The study aim is to determine whether a 12-month digitally delivered behaviour change solution for patients with heart failure improves symptom frequency, mental health, quality of life, medication adherence, and self-care behaviour. The primary and secondary endpoints will be captured at 6- and 12-months follow-up visits to assess longer term effect on outcomes.

Heart Failure (HF) is one of the most common causes of morbidity and mortality in developed countries with a prevalence rate of 4.2% of the adult population and 11.8% among people ≥60 years of age. Worldwide HF affects about 26 million people and poses a significant burden on healthcare providers and patients. People with HF may have severe symptoms, and some may need a heart transplant or implantation of a ventricular assist device. Important modifiable HF risk factors are smoking, physical inactivity, overweight and obesity, and an unhealthy diet. Lifestyle changes by HF patients are known to reduce HF-related hospital (re)admission, morbidity and mortality.

Guideline-directed treatment of HF includes among others pharmacotherapy, implantation of devices, regular exercise, and enrolment in a multidisciplinary care management program. Components of the multidisciplinary care management program are among others: patient education with an emphasis on adherence and self-care, patient involvement in symptom monitoring, and follow-up after discharge (for instance through remote monitoring). Adherence to the recommendations has proven difficult. A digitally delivered solution that provides remote symptom monitoring and lifestyle intervention support may support HF patients to halt or reverse disease progression and improve their quality of life. This study aims to digitally provide remote symptom monitoring and lifestyle intervention via a mobile platform (Sidekick Health) with the primary aim to determine the effectiveness of adding Sidekick Health's digital solution for HF patients to the standard care treatment by changes in the KCCQ-12 scores. The secondary aims are to determine the effect on other clinical outcomes (echocardiograms, biomarkers, metabolic syndrome symptoms, HF disease progression), other health-related outcomes (self-care, medication adherence, cardiorespiratory fitness, disease knowledge, smoking status, and anxiety, depression, and stress-levels), and cost-effectiveness.

Inclusion Criteria:

• Adults with confirmed congestive HF registered at the outpatient heart failure clinic at the Landspitali University Hospital
• Participants should be on one of these medications for heart failure treatment: angiotensin-converting enzyme (ACE) inhibitors, angiotensin receptor blocker (ARB) inhibitors, or Angiotensin Receptor-Neprilysin Inhibitor
• Participants with all stages of HF will be included (NYHA classes I-IV)
• Started their medical HF treatment at least 1 month prior to study enrollment
• Participants should be willing and able to comply with study procedures and attend the scheduled visits
• Capacity to consent to informed consent

Exclusion Criteria:

• HF due to reversible causes (e.g., myocarditis) or severe aortic valve stenosis
• Not owning a smartphone compatible with the Sidekick Health digital solution
• Not knowing how to operate a smartphone
• Moderate to severe dementia
• Unable to understand written and verbal instructions in Icelandic.
• estimated Glomerular Filtration Rate (eGFR) <15 ml/min
• Planned dialysis in the next 6 months
• Planned cardiac transplant surgery
• Active drug/alcohol abuse
• Other serious illness (e.g., cancer, endocarditis)

Anonymized individual participant data (IPD) may be shared with other researchers for relevant research purposes following complementary ethical review and approval from the Ethical Review Board.

The outcome assessor will be blinded for group assignment at the 3, 6, and 12 month follow-up visit.