I was probably the fittest I had ever been for 20 years when I had a bypass- No warning- not overweight- correct diet etc. While I was in hospital, my riding mate had indigestion- went to the Doctors and immediate Hospitalisation. He was having a heart attack. He was given the stress test- X-rays- Angiogramme and declared fine. Two years later on a bike ride he had Indigestion again and was dead in 5 minutes.

Bike riding or any form of exercise does not eradicate Heart problems- but it will make you fit enough to get through them.