A large-scale randomized trial has shown that remote atrial fibrillation screening using a wearable ECG patch produces a modest but statistically significant increase in AF diagnosis rates among older adults at elevated stroke risk. The AMALFI trial, presented at ESC Congress 2025 and simultaneously published in JAMA, found that 6.8% of participants who wore a 14-day ECG patch received an AF diagnosis within 2.5 years, compared to 5.4% in the usual care group.
Trial Design and Population
The investigator-initiated AMALFI trial recruited 5,040 participants aged 65 years and older from 27 primary care practices across the UK. Participants had a mean age of 78 years, with 47% being female and 19% having a prior stroke or transient ischemic attack. All participants had elevated CHA2DS2-VASc scores (≥3 for men, ≥4 for women) but no previous diagnosis of AF or atrial flutter.
The trial employed a fully remote approach, with participants randomized 1:1 to either receive an ECG patch monitor by mail or continue with usual care. The Zio XT patch from iRhythm was used for 14-day continuous ambulatory monitoring, with participants instructed to self-apply the device and return it for analysis.
Key Findings and Clinical Outcomes
The primary outcome showed a ratio of proportions of 1.26 (95% CI 1.02 to 1.57; p=0.03) favoring the intervention group. Professor Louise Bowman from Oxford Population Health, the trial's chief investigator, noted that "AF is associated with an increased risk of stroke, but AF can be difficult to detect as it often occurs without symptoms and/or infrequently."
Notably, 85% of participants assigned to the patch group actually wore and returned the device, with average wear time close to the full 14-day period. The patch detected AF in 4.2% of participants, revealing important patterns in AF burden distribution.
AF Burden Patterns and Treatment Impact
The study revealed a bimodal distribution of patch-detected AF burden. According to the results, 33% of cases had 100% burden, meaning participants were in AF throughout the entire monitoring period, while 55% had an AF burden below 10%.
Dr. Rohan Wijesurendra from Oxford Population Health explained: "About one-third of individuals had 100% AF burden — they were in AF all the time — but over half the individuals had a low burden of AF, less than 10%. This is important because increasing data suggests a low burden of AF may be associated with a slightly lower stroke risk than individuals who have a higher burden of AF."
The intervention led to increased anticoagulation exposure, with mean exposure to oral anticoagulation reaching 1.63 months in the intervention arm compared to 1.14 months in the control arm (difference 0.50 months; 95% CI 0.24 to 0.75; p<0.0001).
Stroke Outcomes and Clinical Implications
Despite the increased AF detection and anticoagulation use, stroke rates remained similar between groups. Stroke occurred in 2.7% of participants in the intervention arm and 2.5% in the control arm (event rate ratio 1.08; 95% CI 0.76 to 1.53).
A significant finding was that AF diagnosis unrelated to the patch occurred more commonly than anticipated in both groups. Wijesurendra noted: "AF diagnosis unrelated to the patch was much greater than we had imagined in both the patch arm and the usual care arm. Together, this meant that the difference between the arms at 2.5 years was much closer than originally estimated."
Future Implications for Population Screening
The researchers positioned AMALFI as "a simple remote trial, with the idea being that this could be expanded to a national screening program, for example, with minimal cost and minimal impact on participants and health care professionals."
Wijesurendra concluded: "Our trial shows that remote AF screening with an ECG patch monitor in older patients at moderate-to-high stroke risk leads to a modest increase in AF diagnosis and anticoagulation exposure. However, AF diagnosis unrelated to the patch occurred more commonly than anticipated and over half of the patch-detected AF burden was low burden (below 10%). This suggests that AF screening in this setting may have limited impact on stroke events."
The researchers indicated that longer-term and cost-effectiveness analyses of AMALFI are planned to provide additional insights into the clinical utility of remote AF screening programs.
