This study will evaluate the Heartfelt device, a novel, passive monitoring system that detects early signs of fluid build-up in patients (oedema) with heart failure by measuring changes in foot and lower leg volume through capture of 3D images. The trial will assess whether this device, when added to standard NHS care, improves quality of life and reduces heart failure-related events compared to standard care alone.

Heart failure often causes fluid build-up in the legs and lungs, leading to symptoms like swelling and breathlessness. Spotting these signs early is important to help prevent worsening health and hospital admissions. While patients are encouraged to monitor their weight and symptoms, this can be hard to keep up with.

The study will involve 300 participants from at least 15 NHS hospitals and GP practices across the UK. People will be randomly placed into one of two groups: one will receive standard NHS care (including regular weight checks and symptom monitoring), and the other will receive the same care plus the Heartfelt device. The trial is partly blinded: participants may see technical messages (e.g. if the device goes offline), but only the group using the device will trigger clinical alerts.

The Heartfelt device takes daily images of the feet to track changes in size, without the need for any extra effort from the user. If important changes are spotted, alerts are sent to the clinical team so they can act quickly.

The study will look at quality of life, how often the device sends useful data, healthcare use, and how teams respond to alerts. It will also explore how easy the device is to use and whether it offers good value for money.

Patients will help shape the study to make sure the findings are relevant and useful for future care.

Inclusion Criteria: Participants are eligible if they meet all General Criteria and at least one of Pathways A, B, or C.

1. General Criteria (all participants must meet)

• Aged ≥18 years, AND
• Diagnosis of heart failure (any aetiology or LVEF classification), AND
• Documented or patient-reported moderate to severe leg oedema, AND
• Lives in the UK with a home environment suitable for installation of the Heartfelt device

Pathway A: High risk patient with daily diuretics

• Currently prescribed ≥40 mg/day of furosemide (or equivalent loop diuretic, eg. bumetanide or torsemide) for at least one month, AND
• Any cardiorespiratory admission** in the last 12 months (Includes outpatient IV diuretics, subcutaneous loop diuretics, or escalation to combination therapy with a loop diuretic and a thiazide or thiazide-like diuretic (eg: metolazone, bendroflumethiazide, indapamide etc).

Pathway B: High risk patient without daily diuretics

• Patients prescribed SGLT2 inhibitor (eg; dapagliflozin or empagliflozin) , AND

• Patients prescribed oral furosemide ≥40mg/day but advised to take it only as needed AND either:

  a) at least two admissions* caused or complicated by worsening heart failure in the previous 12 months, OR b) a measurement of plasma NT-proBNP exceeding 1,000 ng/L (pg/mL) in the previous 12 months Pathway C: Implanted Haemodynamic Monitoring Devices (minimum n=10 participants)

• Uses an implantable device designed to monitor congestion (e.g. CardioMEMS, HeartLogic, or equivalent)

• Enrichment criteria: Patients must also meet a minimum total score of 4 from the characteristics below.

  1. NYHA class III and IV (score: 2)

  2. ≥80 mg/day Furosemide or equivalent loop diuretic (score: 2)

  3. <3 Number of times the patient has weighed themselves in the last 2 weeks (score: 2)

  4. Help for essential daily activities required (score: 2)

  5. GRMT score <5 (score: 2)

  6. Use of a walking stick, walker or mobility scooter (score: 2)

  7. >2 Number of HF events in last 12 months (score: 2)

  8. Aged over 75 (score: 1)

  9. Health issues limiting daily activities (score: 1)

  10. Help getting to medical appointment required (score: 1)

  11. Problematic / not tolerated uptitration of medications:

      MRA (score: 1) SGLT2i (score: 1) Other (score: 1)

  12. English as a second language (score: 1)

  13. eGFR 20-45 (score: 1)

  14. Patient unable to regularly attend appointments for any reason (score: 1)

  15. >3 Number of co-morbidities (score: 1)

Exclusion Criteria:

• Amputation of both feet
• Bed-bound for more than 20h per 24h period
• Bandages to lower limbs every day
• Regular wheelchair user inside their home
• No fixed abode
• Participation in another interventional trial that may interfere with endpoints
• Life expectancy <6 months, in the opinion of the investigator
• Inability to provide informed consent due to cognitive impairment
• Language barriers that preclude understanding of trial procedures (unless translation resources are available in relevant language)
• Inability to install the device (even with assistance) allowing at least 6 months of data capture by the end of the study.
• Patients with severe aortic stenosis or awaiting a heart procedure or surgery
• Patient with end stage renal disease (eGFR <20)
• Pregnancy or lack of contraceptive measures if of child-bearing potential

Individual participant data (IPD) will only be shared if approved by the Trial Management Group and that suitable ethics approvals has been received for sharing of such information.

Both participants and care providers will be blinded, thus will not know whether patients are in the control or intervention arm.