A RANDOMIZED CLINICAL TRIAL OF SCREENING FOR ATRIAL FIBRILLATION WITH A 14-DAY PATCH MONITOR: ANALYSIS OF ECG RECORDINGS FROM THE GUARD-AF STUDY

ABSTRACT

Background: Screening for atrial fibrillation (AF) is attractive because AF can remain undiagnosed and AF-related stroke can be prevented by anticoagulants (OAC). Methods: A randomized trial of screening for AF in individuals ≥70 years old without AF. Stroke and major bleeding are the efficacy and safety outcomes, ascertained from claims databases and electronic health records. Screening is done using a Zio®XT 14-day continuous cardiac rhythm patch monitor and compared, 11, to usual care. Use of OAC for detected AF is decided by patients and their physicians. The planned sample size was 52,000 recruited from U.S. primary care practices. Enrollment was severely hampered by the COVID-19 pandemic and stopped May 31, 2021 with 11,931 participants. Follow-up for stroke and bleeding events continues. Here, we report patch monitor findings from the 5,965 participants randomized to the screening arm. Results: 5,720 (96%) participants returned patches with analyzable data, the largest sample of patch monitor AF screening to date. Median (IQR) age was 75 (72, 79) years;57% were women. Median wear time was 13.9 (13.7, 14.0) days and median analyzable time was 98.4% (95.6, 99.5). 255 (4.5%) participants had AF, including 30 (0.5%) with 100% AF. 100% AF was more common in those age ≥80 (1.0%) than among younger participants (0.40%), p<.01. In the 225 participants with paroxysmal AF (PAF), median AF “burden” was 0.48% (0.016-2.5) of time monitored [78 (3.2, 454) minutes]. Median number of AF episodes during monitoring was 3 (1, 19). Median longest single AF episode was 60 (3-278) minutes. AF burden and length of longest episode were highly correlated (r=0.79, p<.001). Neither of these measures of PAF were associated with either age or sex. Conclusion: In GUARD-AF’s older primary care population, 0.5% of screened participants had persistent AF and 4% had PAF detected within 2 weeks of monitoring. In those with PAF, average AF burden was low but >25% had an episode of ≥4.6 hours of continuous AF, suggesting increased stroke risk. The need for stroke-preventive interventions (e.g., OAC) for screen-detected PAF remains a critically important research question.