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Effect of Screening for Undiagnosed AF on Stroke Prevention
Quick Takes
- GUARD-AF was a randomized prospective trial to assess whether screening for atrial fibrillation (AF) using a 14-day continuous electrocardiographic (ECG) monitor in people ≥70 years seen in primary care practice would reduce stroke hospitalizations.
- GUARD-AF was a prematurely early terminated clinical trial, and it failed to demonstrate that screening for AF using a 14-day continuous ECG monitor in people ≥70 years of age seen in primary care practice reduced stroke hospitalizations.
Study Questions:
Does screening for atrial fibrillation (AF) using a 14-day continuous electrocardiographic (ECG) monitor in people ≥70 years of age seen in primary care practice reduce stroke hospitalizations?
Methods:
GUARD-AF (Reducing Stroke by Screening for Undiagnosed Atrial Fibrillation in Elderly Individuals) was a prospective, randomized controlled trial. Participants in primary care practices were screened for AF using a 14-day continuous ECG monitor. Oral anticoagulation was not mandated; rather, it was the result of the physician/patient decision-making. The primary efficacy and safety outcomes were hospitalization due to all-cause stroke and bleeding, respectively.
Results:
A total of 149 primary care sites in the United States participated. The trial was prematurely terminated by the sponsor. The study enrollment was 11,905 participants. Median follow-up was 15.3 months. Median age was 75 years, and 56.6% were female. Diagnosis of AF was 5% in the screening group and 3.3% in the usual care group, and initiation of oral anticoagulation after randomization was 4.2% and 2.8%, respectively. The risk of stroke in the screening group was 0.7% versus 0.6% in the usual care group. The risk of bleeding was 1.0% in the screening group versus 1.1% in the usual care group.
Conclusions:
The authors conclude that in this prematurely early terminated clinical trial, screening for AF using a 14-day continuous ECG monitor in people ≥70 years of age seen in primary care practice did not reduce stroke hospitalizations.
Perspective:
AF is associated with a four- to five-fold increase in the risk of stroke, and oral anticoagulation significantly reduces the risk of stroke. However, no study has yet established that AF screening in the general population lowers stroke rates. The authors of this ambitious trial were stymied by the COVID pandemic, which resulted in slow enrollment and premature termination of the trial by the sponsor. Admittedly, there was also a lower-than-expected number of clinical events and there was a relatively low (55%) use of oral anticoagulants among cases of newly diagnosed AF (the trial did not mandate oral anticoagulation; the decision about anticoagulation was up to the physician and the patient). The finding—that screening for AF using a 14-day continuous ECG monitor in people ≥70 years of age seen in primary care practice did not reduce stroke hospitalizations—suggests that a very large population of the elderly at high risk for ischemic stroke would need to be studied with several years of follow-up in order to assess clinical benefit of screening for AF to reduce stroke risk.
Clinical Topics: Anticoagulation Management, Arrhythmias and Clinical EP, Anticoagulation Management and Atrial Fibrillation, Atrial Fibrillation/Supraventricular Arrhythmias, Vascular Medicine
Keywords: Anticoagulants, Atrial Fibrillation, Electrocardiography, Stroke
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