Screening for Atrial Fibrillation: More Problematic Than You Might Think!
Dr. A. John Camm's session at AF2017 highlighted the importance of screening for atrial fibrillation in modern health environments.
At first sight, it seems obvious that we should screen the older population for atrial fibrillation (AF), A. John Camm, MD (St. George’s University of London and Imperial College, London, United Kingdom) said to AF Symposium News before his presentation. “After all, this is a common condition in the elderly that often exists in an asymptomatic, subclinical form, and can be easily diagnosed and treated to prevent serious consequences such as death, debilitating stroke, heart failure, recurrent hospitalizations, and loss of work and independence.
So, why is AF screening not instituted in modern health care environments? There are criteria for conditions for which screening is appropriate that have been endorsed by the World Health Organization, and screening for atrial fibrillation seems to ‘fit the bill.’ However, screening councils/agencies around the world have resisted pleas of physicians to introduce screening for AF,” he continued.
It has been argued that asymptomatic AF, revealed by screening programs, may not have the same likelihood of complications as AF presenting clinically. Multiple epidemiological studies that have relied on occasional ECGs suggest otherwise. Sub-analyses of randomized clinical trials such as AFFIRM, or carefully collected registries (e.g., the Belgrade study, EURObservation study, etc.), also suggest that complications are not significantly less, and sometimes occur even more, than in AF that has presented clinically.
Dr. Camm remarked: “Not defeated by these data, the clinical screening brigades point out that physicians do not treat patients with AF according to guidelines — so why should more patients be identified simply to be mistreated? They point to the unsettled elements of diagnosis and therapy about which we argue: how much atrial tachyarrhythmia constitutes AF, rate versus rhythm control, ablation versus antiarrhythmic drugs, which ablation technique or which antiarrhythmic drug, anticoagulants versus aspirin, or vitamin K antagonists versus direct oral anticoagulants. These debates are typical in any vibrant and progressive medical arena, but are misinterpreted as confusion and ignorance. However, everyone knows that complications of AF are common, that the arrhythmia can be diagnosed early during its course, even when asymptomatic, and that treatment is effective and valuable.”
According to Dr. Camm, “In the last few years, several circumstances have come to the fore in which we are less certain of our ground. We can now observe short runs of asymptomatic atrial tachyarrhythmias on the logs of implanted devices such as pacemakers, ICDs, and monitors. We might be sure that the arrhythmia is ‘atrial fibrillation,’ but we are not confident that the associated risk of thromboembolism is significant and usefully reduced using anticoagulant therapy. The stroke risk is almost certainly less than when the arrhythmias present clinically, but may still be enough to warrant treatment.” Clinical trials are underway, but meanwhile, physicians have little guidance as to how to treat these patients.
He added: “Similarly, a problem presents in patients who have suffered an embolic stroke of uncertain cause and undergo continuous ECG monitoring, which then presents a spell of asymptomatic AF — perhaps weeks, months, or years after the ischemic event: is anticoagulant therapy better than antiplatelet treatment?” Again, clinical trials will provide evidence, but results will take time. All forms of screening have not yet been thoroughly evaluated.
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“There is not a single study that shows that we can screen for and identify asymptomatic AF, treat it appropriately, and demonstrate a reduction of irretrievable harm such as stroke, disability, or death,” explained Dr. Camm. “We do know that we can find this arrhythmia in asymptomatic people, and that we can discover patients with known AF who are not adequately treated, using opportunistic screening in those 65 years or older (1-2%), or systematic screening in people 75 years or older (3-4%). Also, we know that instituting anticoagulant therapy will reduce mortality and cerebrovascular accidents in patients with AF. It is much more difficult to go from screening to therapy, and show that improved outcomes result. Large studies will be needed, and no one has yet persuaded those funding medical research or healthcare that such studies are needed.”
He noted that governments, councils, and agencies responsible for the introduction of AF screening programs are also worried that identifying patients with asymptomatic arrhythmia will lead to more than simply recommending stroke prevention therapy. Patients would undoubtedly be evaluated regarding the burden of the arrhythmia, subclinical symptoms, ventricular dysfunction, left atrial fibrosis, underlying comorbidities, etc.
"This long catalogue of evaluation and consequent treatment might involve substantial costs and undoubtedly ruin any simple cost-effectiveness calculation focused on stroke prevention,” said Dr. Camm. “But why should this be such a concern? Early identification of AF will lead to more effective treatment and the avoidance of investigations and therapies that must be introduced when the arrhythmia has already gained a foothold and is less likely to respond to therapy.”
“Practicing physicians are of one mind — we need to find those that have subclinical AF, offer appropriate evaluation and treatment, and avoid the expensive and destructive complications of the arrhythmia,” he concluded. “It is simple and cheap to detect AF; it is also simple and cheap to offer therapy to prevent stroke and reduce mortality. Therefore, the European Society of Cardiology AF Guidelines Task Force has recently made some definite recommendations relating to AF screening. Opportunistic screening in people 65 years old or older is strongly recommended, and systematic screening for people 75 years old and older should be considered. Everyone who is convinced of its value must support screening for atrial fibrillation.”