No Intervention: Control group No intervention was made by the researcher during the study. Only data was collected. At the end of the study, visual training based on the planned Health Belief Model was given and all patients who continued the study were given brochures and heart-shaped key chains designed by the researchers.

Experimental: intervention group The sample of this simple-randomized controlled experimental study consisted of heart failure patients who applied to Manisa Celal Bayar University (MCBU) Hafsa Sultan Hospital Cardiology Polyclinic between September 2021 and March 2022. Patients who were determined by drawing lots according to their protocol numbers using the simple random sampling method were assigned to the intervention group. Patients assigned to the intervention group were given planned training based on the Health Belief Model. The intervention group was followed up for six months. A total of three interviews were conducted with the intervention group (First interview, 3rd month interview and 6th month interview).

Patients in the intervention group received HBM based training for a period of 6 months. During the training, one-on-one interviews were provided with each patient. Patients were shown a power point presentation, a brochure, and 3 training videos. Any questions patients had were answered one-on-one.

In order to monitor the effectiveness of the intervention in the study, a 6-month follow-up was conducted and data were collected from the intervention group 3 times (before the intervention, at 3 months and at 6 months) and from the control group twice (at the first interview and at 6 months) through data collection forms.

HBM-based education program was applied to the intervention group as an intervention.

Data collection tools were "Patient Information Form", "Memorial Symptom Assessment Scale - Heart Failure (MSAS-HF)" and "Health Belief Model Scale in Heart Failure (HBM-HF)".

Patient Information Form: A total of 15 questions are included, including sociodemographic information (such as age, gender, marital status, education status, employment status, occupation and income status) and additional information regarding HF/HF treatment (perceived health status, compliance with diet, exercise, treatment compliance, regular doctor visits, etc.) of the participants.

In the study, 3-month data were collected from the intervention group using the same measurement tools.

MSAS-HF: The scale is used to evaluate the symptoms experienced by patients with HF. It consists of three sub-dimensions in total (physical symptoms, psychological symptoms, and HF symptoms). For the symptoms encountered, it is expected to rate the frequency and severity of the symptom with a four-point Likert-type assessment, and the discomfort with a five-point Likert-type assessment. In the calculation, symptom load is first calculated for each symptom. The load of the unseen symptom is evaluated as zero. The Cronbach alpha values of the scale were reported as 0.53 for physical symptoms, 0.63 for psychological symptoms, and 0.55 for HF symptoms.

In the 6th month of the study, after the educational intervention was completed, data were collected again from the intervention and control groups through data collection forms.

HBM-HF: The scale was developed to assess the attitudes and beliefs of HF patients towards their disease. The scale consists of 24 items and five sub-dimensions (perceived susceptibility, perceived severity, perceived benefits, perceived barriers, self-efficacy) and is a five-point Likert-type scale. The items of the perceived barrier sub-dimension in the scale are reverse coded. The scale does not have a total score and each sub-dimension is calculated independently. Higher scores indicate higher perception of susceptibility, perceived severity, perceived benefits, and good self-efficacy, while lower scores indicate stronger perception of barriers. The Cronbach's alpha coefficients of the sub-dimensions are 0.91, 0.86, 0.88, 0.75, and 0.84, respectively.