The technology

Reveal LINQ ICM (Medtronic) is an insertable cardiac monitoring device (also known as a cardiac event recorder or implantable loop recorder). It is indicated for people with clinical symptoms of cardiac arrhythmias and for people who have transient symptoms that suggest cardiac arrhythmia.

This briefing focuses on the Reveal LINQ ICM for detecting AF in people who have had cryptogenic stroke (which includes cryptogenic transient ischaemic attack [TIA] and embolic stroke of undetermined source [ESUS]). Other uses of the device, such as cardiac monitoring after transient loss of consciousness, are beyond the scope of this briefing.

Reveal LINQ ICM is a small (45 mm × 7 mm × 4 mm) wireless device that is inserted under the skin on the chest wall using an incision of less than 1 cm. The device weighs 2.5 g and has 2 electrodes, which monitor the patient's subcutaneous ECG, and an embedded accelerometer, which measures patient activity. Reveal LINQ ICM has a dedicated AF detection algorithm that detects true AF based on incoherence in the R–R interval of an ECG wave over a minimum of 2 minutes.

Cardiac information is recorded by the device in response to either automatically detected arrhythmias or patient activation. The memory capacity of the device can store up to 27 minutes of ECG recordings from automatically detected arrhythmias, up to 30 minutes of ECG recordings from patient-activated episodes and 2 minutes of the longest AF episode stored since the last interrogation. New ECGs overwrite older ones when the storage capacity is met. Reveal LINQ ICM is a magnetic resonance (MR)-conditional device; this feature allows the safe scanning of a patient implanted with Reveal LINQ in an MR system.

The system also includes a patient assistant and a patient monitor, which patients can use unsupervised when not in hospital. The patient assistant is a battery-powered, hand-held radiofrequency device, which when held in front of an implanted ICM can activate the ICM to record cardiac data. When the patient monitor is plugged in within 2 metres of the patient and has adequate cellular signal, data from the ICM is wirelessly sent to the patient monitor and uploaded via the Medtronic CareLink network service (see NICE's advice on CareLink for remote monitoring) for review by a physician.

Current care pathway

Some people with cryptogenic stoke will have AF, which puts them at increased risk of subsequent stroke. If AF is diagnosed, anticoagulant therapy can be offered to reduce this risk. People with cryptogenic stroke are routinely assessed for undiagnosed AF. This typically involves using a standard ECG device to monitor heart rhythm over a short period (typically a few seconds). This can be effective at detecting permanent AF, but may miss intermittent AF.

If a person with cryptogenic stroke is suspected to have intermittent AF, they may be offered heart-rhythm monitoring using a 24‑hour ambulatory ECG or a 24‑hour event recorder. Extended ECG monitoring may be done for 7 or 30 days. In some cases, longer-term monitoring using an implantable cardiac monitor may be needed; this is put into the person's chest by a cardiologist in a catheterisation laboratory.

Currently there is variation in NHS care pathways on how long an episode of AF should last for the person to be diagnosed as having AF. Some clinicians diagnose and treat an AF episode of any length of time; others will only consider treatment if an AF episode has exceed a threshold varying from 30 seconds to 6 hours. The most common threshold used in NHS care pathways is 2 minutes. This variation means that the number of false positives (people diagnosed with AF who do not actually have the condition) and the number of false negatives (people who do have AF, but is it 'missed' by the monitoring device) varies.

The following publications have been identified as relevant to this care pathway:

Innovations

Reveal LINQ has a proprietary AF detection algorithm with an enhanced p‑wave evidence score, which is designed to reduce the false positive detection rate. Reveal LINQ ICM is also smaller than other implantable monitoring device and can be implanted in an outpatient setting rather than in a cardiac catheterisation laboratory.

Reveal LINQ ICM has a memory capacity of 59 minutes. It can provide continuous monitoring for up to 3 years.

Population, setting and intended user

Reveal LINQ ICM is intended to be used to detect AF in people who have had cryptogenic stroke including TIAs and ESUS. The device can be inserted in an outpatient or day-case setting. The procedure is done by a healthcare professional such as a doctor or nurse in cardiology, neurology or stroke medicine, or a cardiac physiologist. Reveal LINQ ICM is intended to replace ICMs that need implanting in a catheterisation laboratory and non-invasive ECG monitoring methods used to detect AF in people who have had cryptogenic stroke.

Costs

Technology costs

Table 1 Estimated technology costs*

Description

Cost

Cost of Reveal LINQ with MyCareLink patient monitor (excluding VAT)

£1,800

Follow-up costs; 2 per year over 3 years

£474

Estimated daily cost over 3 years of continuous monitoring

£3.05

* Additional procedure costs are: cost of implant plus consumables, £96; cost of explant plus consumables, £889.

Costs of standard care

Electrocardiogram monitoring or stress testing (EY51Z) costs are £122 on the outpatient tariff or £369 for a day case.

Costs of implantable loop recorders (same cost for day-case and outpatient procedures):

  • £3,982 for implanting electrocardiography loop recorder with critical care (CC) score 3+ (EY12A)

  • £3,878 for implanting electrocardiography loop recorder with CC score 0–2 (EY12B).

Resource consequences

Using Reveal LINQ ICM would lead to increased costs compared with non-invasive cardiac rhythm monitoring. This could be offset if the device can diagnose AF more effectively than existing heart-rhythm monitors, which in turn could prevent more strokes. Diamantopoulos et al. (2016) estimated the cost effectiveness from an NHS perspective of ICMs for detecting AF in people with cryptogenic stroke; this was done using a lifetime Markov model. The analysis used data from literature and a multicentre RCT comparing Reveal XT (a predecessor model) with conventional ECG monitoring (CRYSTAL‑AF trial; Sanna et al. 2014). Patients monitored with an ICM had fewer recurrent strokes and reduced costs related to stroke and the post-stroke period. However, overall costs remained higher than standard care (£19,631 compared with £17,045). The base-case incremental cost-effectiveness ratio (ICER) when patients with AF were treated with non-vitamin K oral anticoagulants (NOACs) was £17,175 per quality-adjusted life year (QALY) and £13,296 per QALY when warfarin replaced NOACs.

If the device can be implanted by a specialist nurse or other healthcare professional, and if it can be used in place of an invasive heart-rhythm monitor – which are implanted in a in a catheterisation laboratory – it may lead to cost savings. Kanters et al. (2016) did a cost comparison in hospitals in the UK, France and the Netherlands. It looked at the costs of implanting Reveal XT in a catheterisation laboratory compared with inserting Reveal LINQ outside a catheterisation laboratory. The estimated cost savings were: €662 in the UK; €781 in France; and €682 in the Netherlands.

Reveal LINQ ICM is used in NHS cardiology departments for other indications, including transient loss of consciousness. These services may need expanding if use of the device was extended to people with cryptogenic stroke. The cost of training a person to insert and program the Reveal LINQ ICM device is included as part of the Reveal LINQ ICM with CareLink service.

According to the company, 17 NHS organisations currently use Reveal LINQ ICM for detecting AF in cryptogenic stroke. If adopted it would be used alongside a range of non-invasive heart-rhythm monitors.