Last week, Samsung previewed One UI 5 Watch, the first major One UI Watch platform update since last year's One UI Watch 4. Subsequently, the company has confirmed that the software will feature passive irregular heart rate detection following FDA approval in the US. For context, the Galaxy Watch5 series could already detect irregular heart rates but only with the ECG app open and while running an electrocardiogram.
As the images below show, One UI 5 Watch should notify you when it detects an irregular heart rhythm, dubbed Irregular Heart Rhythm Notifications (IHRN). According to Samsung, the feature is opt-in, which you will be able to do through the Samsung Health app. Once enabled, One UI 5 Watch will collect heart rate sensor data automatically to detect cardiac arrhythmias.
Samsung will debut IHRN in 'upcoming Galaxy Watch devices later this year'. In other words, the feature will launch with the Galaxy Watch6 series, which will be available in numerous styles and sizes. However, the functionality is also headed to the Galaxy Watch4 and Galaxy Watch5 series, presumably by way of their One UI 5 Watch updates. Samsung has not set a timeline for One UI 5 Watch upgrades yet, but IHRN will likely be limited to markets in which Samsung has received regulatory approval.