This study was a randomized clinical trial (pretest and posttest with a control group design, Multimedia Appendix 1), which was conducted in 2018 in the cardiac care units of Mashhad Medical Center, Iran. After obtaining approval from the ethics committee affiliated with the Iran University of Medical Sciences (code: 1396.9411449003) and registration on the website of clinical trials (code: IRCT2017061934647N1), willing patients signed the letter of consent before the study. This study adhered to the basic ethics principles and the tenets of the Declaration of Helsinki.

In this study, patients with HF who were admitted to the cardiac care unit were selected using the following inclusion criteria: age of 18-65 years, being literate, class II or III of HF according to the New York Heart Association classification, patients admitted to the hospital due to exacerbation of HF, having a smartphone or a tablet with the Android operating system, and ability to use a smartphone and the app. Patients who met the following criteria were excluded from analysis: unwillingness to continue participation in the study, no use of the app for 1 week (each patient used a one-time password to enter the software), and death.

The sequential sampling method was used. The randomized block method with the ratio of 1:1 and no permutation was used to assign the patients to the groups. Different modes of assignments to the groups were written on 4 cards and placed in opaque envelopes. Next, the envelopes were placed in a box. A research collaborator who was unaware of the assignment process took the envelopes from the box and determined each patient’s place in the groups. This process was continued until the desired sample size was achieved. It should be noted that due to the nature of the intervention, there was no possibility of blinding the subjects. To estimate the sample size at 95% confidence interval, 80% power, assuming that the effect size of the intervention on the QoL in the intervention group compared to the control group would be at least d=10.5 and SD=18 [26] and with 25% possibility of sample dropout, the sample size was considered as 60 people in each group (Figure 1).

Data were collected from the patients’ medical records and through interviews using the demographic data form, health information form, and Minnesota Living with Heart Failure Questionnaire (MLHFQ).

Demographic data form: A researcher-made demographic form was prepared on the basis of literature review. It was completed before the intervention by examining a patient’s medical file and interviewing him/her. The content validity of this form was assessed and approved by an expert panel.

Health information form: This was a researcher-designed form that was prepared on the basis of literature review. This form was completed before the intervention by examining the patient's medical file and interviewing him/her. The content validity of this form was assessed and approved by an expert panel.

MLHFQ: The MLHFQ is the most common tool for investigating the QoL of patients with HF [27]. The validity and reliability of the Farsi version of this tool have been assessed and approved using the calculation of the Cronbach α coefficient of .95 and reliability score of 0.90 [28]. This questionnaire assesses the patients’ perceptions of the effects of dysfunctional illness on their physical, economic, social, and psychological functions. This questionnaire consisted of 21 items on the 6-point Likert scale from 0 (some limitations) to 5 (maximum limitations). The score range was between 0 and 105, with a high score indicating a poor QoL. In this questionnaire, 9 questions were related to physical function, 5 questions covered the psychoemotional aspect, and 7 questions examined the socioeconomic conditions. The questionnaire was designed to be opened and filled out using the Google platform on their smartphones. The patients were asked to fill the questionnaire, and those with a poor and moderate QoL and a score more than 24 entered the study. Further, 3 months after the starting point of the study, the same questionnaire was sent to the patients via the smartphone’s virtual social network to be filled out. A follow-up phone call was made to ask the patients to fill the questionnaire. Finally, for reliability, the Cronbach α coefficient was calculated to be .71. The patients were asked to fill the questionnaires, and a researcher who was blinded to the study process gathered these questionnaires at the beginning of this study and at 3 months after the patients entered the study.

An Android-based smartphone app was developed and evaluated [25]. This interactive app (Figure 2) can be used both online and offline. The main characteristics of this app are profiles, reminders, educational content, educational videos, daily messages, pharmacy guides, frequently asked questions, daily recording of physical and psychological symptoms, and vital signs and sending alerts as needed. This app was evaluated by patients, health care providers, nurses, physicians, and programmers, thereby indicating its simple and convenient use and consistency with the principles of the American Heart Failure Association and the Institute of Health Information Technology [25]. This app has the following features: (1) informing: information about disease, symptoms, symptom management, treatment, and care in various formats (text, photos, and videos); (2) instruction: provision of instructions for the user of the app; (3) recording: ability to record user’s information under the subsets of collecting information, sharing information with the researcher, evaluating information, and intervening, as needed; (4) displaying: displaying data regarding symptoms, vital signs, and weights graphically and textually, as well as the ability to extract the PDF and XML formats; (5) guiding: provision of guidance based on the data given by the user and provision of appropriate advice through communication with the researcher; (6) reminder or alert: reminding the user regarding the time of taking medicines, performing tests, and other requirements; and (7) interaction: bilateral interaction between the researcher and patient [25]. This app was provided to patients to use for 3 months.

