iRhythm's Zio Long-Term ECG Monitoring Shows Consistent Performance Across Asian and Non-Asian Populations
Key Insights
A large-scale analysis of over 400,000 patients demonstrates that iRhythm's Zio (search) 14-day ECG monitoring system performs consistently across Asian and non-Asian populations, with comparable wear times and arrhythmia detection rates.
Despite lower baseline prevalence of cardiovascular conditions, Asian patients showed similar atrial fibrillation detection rates (14.0% vs. 14.3%) and total arrhythmia yield (79.8% vs. 82.9%) compared to non-Asian patients.
The findings support the generalizability of long-term continuous ECG monitoring technology across diverse patient populations, addressing concerns about racial and cultural factors affecting device performance.
iRhythm Technologies has presented compelling evidence that its Zio (search) long-term continuous ECG monitoring system delivers consistent performance across diverse patient populations, with new data showing comparable effectiveness in Asian and non-Asian patients. The findings, presented at the Asia Pacific Heart Rhythm Society (APHRS) 2025 scientific sessions, analyzed over 400,000 U.S. patients monitored between 2018 and 2022.
Comparable Performance Across Populations
The large-scale analysis, led by Dr. Hiro Kawata, examined device compliance, performance, arrhythmia detection, and repeat-testing rates between Asian patients (3.4% of the cohort) and non-Asian patients. Key performance metrics demonstrated remarkable consistency between groups, with median wear time of 13.6 days for Asian patients versus 13.0 days for non-Asian patients, and analyzable ECG duration of 12.9 days versus 12.2 days, respectively.
"These findings show that factors such as skin type, lifestyle, and adherence did not affect wear time, analyzable time, or arrhythmia detection, indicating the device performs equally well in Asian patients," said Dr. Hiro Kawata, Consulting Medical Director for iRhythm Technologies and presenting author.
Consistent Diagnostic Yield Despite Different Risk Profiles
Despite Asian patients having lower baseline prevalence of atrial fibrillation, heart failure, and coronary artery disease, the study revealed similar diagnostic outcomes. Asian patients showed an atrial fibrillation detection rate of 14.0% compared to 14.3% in non-Asian patients. The total arrhythmia yield was also comparable at 79.8% versus 82.9% for Asian and non-Asian groups, respectively.
Repeat monitoring rates remained low and similar between groups at 14.8% for Asian patients versus 15.4% for non-Asian patients. These findings align with previously published CAMELOT and AVALON studies, which demonstrated lower repeat testing rates with Zio (search) long-term continuous monitoring compared to other ambulatory monitoring services.
Addressing Clinical Concerns in Diverse Populations
The analysis specifically evaluated whether racial and cultural differences, including skin type, skin preparation, device tolerability, and lifestyle factors, might impact compliance and effectiveness in ambulatory cardiac monitoring. The comprehensive assessment leveraged Zio (search) ECG data linked to medical claims data, enabling researchers to examine patient race, comorbidities, and outcomes across a large, diverse population.
"Although these results are based on Asians residing in the United States and further confirmation is needed to determine whether the same performance is observed in Japanese patients, they provide valuable insight into its potential utility in Japan," said Dr. Itsuro Morishima, Ogaki Municipal Hospital, Ogaki, Japan, and co-author.
Expanding Evidence Base Challenges Short-Term Monitoring
Complementing these population-specific findings, iRhythm announced the publication of a major study in Heart Rhythm journal examining over 1.1 million patients. This research revealed significant limitations of short-term monitoring approaches, showing that 24-48-hour Holter monitoring can miss actionable arrhythmias even in patients reporting daily symptoms.
The study found that nearly two-thirds (64%) of daily-symptom patients with actionable arrhythmias were undetected in the first 48 hours of monitoring. The mean time to first detected arrhythmia exceeded 48 hours for all arrhythmia types, regardless of symptom frequency. Additionally, symptom-rhythm correlation was notably low for most arrhythmias, with less than 20% of patients documenting a symptom coinciding with an arrhythmic episode.
"These findings challenge the long-held clinical assumptions and payor guidelines that frequent symptoms justify short-duration monitoring," said Mintu Turakhia, MD, Chief Medical and Scientific Officer and EVP of Advanced Technologies at iRhythm.
Market Expansion and Clinical Impact
The timing of these findings is particularly relevant as Japan represents the second-largest market worldwide for ambulatory cardiac monitoring, with approximately 1.6 million tests prescribed annually. iRhythm has introduced the Zio (search) ECG Recording and Analysis System in Japan through exclusive distribution partner Senko Medical Instrument Co., Ltd. (search), leveraging a deep-learned artificial intelligence algorithm approved by Japan's Pharmaceuticals and Medical Devices Agency (PMDA).
The Zio (search) system enables up to 14 days of continuous, uninterrupted ECG monitoring, representing a significant advancement over other ambulatory cardiac monitoring options in Japan, including wired Holter monitors that capture only 24 to 48 hours of data and other patch-based devices limited to 7 days or less of use.
Supporting Evidence from Home Enrollment Studies
Additional data presented at the American Heart Association Scientific Sessions 2025 demonstrated successful patient self-application and activation of Zio (search) devices through home enrollment pathways. Among 742,268 Zio devices analyzed, researchers found that median wear time and percent analyzable ECG time were high and comparable between in-clinic and home-based applications (>13.8 days and >98%, respectively).
Early wear terminations were infrequent (≤2% for both groups), and patients using the MyZio mobile app showed fewer early terminations, greater analyzable time, and higher compliance rates with device return for analysis within 45 days (93% vs. 80%).
The comprehensive evidence base now encompasses more than 135 peer-reviewed publications, over 2 billion hours of curated heartbeat data, and more than 12 million patient reports generated since the company's inception, reinforcing iRhythm's position in advancing cardiac arrhythmia detection and management worldwide.