriers to change by asking evocative questions, acknowledging patient autonomy and personal responsibility, and reserving judgment. The current study demonstrated that MI can achieve significant effects on exercise and QOL in heart failure patients with comorbid conditions. Using a repeated measures approach, we found that the positive effects of the exercise did not last for three months. This methodology highlights the value of multiple measurements of patient outcomes over time when developing strategies to promote health behaviors.

This study has shown that nurse-led MI has beneficial effects in patients with heart failure. Patients in the intervention group demonstrated greater improvements in their engagement in exercise and QOL than those in the control group. Furthermore, MI generally requires less contact time than other behavior change strategies, and is delivered effectively in this study. The results of this study provide an empirical basis for future efforts to develop effective strategies to improve exercise participation and QOL in patients with heart failure in Korea. Future studies should recruit patients with heart failure from other regions to increase the generalizability and establish the validity of the current results. In the future, we propose a study to analyze the differences in the effectiveness or compliance of interventions according to the type and number of comorbidities.