Patients in the intervention group received the smartphone-based app besides routine care. It was installed on their Android phones, and the patients were taught how to use the program via a 30-minute face-to-face session. The app brochure was also provided to the patients. The method of measuring vital signs, monitoring symptoms, and recording them in the app were taught to patients via the educational content of the app. Every week for 6 consecutive weeks and then every month for about 2 months, notifications were sent to the patients to remind them to use the app. Patients were asked to enter their daily vital signs, symptoms, and weight in the app, which provided the opportunity for health care providers to telemonitor the changes in the data in the text and graph format. In addition, patients could evaluate their daily conditions and its changes by visualizing the recorded data in the shape of a graph. Further, the daily use of the app by the patients was evaluated by the management panel on the internet and encouragements for the use of the app were provided, as needed. Patients and researchers could interact with each other depending on the patients’ needs. During the app usage period (3 months), the patients were supported in terms of how to use the program. To provide support, the researcher’s telephone number was provided to the patients for contact purposes, if needed. The patients in the control group received routine care, which included the provision of a brochure and the method of taking medicines and referral to the doctor at a clinic 2 weeks later. Moreover, the patients in the control group were provided with the smartphone-based app after data collection.

Descriptive statistics (frequency, mean, and SD) were used to analyze the qualitative and quantitative data. The Kolmogorov-Smirnov test was used to assess the normal distribution of the quantitative variables. The two-sided t test was used to compare the quantitative variables. The chi-square and Fisher exact tests were used for comparing the qualitative variables between the 2 groups. The two-factor analysis of variance was used for determining the effect of the demographic and health information on the QoL in order to investigate the effects of 2 factors (intervention and demographic and health information) on the dependent variable. The repeated measure analysis of variance test was used to determine the effect of the intervention over time. The Cohen effect was used to assess the effect of the intervention. All statistical tests were performed using the SPSS V.22 software (IBM Corp). The significance level was set as P<.05.

In this study, according to the findings, changes in the QoL score and its dimensions in the intervention group were more than those of the control group, and the effect size of the intervention was high. Therefore, use of a smartphone-based app increased the QoL and its dimensions in patients with HF. It is believed that new technologies such as apps can increase patients’ satisfaction with medical care and improve their relationships with health care staff and subsequently improve their QoL [29]. Such programs can increase the motivation of the patients to make changes in their lifestyles and increase their QoL. Further, any intervention that reduces the rate of hospitalization and symptoms in patients with HF can improve their QoL. A smartphone app that can record symptoms and provide intelligent responses to the patients’ symptoms and related changes in each week and month can help them manage their symptoms effectively. This app can cause a significant improvement in patients’ QoL [29]. The app provides the possibility of continuous monitoring of patients even if they are not hospitalized. Moreover, this app and its use are not limited to a specific time and place [30]. In this study, there was a possibility to contact the health care provider via this app, and caregivers could help with reducing the patient’s or family’s ambiguities with regard to the patient’s health condition.

Interventions that improve QoL are integral parts of the management of HF [9]. They can be performed by the therapist as a continuous process of follow-up and monitoring. However, in a review study, wherein the effect of the use of mobile-based apps on the QoL of patients with HF was studied, only a limited number of apps had the required criteria for caring of patients with HF and most programs were commercial rather than functional. Moreover, app use had little impact on the QoL of patients [31]. In the production of the “My Smart Heart” app, efforts were made to reduce the limitations of the existing apps and improve the QoL of patients. The results of our study shows that the effect of this intervention on the QoL of patients with HF was high. In line with the results of this study, a study after 6 months of intervention in patients with myocardial infarction found that the mean score of QoL in the intervention group increased compared to that in the control group [32].

The smartphone-based app used in our study provides a novel telemonitoring and education method for patients with HF. This study was conducted on those patients who were able to communicate and were literate, with an ejection fraction of less than 45%. For generalizability, similar studies should be conducted in illiterate patients. In this study, the effect of the intervention was studied after 3 months, but the long-term effects of the intervention need to be further researched. In this study, the mediator effects of knowledge and self-care improvement were not evaluated, and therefore, these should be investigated in future studies. Within 3 months of the study process, some medication errors were identified. Therefore, studies should be performed to demonstrate the efficacy of software in improving patient safety and reducing medication errors.

Our study showed that the use of a smartphone-based app increased the QoL of patients with HF. Interventions that improve QoL constitute an integral part of the management of HF, which can be carried out by the health care provider through continuous follow-up of patients using such apps. Nurses as well as patients and their families can use smartphone-based interactive software. Provision of facilities such as counselling centers can provide patients and their families with information about how to use this software to improve their QoL. The results of this research can be considered by nursing managers for patient education. However, it is necessary to study the cost-effectiveness of such interactive software. This method can be used by nurses and other health care providers in HF clinics and heart transplantation centers to improve patients’ and families’ satisfaction with health care, which needs to be further studied in the future.