My late uncle had two bypass operations before he turned 45. His son decided it would be a good idea to get a calcium scan. His score was 750. They then followed up with a cardiac catheterization and they found several severe blockages. Within two weeks of getting his cardiac calcium score, he had a quadruple bypass. It was his story that got me to finally get one. Good thing I did. My results were pretty bad but not bad enough (yet) to require bypass surgery.
Strangely enough, my older brother got a score of 0, which blows my mind.
I think a lot of it has to do with high cholesterol. My cholesterol has been high for much of my adult life, even while taking statins.