Irregular Rhythm Notification Feature (IRNF)

by Apple  · Based in United States → — Proactive heart health insights from your wrist.
Cardiology Family Medicine Internal Medicine
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Included with apple watch purchase
Regulatory Status Disclosed

Overview

The Irregular Rhythm Notification Feature (IRNF) is a software-only mobile medical application integrated with the Apple Watch. It is designed to analyze pulse rate data to identify episodes of irregular heart rhythms suggestive of atrial fibrillation (AFib) and provide timely notifications to the user. Intended for over-the-counter (OTC) use, the IRNF serves as a pre-screening tool that can supplement a clinician’s decision to screen for possible AFib. It is crucial to note that IRNF is not intended to replace traditional methods of diagnosis or treatment, nor is it designed for individuals under 22 years of age or those previously diagnosed with AFib. Data collected by the feature is saved to the Apple Health app, allowing users to share this information with their physicians.

Reviewed by Pouyan Golshani, MD — Interventional Radiologist

Key Features

  • Irregular rhythm detection suggestive of AFib
  • User notifications for detected irregular rhythms
  • Background heart rhythm checks during periods of stillness
  • Data saved securely to the Apple Health app on iPhone
  • Ability for users to export and share health data with physicians
  • Over-the-counter (OTC) availability and ease of use
  • Machine learning-based algorithm for improved AFib differentiation (IRNF 2.0)
  • Onboarding process with educational materials

Use Cases

  • Early screening for potential Atrial Fibrillation (AFib) in asymptomatic individuals
  • Empowering users with personal insights into their cardiovascular health
  • Facilitating more informed conversations between patients and their healthcare providers
  • Supplementing a clinician's decision-making process for AFib screening
  • Tracking a history of irregular rhythm notifications for review

What Physicians Need to Know

ECG/EKG Analysis Capability
The Irregular Rhythm Notification Feature (IRNF) analyzes pulse rate data using the Apple Watch's photoplethysmography (PPG) sensor to identify episodes of irregular heart rhythms suggestive of atrial fibrillation (AFib). While IRNF itself uses PPG, the Apple Watch also features a separate ECG app that can generate a single-lead ECG waveform and classify it as sinus rhythm, AFib, high or low heart rate, or inconclusive.
Arrhythmia Detection Accuracy
IRNF is designed to identify irregular heart rhythms suggestive of AFib. In a study of individuals with known AFib, the IRNF demonstrated a 'by subject' sensitivity of 72%, 100% specificity, 100% positive predictive value (PPV), and 90% negative predictive value (NPV). For AFib episodes lasting an hour or longer, the 'by episode' sensitivity was 60.0% with a PPV of 95.5%. Another study indicated that among participants receiving an irregular rhythm notification who subsequently wore an ECG patch, 41.6% had AFib detected by the patch. During concurrent wear, 78.9% of those with an AFib notification showed concordant AFib on the ECG patch, and 98.2% showed AFib or other clinically relevant arrhythmias. The Apple Heart Study, involving 400,000 participants, found that 84% of wearers who received irregular heartbeat notifications were in atrial fibrillation. IRNF 2.0 has shown a sensitivity of 88.6% and specificity of 99.3% for AFib detection. It's important to note that the feature is not intended to detect every instance of irregular rhythm, and a lack of notification does not rule out a disease process.
Cardiac Monitoring Integration
IRNF is a software-only mobile medical application that functions with the Apple Watch and integrates with the iPhone's Health App. This integration allows users to securely store, manage, and share their health data. The feature operates as a background screening tool, analyzing pulse rate data opportunistically when the user is still to ensure more accurate readings.
AHA/ACC Guideline Alignment
The American College of Cardiology (ACC) has provided guidance on using Apple Watch for cardiovascular care, recognizing IRNF as an FDA-authorized feature for adults 22 and older. The ACC's tool suggests that the Apple Watch is best suited for general health and wellness, preclinical scenarios, or in specific clinical situations where an arrhythmia has already been identified and is being managed. It also advises that for clinical situations requiring real-time data notification to clinicians, a continuous ECG monitor is strongly recommended. IRNF is intended to pre-screen for irregular rhythms suggestive of AFib and can supplement a clinician's decision for AFib screening.
Real-Time Alert Capability
IRNF provides notifications to the user upon detecting and confirming episodes of irregular heart rhythms suggestive of AFib through multiple readings. The feature performs occasional background checks of heart rhythms, typically when the user is stationary, and alerts the user if an irregular rhythm suggestive of AFib is identified. However, it is not a continuous monitor and should not be solely relied upon to detect all instances of AFib.
Physician Tip

Advise patients that the Irregular Rhythm Notification Feature (IRNF) is a screening tool for irregular heart rhythms suggestive of AFib, not a diagnostic device. It is intended for over-the-counter use in individuals aged 22 and over who have not been previously diagnosed with AFib. Emphasize that a notification warrants a consultation for further evaluation, but the absence of a notification does not guarantee the absence of heart disease. The data collected can be a valuable supplement to clinical decision-making for AFib screening. For continuous rhythm monitoring or real-time alerts to clinicians, traditional medical devices are still recommended. Remind patients that IRNF cannot detect heart attacks and they should seek emergency care for symptoms like chest pain.

