Screening for atrial fibrillation, revisited

In 2018, the U.S. Preventive Services Task Force (USPSTF) concluded that there was insufficient evidence to assess the balance of benefits and harms of screening for atrial fibrillation (AF) with electrocardiography. However, the proliferation of wearable devices capable of detecting brief episodes of cardiac arrhythmias raised the question of whether screening high-risk patients outside of the office, analogous to home blood pressure monitoring, might prove beneficial. In a scientific statement, the American Heart Association discussed the knowledge gaps regarding the risk of stroke and benefits and harms of initiating long-term anticoagulation in persons with subclinical AF.

Two randomized screening trials published in 2021 provided a mixed picture. In the LOOP Study, 6004 Danish adults aged 70 to 90 years with stroke risk factors were randomized in a 1:3 ratio to receive an implantable loop recorder (ILR) or routine medical care. ILR participants were contacted if they had atrial fibrillation lasting for at least 6 minutes and recommended to start anticoagulation. Control participants received electrocardiography as needed from their primary care physicians. After a median follow-up of 64.5 months, 32% of patients in the ILR group and 12% of patients in the control group had atrial fibrillation detected, with similar proportions initiating oral anticoagulation. However, there was no significant difference in the primary outcome of stroke or systemic arterial embolism (4.5% of patients in the ILR group vs. 5.6% in the control group). Rates of major bleeding were not statistically different between the groups.

In the STROKESTOP trial, 28,768 Swedish adults aged 75 or 76 years were randomized to receive an invitation to screening with a handheld single-lead electrocardiogram twice daily for 2 weeks or usual care. After nearly 7 years of follow-up, a composite outcome of stroke, systemic embolism, hospitalization for bleeding, or all-cause mortality was slightly less likely to occur in the intervention group (NNT=93), but differences in individual outcomes were not statistically significant.

Reviewing these trial results and additional data, the USPSTF recently updated its 2018 statement and concluded that the evidence remains insufficient to make a recommendation. An accompanying editorial in JAMA Internal Medicine by Drs. John Mandrola and Andrew Foy (who authored a 2019 editorial on the downsides of detecting asymptomatic atrial fibrillation in AFP) noted that despite the potential benefits of widespread cardiac rhythm monitoring on cardiovascular and stroke risk, it "will also lead to misdiagnosis and downstream cascades of care" and that the "work-up of [arrhythmias] can lead to anxiety, iatrogenic harm, and excess health care costs."