And you got your medical degree where?
Ride London:
2014: 36 year old male, cardiac arrest
2015: 55 year old male, cardiac arrest
2016: 48 year old male, cardiac arrest
2017: 67 year old male, cardiac arrest
I'm not saying the risk is huge, and I don't know if any of these people would have survived the year out if they had not done the ride, or indeed if cycling gave them a longer life than they would have had, but you can't just say there is no risk of dying from exertion cycling.
I agree with most of the other posters. Do what you feel comfortable with. If you want to keep pushing it but feel concerned, then talk to you GP.
Disclaimer: I know cardiac arrest and heart attack aren't the same thing.
I agree your asking for trouble, when squash was popular in the 90s I played a lot and their was no end of people having heart attacks and that was a typical sport where people went to the limit on heart rates