Strange for this to happen in Italy, where athletes including footballers are given cardiac screenings at a young age. Must be something extra-ordinary obviously. Rest in Peace, 25 is no age for a young man to die.
Know a young woman who died in front of her little girl, who was then alone all day. They never found out the cause. Think the problems are in the electrical systems in the heart and can be difficult to detect. One expert says you can be fine one month and pass a test, then the problems appears within weeks. The only good thing to come of this is that high profile cases result in more research and then others may be saved.
When my Dad was 65 he had a major health check and the doctor shook his hand and said "Congratulations, you have the heart of a man 30 years younger than you." 3 weeks later he dropped dead in front of me. Fran is right, sometimes, even with all the technology they have today, there are things you just can't screen for.