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This prospective randomized trial evaluated the accuracy of AF detection by four external ambulatory ECG monitors (ECMs) compared to a permanent pacemaker (industry gold standard).
The study demonstrated that Zio monitors are as accurate as the gold standard in AF burden detection and more accurate than other ECMs at detecting AF burden (including an event monitor and Bardy CAM). In the study, Zio was found to be superior in AF detection.
Zio monitor AF burden vs. permanent pacemaker AF burden
Graph modified from Eysenck Fig 2, n=21 observations
Researchers (Stanford Machine Learning Group & iRhythm Technologies) jointly developed a deep-learned ECG analysis algorithm that leveraged Zio data and sought to demonstrate human, expert-level annotation performance. The researchers stated the following findings:
- “With specificity fixed at the average specificity achieved by cardiologists, the sensitivity of the DNN [deep neural network] exceeded the average cardiologist sensitivity for all rhythm classes.”
- “The DNN appears to recapitulate the misclassifications made by individual cardiologists, as demonstrated by the similarity in the confusion matrices for the model and cardiologists.”
The mSToPS study is a pragmatic, prospective, randomized, direct-to-participant clinical trial of 2,659 asymptomatic adults. Participants for the study were invited from a healthcare system and Medicare Advantage populations. The study based inclusion invitations on criteria identifying, “as broad a population as possible that might have an increased likelihood of having undiagnosed AF,” said Steinhubl et al. in the study publication.
Results at 4 months following clinical trial enrollment found 3% more new cases of AF diagnosed in the immediate, self-applied Zio monitoring group than the group who delayed monitoring for 4 months. Zio also detected other actionable arrhythmias, including ventricular tachycardia (VT), pause, AV block, and symptomatic supraventricular tachycardia (SVT).
At one year, active monitoring was associated with an increase in therapy, including initiation of anticoagulants and antiarrhythmic medication and new pacemakers, as well as increased outpatient physician office visits.
In this study, Zio is shown to improve the diagnosis of atrial fibrillation for some asymptomatic individuals relative to routine care.
The three-year follow-up of the mSToPS clinical trial reported statistically significant higher rates of newly diagnosed AF in asymptomatic patients who wore a Zio XT monitor for AF screening compared to those in the control group: 11.4% vs. 7.7%, respectively.
In the 4 weeks surrounding clinical diagnosis of AF in any patient (either in the actively screened group or in the control group), clinical events were common: 10.2% were newly diagnosed with heart failure, 9.2% had a myocardial infarction, 6.6% had a stroke, and 1.5% experienced systemic emboli. Cumulatively, 42.9% of patients who were diagnosed with AF through standard clinical care were hospitalized.
Very importantly, fewer clinical events occurred in the group screened with Zio XT, Steinhubl et al. said in the study. “For those [newly] diagnosed [with AF] via screening [with Zio XT], none experienced a stroke, myocardial infarction or systemic emboli in the period surrounding their AF diagnosis, and only 1 person (2.3%) had a new diagnosis of heart failure.”
The investigators acknowledged that the study’s prespecified combined primary endpoint (death, stroke, systemic emboli, or myocardial infarction) could only be considered exploratory. Despite this limitation, this is the first published study to describe the early-term clinical consequences of active ECG screening with Zio XT.
The KP-RHYTHM study is a retrospective cohort study that examined 1,965 adults with paroxysmal atrial fibrillation (PAF) across two large integrated healthcare systems who used Zio.
Researchers sought to discover if there was an association between AF burden and the risk of ischemic stroke and other thromboembolism (TE) in adults with PAF. The researchers looked at two measurements for each participant, the percent of analyzable wear time with AF occurrences and the longest duration of AF recorded while monitoring.
A median of 4.4% of monitored time was spent in AF, it was non-normally distributed. The longest continuous episode of AF had a median duration of 171 minutes.
The study discovered that:
- AF burden ≥ 11.4% led to a more than 3x increase of stroke or TE events.
- There was no association between the duration of the longest AF episode and the risk of stroke.
- Standard risk scores (CHA2DS2-VASc) were also not associated with the risk of stroke.
Author affiliations and conflict of interest: Ms. Lenane is an employee of iRhythm Technologies, Inc.
Funding: “This study was supported by a research grant from iRhythm Technologies, Inc.”
Role of the funder: “The funder had no role in the design and conduct of the study; collection, management, analysis, and interpretation of the data; preparation or approval of the manuscript; and decision to submit the manuscript for publication. The funder did provide data from the studied Zio XT patches and also participated in reviewing the manuscript.”
Additional contributions: “We thank Alda I. Inveiss, MPH, Kaiser Permanente Northern California, and Martha Livingston, CRA, iRhythm Technologies, Inc[.], for their expert technical assistance. These individuals were not compensated specifically for their contributions.”
In this observational study from 3 academic emergency departments, 174 adult patients who presented with symptoms of palpitations, syncope, or dizziness that may be attributed to arrhythmias were discharged with Zio monitors.
Nearly half, 47.7%, of the patients in the study had 1 or more clinically actionable arrhythmias while wearing Zio. The median time for the first triggered ventricular tachycardia arrhythmia was 3.1 days and the median time for the first triggered sinus pauses was 4.2 days. Both time frames were outside of the detection window of Holter monitoring.
Schreiber et al. wrote, “In our study, the overall diagnostic yield was 63.2%, which is considerably higher than traditional 48-hour Holter monitoring.”
In this prospective head-to-head comparison study of 14-day Zio monitor vs. 24-hour Holter monitors, 146 patients wore both types of monitors simultaneously. The findings were as follows:
- Over the total wear time of both devices, Zio monitors detected 57% more arrhythmias than Holter monitors (96 arrhythmia events vs. 61 arrhythmia events).
- More physicians reported that Zio achieved a definitive diagnosis compared to Holter (90% vs. 64%).
- A total of 81% of patients preferred Zio over Holter monitors, which may account for the longer wear time and improved arrhythmia detection (11.1 days vs. 24 hours).
This retrospective study evaluated patient compliance, timing to arrhythmia, analyzable time, detection, and diagnostic yield of Zio monitors in 26,751 patients.
Arrhythmias were detected in over 60% of patients. Over half of patients had their first symptomatic arrhythmia occur beyond the initial 48 hours of monitoring. Data showed that median analyzable time of Zio monitors was 99% of total wear time and diagnostic yield increased significantly after 48 hours.
Author affiliations: “Dr. Kumar is the founder and former chief medical officer of iRhythm Technologies, Inc. (San Francisco) and retains a significant equity share in the company.”
Funding: “This project was supported by a grant from iRhythm Technologies, Inc. (San Francisco, CA). Dr. Turakhia is supported by Veterans Health Services Research and Development Career Development Award CDA09027-1 (Washington, DC) and American Heart Association National Scientist Development grant 09SDG2250647 (Dallas, Texas).”
In this prospective head-to-head comparison study of Zio monitors vs. 24-hour Holter monitors, Zio monitors identified AF events in 18 additional individuals and the clinical classification of AF (persistent or paroxysmal) changed in 21 patients after Zio monitoring. Clinically actionable arrhythmias were first recorded on the Zio monitor after 24 hours of monitoring (outside of the Holter monitoring window).
Longer continuous monitoring with Zio resulted in a meaningful change in clinical management, including changes in cardiovascular medications, devices, or procedures, for 28.4% of patients.
“The research reported in this article was supported by a restricted research grant from iRhythm Technologies, Inc., San Francisco, CA.”