Dr. Yusuf Bozkurt

Name of the Study: ReducinG stroke by screening for UndiAgnosed atRial fibrillation in elderly inDividuals (GUARD-AF)

Published in Congress: ESC 2024

Link: https://www.jacc.org/doi/full/10.1016/j.jacc.2024.08.019

Background:
Atrial fibrillation (AF) is the most common cardiac arrhythmia in adults and significantly increases the risk of ischemic stroke, particularly in elderly individuals. This stroke risk can largely be mitigated through long-term oral anticoagulant (OAC) therapy. However, AF can often be asymptomatic, leaving patients untreated and leading to diagnosis only after an ischemic stroke has occurred. Recent studies have shown that prolonged screening can improve AF detection, but no trials have yet demonstrated a reduction in stroke rates through AF screening. Clinical guidelines for AF screening vary on this issue.

Objective:

The primary objective of the GUARD-AF study is to determine whether a 14-day continuous single-lead ECG patch used to screen individuals aged 70 and older can identify undiagnosed AF cases and whether OAC therapy initiated after detection can reduce stroke rates.

Methods:
GUARD-AF is a screening trial that includes individuals aged 70 and older without a prior diagnosis of AF or atrial flutter. Participants were randomly assigned to either a screening group, in which they were monitored using a 14-day continuous single-lead ECG patch or to a control group receiving standard care without additional monitoring. The trial does not provide any medications (e.g., anticoagulants), and the management of detected AF cases is determined by the patient and their primary care physician. The primary efficacy endpoint is hospitalization due to ischemic or hemorrhagic stroke, and the primary safety endpoint is hospitalization due to bleeding events.

Results:
Due to the impact of the COVID-19 pandemic, the study was terminated earlier than planned, with a total of 11,931 participants enrolled from 149 primary care centers. Of the 5,965 participants in the screening group, 5,713 (96%) successfully completed the monitoring and had analyzable results. The median follow-up was 15.3 months (Q1-Q3: 13.8-17.6 months). All participants were over the age of 70, with a median age of 75 (Q1-Q3: 72-79). The cohort was composed of 56.6% women, 88.1% White, 7.1% Black, and 3.6% Asian participants.
The stroke risk in the screening group was 0.7%, compared to 0.6% in the standard care group (HR: 1.10; 95% CI: 0.69-1.75). The bleeding risk was 1.0% in the screening group and 1.1% in the control group (HR: 0.87; 95% CI: 0.60-1.26). AF diagnosis rates were 5% in the screening group and 3.3% in the control group, with post-randomization initiation of OAC therapy at 4.2% and 2.8%, respectively.
During the median follow-up period, 37 participants in the screening group (0.7%) were hospitalized for stroke, compared to 34 participants in the control group (0.6%). The rate of hospitalization for bleeding, the primary safety endpoint, was similar across both groups—52 (1.0%) in the screening group versus 60 (1.1%) in the control group. Additionally, the researchers noted that ECG screening led to a 52% increase in AF diagnoses and a parallel rise in the initiation of OAC therapy.

Conclusion:
This study found no evidence that screening for AF with a 14-day continuous ECG monitor in individuals aged 70 and above in primary care settings reduces stroke-related hospitalizations.

Interpretations:
The findings from the GUARD-AF study highlight both the potential benefits and limitations of AF screening in elderly populations. While screening with a 14-day continuous ECG monitor resulted in a 52% increase in undiagnosed AF detection, this early diagnosis did not lead to significant differences in clinical outcomes, such as stroke or major bleeding. The low median AF burden and short episode duration (median 0.48% AF time, longest episodes <40 minutes) suggest that not all screen-detected AF cases carry the same stroke risk. The early termination of the study due to the COVID-19 pandemic limited the power to detect long-term clinical benefits, particularly regarding stroke prevention. Larger-scale trials are necessary to clarify the clinical benefits of AF screening and to determine optimal management strategies for screen-detected AF cases.