Study: iRhythm’s Long-Term Continuous Monitoring Tech Improves AFib Detection

iRhythm Technologies Inc. announced results from an Oxford University-led clinical trial indicating the Zio long-term continuous monitoring (LTCM) service increased atrial fibrillation (AFib) detection and a shorter time to diagnosis.

Published in the Journal of the American Medical Association (JAMA), the Active Monitoring for Atrial Fibrillation (AMALFI) parallel group trial is assessing whether home-based AFib screening for people ages 65 years or older with moderate to high-risk stroke risk factors—using an on-label Zio XT LTCM device with monitoring up to 14 days—could improve AFib detection compared to usual care over 2.5 years of follow-up. Participants were randomized, half were assigned to wear the Zio LTCM device for 14 days in addition to their usual care, while the other half continued with their usual care and did not receive a monitoring device.

The controlled study enrolled 5,040 eligible participants identified through an automated electronic records search in 27 participating U.K. primary care practices and was an entirely remote study, with no physical study sites or in-person visits. Compared to prior screening trials, AMALFI enrolled patients with a higher comorbidity burden: 73% were age ≥75, 19% had a prior stroke or transient ischemic attack, 28% had diabetes, and 18% suffered from chronic kidney disease. Still, in this older population who self-applied the device at home, the median Zio LTCM device wear time in the intervention arm was 13.9 days and had a high (98.8%) analyzable time.

“The AMALFI results show that home-based, long-term continuous monitoring with Zio can improve the timely detection and diagnosis of atrial fibrillation,” said Mintu Turakhia, M.D., chief medical and scientific officer and executive vice president of Advanced Technologies at iRhythm. “These findings add to the growing evidence that population health approaches to identify undiagnosed arrhythmias can be implemented at scale—demonstrated here through primary care in the U.K.—and can enable prompt therapy such as anticoagulation, rate and rhythm control, and cardiovascular risk factor reduction.”

At 2.5 years of follow-up, the randomized study found that home-based screening with the Zio LTCM service led to a modestly higher increase in new diagnosis of AFib in 172/2,520 (6.8%) participants in the intervention arm vs. 136/2,520 (5.4%) participants in the control arm (ratio of proportions 1.26, 95% CI 1.02-1.57, p=0.03), and a faster time to diagnosis with AFib recorded at a median of 103 days (IQR 43-539) in the intervention arm vs. 530 days (IQR 276-688) in the control arm, using an intention to screen analytic approach. Participants in the intervention arm were more likely to be prescribed oral anticoagulation for stroke prevention, with an average of 1.63 months exposure compared to 1.14 months in the control arm over the study period (difference 0.50 months, 95% CI 0.24-0.75, p<0.001).

“Atrial fibrillation can be difficult to detect as it often occurs without symptoms or infrequently. New technology enables home-based, longer-duration monitoring that can identify episodes which might otherwise be missed,” said Louise Bowman, professor of Medicine and Clinical Trials at Oxford Population Health and study co-author. “AMALFI showed that home-based monitoring is feasible and provides evidence that it can be initiated at scale using primary care health records with minimal burden on patients and practices.”

AFib is a common but often undiagnosed heart rhythm disorder that substantially increases the risk of stroke, heart failure, cardiovascular hospitalization, and health care utilization, making early detection and timely treatment vital to reduce stroke risk, ensure heart rate control, and restore normal sinus rhythm. As the National Health Service (NHS) in the U.K. is placing greater emphasis on disease prevention and early detection and has prioritized a shift toward upstream care by moving resources into community and primary care, the study has notable implications:

Screening with Zio LTCM results in earlier and more frequent AFib diagnosis. In AMALFI, screening with the Zio LTCM service led to an increase in AFib detection versus usual care (6.8 vs. 5.4%) that was sustained over long-term follow up, and a faster time to diagnosis versus usual care (103 vs. 530 days). The primary endpoint was assessed over 2.5 years, providing ample opportunity for AFib detection in the control group through usual care. Yet even with this lengthy follow-up period, the benefit of a single 14-day monitor at baseline was sustained, supporting the durability of the intervention effect. AMALFI was not powered to detect differences in clinical outcomes, such as stroke.

Primary care–initiated, home-based diagnostic monitoring is feasible. AMALFI was an entirely remote, prospective study with no physical sites or in-person visits. Participants were identified through an automated search of electronic health records in primary care practices. Participants in the intervention group received Zio LTCM devices by mail, self-applied them at home, wore them for 14 days, and returned them by post for analysis.

The Zio LTCM service has been available in the United States since 2008 and was introduced in the United Kingdom in 2014. In the United Kingdom, the service consists of the Zio XT wearable sensor, a single-use ambulatory ECG patch monitoring device worn for up to 14 days to capture continuous, uninterrupted data. Recorded data is processed using a UKCA-marked deep-learned algorithm that detects 13 arrhythmia types plus sinus rhythm and artifact and is then curated and verified by qualified cardiographic technicians to generate a Zio end-of-wear report that helps clinicians make the right diagnosis the first time.^1-4 Designed to be simple to self-apply and wear during daily activities, the Zio LTCM service is available for home enrollment—allowing patients to receive and apply the device at home without visiting a clinic—and can also be initiated in the primary care setting.

“Patients at our clinic benefit from home-based monitoring with the Zio device, which is easy to apply and use, allowing their entire diagnostic journey to take place without repeated trips to the clinic and fitting easily into daily life,” said James Rosengarten, consultant cardiologist and electrophysiologist at East Kent Hospitals University NHS Foundation Trust in the U.K. “At the same time, the Zio service provides clinicians with clear, high-quality insights that streamline diagnosis and help ensure timely, effective care.”

These published results add to iRhythm’s clinical evidence program, encompassing more than 125 original research manuscripts,⁵ insights derived from over 2 billion hours of curated heartbeat data⁶ and more than 10 million patient reports posted since the company’s inception.

Trial funding was provided by the National Institute for Health and Care Research (NIHR) Oxford Biomedical Research Centre and the British Heart Foundation. iRhythm Technologies supported the study by providing the Zio LTCM service (Zio XT monitoring devices, ECG analysis, and cardiac technician data review) at no charge.

iRhythm is a digital healthcare company developing 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. Outside of the United Kingdom, iRhythm offers its Zio cardiac monitoring solutions in Austria, Japan, the Netherlands, Spain, Switzerland, and the United States.

References
¹ Data on file. iRhythm Technologies, 2020.
² Hannun et al. Cardiologist-level arrhythmia detection and classification in ambulatory electrocardiograms using a deep neural network. Nat Med. 2019;25:65-69. https://doi.org/10.1038/s41591-018-0268-3
³ Deep learned algorithm is only available in the United States, European Union, Switzerland, United Kingdom, and Japan. ​
⁴ FDA 510K clearance, CE mark, UKCA mark, and PMDA-approval.
⁵ Data on file. iRhythm Technologies, 2025.
⁶ Data on file. iRhythm Technologies, 2024.