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Study Summary

The mSToPS trial investigated if screening for atrial fibrillation (AF) by wearing an electrocardiogram (ECG) patch can improve clinical outcomes. The trial was an investigator-initiated, direct-to-participant, siteless, prospective, matched, observational control study. The study population were Aetna insurance members who agreed to wear an ECG patch (iRhythm Zio) for up to 2 weeks. A total of 1718 actively monitored participants (mean age 73.8 years, 40.7% female, mean CHA2DS2-VASc=3) were matched with a cohort of 3371 observational controls, and both groups were followed for a mean duration of 29 months (see accompanying Hurst’s Central Illustration). Overall, 11.4% of the actively monitored participants and 7.7% of the control group were diagnosed with AF (P <0.01). The incidence of the primary outcome (death, stroke, systemic embolism, or myocardial infarction) was significantly lower in the actively monitored group, both in patients with newly diagnosed AF (adjusted HR 0.53, P <0.01) and the entire cohort (adjusted HR 0.79, P <0.01).The primary safety end point of hospitalization for bleeding was significantly lower in the actively monitored group (adjusted incident rate ratio 0.47, P = 0.01).


Study Strengths: This was a large, siteless, nationwide, prospective cohort study with a unique direct-to-patient design to assess the utility of ambulatory ECG monitoring with a patch in the detection of AF and improvement of clinical outcomes. By using a population within one payor, the researchers were able to keep a clear track of patient demographic information and both claims and follow-up data.

Study Limitations: The study population included patients who voluntarily agreed to wear an ECG patch, which may have resulted in bias — in addition to differences in other unmeasured confounders, patients in the actively monitored group may have been more aggressive in seeking clinical care than would have been patients in the observational cohort. Clinical end points were determined on the basis of claims data, which are reliant on both physician discretion, as well as the length of participant enrollment in the health insurance plan (which was <3 years for some participants). Lastly, all treatment decisions were at the discretion of the patients’ physician, and anticoagulant use among patients with newly diagnosed AF was low (<50% in both groups).

Next Steps/Clinical Perspective: The mSToPS trial demonstrated improved clinical outcomes in patients who were actively monitored for AF with an ECG patch compared to a matched observational control population. The study methodology demonstrates a manner by which clinical research can be more patient centric and inclusive, especially in the realm of ambulatory ECG monitoring and AF detection. Drawing strong conclusions from the study is difficult, however, given its significant limitations both with regards to potential bias introduced by self-selection of the experimental cohort as well as unclear use of anticoagulants. The study is hypothesis-generating and suggests that in a select population of individuals, perhaps those identified to be high risk of complications from thromboembolism, asymptomatic screening for AF detection may lead to improvement in long-term clinical outcomes. Further randomized clinical trials are needed to determine if this approach is both efficacious and cost-effective.

Trial Reference

Steinhubl  SR,  et al. LBS.06: To screen or not to screen, and then what? Studies of detection and treatment of AF. Presented at: American Heart Association Scientific Sessions; Nov. 13-17, 2020 (virtual meeting)

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