Continuous rhythm monitoring with implantable cardiac monitors and wearable devices with real-time smartphone alerts during AF episodes: a feasibility study

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Atrial fibrillation (AF) is the most common heart rhythm problem in adults and affects 1 in 50 people in the UK. It is caused by the upper chambers of the heart – the atrias, beating irregularly, resulting in blood being pumped around the body less effectively. This increases the risk of blood clots, which if they travel to the brain, can cause a stroke.

To protect against this, many people with AF take anti-coagulant medication (“blood thinners”) to reduce the risk of a clot forming. However, taking this kind of medication daily comes with its own risk of harmful side effects ranging from easy bruising to excessive bleeding. Many people with AF will only experience occasional episodes, as little as a few times a year, and yet will be on daily anti-coagulant medication. Recent research has indicated that in patients with long-gaps between episodes of AF, shorter periods of anti-coagulant medication can be enough to protect against stroke. Therefore, these patients are exposing themselves to the potential harmful side effects of anti-coagulants all year round, when they may only need them for a few days each year.

Professor Betts and his team have developed a more tailored approach to continuous monitoring of AF. The project involved the use of the LINQ II implantable cardiac monitor, which is the size of a paperclip and is injected under the skin where it can constantly monitor heart rhythm and send through alerts if AF occurs. The team then built a new software for this monitor which allows for alerts to be sent directly to patients’ phones, letting them know when their heart is beating irregularly, so that they could take their medication. This novel software works 24/7 and sends alerts automatically. The results showed that for this new system, the average time from AF episode to patient alert was 2.5 hours, considerably lower than when using the existing software system.

The research team then compared the implantable cardiac monitor with two wearable pieces of heart rate monitors – the Apple watch and the Skylabs CART-I ring, over three months. The team wanted to see if the wearable technology was as accurate as the implantable one, which could benefit patients who would prefer not to have a device implanted. The findings from this research suggests the wearable devices are not as sensitive as the implantable cardiac monitor, and so that remains the gold standard going forward.

Overall, however, this study demonstrated the potential of the so-called “pill in the pocket” system for tailored management of atrial fibrillation.

These findings have led to the research team securing funding for a further study which aims to test the new software in a larger population group. This is a key step in changing how AF is managed in patients, to reduce the risks of constant medication and empower them to manage their condition in a proactive, responsive way. This study, the RESPOND-AF trial is currently recruiting participants and is due to be completed in 2027.