Table 2.

Data collection

BASELINE
Patients: Self-administered questionnaires (by mail)
Depression	Patient Health Questionnaire 9-item Subscale Depression (PHQ-9) [26-28]/Hospital Anxiety and Depression Scale [29,30] – Subscale Depression (HADS-D)/PROMIS Depression Scale [31,32]
Anxiety	Patient Health Questionnaire 7-item Subscale Generalized Anxiety Disorder Assessment (GAD-7) [33-35]/Hospital Anxiety and Depression Scale [29,30] – subscale anxiety (HADS-A)/PROMIS Anxiety Scale [31,32]
Treatment of Anxiety and Depression	Medication intake/Utilization of psychotherapy or other therapies (e.g. music therapy, occupational therapy, relaxation training)
Social support	Lubben Social Network Scale (LSNS) [36]/ENRICHED Social Support Instrument (ESSI) [37]
Stress	Patient Health Questionnaire - Subscale Stress (PHQ-D) [26,38]
Compliance	Morisky Medication Adherence Scale (MMAS-8) [39-41]
Quality of life	EQ-5D-5 L [42]
Self-efficacy	General Self-efficacy Scale [43]
Lifestyle	Salt restriction: Do you pay attention to your diet?/Fluid intake: How much do you drink daily?/Weight control: How often do you weigh yourself?/Vaccination: Did you receive a flu shot within the last year? Have you been vaccinated against pneumonia?/Alcohol intake: At occasions you drink alcohol, how much alcohol do you consume on average?/Smoking status and cigarette consumption: If you smoke occasionally or regularly: How much do you consume on average?
Physical Activity/Capacity	How often do you engage in physical activity? Based on Verghese [44]/Self-rated physical capacity according to NYHA class
Socio-economic status	Household income per capita
Sociodemographic data	Gender/Age/Height/Weight/Type of insurance/Marital status/Status of living/ Nursing care/Employment status/ Education [45]/Migration status/ Citizenship
Contact to the GP	Last contact/Frequency of contacts within the last 6 month/Years of being patient of the actual GP
GPs: Telephone-interview with insight in the medical record
Validation of heart-failure diagnosis	Does the patient have heart failure?/Severity level according to New York Heart Association (NYHA) class/Ejection fraction
Size of practice	Number of GPs in the practice/ Practice type (single practice/practice sharing/group practice)/Number of patients insured by the statutory health insurance per quarter/ Percentage of private patients
Familiarity with the patient	Are you the regular GP of the patient?/How well do you know the patient? (Scale 1 to 10)
Comorbidity	Charlson Comorbidity Index [46]/Which additional diseases does the patient have?
Depression/Anxiety	Does the patient have any symptomatology of depression/anxiety? If yes, please specify/Had the patient any symptomatology of depression/anxiety in the past?
Measures taken if depression/anxiety is recognized	What treatment have you prompted?
Treatment of heart failure	What difficulties have you encountered when treating the heart failure in this patient? Have there been any reasons to deviate from the recommended pharmacological treatment?
Sociodemographic data of the GP	Age/Gender/Years of practice/Speciality/Additional trainings
12-MONTH FOLLOW-UP
Patients: Self-administered questionnaire (by mail)
All measures according to baseline; additional data:
Hospital admission within the last 12 month	Number of Hospital Admissions/Date of admission/Length of stay/Admission diagnosis/Emergency vs. pre-scheduled hospitalization
Change of GP	Did you change your GP within the last 12 month? If yes: How many months ago did you change your GP?
GP: Information from medical records (provided by phone)
Survival	Mortality within the last 12 month/Date of death/Course of death
Hospital Admission	Number of Hospital Admissions/Date of Admission/Length of stay/Admission diagnosis/Emergency vs. pre-scheduled hospitalization/