High Blood Pressure and Cardiovascular Disease | Hypertension
IRhythm Data Highlights Benefits Of Zio Long-term Heart Monitoring
The next-generation Zio monitor. [Image courtesy of iRhythm]iRhythm Technologies (Nasdaq: IRTC) + announced results from two large, real-world analyses demonstrating the benefits of its Zio system. The retrospective analyses drew on data from more than 1.1 million patients using Zio long-term continuous monitoring ECG devices. Investigators presented findings at the American College of Cardiology (ACC) 2025 Scientific Sessions in Chicago.
Results demonstrated that short-term (24-48-hour) monitoring, like with Holter devices, fails to detect a significant proportion of actionable arrhythmias, even in patients reporting "daily symptoms." Investigators also found that symptom-rhythm correlation (SRC) comes in notably low for most arrhythmias. This underscores that the selection of monitoring duration based on the frequency of symptoms alone can lead to undetected arrhythmias.
Altogether, iRhythm says the findings highlight the benefits of Zio and the limitations of shorter-term Holter monitoring. The company says the data builds on its comprehensive clinical evidence program and emphasizes its ongoing commitment to expanding evidence that supports improved patient outcomes.
"These findings challenge the long-held assumption that frequent symptoms justify short-duration monitoring," said Dr. Mintu Turakhia, iRhythm chief medical and scientific officer and EVP of product innovation. "They reinforce the limitations of Holter-duration monitoring and highlight the value of Zio long-term continuous monitoring up to 14 days. Once again, iRhythm's real-world data are contributing evidence that can help guide both clinical practice and payer policy."
A look at the gaps in short-term Holter monitoring reported by iRhthymiRhythm says that, among daily symptom patients diagnosed with actionable arrhythmias, 64% went undetected through two days of monitoring. That indicates that 24-48-hour monitoring, like with Holter, would have failed to detect them, the company says.
Additionally, non-daily symptom patients had had an 80.9% arrhythmia yield, compared to 69.1% in daily symptom patients. This indicates that greater symptom frequency does not necessarily reflect increased arrhythmia burden. Across all arrhythmia types, the mean time to the first detected episode came in at greater than 48 hours, regardless of symptom frequency. IRhythm again noted that this points to the limitations of short-term monitoring.
In another study, iRhythm determined that symptoms alone proved unreliable. With most arrhythmia types, fewer than one in five patients in the analysis documented a symptom coinciding with an arrhythmic episode. Symptom-rhythm correlation came in higher for patients reporting daily vs. Non-daily symptoms.
Even for AFib (the most commonly symptomatic arrhythmia), iRhythm says more than half of all cases registered as asymptomatic. Meanwhile, Zio frequently detected ventricular tachycardia, AV block and significant pauses without patient-reported symptoms. This suggested that selection of monitor duration should not be based on symptom frequency alone, and that long-term continuous monitoring may offer advantages over other monitoring types with shorter duration or those which rely on patient triggered events to initiate recording.
IRhythm Unveils New Real-World Data At ACC.25 Demonstrating The Benefits Of Zio® Long-Term Continuous Monitoring For Arrhythmia Detection
SAN FRANCISCO, March 31, 2025 (GLOBE NEWSWIRE) -- iRhythm Technologies, Inc. (NASDAQ:IRTC) today announced results from two large real-world retrospective analyses presented at the American College of Cardiology (ACC) 2025 Scientific Sessions in Chicago, IL. Drawing on data from more than 1.1 million patients who used iRhythm's Zio® long-term continuous monitoring (LTCM) ECG devices, these studies demonstrate that short-term (24–48-hour) monitoring, such as with Holter devices, fails to detect a significant proportion of actionable arrhythmias—even in patients reporting "daily symptoms"—and that Symptom–Rhythm Correlation (SRC) is notably low for most arrhythmias, underscoring that selection of monitoring duration based on the frequency of symptoms alone can lead to undetected (missed) actionable1 arrhythmias. Together, these findings highlight the benefits of Zio® long-term continuous monitoring (LTCM)2 and the limitations in 24–48-hour Holter monitoring still prevalent in current clinical practices and payer policies.
Zio LTCM " Daily Symptoms " Study : Gaps in Short-Term Holter Monitoring
Zio LTCM " Symptom–Rhythm Correlation (SRC)" Study : Symptoms Alone Are Unreliable
"These findings challenge the long-held assumption that frequent symptoms justify short-duration monitoring," said Mintu Turakhia, MD, iRhythm Chief Medical and Scientific Officer and EVP of Product Innovation. "They reinforce the limitations of Holter-duration monitoring and highlight the value of Zio long-term continuous monitoring up to 14 days. Once again, iRhythm's real-world data are contributing evidence that can help guide both clinical practice and payer policy."
