Zio: IRhythm Technologies, Inc. Unveils New Real-World Data at ACC.25 Demonstrating the Benefits of Zio Long-Term Continuous Monitoring for Arrhythmia Detection

iRhythm Technologies, Inc. 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 (LTCM2 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: 64% Undetected in the First 48 Hours: Among daily-symptom patients--those with daily or greater symptom frequency-- diagnosed with actionable arrhythmias, nearly two-thirds went undetected through two days monitoring--indicating that 24-48-hour monitoring, such as with Holters, would have failed to detect them. Higher Yield for Non-Daily Symptom Patients: Non-daily symptom patients--those with symptoms occurring with a frequency less than once per day--had an 80.9% arrhythmia yield versus 69.1% in daily-symptom patients, demonstrating that greater symptom frequency does not necessarily reflect increased arrhythmia burden. 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. Taken together, these figures illustrate both the clinical urgency and health-economic rationale for long-term continuous monitoring. While 24-48-hour Holters 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 arrhythmia 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 arrhythmia. The Cardiac Ambulatory Monitor EvaLuation of Outcomes and Time to Events (CAMELOT) study, published in the American Heart Journal, further demonstrated that Zio LTCM service had the higher yield of specified arrhythmia diagnosis and the lowest likelihood of repeat testing compared to all other monitoring services. 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 in patients with frequent or daily symptoms, and help contain healthcare resource utilization. iRhythm Technologies, Inc. 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 (LTCM2 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: 64% Undetected in the First 48 Hours: Among daily-symptom patients--those with daily or greater symptom frequency-- diagnosed with actionable arrhythmias, nearly two-thirds went undetected through two days monitoring--indicating that 24-48-hour monitoring, such as with Holters, would have failed to detect them. Higher Yield for Non-Daily Symptom Patients: Non-daily symptom patients--those with symptoms occurring with a frequency less than once per day--had an 80.9% arrhythmia yield versus 69.1% in daily-symptom patients, demonstrating that greater symptom frequency does not necessarily reflect increased arrhythmia burden. 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. Taken together, these figures illustrate both the clinical urgency and health-economic rationale for long-term continuous monitoring. While 24-48-hour Holters 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 arrhythmia 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 arrhythmia. The Cardiac Ambulatory Monitor EvaLuation of Outcomes and Time to Events (CAMELOT) study, published in the American Heart Journal, further demonstrated that Zio LTCM service had the higher yield of specified arrhythmia diagnosis and the lowest likelihood of repeat testing compared to all other monitoring services. 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 in patients with frequent or daily symptoms, and help contain healthcare resource utilization.