It doesn’t apply to Z wave per se. However, there are multiple community written smartapps that have implemented some kind of heartbeat function to determine whether the device is still connected to the network or otherwise operational.
So my first question would be can you determine from the logs exactly what put that entry into the log? Was it a smartapp or something else?
You probably already know this next bit, but just in case someone else finds this thread later, here’s how to read the logs: