Immediate ECG Monitoring Cuts Mortality in Unexplained Syncope

Immediate ambulatory ECG monitoring initiated in the emergency department (ED) did not reduce recurrent syncope but more than doubled arrhythmia detection and was associated with a 50% reduction in all-cause mortality at 1 year, according to results from the ASPIRED trial presented in a Hot Line session at the European Society of Cardiology (ESC) Congress 2026 in Munich, Germany, and published simultaneously in the New England Journal of Medicine.¹

"It can be difficult to determine the cause of syncope in the ED as many rhythm disturbances occur intermittently and are no longer present by the time patients arrive in hospital. Some patients then have to wait weeks or even months for investigations," Matthew Reed, MD, principal investigator of ASPIRED and professor at The Usher Institute, Edinburgh, United Kingdom, said in a statement. "Prior to the trial, preliminary evidence suggested that cardiac monitoring, initiated during the ED visit, was beneficial for detecting arrhythmias. The ASPIRED trial therefore evaluated whether fitting patients with a 14-day ECG monitor immediately after ED assessment could improve their clinical outcomes."

ASPIRED Trial Design, Primary Results

ASPIRED was conducted at 45 hospitals across the United Kingdom. Adults with unexplained syncope after ED evaluation were randomly assigned in a 1:1 ratio to 14-day ambulatory cardiac monitoring or their hospital's standard management practice. Patients in the monitoring group wore a small, waterproof, leadless, non-invasive heart monitor continuously recording cardiac rhythm, with a button to press if another syncopal event occurred; patients in both groups recorded syncopal episodes in a paper diary.¹

A total of 2234 patients underwent randomization (n = 1123 to the intervention group and n = 1111 to the standard-care group), making ASPIRED the largest randomized trial to date evaluating immediate ambulatory ECG monitoring in unexplained syncope.¹

After exclusion of patients with no follow-up data, 1970 patients (n = 1004 intervention and n = 966 standard-care) were included in the primary analysis; the mean age was 58.3 years, and 52.1% were male.¹ For the primary endpoint, no significant difference was observed in the mean number of self-reported syncope episodes at 1 year between the monitoring and standard-care groups (1.37 vs 1.58; incidence rate ratio, 0.89; 95% CI, 0.68-1.18; P = .42).¹

Arrhythmia Detection, Treatment, and Mortality Findings

Monitoring more than doubled the detection of clinically significant cardiac arrhythmias compared with standard care (22% vs 9%) and led to substantially earlier diagnosis (median 22 days vs 55 days).¹ Monitoring also increased the proportion of patients receiving appropriate treatment, including pacemaker implantation (6.8% vs 4.6%) and antiarrhythmic therapy (10.8% vs 7.3%).¹

Monitoring was associated with a 50% relative reduction in all-cause mortality at 1 year (1.5% vs 2.9%), and patients reported high acceptability of the device. Mortality was a secondary rather than a prespecified primary end point, and Reed noted further research is needed to confirm and explain this survival signal. A total of 49 adverse events were reported in the intervention group compared with 8 in the standard-care group, though only 1 serious adverse event occurred in each group.¹

Reed summarized the trial's clinical implications despite the negative primary end point. "Although immediate ECG monitoring did not reduce recurrent fainting, it enabled earlier identification of serious cardiac rhythm disorders, allowing patients to receive treatment much sooner, reducing uncertainty and anxiety, and potentially preventing avoidable deaths," Reed said. "These findings suggest that early monitoring should be considered as part of routine ED care for patients with unexplained syncope, while further research explores the observed survival benefit."

References

1. ESC. Wearable monitor improves diagnosis of heart rhythm disorders after fainting. August 31, 2026. Accessed September 2, 2026. https://www.escardio.org/news/press/press-releases/wearable-monitor-improves-diagnosis-of-heart-rhythm-disorders-after-fainting/

2. Reed MJ, Grubb N, Lang C, et al. Immediate ambulatory electrocardiographic monitoring in syncope. N Engl J Med. 2026. doi:10.1056/NEJMoa2605812

3. Reed MJ, Grubb N, Lang C, et al. Multicentre open label randomised controlled trial of immediate enhanced ambulatory ECG monitoring versus standard monitoring in acute unexplained syncope patients: the ASPIRED study. BMJ Open. 2023;13:e069530.