Pushups with an AICD

My husband had an AICD put in his chest last week due to him suffering from a Sudden Cardiac Death episode.  He is a 41 year old male with an extremally healthy heart that for some reason we can not find out stopped working during exercise one day.  they told him that because they had to shock him 3 times with the external defibrillator that they had to put in a internal defibrillator no matter what.  We are not to happy about that but he did it anyway's.  My questions are this...Did they really have to put the defiibrillator in just because they shocked him? and can he ever get back to running and doing push-up's?  He is in the Army and 3.5 years away from retiring at 20 year's which has been a goal from long ago.  now they are talking about medically retireing him which we don't want.  

[CCF HeartMD5]

An implantable defibrillator is indicated if someone is successfully rescuscitated after an episode of sudden cardiac death caused by a dangerous heart rhythm such as ventricular tachycardia or ventricular fibrillation.  The thought is that if someone has had one episode of sudden cardiac death¸ they are more likely to have another. One he has recovered from the device implantation, there should be little limitations on his activity such as running or push ups.  The army may have their own criteria for medical retirement, but your husband likely should be able to resume all activity with the defibrillator in place.