Arrhythmias: A Growing Burden for Patients and Health Systems
Up to five percent of the general population—around 16 million Americans—experience arrhythmias,3 in which the heart may beat too quickly, too slowly, or sporadically. If left untreated, certain arrhythmias can damage the heart, brain, or other organs4 and increase the risk of stroke or death.5,6,7 Beyond these clinical concerns, the financial toll of undiagnosed arrhythmias is substantial. It's estimated that undiagnosed atrial fibrillation alone costs the U.S. $3 billion per year,8 while heart failure costs could reach $70 billion by 2030.9 Taken together, these figures illustrate both the clinical urgency and health-economic rationale for long-term continuous monitoring.
Implications for Clinical Care and Payer Policy
While 24–48-hour Holter monitoring is widely used in current clinical practice and historically supported by payer policies—especially for patients reporting daily symptoms—these new findings indicate that 64% of daily-symptom patients with actionable arrhythmias remain undetected following the first 48 hours of monitoring, which could lead to missed diagnoses and delayed care. In contrast, Zio LTCM provides uninterrupted, continuous monitoring for up to 14 days, enabling more accurate and timely detection of actionable arrhythmias. The C ardiac A mbulatory M onitor E vaL uation of O utcomes and T ime to Events (CAMELOT) study, published in the American Heart Journal, further demonstrated that Zio LTCM service had the highest yield of specified arrhythmia diagnosis and the lowest likelihood of repeat testing compared to all other monitoring services.10,11,12,13 As healthcare systems increasingly adopt value-based care models, extending monitoring beyond 48 hours can improve patient outcomes, reduce missed diagnoses, and help contain healthcare resource utilization.
New Data Add to iRhythm's Clinical Evidence Base for LTCM
These new data build on iRhythm's comprehensive clinical evidence program, encompassing more than 125 original research manuscripts,14 insights derived from over 2 billion hours of curated heartbeat data15 and more than 10 million patient reports posted since the company's inception—underscoring the company's ongoing commitment to expanding evidence that supports improved patient outcomes.
About the iRhythm Studies Presented at ACC.25
"Arrhythmias in Patients with Daily vs. Non-Daily Symptoms Undergoing Long-Term Continuous Patch ECG Monitoring"
Holter monitoring of 24-48 hours remains in common use for patients with frequent or daily symptoms based on clinician or payer preferences. This retrospective cohort study sought to determine the percentage of arrhythmias detected by LTCM before and after 48 hours of monitoring in patients with daily (≥ 1/day) and non-daily (<1/day) symptoms. Researchers compared yield in patients ≥18 years prescribed a Zio® monitor or Zio® XT LTCM worn for >7 to 14 days from June 2023 to July 2024. These devices include a patient-activated button to document symptomatic episodes. Symptom frequency was measured as button presses/day and stratified by daily (≥1/day) or non-daily (<1/day). ECG data was analyzed via a deep-learned AI algorithm and confirmed by cardiographic technicians. Nearly two thirds (64%) of daily-symptom patients with actionable arrhythmias were undetected in the first 48 hours and the man time to first detected arrhythmia was >48 hours for all arrhythmia types, regardless of symptom frequency, suggesting that Holter (<48 hour) may be inadequate even for these patients.
"Symptom-Rhythm Correlation Patterns in Patients Undergoing Ambulatory ECG Monitoring: Analysis of Over 1 Million Patients"
Symptoms are the most common indication for ambulatory cardiac monitoring, yet Symptom–Rhythm Correlation (SRC) has not been well described across various arrhythmias. Researchers assessed SRC in patients ≥18 years who wore a Zio® monitor or Zio® XT LTCM for >7 to 14 days between June 2023 and July 2024. These devices include a patient-activated button to mark symptomatic episodes, and episodes within ±45 seconds of a recorded arrhythmia were considered rhythm-correlated. ECG data was analyzed via a deep-learned AI algorithm and confirmed by cardiographic technicians. Atrial fibrillation (AF) and ectopic beats were the rhythms most-correlated with patient symptoms. Overall symptom-rhythm correlation was low (i.E., <20% for most rhythms), but higher for patients with Daily Symptoms than Non-Daily Symptoms.
About iRhythm TechnologiesiRhythm is a leading digital health care company that creates trusted solutions that detect, predict, and prevent disease. Combining wearable biosensors and cloud-based data analytics with powerful proprietary algorithms, iRhythm distills data from millions of heartbeats into clinically actionable information. Through a relentless focus on patient care, iRhythm's vision is to deliver better data, better insights, and better health for all. To learn more, please visit https://www.Irhythmtech.Com/.