The Irregular Rhythm Notification Feature is deeply integrated with the Apple ecosystem, specifically the Apple Watch (Series 1 or later) and the Health app on iPhone. This allows for seamless data collection from the Apple Watch's PPG sensor and secure storage and management within the Health app. Users can share their health data, including IRNF notifications and associated rhythm data, with their physicians by exporting it from the Health app.

Details

Category Cardiology AI, Wearables & Remote Monitoring (RPM)
Pricing Included with apple watch purchase — Included with Apple Watch purchase
DeploymentDevice-based (Apple Watch), integrated with the iPhone Health app.
Compliance
BAA AvailableUnknown AI-estimated
HIPAA CompliantUnknown AI-estimated
FDA Status Yes AI-estimated

The Irregular Rhythm Notification Feature (IRNF) received De Novo classification from the FDA in 2018 (DEN180042). An updated version (IRNF 2.0) received 510(k) clearance (K231173) on July 21, 2023, classified as a Class II medical device: Photoplethysmograph Analysis Software For Over-The-Counter Use.
Integrations
EHR Not specified
Specialties Cardiology, Family Medicine, Internal Medicine

What the Web Says

The Apple Watch's Irregular Rhythm Notification Feature (IRNF) is designed to alert users to potential atrial fibrillation (AFib), a common type of irregular heartbeat. It works by occasionally checking heart rhythms in the background using photoplethysmography (PPG) and notifying users if an irregular rhythm suggestive of AFib is detected through multiple readings. While not a diagnostic tool, it aims to facilitate earlier conversations with healthcare providers about potential heart health issues.

Overall: Mixed

Strengths

  • Early detection of potential AFib in asymptomatic individuals.
  • Can provide critical data to physicians for more informed conversations.
  • FDA-cleared for detecting irregular rhythms suggestive of AFib.
  • May help identify new AFib cases that might otherwise go unnoticed.
  • User testimonials suggest it has prompted timely medical intervention.
  • Continuous and unobtrusive rhythm monitoring.

Limitations

  • High rate of false positives, potentially leading to unnecessary anxiety, doctor visits, and medical testing.
  • Not designed for individuals already diagnosed with AFib.
  • Does not constantly monitor for AFib and may miss some episodes.
  • Cannot detect heart attacks, blood clots, stroke, or other heart conditions.
  • Physicians may vary in their approach to managing alerts due to a lack of uniform clinical practice guidelines.
  • PPG-based detection has limitations, including susceptibility to motion artifacts and indirect measurement compared to ECG.

Based on reviews from: Oklahoma Heart Hospital, Latest Updates 4, PMC - NIH, Apple Support, Men's Health, Reddit, ResearchGate, CNET, CardioSmart u2013 American College of Cardiology, YouTube

Last updated: 2026-07-21

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Press & Coverage

Medical News Observer
Irregular Rhythm Notification Feature (IRNF): Advanced Heart Rhythm Monitoring on Apple Watch and iPhone - Medical News Observer
The Irregular Rhythm Notification Feature (IRNF) 2.0 is a software-only mobile medical application for Apple Watch and iPhone that analyzes pulse rate data to identify irregular heart rhythms suggesting atrial fibrillation (AFib) and provides notifications. It operates as a background screening tool and integrates with the iPhone's Health App for data management and user education.
2023-12
Apple Press Release
ECG app and irregular heart rhythm notification available today on Apple Watch
Apple announced the availability of the ECG app and irregular rhythm notification feature on Apple Watch, which can occasionally check heart rhythms in the background for signs of AFib. These features received De Novo classification from the FDA, making them available over-the-counter.
2018-12
MyStrategist
Apple Wins FDA Clearance for Machine Learning-Based AFib Notification - MyStrategist
Apple received a 510(k) clearance from the FDA for an update to its Irregular Rhythm Notification Feature (IRNF) app, leveraging machine learning to differentiate between AFib and non-AFib rhythms. This marks Apple's second 510(k) and fourth overall FDA authorization for its health products.
2021-11
Apple Support
Heart health notifications on your Apple Watch
This Apple Support article explains how the irregular rhythm notification feature on Apple Watch works, occasionally checking for irregular rhythms suggestive of AFib when the user is still. It also provides instructions on how to enable these notifications and what to do if a notification is received.
2025-09
Apple Regulatory Information
Irregular Rhythm Notification Feature Instructions for Use INDICATIONS FOR USE - Apple Regulatory Information
This regulatory document outlines the Indications for Use for the Irregular Rhythm Notification Feature (IRNF), stating it's a software-only mobile medical application for Apple Watch to identify irregular heart rhythms suggestive of AF. It's intended for over-the-counter use and not for individuals under 22 or those already diagnosed with AF.
unknown
FDA
DEN180042.pdf - accessdata.fda.gov
This FDA De Novo summary details the Irregular Rhythm Notification Feature (IRNF) as a software-only mobile medical application for Apple Watch, analyzing pulse rate data to identify irregular heart rhythms consistent with AFib. It is a background screening tool and part of the Health App, requiring user opt-in and onboarding.
unknown
PMC
Accuracy of the Apple watch for detection of AF: A multicenter experience - PMC
A study published in PMC investigated the accuracy of the Apple Watch's irregular rhythm notification (IRN) feature for detecting AF in subjects with a previous diagnosis of nonpermanent AF. The IRN uses photoplethysmography to identify prolonged episodes of irregular rhythm.
2023-03
PMC - NIH
Physician Responses to Apple Watch-Detected Irregular Rhythm Alerts - PMC - NIH
This study examined physician responses to hypothetical cases of asymptomatic patients presenting with Apple Watch irregular rhythm notifications. It found that physicians often opted for further diagnostic testing and sometimes medical intervention, highlighting a need for uniform clinical practice guidelines.
unknown

