Screening for atrial fibrillation: look harder, look longer, and improve stroke outcomes with oral anticoagulation

This editorial refers to ‘A prospective 5-year follow-up after population-based systematic screening for atrial fibrillation’ by J. Engdahl et al., on pages f306–f311. Oral anticoagulation with vitamin K antagonists (VKAs, i.e. warfarin) and non-VKA oral anticoagulants (NOACs) significantly reduces thromboembolism and all-cause mortality in patients with atrial fibrillation (AF).1 Nevertheless, there are still substantial numbers of AF patients admitted with ischaemic stroke, who are on antiplatelet alone or no oral anticoagulant. In the Swedish Riks-Stroke register including 94 083 patients with ischaemic stroke, 8.1% were associated with previously unknown AF and only 16.2% received oral anticoagulant within 6 months before stroke onset.2 This can perhaps be explained by the fact that approximately one-third of patients did not report any symptoms commonly attributable to AF (e.g. palpitations, shortness of breath, or chest pain), leading to a prolonged delay in AF diagnosis and timely initiation of anticoagulation therapy. Many patients with so-called embolic stroke of uncertain source (ESUS) may have AF if we look hard enough for long enough, using more sophisticated ECG monitoring.3 Given the increasing prevalence of AF, the identification of patients with asymptomatic AF has gained much attention, and thus, AF screening is now part of the holistic strategy to prevent stroke and mortality.4 Does symptomatic status matter, with regard to AF-related adverse outcomes? A substudy of the AFFIRM (Atrial Fibrillation Follow-up Investigation of Rhythm Management) trial demonstrated that the presence or absence of symptoms associated with AF were not significantly associated with the risk of mortality.5 On the other hand, the EurObservational Research Programme Atrial Fibrillation (EORP-AF)6 study emphasizes the negative prognostic implications of the asymptomatic nature of AF with a higher risk of mortality and ischaemic stroke with asymptomatic compared with symptomatic patients. Finally, a systematic review of the literature demonstrated no significant difference in all-cause death [risk ratio (RR) 1.38, 95% confidence interval (95% CI) 0.82–2.17), cardiovascular death (RR 0.85, 95% CI 0.53–1.36), and stroke or thromboembolism (RR 1.72, 95% CI 0.59–5.08) between asymptomatic and symptomatic AF patients,7 thus highlighting that stroke prevention with oral anticoagulation therapy is recommended irrespective of the presence or absence of symptoms. Hence, screening for asymptomatic AF may be a cost-effective use of health care resources in elderly populations (≥65 years) and in patients with recent ischaemic strokes. Early detection of AF before detrimental outcomes has clinical importance for timely initiation of AF therapy. Current ESC guidelines now recommend opportunistic AF screening through pulse taking or ECG strip recording in patients ≥65 years of age and also suggest systematic screening in patients aged ≥75 years, or those at high risk for ischaemic stroke.8 However, screening of previously undiagnosed AF remains challenging due to the short, self-terminating, or asymptomatic nature of AF. A substantial number of studies have investigated the impact of screening on the detection of previously undiagnosed AF. Studies published prior to 2017 have been summarized in a recent EHRA/HRS/APHRS/SOLEACE consensus document, and these include 3 randomized control trials and 23 prospective cross-sectional studies.4 In the largest, the Belgian national screening programme including unselected volunteers from the age of 18 years, the prevalence of previously undiagnosed AF was 0.92% (603/65 747 patients) using a handheld ECG device.9 In general, the weighted average for the detection rate of new AF cases in screened groups across all studies was 0.9% (95% CI 0.7–1.1), which means the need to screen almost 110 patients to detect one AF. However, these different studies included a variety of different populations using many different screening programmes and devices such as pulse palpation, 12-lead ECG, handheld ECG devices, smartphone apps, single-, or multi-lead devices. One randomized control trial comparing AF screening to routine care in patients with no history of AF but having one or more relevant AF risk factors demonstrated that the rate of AF detection was higher in the screening group than in routine care group at 6 months (1.7 vs. 0.2%, P = 0.02); however, because of the small number of patients, this study failed to evidence any significant difference between two groups after 2 years of follow-up (2.5 vs. 1.3%, P = 0.13).10 Although screening devices are still limited by patient’s skills and compliance, the sensitivity/specificity, cost-effectiveness, and feasibility of AF screening is now widely recognized.4 In any case, there is highly effective therapy to prevent strokes, using oral anticoagulation. Nevertheless, previous observational cohorts have demonstrated that only half of patients with newly diagnosed AF using conventional ECG recording received oral anticoagulation, although geographical differences are evident in uptake. In the current issue of Europace,11 Engdahl et al. used a stepwise screening strategy with the 12-lead ECG and 2-week of ambulatory intermittent ECG monitoring in all participants in a municipality of Sweden born in 1934–1935. The proportion of patients with oral anticoagulation increased after the screening, as compared with before the screening. After 5 years of follow-up, ∼90% of patients were still treated with oral anticoagulants, which suggests a high level of disease education and accompanying framework available to these patients. Importantly, the incidence of ischaemic stroke was reduced after the screening from 14.5 to 9.1 per 1000 persons per year (P = 0.003), whereas in a control area where no AF screening was carried out, there was no significant change in the incidence from 12.7 to 11.2 per 1000 persons per year over the same time period (P = 0.31). This finding is the first report of a significant impact on long-term outcomes attributable to an AF screening and management. This study highlights the clinical importance of AF screening in general population and suggests a clear benefit of a systematic AF screening programme that incorporates a well-defined referral pathway and strategy for initiating anticoagulation therapy. Nevertheless, this study was not a randomized comparison, and individuals not attending the screening trials might be less health aware and receive no or suboptimal anticoagulation therapy. In the general population, there is often not enough information and education about AF per se, the consequences of AF, and the risks and benefits of treatment. In order to urge more people to have interest in AF screening, public awareness campaigns including patient education and public engagement are also needed.12 In conclusion, the detection of asymptomatic AF remains challenging, but clinically important for timely management of AF patients. Screening for AF provides an opportunity to identify patients potentially at risk of stroke, leading to a pathway for appropriate diagnosis and management. Things can only improve. Conflict of interest: none declared. The opinions expressed in this article are not necessarily those of the Editors of Europace or of the European Society of Cardiology.