with Fadiga, this was the situation:
English club Bolton Wanderers signed Fadiga for the 2004–05 season, after he passed a medical. However, before he made an appearance for Bolton, he collapsed prior to a match in October, and had to be fitted with a defibrillator due to an irregular heartbeat. Despite stating his desire to return to the game, medical specialists urged him to retire, warning that if during a game his chest was knocked the defibrillator could fail, leading to instant death. However, following a period of rest and passing a medical, Fadiga returned to the Bolton squad in early 2005 and played in five games.
Obviously things have changed a lot since then with Muamba/Morosini/etc, so I dont know what Serie A law is now. But I believe Italy was trying to be stricter than other countries with the heart thing, so it wouldnt surprise me if Lyran's post is true.