Introducing implantable cardiac monitors to support detection of atrial fibrillation after cryptogenic stroke at Salford Royal NHS Trust

• Add implantable cardiac monitoring to the care pathway for people following cryptogenic stroke where AF was suspected to be the cause
• Continue to develop the ESUS (embolic stroke of unknown source) service
• Increase the proportion of eligible patients receiving an implantable cardiac monitor following cryptogenic stroke
• Implant the cardiac monitor within 12 weeks of the cryptogenic stroke

Stroke affects over 100,000 people annually in the UK and is the 4th leading cause of mortality. AF confers a 5 fold increase in stroke and stroke risk is independent of AF subtypes (paroxysmal, persistent or permanent).In addition, AF is a frequent cause of recurrent strokes.

In 2016, Salford Royal developed a consensus on ECG monitoring following cryptogenic stroke. People with ischaemic stroke are routinely assessed for undiagnosed AF at Salford Royal. If AF is diagnosed, anticoagulant therapy can be offered to reduce the risk of recurrent stroke. At Salford Royal, initial assessment of a stroke patient involves a clinical examination (pulse check) and using a standard 12-lead ECG device to monitor heart rhythm. This can be effective at detecting persistent or permanent AF, but may miss intermittent or paroxysmal AF (PAF).

If AF is still suspected as a cause of stroke, some patients will be offered extended cardiac monitoring. Currently at Salford Royal NHS Foundation Trust, 5 day non-invasive ambulatory monitoring (applied as an inpatients) is standard of care for non-invasive cardiac monitoring. This practice was implemented during a quality improvement initiative at the trust in 2019. However, the team were aware that even with this thorough investigative pathway, some cases of AF may still be missed because monitoring was limited to 5 days.

The team were aware of the CRYSTAL AF study which emphasised the importance of extended cardiac monitoring for detection of AF after cryptogenic ischaemic stroke/TIA. It concluded that ECG monitoring with an Implantable Loop Recorder (ILR) was superior to conventional follow-up.

The REVEAL LINQ device is an ILR device which provides a proprietary AF detection algorithm, which is designed to reduce false positive detections. It is a small size and easily inserted by appropriately trained individuals.

Given the information from the CRYTSTAL AF study and the developments in technology with the availability of REVEAL LINQ, Salford Royal set up a protocol following a multi-disciplinary consensus involving cardiologists, neuro-radiologists and stroke physicians to begin implanting REVEAL LINQ in suitable people.

To adopt REVEAL LINQ in the most effective way (ensuring all suitable patients are considered and it is inserted in those likely to achieve the highest yield), the trust developed a dedicated ESUS (embolic stroke of unknown source) service with a lead stroke consultant and outpatient clinic.

All potentially eligible patients are referred to the ESUS service to ensure standardised care and access to healthcare professionals with expertise in this aspect of stroke medicine. At first the service  is being offered to patients within the Salford catchment area but suitable patients across  Greater Manchester are also being offered this service.  

Salford Royal have developed a novel pathway guiding ILM insertion after acute stroke. The intended place in therapy for REVEAL LINQ ILM is in addition to standard care for patients after cryptogenic stroke or ESUS, whose PAF remains undiagnosed by standard stroke care. The trust have developed detailed policy document about using these devices and it includes the following inclusion criteria:

1. Embolic stroke of Unknown Source (ESUS)
2. Patients considered suitable for long term anticoagulation
3. Modified Rankin Score (mRs) ≤3

See key learning section for the trusts detailed exclusion criteria.

At the trust, it is the responsibility of the treating stroke clinician to ensure guidance is met prior to referring for ILR implantation. The clinician will also discuss the procedure explaining the risks, although the responsibility for formal consent rests with the individual doing the procedure. Follow-up following procedure will be undertaken by both Cardiology and Stroke department.

Referral Process and Follow-up

Patients meeting the criteria will be referred from the ESUS clinic (paper referral) directly for ILR implantation. It is anticipated that implantable loop recorders would be inserted within 12 weeks of an acute stroke.

The device is implantable in the cardiac catheter laboratory by either an advanced nurse practitioner or cardiac physiologist under local anaesthetic.

Post Implant, the Cardio-Respiratory Investigations department arrange 3 monthly virtual follow-up and highlight arrhythmias to the referring physician and/or cardiologist. It is anticipated that these patients will have a 1 year follow-up in the stroke clinic as well or earlier if AF detected.

Monitoring with LINQ-CareLink will continue until either an arrhythmia is detected or battery runs down (occurs at approximately 3-years post implant). It is not current practice to explant LINQ ILRs unless there is a specific medical reason to do so or at the request of the individual patient.

During the data collection period (March 2019 - August 2020), 87 patients were referred to the ESUS service and 18 were sent for ILR. One case of paroxysmal atrial fibrillation has been detected so far.

They have found it difficult to meet the target of implanting an ILR within 12 weeks of the acute stroke. This is because of delays in the tests required before the ILR can be inserted (that are required to assess suitability for ILR).

Following this success with people following cryptogenic stroke, in line with DG41, they are planning to explore extending this service to patients following TIA in the future. They are aware of the importance of the effectiveness of diagnostic pathways for TIA in ensuring appropriate people are identified.

• Collaboration between cardiology and the stroke service is important to developing a clear care pathway for these people
• Development of a robust arrhythmia detection pathway prior to insertion of ILR.
• Developing a dedicated service, where the clinical staff have experience and expertise in identifying the most suitable people in which to insert an ILR
• To increase capacity consider training more staff to insert REVEAL LINQ. The team are currently aiming to develop a training programme for members of the stroke team, in particular consultant stroke physicians and advanced practitioners, to be trained in inserting the devices

The trust developed the following inclusion and exclusion criteria:

The following Inclusion criteria should be considered when referring for ILR insertion:

1. Embolic stroke of Unknown Source (ESUS)
2. Patients considered suitable for long term anticoagulation
3. Modified Rankin Score (mRs) ≤3

When considering diagnosis of ESUS the following criteria and/or conditions should be excluded when referring for ILR insertion:

• Significant intracranial narrowing or extracranial stenosis (≥50%) or occlusions supplying the area of ischemia or dissection of intra/extracranial arteries supplying the infarcted area.
• Evidence of cardioembolic pathologies (major cardiac sources) including:

1. Exclusion of atrial fibrillation: No history of atrial fibrillation, atrial fibrillation on baseline ECG or on 5 day monitoring.
2. No evidence for atrial asystole, cardiac thrombus, mechanic valve replacement, myxoma or cardiac tumour and endocarditis.
3. Patent Foramen Ovale or other causes of right to left vascular shunting as a possible cause of stroke. Eligible patients aged under 55 are routinely assessed for PFO with contrast echocardiography.

• Lacunar infarct pattern in the region of perforator artery distribution (<1.5 cm CT, <2.0 cm DW-MRI).
• Rare stroke aetiologies like: migrainous infarction, vasculitis, genetic aetiology, or thrombophilia when considered relevant.
• Known or suspected malignancy (clinical and/or radiological)