Two-week monitor after unexplained fainting identifies life-threatening heart conditions
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Fitting a wearable heart monitor for 14 days when patients go to the ER with unexplained fainting improves detection of life-threatening heart problems, according to the results of a trial presented at the European Society of Cardiology Congress in Munich.
Using the two-week monitor, which is about the size of a car key fob, more than doubled the detection rate of heart rhythm problems in the study of 2,234 people. After one year, heart rhythm problems were identified in 22% of the monitor group, compared with 9% of those who received standard care.
The death rate after one year in the two-week monitoring group, at 1.5%, was almost half that of the standard care group, at 2.9%.
Heart rhythm problems, known as arrhythmias, were identified in an average of 22 days in those with chest-worn monitors, compared with 54.5 days with standard care. This included life-threatening arrhythmias such as complete heart block, ventricular tachycardia and a pause in the heartbeat of more than six seconds.
As a result of increased and quicker detection, more people who used the chest-worn monitor started treatment for their arrhythmia. The findings are also published in the New England Journal of Medicine.
Professor Matthew Reed, professor of emergency medicine at the University of Edinburgh, who led the study, said, "We were able to begin patient monitoring within 72 hours of people arriving at the ER, much faster than the current standard. 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.
"We believe that the lower death rate seen for this group is strong evidence that this new strategy can save lives. Hopefully it will be adopted by hospitals across the country, so that fewer people with a potentially life-threatening condition slip through the net."
The researchers estimate that around 650,000 people visit the ER with unexplained fainting each year in the UK. Regular unexplained fainting can seriously affect patients' lives, preventing them from doing day-to-day tasks such as driving. Although in many cases the cause is harmless, fainting episodes can be a sign of abnormal heart rhythms, some of which can be dangerous.
Arrhythmias in these patients are hard to diagnose. People who have fainted have usually recovered by the time they reach the ER, meaning their heart rhythm has likely returned to normal, and tests performed in the ER won't show any abnormalities.
Currently, patients with unexplained fainting are referred for tests such as a Holter monitor—a small wearable device that records the heart's rhythm—to try to identify arrhythmias. But a Holter monitor is usually worn for only 48 hours, so it can identify an arrhythmia only in this small time window.
Patients must also attend an outpatient cardiology clinic first, meaning that monitoring is done at any point from six weeks to two years after they visit the ER.
The new heart monitor is smaller and is worn in the middle of the chest. It can be worn continuously for the two-week period. In the trial, half of the study volunteers who attended one of 45 UK emergency departments with unexplained fainting were fitted with the new monitor. The other half received the current standard monitoring.
Data from the monitors were sent to clinicians after the two-week monitoring period, who then determined whether recordings showed signs of an arrhythmia and whether treatment was needed. If the monitor had picked up a serious arrhythmia, the patient's clinician was alerted within 24 working hours.
There was no difference in the average number of fainting episodes reported after one year—1.37 in the monitor group, compared with 1.58 in the standard care group.
However, improved detection of arrhythmias meant two-week monitoring improved the number of people receiving treatment. In the monitoring group, 10.8% were given antiarrhythmic medication, and 6.8% had a pacemaker implanted, versus 7.3% and 4.6%, respectively, in the standard care group.
The researchers hope that now the new strategy has been shown to help doctors treat more dangerous heart problems and reduce death rates, it will become standard practice in the NHS.
Professor Bryan Williams, chief scientific and medical officer at the British Heart Foundation, said, "This large trial is a good example of how BHF investment in research can drive life-changing innovations in health care. The study shows that monitoring the heart with simple new technology after a patient has had a sudden collapse can identify potentially life-threatening disturbances in heart rhythm that can be treated to reduce the risk of death.
"The results of this trial should certainly help inform future clinical practice when treating patients with sudden unexplained collapse."
Stephen's story
Stephen, from West Lothian, joined the trial after fainting while exercising on an elliptical trainer. The 68-year-old had been diagnosed with atrial fibrillation, a common arrhythmia that affects the top chambers of the heart and can raise a person's risk of having a stroke, when he was 49. However, he had never fainted until he did so twice within a week in August 2023.
"The first time came on all of a sudden," he said. "I was sitting in a chair in the living room, and I started fading in and out. I lost consciousness for a few seconds, and I had no idea what had happened. It was so out of the blue that I thought I should go to the doctor."
Stephen's doctor sent him to the hospital, where he was kept for the day while clinicians did standard checks. These did not flag any issues, so he was sent home and told to return if the symptom happened again.
"The next day, I was on the elliptical trainer, and I just passed out," he said. "This time, I was in the hospital for three days. They kept an eye on me, and they thought it might be exercise-related. I was given a stress test on a treadmill, which went all right."
It was at this point that a nurse asked Stephen if he'd like to join the trial.
"I didn't need any extra time to think it over. I thought it was a great opportunity to help others who might be in a similar situation. It's always important to get involved in things like this," he said. "The device is very user-friendly; it goes in the middle of your chest, and it's small enough that it doesn't get in the way at all. You can wear it whatever you're doing, even in the shower, and you hardly notice it."
He wore the monitoring device for 14 days but didn't experience any episodes of fainting during that time. However, the data from Stephen's device showed that his atrial fibrillation was not being controlled by his medication. The condition was causing his heart to beat at 227 beats per minute at certain points, a dangerously high number.
The clinicians caring for Stephen raised his dosage of bisoprolol, a medication that can help control heart rate.
"They advised me on all the different treatment options, and I decided to stay on the medication rather than have a cardiac procedure and see how I go. I'm very glad I took part in the trial and that this was picked up. I haven't fainted since. It looks like the treatment has been working, so I'm really happy," he said.
"The doctor signed me off, and I don't need regular checkups, but the door is always open to go back if I need to. Touch wood, it won't happen again, but if it does, I'm definitely in a better place to deal with it now."
Publication details
New England Journal of Medicine (2026).
Journal information: New England Journal of Medicine
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CardiologyEmergency medicineCommon illnesses & Prevention Provided by British Heart Foundation Who's behind this story?
Gaby Clark
MA in English, copy editor since 2021 with experience in higher education and health content. Dedicated to trustworthy science news. Full profile →
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