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VIDEO: Screening ECG patch boosts AF diagnoses ninefold

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Seek and you will find AF; then what?

Results from several studies have now shown that some kind of monitoring for AF in asymptomatic, at-risk people results in an increased diagnosis of subclinical AF. Study results also suggest that, in general, people diagnosed with subclinical AF are at a lower risk of stroke than patients with symptomatic AF. As of now, no prospective study has evaluated the efficacy of anticoagulant therapy in people diagnosed with subclinical AF, although such studies are now in progress. Until we have these results, the question of how to manage patients with subclinical AF remains unanswered.

Dr. N.A. Mark Estes professor of medicine and director of the New England Cardiac Arrhythmia Center at Tufts Medical Center in Boston. Mitchel L. Zoler/MDedge News

Dr. N.A. Mark Estes

N.A. Mark Estes, MD , is professor of medicine and director of the New England Cardiac Arrhythmia Center at Tufts Medical Center in Boston. He has been a consultant to Boston Scientific, Medtronic, and St. Jude. He made these comments as designated discussant for the mSToPS report.



– An ECG patch worn twice for a total of about 24 days produced a nearly ninefold increase in the number of high-risk people diagnosed with atrial fibrillation, compared with those followed with usual care in a randomized trial with 2,655 people.

During 4 months of follow-up, 1,364 high-risk people assigned to ECG patch screening had a 5.1% rate of new atrial fibrillation (AF) diagnoses, compared with a 0.6% rate among 1,291 controls who wore the patch but were identified with new-onset AF using standard follow-up that did not take the patch data into account. This was a statistically significant difference for the study’s primary endpoint, Steven R. Steinhubl, MD, said at the annual meeting of the American College of Cardiology.

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In addition to proving that the ECG patch can better identify asymptomatic people who have AF than conventional means – usually waiting until a stroke occurs or for symptoms to appear – the noninvasive and relatively low-cost patch also gives researchers a new way to try to address the more fundamental medical question created by this line of investigation: How clinically important are relatively brief, asymptomatic episodes of atrial fibrillation, and are patient outcomes improved by treatments begun in this early phase?

The study results “show we can look beyond implantable devices with a less expensive, noninvasive way” to identify patients with asymptomatic AF and determine its natural history and need for intervention, Dr. Steinhubl said in a video interview.

The mSToP (mHealth Screening to Prevent Strokes) trial ran at Scripps and began by identifying more than 359,000 U.S. residents with Aetna health insurance who met the study’s definition of having high AF risk, either by being at least 75 years old, or at least 55 years old and male or at least 65 years old and female. To qualify as high risk those younger than 75 years also had to have at least one clinical risk factor, which could include a prior cerebrovascular event, heart failure, hypertension plus diabetes, obstructive sleep apnea, or any of six other comorbidities. The researchers also excluded potential participants because of several factors, including a history of atrial fibrillation or flutter, current treatment with an anticoagulant, end-stage renal disease, and patients with an implanted pacemaker or defibrillator.

They invited more than 100,000 of these qualifying Aetna beneficiaries to participate, and 2,655 agreed and received by mail a pair of ECG measurement patches (Zio) with instructions to wear one for 2 weeks at the start of the study and to wear the second during the final 2 weeks of the 4-month study period. The participants averaged 73 years of age, and their average CHA2DS2-VASc score was 3.

All patients in the study were told to wear their patches and mail them in, but the researchers used the collected ECG data for diagnosing AF in only the 1,364 patients randomized to the active arm. The ECG findings for the 1,291 controls wasn’t provided to their physicians, and so any new-onset AF had to be found either by symptom onset or incidentally. About one-third of the people assigned to each of the study arms never wore their patches. Those who wore their patches did so for an average of nearly 12 days each. Diagnosis of new-onset AF was based on finding either at least one AF episode recorded by the patches that lasted at least 30 seconds or an AF diagnosis appearing in the patient’s record. The average AF burden – the percentage of time a person with incident AF had an abnormal sinus rhythm – was 0.9%.


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