Feasibility Study of a New Peripheral Oedema Monitor for Heart Failure

The Heartfelt-1 device is a CE (Conformité Européenne = European Conformity) mark medical device used to measure biometric parameters of the foot and lower leg. The study aims at assessing the usefulness in patients suffering from heart failure, who have peripheral oedema. Models used for the measurements of foot and lower legs have not yet been validated for this group of patients, who are likely to have feet with abnormal surface contours and appearance secondary to oedema. Peripheral oedema can be a leading indicator of heart failure de-compensation which can lead to hospitalisation of patients, and therefore the device could be a useful clinical tool to monitor patients in their home. The Heartfelt-1 device has the ability to recognise the patient's feet (amongst an average size household setting), and trigger automatically the measurements when the feet are naked (for example as the patient goes in and out of bed). This makes the device an obvious choice for patients with compliance issues with current methods of monitoring (e.g. daily use of weighing scales) and treatment (e.g. diuretics) if it could be validated in this patient group.

The study has two general aims:

The first is to collect a time-series of data on inpatients with peripheral oedema caused by heart failure, as they receive intravenous or oral diuretic treatment to remove excess fluid and achieve optimal body weight and fluid balance. This data will be used both to determine the attainable resolution of foot biometric measurements on a patient as their fluid status changes, and also to further develop the algorithms used in the device and make them usable on a wide range of feet/lower legs which have been deformed by oedema. The data required for this study are images taken using the Heartfelt-1 device, as well as validation measurements such as the figure of eight using a medical grade tape measure, callipers, or the water displacement method using a volumetric gauge, at multiple time-points whilst the peripheral oedema reduces.

The second, on a second group of stable ambulatory (Heart Failure) HF patients with variable levels of oedema, is to evaluate the performance of the Heartfelt-1 device in determining foot biometric parameters one a wide range of patients at a single point in time. Patients with stable chronic heart failure will have their foot/lower legs measured by the Heartfelt-1 device, as well as standard medical measurement (figure of eight using a medical grade tape measure, callipers) and gold standard measurement (water displacement method using a gauge), as well as the patient's weight and a clinical grading of oedema. These will be compared and an estimate of the accuracy of the Heartfelt-1 device over this wider patient group can be extrapolated.

Inclusion criteria

• Inpatients with admission for de-compensated heart failure requiring increase or initiation of diuretic therapy for fluid congestion.
• Patients attending cardiology outpatients at the Royal Brompton hospital with a diagnosis of heart failure and fluid retention.
• Cardiology patient without fluid retention (cardiology controls) Non-Cardiology patient without fluid retention (controls)

Exclusion criteria

• Patients unable to provide informed consent.
• Unstable arrhythmias in previous 48 hours
• Systolic BP<90mmHg or need for inotropic support
• Ulceration on lower limbs (below shin) - excluded from water displacement but could have image recording and calipers
• Inability to transfer from bed to chair
• Patients with broken skin or cellulitis will not have their foot volume measured using the water displacement equipment to reduce the risk of infection for the patient and other participants.