The increasing prevalence of wearable technology has transformed personal health monitoring, offering a non-invasive method for screening certain conditions. Atrial fibrillation (AFib), the most common heart rhythm disorder, often goes undetected because it can be asymptomatic, yet it increases the risk of stroke fivefold. Consumer smartwatches and trackers provide a continuous, accessible way to monitor for the irregular heart rhythm characteristic of AFib, offering early prompts to seek medical advice. These devices serve as a preliminary screening tool, allowing individuals to take a proactive role in their cardiovascular health by passively and actively checking their heart rhythm.
Technology Used for AFib Detection
Smartwatches primarily utilize two distinct technologies for heart rhythm monitoring: Photoplethysmography (PPG) and Electrocardiogram (ECG). PPG uses optical sensors, often green light-emitting diodes, to detect changes in blood volume underneath the skin at the wrist. These sensors measure the pulsation of blood flow, allowing the device to track a user’s heart rate continuously and passively. The irregularity of the pulse intervals detected by PPG is the basis for alerting a user to a potential atrial fibrillation event.
PPG is the primary technology for initial, passive screening, as it does not require active user engagement. Conversely, the ECG feature requires the user to place a finger on a metallic sensor, often the crown or bezel, to complete an electrical circuit. This action records the heart’s electrical activity, generating a single-lead electrocardiogram tracing. The ECG function is used for on-demand verification to confirm an irregular rhythm first flagged by the PPG sensor or when the user feels symptoms.
Key Criteria for Selecting a Monitoring Watch
When selecting a watch for AFib monitoring, consumers should prioritize features that ensure reliability and utility in a medical context. The primary consideration is regulatory clearance, specifically from the U.S. Food and Drug Administration (FDA) or equivalent international bodies. FDA clearance indicates that the device’s AFib detection algorithm and hardware have been validated to meet specific performance and accuracy standards. Without this clearance, the device is considered a general wellness product, and its heart rhythm data may hold less medical weight when speaking with a physician.
Battery life is a practical consideration, as continuous monitoring is necessary for detecting often-intermittent AFib episodes. A short battery life may cause the device to miss events that occur overnight or away from a charger. The ability to easily export the heart rhythm data in a shareable format, such as a PDF of the ECG tracing, is necessary for communication with a healthcare provider. Finally, the comfort and fit of the watch are important because a loose fit can introduce motion artifact, which degrades the quality of PPG readings and leads to inaccurate results.
Reviewing Top FDA-Cleared Wearables
Several leading smartwatches and trackers have received FDA clearance for their AFib detection capabilities, offering consumers robust options.
- Apple Watch (Series 4 and newer): Utilizes a continuous PPG sensor for irregular rhythm notifications and a single-lead ECG app for on-demand checks. The ECG app produces a shareable waveform for a physician. It requires an iPhone for full functionality and is typically priced at the higher end of the market.
- Samsung Galaxy Watch series (e.g., Galaxy Watch 6): Incorporates both PPG and single-lead ECG functionality with FDA clearance, integrating well within the Android ecosystem. Its automated AFib detection algorithm has comparable sensitivity and specificity to the Apple Watch. These watches are generally mid-to-high range in price.
- Fitbit Sense series and Charge 6 tracker: Feature FDA-cleared PPG algorithms for passive irregular rhythm notifications, with the Sense 2 and Charge 6 also including an on-demand ECG app. Fitbit’s strength is its long battery life, often lasting several days, enhancing continuous background monitoring. These devices are compatible with both iOS and Android.
- Withings ScanWatch: A hybrid option offering a traditional watch appearance with both PPG and a medical-grade ECG. It is often chosen by those prioritizing discretion and extended battery performance.
Understanding Accuracy and Medical Limitations
While consumer wearables are effective screening tools for AFib, they have inherent medical limitations. The devices are designed to screen for an irregular heart rhythm and alert the user to a potential problem, but they do not provide a definitive medical diagnosis. Only a physician, using a medical-grade 12-lead electrocardiogram or Holter monitor, can definitively diagnose atrial fibrillation. Users must understand this distinction between screening and diagnosis when interpreting notifications.
A limitation of these devices is the potential for false positive results, where the watch flags an irregularity that is not actually AFib. These inaccuracies can be triggered by rapid movements, poor sensor contact, or other common arrhythmias that algorithms may misinterpret. Studies show that a percentage of automated readings can be inconclusive, often requiring a physician to manually review the tracing. Wearables are also not validated for use in individuals with pre-existing conditions like pacemakers. The data generated by a watch is supplementary information to guide a conversation with a cardiologist, who can contextualize the findings within the user’s overall health profile.