Hello, I think this could be related to your other issue with the datastore that we are discussing in another thread.
Since it's a storage issue (not a regular heartbeat, but vmfs.heartbeat), I don't think it is visible in the console.
As far as I understand in most cases there is some issue with accessing a datastore. From what I can see in the internet most of folks who has the issue, were able to fix it after contacting vmware support. I would recommend you to discuss this issue and all the related storage connectivity issues you have with VMware support team.
Here are few examples:http://www.adfrad.com/2012/04/dell-md3200i-vmware-esx-hanging-issues.htmlhttp://techblog.sunsetsurf.co.uk/2010/08/vmware-esx-4-0-iscsi-volume-problems