AFib (Atrial Fibrillation)
An irregular, often rapid heart rhythm originating in the heart's upper chambers, one of the most common cardiac conditions detectable by consumer wearables through FDA-cleared algorithms.
Atrial fibrillation, commonly abbreviated AFib, is an irregular and often rapid heart rhythm caused by chaotic electrical signals in the heart's upper chambers (the atria). It's one of the most common sustained heart rhythm abnormalities, and it matters clinically because it meaningfully raises the risk of stroke and other cardiovascular complications, particularly when it goes undetected and untreated.
AFib is also one of the best-established use cases for consumer wearable health technology. Several wearables, including Apple Watch and Fitbit devices, carry FDA-cleared features that use a combination of optical heart-rate sensing (and, for ECG-capable devices, single-lead electrocardiogram readings) with machine learning algorithms to flag possible irregular rhythms consistent with AFib. In a landmark 2019 study, roughly 420,000 participants wore a consumer smartwatch that monitored for irregular pulse in the background; a small fraction received a notification, and among those who followed up with a clinical-grade ECG patch, a substantial share were confirmed to have AFib, often with no prior symptoms.
A wearable AFib notification is a screening signal, not a diagnosis. Clinical confirmation, typically via a longer-duration ECG monitor or an in-clinic ECG, is required before any treatment decision, and a meaningful share of wearable-flagged notifications do not end up confirmed as true AFib on follow-up.
A person with no cardiac symptoms receives an irregular rhythm notification from their smartwatch during normal daily wear. Following up with their physician and a clinical ECG patch confirms intermittent AFib, a case where wearable screening surfaced a condition that likely would not have been caught otherwise until a later, potentially more serious, event.