Apple has released watchOS 6.1.3 to the public with important bug fixes and small improvements. It comes three weeks after watchOS 6.1.2.
The update includes ‘critical’ bug fixes, with one fix addressing an issue that stopped the irregular heart beat notifications on Apple Watch Series 4 and 5 from appearing for users in some countries. This fix is also included with watchOS 5.3.5, for users with an older iPhone that can’t upgrade to iOS 13 and therefore the latest version of watchOS.
You can update your Watch by going to Settings > General > Software Update (directly on the Watch) or opening the iPhone app and General > Software Update.