LAUSR

Atrial fibrillation (AF) profoundly affects individual patients and the health system at large. The substantial morbidity, mortality, and health-related expenditures associated with this exceedingly common arrhythmia cannot be underestimated.1 Indeed, the association between AF and increased risk of stroke (often debilitating) is well established.2 As such, screening for AF is of paramount interest to public health. In 2018, the US Preventive Services Task Force (USPSTF) found that available evidence was insufficient to assess the balance of benefits and harms of using the electrocardiogram (ECG) to screen for AF; moreover, they reported that ECG screening may not detect more AF than usual care (ie, pulse palpation).3 The USPSTF is now broadening the scope of its initial recommendation: for adults aged 50 years and older without a diagnosis or symptoms of AF and without a history of transient ischemic attack or stroke, “the current evidence is insufficient to assess the balance of benefits and harms of screening for AF” (I statement).4,5 At the same time, through a rigorous systematic review, the USPSTF recognizes that there is adequate evidence that intermittent screening strategies and continuous screening may identify undiagnosed AF more effectively than usual care.4,5 However, the central issue rests on the inadequate evidence base for the benefits that can result from broad AF screening. The outcomes that may result—specifically, initiating anticoagulant therapy from incidentally discovered AF or even early rhythm control strategies—may result in harm. Future opportunities lie in refining the populations considered for screening. For example, a 2019 USPSTF recommendation states that abdominal aortic aneurysm screening is not recommended for all patients but rather the high-risk subset of men who are aged 65 to 75 years and previously smoked.6 Similarly, for lung cancer screening, the USPSTF recommends low-dose chest computed tomography only for individuals aged 50 to 80 years who have a 20 pack-year smoking history and currently smoke or have quit within the past 15 years.7 Although AF is more prevalent than these conditions, it is plausible that screening an entire population above a specific age threshold will fail to demonstrate merit compared with an approach of targeted screening. As the new USPSTF recommendation notes,4,5 the evidence base for optimal screening and the effectiveness of treatment is limited. This is, in large part, because available studies offer different approaches regarding optimal screening, deriving stroke risk, and informing treatment thresholds. Understandably, studies approach screening using a binary screening for AF (ie, present or absent). Our current practice is to measure risk in terms of ordinal stratification scores. However, identifying patients with or without AF and assessing their stroke risk with a number is misaligned with the remarkable heterogeneity in patients with AF.8 AF lies along a spectrum of importance, and several studies have suggested that assessing the burden of AF, rather than the presence or absence, may be a better approach. One such study is the recently published LOOP trial,9 which enrolled approximately 6000 older patients without AF with a median CHA2DS2-VASc score of 4 and randomized them to implantable loop recorder (ILR) monitoring or usual outpatient care. The intervention group was focused on early AF detection, whereas the primary end point was a clinical outcome: time to first stroke or systemic arterial embolism. The study included a recommended intervention of anticoagulation if AF greater than 6 minutes was discovered. Patients were followed-up for approximately 5 years. Not surprisingly, detected AF was significantly higher in patients with an ILR (32% vs 12%). Among those with a diagnosis of AF, 30% of patients with ILRs received anticoagulation vs 13% of + Related article at jama.com