I also have a cardiologist.
It takes the form of a combination of very high output training (BJJ) coupled with regular, sustained aerobic training at a high percentage of my aerobic capacity (running and plyometrics).
It sounds like I'm being flip, or worse, self-satisfied - but I am quite serious.
If my heart started behaving strangely, or weakened in some way, I would notice immediately. It would be quite marked. Things that I partake in, and think about, and feel, would suddenly be off.
Or to put it more technically, I am running my body at a much lower set of tolerances where defects are immediately identifiable.[1]
I have a suspicion that my cardiologist is actually better than the apple one, since I could feel some differences that might not yet manifest themselves in some kind of measurable heart output.
The downside to all of this, in the faraway future (I am currently 42 years old) is that "heart trouble" might manifest itself during exercise in a sudden and acute fashion that leaves me dead. On the other hand, the exercise makes that, statistically, less likely.
I also enjoy it very much, so there's that.
[1] https://www.keyence.com/ss/products/measure/measurement_libr...