A two-week wearable heart monitor fitted shortly after patients attend A&E with unexplained fainting can more than double detection of potentially life-threatening heart rhythm problems, according to a UK trial funded by the British Heart Foundation (BHF).

A study involving 2,234 people across 45 UK A&E departments, found that arrhythmias were detected in 22% of patients given the chest-worn monitor, compared with 9% receiving standard care. The devices also identified abnormalities substantially sooner, at an average of 22 days compared with 54.5 days under standard care.

Notably, the researchers also observed a lower death rate after one year among patients who received early monitoring: 1.5%, compared with 2.9% in the standard-care group.

The findings, presented at the European Society of Cardiology Congress in Munich this week and published in the New England Journal of Medicine, could support a change in how patients with unexplained fainting are investigated.

Around 650,000 people attend A&E with unexplained fainting in the UK each year. Although fainting is often harmless, it can sometimes be caused by an arrhythmia, including potentially fatal disturbances such as complete heart block or ventricular tachycardia.

Diagnosing these conditions can be difficult because a patient's heart rhythm will often have returned to normal by the time they reach hospital. Current practice can involve referral for a Holter monitor, typically worn for around 48 hours, but patients may wait weeks or months before monitoring begins.

In the trial, half of the participants were fitted with a monitor within 72 hours of attending A&E. The device, roughly the size of a car key fob, was worn continuously on the chest for 14 days, with recordings assessed by clinicians after monitoring. Serious arrhythmias triggered an alert within 24 working hours.

The earlier monitoring led to more patients receiving treatment. Anti-arrhythmic medication was prescribed to 10.8% of patients in the monitoring group, compared with 7.3% receiving standard care, while 6.8% received a pacemaker compared with 4.6%.

Professor Matthew Reed, professor of emergency medicine at the University of Edinburgh, who led the study, said: “Continuous data on a patient’s heart rhythm for two weeks is invaluable to cardiologists when they are trying to diagnose an arrhythmia.

“As the results show, more patients with hidden heart rhythm problems were identified, and their treatment could be sped up.”

The researchers hope the findings will support wider adoption of early monitoring across the NHS.

Professor Bryan Williams, chief scientific and medical officer at the BHF, said the trial demonstrated how investment in research could translate into “life changing innovations in healthcare”, adding that the findings should help inform future clinical practice for patients experiencing sudden unexplained collapse.