Media ContactKassandra Perryirhythm@highwirepr.Com
Investor ContactStephanie Zhadkevichinvestors@irhythmtech.Com
1 Actionable Arrhythmias defined as Atrial Fibrillation ≥30 sec, Supraventricular Tachycardia ≥90 bpm & ≥30s, Ventricular Tachycardia ≥100 bpm & ≥4 beats, any Ventricular Fibrillation, Pause ≥3 sec, and/or Atrioventricular Block (any 2nd Degree or Complete Heart Block).2 The Zio monitor is a prescription-only, single-use ECG monitor that continuously records data for up to 14 days. It is indicated for use on patients who may be asymptomatic or who may suffer from transient symptoms such as palpitations, shortness of breath, dizziness, lightheadedness, pre-syncope, syncope, fatigue, or anxiety. 3 Desai et al. Arrhythmias. In: StatPearls. Treasure Island (FL): StatPearls Publishing; June 5, 2023. Https://pubmed.Ncbi.Nlm.Nih.Gov/32644349/4 National Heart, Lung, and Blood Institute. Arrhythmias - What Is an Arrhythmia? Www.Nhlbi.Nih.Gov. Published March 24, 2022. Accessed April 25, 2024. Https://www.Nhlbi.Nih.Gov/health/arrhythmias5 Ataklte et al. Meta-analysis of ventricular premature complexes and their relation to cardiac mortality in general populations. The American Journal of Cardiology. 2013;112(8):1263-1270. Doi:10.1016/j.Amjcard.2013.05.0656 Lin et al. Long-term outcome of non-sustained ventricular tachycardia in structurally normal hearts. PLOS ONE. 2016;11(8). Doi:10.1371/journal.Pone.01601817 Wolf et al. Atrial fibrillation as an independent risk factor for stroke: The Framingham Study. Stroke. 1991;22(8):983-988. Doi:10.1161/01.Str.22.8.9838 Turakhia et al. Economic Burden of Undiagnosed Nonvalvular Atrial Fibrillation in the United States. The American Journal of Cardiology. 2015;116(5):733-739. Doi:https://doi.Org/10.1016/j.Amjcard.2015.05.0459 Heidenreich et al. Forecasting the Impact of Heart Failure in the United States: A Policy Statement From the American Heart Association. Circulation: Heart Failure. 2013;6(3):606-619. Doi:https://doi.Org/10.1161/hhf.0b013e318291329a10 Reynolds et al. Comparative effectiveness and healthcare utilization for ambulatory cardiac monitoring strategies in Medicare beneficiaries. Am Heart J. 2024;269:25–34. Https://doi.Org/10.1016/j.Ahj.2023.12.00211 A specified arrhythmia refers to an arrhythmia encounter diagnosis as per Hierarchical Condition Categories (HCC) 96.
12 Based on previous generation Zio XT device data. Zio monitor utilizes the same operating principles and ECG algorithm. Additional data on file.13 Zio LTCM service refers to Zio XT and Zio monitor service.14 Data on file. IRhythm Technologies, 2025.15 Data on file. IRhythm Technologies, 2024.
IRhythm Digital Heart Monitoring Service Backed By NICE
A heart monitor developed by iRhythm has become the first product to be endorsed by NICE in a pilot project covering digital health technologies.
In new guidance, the health technology assessment (HTA) agency has recommended iRhythm's Zio XT service for detecting abnormal heart rhythms – provided NHS organisations that deploy it collect evidence of its benefits.
The wearable electrocardiogram (ECG) patch and associated software has been tested for its ability to detect atrial fibrillation (AF) in high-risk patients, with investigators reporting higher rates of diagnosis and more use of potentially life-saving anticoagulant therapy among users, but also increased demand on healthcare resources.
Zio XT has been recommended by NICE as an option for people with suspected cardiac arrhythmias who would benefit from ECG monitoring for longer than 24 hours, as a lighter, discreet alternative to Holter monitoring, which requires patients to wear several electrodes as well as a bulky monitor.
iRhythm's device is waterproof, so can even be taken into the shower – an important consideration as it is used for up to two weeks, day and night.
NHS patients will have access to Zio XT for three years while more data is collected to address "evidence gaps about its benefit", according to NICE. After that period, NICE will look at the new evidence before making a final recommendation.
Assuming NHS trusts take up the tech, it could be available for more than 150,000 people in the UK, according to the HTA. As it stands, there are more than 1.2 million people with diagnosed AF in the country, and another 500,000 are thought to be undiagnosed.
People with AF are more likely to suffer a stroke, and the risk is much higher in people who are unaware they have the heart rhythm disorder.
Monitoring patients for up to 14 days means that more data from each patient will be available to review, potentially improving its ability to spot arrhythmias.
At the end of the monitoring period, users remove the patch and send it via freepost for analysis using artificial intelligence algorithms, with the findings forwarded to their clinician.
Currently 12 hospital trusts across England are evaluating the Zio XT service, which costs £265 per patient, according to NICE, which says it is likely that Zio XT will be cost saving – or at least similar in cost – to Holter monitoring.
"Throughout the COVID-19 pandemic we have seen a number of cardiac patients avoiding hospitals and suffering in silence, even when experiencing serious conditions such as strokes," said iRhythm's EMEA vice president Justin Hall.
"This has led to a backlog of patients requiring care, putting additional pressure on medical staff and services," he added. "Services like Zio can help ease this backlog, offering clinically-validated services remotely."
Earlier this year, iRhythm won a UK government AI in Health and Care Award for Zio XT, securing funding to trial the service in selected sites across the country over the next three years.
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