A large-scale randomized trial found that primary care screening for atrial fibrillation using a wearable electrocardiogram device increased diagnoses by 52% compared with usual care but did not significantly reduce the rate of hospitalizations for stroke.

Atrial fibrillation (AF) affects more than 40 million individuals worldwide. Current estimates suggest that one in three Europeans will develop AF during their lifetime. Individuals with AF face a fivefold increase in the risk of stroke.

Recent trials have demonstrated that one-time brief screening for AF may not significantly increase diagnoses. Other trials investigating longer-term screening found an increase in AF diagnoses, primarily paroxysmal AF. 

In the GUARD-AF trial, presented at the European Society of Cardiology (ESC) Congress 2024, researchers recruited 11,905 patients from 149 U.S. primary care sites. The patients had a median age of 75 years, and 57% of them were female. The screening group (n = 5,952) used the Zio XT continuous electrocardiogram (ECG) patch monitor for 14 days, while the control group (n = 5,953) received usual care. The study was terminated early due to the COVID-19 pandemic.

The trial was one of the largest to date using a 14-day, patch-based continuous ECG monitor as the screening strategy for AF. It began in December 2019 and aimed to examine whether AF screening using the continuous ECG patch monitor could identify older adults with undiagnosed AF, resulting in a reduced rate of any stroke compared with usual care.

Among the key findings were:

• AF diagnoses: 5% (n = 284) in the screening group vs 3.3% (n = 196) in the usual care group
• Oral anticoagulant therapy initiation: 4.2% (n = 239) in the screening group vs 2.8% (n = 167) in the usual care group
• Stroke events: 37 in the screening group vs 34 in the usual care group (numerically higher)
• Bleeding events: 52 in the screening group vs 60 in the usual care group (numerically lower).

The median follow-up period was 15 months. Among the patients randomly assigned to undergo screening, 5,684 (96%) of them returned ECG monitors with analyzable results.

The researchers used Medicare claims and Kaiser Permanente data to determine clinical outcomes. The study's early termination resulted in a lower than expected number of clinical events, limiting the ability to draw definitive conclusions about the ultimate benefit of AF screening in reducing stroke hospitalization rates.

The ESC has called for cardiovascular disease (CVD) and diabetes screening to be part of national and European Union Health Plans to prevent CVD and educate about cardiovascular health at a population level. This recommendation was based on the fact that CVD, primarily heart attack and stroke, remains the leading cause of death in Europe and worldwide.

The GUARD-AF trial contributed to the ongoing research on AF screening effectiveness. While it demonstrated a significant increase in AF diagnoses and subsequent anticoagulant therapy initiation through continuous ECG monitoring, it did not show a reduction in stroke hospitalization rates. The study's early termination limited its conclusiveness.

Study author Renato Lopes, MD, PhD, of Duke University Medical Center, has received research grants or contracts from Amgen, Bristol-Myers Squibb, GlaxoSmithKline, Medtronic, Pfizer, Sanofi-Aventis; funding for educational activities or lectures from Pfizer, Daiichi Sankyo, and Novo Nordisk; and funding for consulting or other services from Bayer, Boehringer Ingelheim, Bristol-Myers Squibb, Novo Nordisk.