Recipient organisationNIHR Oxford Biomedical Research Centre
NIHR supportRecorded as supported by this research centre
PeriodMar 2025 — Oct 2026
In plain English
AI plain-English summary
Every day, thousands of people with atrial fibrillation take blood thinners they may not need, exposing them to unnecessary bleeding risk. The RESPOND-AF trial tests a radical alternative: patients take the medication only when a smartphone alert tells them an AF episode has started, and stop 30 days after it ends. Current guidelines recommend lifelong daily blood thinners for anyone with AF and a high stroke risk score, regardless of how often or how long their episodes last. But stroke risk is not constant—it spikes after an episode and returns to baseline within a month. Meanwhile, the bleeding risk from daily anticoagulation is constant and can be life-threatening. The trial asks whether intermittent, episode-triggered dosing can preserve stroke protection while cutting bleeding events. If it works, this “pill-in-pocket” approach could transform care for millions. Patients would avoid months or years of unnecessary medication, reducing hospitalisations for major bleeds. The system relies on a small implantable cardiac monitor that beams AF data directly to a smartphone via low-energy Bluetooth, triggering an automated alert. The study, based at John Radcliffe Hospital in Oxford, will follow participants for 12 months. Medtronic provides financial sponsorship.
View original technical description
Atrial Fibrillation (AF) is the most common cardiac arrhythmia and carries an increased risk of stroke. Stroke risk is commonly assessed using the CHA2DS2-VASC scoring system. To reduce stroke risk, guidelines advise AF patients with higher CHA2DS2-VASC scores be treated with oral anticoagulation (OAC), also known as blood thinning medication. OAC reduces the stroke risk, however it also increases the risk of bleeding episodes, which can be major and life-threatening. AF patterns can vary between patients. One patient may have only one 10-minute episode of AF per year, while another may have dozens of episodes lasting hours or days. The guidelines advising daily, lifelong OAC do not distinguish between these patients. However, there is evidence suggesting stroke risk is higher in patients with longer, more frequent AF episodes. There is also evidence that stroke risk increases following an episode of AF, returning to baseline risk after 30 days. For these reasons, we designed the RESPOND-AF trial to assess a new approach, whereby patients only take OAC in response to an AF episode. 30 days after the AF episode ends, the patient stops taking OAC. The aim is to reduce OAC usage for patients, thereby reducing their risk of major bleeding episodes, while maintaining effective blood-thinning when AF occurs. In RESPOND-AF, patients have a small Implantable Cardiac Monitor (ICM) inserted under their skin on the chest. The LINQ-II ICM device (Medtronic) connects directly with patients smartphones via low-energy BlueSync technology. In RESPOND-AF, uniquely, any qualifying episode of AF will trigger an automated smartphone notification to promptly start daily OAC until they are free of AF for 30 days. The study will be conducted at John Radcliffe Hospital, Oxford. Participants will be actively enrolled for a 12-month treatment period. RESPOND-AF has received financial sponsorship from Medtronic.
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