No cause for stroke is found in up to 30% of cases despite extensive investigations. These are called cryptogenic strokes (CS). 1 in 4 stroke survivors will suffer another in 5 years and this is a leading cause of fear and anxiety. A common reason for CS is an undetected heart rhythm disorder called atrial fibrillation (AF). AF occurs intermittently, so it may not be detected during the mandated 24-96 hours of rhythm monitoring that is performed as part of the standard post-stroke investigation strategy.

A randomised controlled study in 2014 showed that whereas this standard monitoring strategy picks up AF in 2% of CS patients, longer-term, continuous monitoring for 12 months can pick up AF in 13% of patients. This suggests the standard strategy may miss AF in a proportion of CS patients and thus also the opportunity to mitigate against further strokes with anticoagulation therapy. Prolonged monitoring has traditionally required a minimally-invasive surgical procedure to implant a recording device under the skin at a specialist centre. A specifically trained team is also required to interpret the large number of recordings this strategy yields.

The Apple Watch (AW) is a wristwatch able to monitor a wearer's heart rate and rhythm regularity and facilitates real- time, single-lead ECG recordings. This over-the-counter, non-invasive device has demonstrated feasibility and has a Certification (CE) Mark for detecting AF. It may offer a potential non-invasive alternative long-term rhythm surveillance strategy to diagnose AF in these patients.

The investigators propose a study in which CS patients will be randomised in a 1:1 ratio to receive additional AW monitoring on top of standard care versus standard care alone. The investigators shall then explore the incidence of AF in the two groups at 1 year and how it impacts clinical outcomes too.

Inclusion Criteria:

• Recent stroke or TIA event (<90 days) that is supported by consistency between symptoms and findings on brain magnetic resonance imaging (MRI) or computed tomography (CT). Patients with TIA will be enrolled only if symptoms at presentation were speech problems, limb weakness, or hemianopsia. Diagnosis shall be made by a Consultant Stroke physician.

• Stroke classified as cryptogenic following extensive investigations to rule out a cause as per local protocol, but to include at least:

  • Trans-thoracic echocardiogram
  • A period of at least 24-hour rhythm monitoring with no evidence of AF.
  • MRI or CT-angiography of the brain

• Sufficient mobility and dexterity to perform an ECG recording on the AW by touching the dial on the watch when worn with the contralateral hand for 30 seconds.

• Access to a smartphone with Apple-operating system (OS) within their household for syncing with their watch.

• Participants must be able and willing to provide written informed consent to participate in the study.

Exclusion Criteria:

• Documented history of AF or atrial flutter.
• Expected to undergo heart surgery in the 1 year following the stroke event.
• Any episode of myocardial infarction, coronary intervention or coronary artery bypass grafting <1 month prior to the stroke event
• Any other indication for oral anti-coagulation.
• Patient has a cardiac implantable electronic device in-situ already or is expected to undergo implantation in the 1 year following the stroke event (excluding implantable loop recorder for the investigation of the CS).
• Previous left atrial (LA) ablation or LA surgery
• Life expectancy less than 1 year