Guidance

2 Heart failure algorithms

2 Heart failure algorithms

Clinical need and practice

2.1

Heart failure is a clinical syndrome caused by any structural or functional cardiac disorder that impairs the heart's ability to efficiently pump blood around the body. The most common symptoms of heart failure are breathlessness, fatigue and oedema. Conditions that can cause heart failure include:

  • coronary heart disease

  • high blood pressure

  • heart rhythm or valve abnormalities and

  • conditions affecting the heart muscle (cardiomyopathies and myocarditis).

    Around 920,000 people in the UK were living with heart failure in 2018 with an estimated 200,000 new diagnoses each year. Heart failure mainly affects people over 65, with an average age at diagnosis of 77.

2.2

Cardiac implantable electronic devices (CIEDs) are recommended as treatment options for some people who have or are at high risk of heart failure. The different types of CIEDs are pacemakers, implantable cardioverter defibrillators, and cardiac resynchronisation therapy devices.

2.3

Remote monitoring is the ability for a CIED to communicate wirelessly with a remote monitoring system. People who have CIEDs must be followed up by hospitals for regular technical reviews of how their device is working. They may also have scheduled appointments, during which the clinical events recorded by the device are monitored. There is a lot of variation in clinical practice and the frequency of these follow-up visits varies according to the person's condition. NICE's guideline on diagnosis and management of chronic heart failure in adults recommends that reviews are offered every 6 months for people whose condition is stable, but clinical experts highlighted that in practice most people would have a review annually. Sometimes clinical reviews are only triggered if the person with the CIED reports worsening symptoms.

2.4

Some CIEDs have algorithm-based remote monitoring incorporated in the device. Heart failure algorithms analyse and collate different clinical data recorded by the device to detect gradual worsening of heart failure. The system can send alerts to healthcare professionals to prompt a review of the stored data. This enables proactive investigation into the cause of the suspected decompensation, potentially before the person even feels symptomatic. This could ensure that people have appropriate treatment as early as possible, reducing the number of unnecessary hospital visits.

The interventions

There are 4 heart failure algorithms that were identified as relevant for inclusion in this assessment. Each algorithm is only compatible with specific CIEDs manufactured by the same company that makes the algorithm.

CorVue (Abbott Medical)

2.5

The CorVue algorithm works with the Merlin.net Patient Care Network (PCN) platform, and is intended for remotely monitoring for the early signs of heart failure in people who have compatible CIEDs. The CorVue algorithm collects intrathoracic impedance data from the CIED and transmits it to the Merlin.net PCN platform via the mobile app (myMerlinPulse). It does this using Bluetooth and an internet or mobile network connection to generate an alert. Or, instead of using the app-based smartphone transmitter, the company can provide a remote monitoring unit (Merlin@Home) that connects via Wi‑Fi, mobile or landline connection. Healthcare professionals can view the data transmitted by the device on the Merlin.net PCN platform. Access to Merlin.net and the mobile transmitter is provided as part of the CIED, and the CorVue algorithm comes free of charge with the CIED devices.

2.6

The CorVue algorithm automatically calculates the mean daily impedance (from 12 daily measurements). It also collects reference impedance data based on the previous 12 to 14 days, which changes continuously based on new impedance readings. If a consistent drop of daily impedance values is detected (13 or 14 consecutive days in congestion) then a congestive event is reported and detected during device check-up. Patient alerts can be activated via remote monitoring if the person wishes.

HeartInsight (Biotronik)

2.7

HeartInsight is a predictive algorithm designed to monitor for early signs of worsening heart failure in people with compatible CIEDs. The algorithm works with the BIOTRONIK Home Monitoring system. The HeartInsight algorithm combines the following 7 parameters into 1 composite score (calculated daily):

  • atrial burden

  • heart rate variability

  • general activity

  • thoracic impedance

  • heart rate

  • heart rate at rest and

  • premature ventricular contractions.

2.8

HeartInsight triggers an alert to healthcare professionals (via text message, email or both) once the prespecified threshold is exceeded for 3 consecutive transmissions (normally 3 consecutive days), indicating higher risk of worsening heart failure. The threshold is customisable. Upon receipt of an alert, a healthcare professional logs on to the Home Monitoring Service Centre website to review and assess the alert.

2.9

The system includes the handheld CardioMessenger device, which transmits data automatically and daily from the CIED to the BIOTRONIK Home Monitoring system via a mobile phone network. Access to HeartInsight has a one-off cost of £450 per person. Standard Home Monitoring is a separate cost.

HeartLogic (Boston Scientific)

2.10

HeartLogic is a diagnostic algorithm designed to monitor for early signs of worsening heart failure in people with compatible CIEDs. It works with the Latitude NXT Patient Management System. Measurements including heart sounds, thoracic impedance, respiration, heart rate and activity are collected by the implanted device. The HeartLogic algorithm then combines these into 1 composite index that indicates decompensation. Boston Scientific's HeartLogic and Latitude NXT Patient Management System work together to provide advanced monitoring and management capabilities for people with heart failure who have CIEDs. The system has daily data transfers to the clinical team. The transmitter can use a mobile phone connection or an internet connection to relay the data. The system is configured to send an alert to a healthcare professional when the index is over a set threshold (customisable by a healthcare professional). Healthcare professionals need to log on to the LATITUDE NXT website to receive alerts. Secondary notification of alerts may be through email or text message. Access to HeartLogic has a one-off cost of £3,650 per person, but discounts may be offered based on purchase volume.

TriageHF (Medtronic)

2.11

TriageHF is an alert-based algorithm used with CareLink remote monitoring. It is a monitoring system for identifying and managing an increased risk of heart failure or worsening heart failure in people with CIEDs. When TriageHF is used within a structured heart failure clinical care pathway it is called TriageHF Plus. TriageHF is hosted on the Medtronic CareLink network for collaborative management of heart failure between clinical teams. The algorithm monitors the following parameters:

  • atrial tachycardia

  • atrial fibrillation burden

  • ventricular rate during atrial tachycardia or atrial fibrillation

  • OptiVol fluid index (which tracks changes in thoracic impedance over time)

  • general activity

  • night ventricular rate

  • heart rate variability

  • percent of ventricular pacing

  • treated ventricular tachycardia or ventricular fibrillation and

  • defibrillator shocks.

    CareLink uses a plug-in monitor or a smartphone app for transmitting data. Using a mobile or landline connection, data is transmitted from the CIED to the CareLink network where it can be accessed by healthcare professionals. Data can be transmitted:

  • manually, if a person notices symptoms

  • automatically, based on TriageHF algorithm alert triggers, or

  • by scheduled transmission, based on a predefined date to replace a routine check.

    For each day the data is transmitted, the TriageHF algorithm generates a daily risk status of a heart failure event occurring in the next 30 days (low, medium or high risk). This is based on the maximum daily risk status for the previous 30 days. A heart failure management report is generated on the daily risk status. The CareLink network sends an alert for people who have high-risk score so that they can be contacted for a telephone consultation. Access to TriageHF and CareLink remote monitoring has a yearly cost of £100 per person.

The comparator

Conventional remote monitoring of heart failure in people with CIEDs

2.12

Standard care for monitoring heart failure in people who have CIEDs is periodic reviews of device function with a cardiac physiologist or cardiologist. A person will also have ad hoc reviews of symptoms with a GP, specialist nurse, cardiologist or a heart failure team. The number and timing of the reviews varies in practice depending on the person's symptoms (see section 2.3). The organisation of heart failure monitoring pathways varies in practice between different trusts, and even between different hospitals.