The defribulator will only go off if the normal sinus
rythm of the heart is out of sync for longer than the parameters it was set to fire. It does not fire due to rapid heartbeat ... only for irregular heartbeats that require a correction.
Whether or not you can safely have sex depends on what your physician has instructed you to do and not to do. I will gaurantee you that that question was answered by him or his staff prior to leaving the hospital after the implant. Look at your discharge instructions. Not knowing how severe your heart condition is or if you suffer from congestive heart failure
, I cannot give you permission to do anything. Ask your cardiologist if you should avoid that kind of activity or not. If he/she says it is ok, then enjoy.