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Screening for Atrial Fibrillation: The Debate

Clinicians debated screening for atrial fibrillation (AF) in a head-to-head viewpoint article.

The case for using screening to combat the growing epidemic of AF is seemingly promising, but there are a number of gaps in the evidence supporting AF screening, noted Patrick Moran, PhD, of Trinity College in Dublin, in The BMJ.

Mark Lown, PhD, MBBS, of University of Southampton in England, disagreed and said the existing evidence is adequate enough to warrant national AF screening initiatives.

AF Screening Defended

As the prevalence of AF increases, there has been a great deal of discussion among international experts concerning AF screening, and the possibility of using anticoagulation to prevent AF-related stroke in screen-detected cases, noted Lown.

There aren’t enough randomized controlled trials on the topic, but findings from cohort studies suggest that AF detected through screening is not a benign condition, such that anticoagulation should be considered for treating AF patients with additional risk factors, he argued.

One cohort study assessing incidentally-detected AF among asymptomatic patients found that anticoagulation therapy was linked with significantly reduced risk of death and adjusted risk of stroke. This finding shows that screen-detected AF is affected by treatment the same as AF detected during routine care, Lown highlighted.

Screening efforts could maximize treatment with appropriate anticoagulation in patients with recently-detected AF, reduce the possible harm of unneeded investigations and inappropriate therapy, and maximize the diagnostic yield of high risk AF, he continued.

When it comes to detecting AF, automated detection algorithms have been shown to have high specificity and sensitivity. Clinicians are able to accurately verify single lead ECG diagnosis of AF, and lessen the risk of treatment among patients with false positive results.

Advances in algorithms and wearable technology are likely to contribute to practical and inexpensive options to assist in stratifying stroke risk and to determine AF burden.

The STROKESTOP screening study, conducted over 14 days, turned up new AF in 3% of the screened cohort, and over 90% of those individuals went forward with anticoagulation therapy.

That anticoagulation works for higher stroke-risk patients is clear, from data like an English study showing that as use rose from 2006 to 2016 among AF patients with a CHA2DS2-VASc score ≥2 (from 48% to 78.6%), more than 75 AF-related strokes leading to hospitalization have been prevented each week in England since 2009.

“The prevalence of AF is rising steeply and is associated with increased risk of heart failure, myocardial infarction, and death, and treatment with anticoagulation is associated with reduction in all these outcomes relative to placebo. Evidence is also growing that AF is associated with cognitive decline and dementia, and if the mechanism is vascular anticoagulation could mitigate the risk,” wrote Lown.

Current evidence contributes to a strong evidence base for introducing AF screening, and the outcomes of large randomized controlled trials would add to the literature.

The U.K. screening committee will reassess recommendations soon, Lown indicated. In the U.S., the Preventive Services Task Force declined to advocate ECG screening for AF in asymptomatic older people, citing insufficient evidence.

Inadequate Evidence

Questions need to be addressed concerning AF screening as it relates to stroke outcomes, the ideal combination of screening strategy, target population, and screening test, and the opportunity cost of enforcing population-based initiatives, Moran argued.

Prior observational and experimental research has shown that screening increases AF detection, but there are no randomized controlled trials showing that screening reduces the severity or incidence of stroke in unscreened versus screened populations, Moran pointed out.

“The growing international momentum behind AF screening should be harnessed to ensure that these important gaps in knowledge are filled, rather than being overlooked as a result of an understandable eagerness to take action on a major challenge facing health systems globally,” Moran wrote.

Some of the possible dangers of AF screening include: the risk of bleeding from anticoagulation therapy, the effects of being identified as a patient with a serious health problem, and the opportunity cost of the health advantages may be lost by using scare resources to implement this intervention, Moran emphasized.

Limited information exists on how the clinical risk profile of the group could be identified through the screening, making it difficult to assess how improvements in stroke outcomes would significantly offset any harms to justify prioritizing screening at the cost of other treatment options. The risks and benefits of screening have been evaluated using simulation models that take into account findings from multiple sources, yet there is low external validity backing these kinds of investigations, Moran continued.

Researchers are currently conducting clinical trials that aim to address many of these concerns, so Moran suggests “we must wait for their results rather than push ahead with implementing a costly public health intervention that may prove difficult to withdraw if these studies do not show significant benefits of screening.”

Considering the screening methods used in prior investigations, the heterogeneity in the target population, and the screening testing, it is uncertain how screening would be incorporated into practice and scaled up. The existing evidence base does not offer a comparable solution that can be used for policy efforts, Moran wrote.

New ECG diagnostic devices such as wearable devices, automated ECG interpretation, and smartphone apps are being developed quickly, making investigations on older technologies obsolete.

The effect of consecutive screening rounds on the detection of paroxysmal or incident disease remains unknown because up until now screening studies have relied on one-off testing in a select population. Simulation modelling investigations account for the only available findings on the cost effectiveness and comparative effective of different screening frequencies and start stages, Moran continued.

Efforts are needed to combat the increase in AF among the aging, global population, noted Moran. “However, in the absence of research that reliably confirms the health benefits of screening and provides sufficient information to guide successful implementation, there remains considerable uncertainty about the potential for screening to reduce the burden of AF related morbidity and mortality in society.”