a few days ago I also had a vibration in my chest from my I.C.D. Lasted just a few seconds but kept repeating at irregular intervals during the day. It came from my I.C.D. The best description is 'like a phone on silent, just vibrates on a call". Spoke to my Pacemaker clinic at my local hospital who asked me to make a Manual Download to thier computer. They called me the next day and said,'Nothing to report in the download. All seemed normal. They also said they had contacted Medtronic who stated that thier I.C.D';s - "do not vibrate!! Well I have news for Medtronic - MINE did!. However I went to sleep that night and it has not repeated itself since. As a aircraft engineer for over 63 years the only thing I can connect with this problem is that during that day, (and unusual for me) is that I had been carrying my mobile in my left breast pocket, (my I.C.D. is also on the left) and I suggest it MUST have been this close proximity which caused the vibration despite Medtronic insisting that this cannot happen. It has not repeated since. Do not know if this helps but felt I should mention this episode on the forum.
Regards Barrie Stubbs