In a real-world analysis of 408,470 U.S. patients monitored with iRhythm’s Zio long-term continuous ECG service, median wear time was 13.6 days for Asian patients versus 13.0 days for non-Asian patients, with analyzable ECG time of 12.9 versus 12.2 days. Atrial fibrillation detection was essentially equivalent at 14.0% versus 14.3%, total arrhythmia yield was 79.8% versus 82.9%, and repeat-monitoring rates were similarly low at 14.8% versus 15.4%. Asians comprised 3.4% of the cohort.
The company presented the findings at the APHRS/JHRS 2025 joint scientific sessions in Yokohama. Investigators linked Zio ECG data with medical claims to compare compliance, performance, and diagnostic yield between Asian and non-Asian patients over monitoring periods up to 14 days. The readout aligns with prior CAMELOT and AVALON studies showing high diagnostic yield and lower repeat testing relative to other ambulatory monitoring strategies, and it arrives as iRhythm rolls out its Zio ECG Recording and Analysis System in Japan via distributor Senko, with its AI interpretation engine cleared by the PMDA.
Strategically, this is evidence to underwrite market expansion rather than a pure scientific surprise. iRhythm is leveraging U.S.-scale data to preempt concerns that skin type, lifestyle, or wear behaviors could degrade patch performance in Asian populations, a common barrier to adoption of wearables across regions. The timing targets Japan’s large and aging arrhythmia population and a market still dominated by 24–48 hour Holter workflows and shorter-duration patches. Consistency in wear and analyzable time is the operational currency for both clinicians and payers; the low repeat-testing signal supports a cost-utility case and helps the company position a 14-day monitoring paradigm as a replacement, not an adjunct, to legacy approaches.
For sites and CROs, the implications are practical. Comparable performance across racial subgroups reduces the operational risk of device-specific variance in multinational trials and registries, simplifying device selection and monitoring plans. Longer continuous reads and fewer repeat tests can reduce scheduling churn, improve data completeness, and strengthen endpoint ascertainment for arrhythmia detection, safety surveillance, and post-ablation follow-up. In Japan, the transition from Holter to 14-day patches will require workflow retooling—patient education, skin prep, supply logistics, and reading center interfaces—while PMDA-cleared AI interpretation raises expectations for auditability, version control, and local validation within sponsor and site quality systems. Competitors will be pressed to produce similarly granular, population-specific evidence as procurement teams and HTA bodies seek generalizability and predictable throughput.
The caveat is that these data derive from Asians residing in the United States, not Japanese patients, and subgroup representation remains small. Adoption in Japan will hinge on locally generated evidence, including head-to-head comparisons with domestic devices, performance in very elderly cohorts, and real-world turnaround times at scale. Reimbursement decisions and coding will determine whether 14-day monitoring displaces rather than supplements Holter testing. Operationally, the company must demonstrate consistent analysis capacity, timely report delivery, and integration with Japanese electronic systems to avoid creating new bottlenecks as volume ramps.
What to watch next: Japanese prospective and claims-linked studies confirming detection rates and adherence in-country; guideline and society positions that normalize extended monitoring; payer stances tied to repeat-testing reductions; and whether sponsors begin standardizing Zio-based monitoring across Asia-Pacific trials to streamline cardiac endpoint collection. The broader signal is that durable, population-agnostic real-world performance—not feature sets—will decide which ECG platforms become default infrastructure for both routine care and study operations.
Jon Napitupulu is Director of Media Relations at The Clinical Trial Vanguard. Jon, a computer data scientist, focuses on the latest clinical trial industry news and trends.