Videos

Product demos, reviews, and walkthroughs for Irregular Rhythm Notification Feature (IRNF).

View all on YouTube

Frequently Asked Questions

IRNF typically functions as a passive monitoring tool, often integrated into wearable devices or continuous cardiac monitors. Data is usually presented through a dedicated clinician portal or can be configured to push notifications, requiring manual entry or specific API integrations for EHR synchronization, which varies by vendor.
Most IRNF systems designed for medical use hold regulatory clearances like FDA 510(k) or CE Mark, indicating their safety and efficacy for their intended purpose. HIPAA compliance is typically addressed through robust data encryption, secure data transmission protocols, and strict access controls, with vendors often providing business associate agreements (BAAs).
Traditional alternatives include 12-lead ECGs for acute assessment, Holter monitors for 24-48 hour ambulatory monitoring, and longer-term event recorders or implantable loop recorders for intermittent symptoms. These methods may be preferred for higher diagnostic yield in specific clinical scenarios or when continuous, long-term, passive monitoring is not the primary need.
Pricing models for IRNF vary, often involving a subscription fee for the monitoring service or being bundled with the cost of the device itself. Reimbursement can be complex, often falling under existing CPT codes for remote physiological monitoring or requiring specific payer policies, which can impact patient out-of-pocket costs and healthcare system budgets.
IRNF systems, while valuable, can have varying sensitivity and specificity, potentially leading to false positives from artifact or non-sustained events, or false negatives in certain rhythm disturbances. Performance can also differ across patient demographics, comorbidities, and activity levels, necessitating clinical judgment for interpretation.
Physicians retain full responsibility for interpreting IRNF data within the broader clinical context and making diagnostic or treatment decisions. While IRNF provides notifications, it is a screening tool, and physicians must exercise clinical judgment, order confirmatory tests as needed, and be aware of the device's limitations to mitigate liability.
IRNF systems typically utilize end-to-end encryption for data transmission, secure cloud storage with access controls, and regular security audits to protect patient data. De-identification or anonymization protocols may also be applied for research or aggregate analysis, further safeguarding individual privacy.

Compare Irregular Rhythm Notification Feature (IRNF)

VS
Irregular Rhythm Notification Feature (IRNF) vs Sleepiz One+
Cardiology AI Adjacent · 65/100
Tool A, Apple's Irregular Rhythm Notification Feature, is designed for proactive consumer heart health screening, specifically for irregular rhythms suggestive of AFib, and is integrated into the Apple…
VS
Irregular Rhythm Notification Feature (IRNF) vs EchoNext
Cardiology AI Adjacent · 65/100
Tool A, Apple's IRNF, is a consumer-focused wearable feature that screens for irregular heart rhythms suggestive of AFib using an Apple Watch and notifies users to consult their…
VS
EchoConfidence (USA) vs Irregular Rhythm Notification Feature (IRNF)
Cardiology AI Adjacent · 60/100
EchoConfidence is an enterprise-grade AI tool for healthcare providers, offering comprehensive echocardiogram analysis and report generation to streamline cardiac diagnostics. In contrast, Apple's Irregular Rhythm Notification Feature is…
VS
Analytic for Hemodynamic Instability (AHI) vs Irregular Rhythm Notification Feature (IRNF)
Cardiology AI Adjacent · 60/100
Tool A (Fifth Eye's AHI System) is designed for continuous, in-hospital monitoring of adult patients to predict hemodynamic instability hours in advance, providing clinical decision support for healthcare…

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Suggest an Edit → | Last Verified: 2026-04-20 | First Added: 2026-04-20

Investors who backed Irregular Rhythm Notification Feature (IRNF)

Funded through the company that built this tool.

Transformer VC
PE T3
Gru00fcnwald, Germany
unknown
Transformer VC is a German-affiliated venture firm with a LinkedIn presence under Transformer Capital but virtually no other public footprint to anchor…
AI/ML in Healthcare Digital Health
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