> who already have a great estimator for 10-year heart disease mortality risk in the coronary calcium score
Heart attack at age 29 survivor here.
CAC scores only show calcified plaque, not vulnerable plaque, which is the sort likely to rupture and cause an event.
You can go get a scan and receive a CAC score of 0, walk away thinking you're perfectly healthy, and then die tomorrow because the scan couldn't detect the massive amounts of non-calcified plaque lining your arteries.
The only non-invasive way to measure vulnerable/soft plaque is via CCTA
See, for example, "Atherosclerotic Plaque in Patients with Zero Calcium Score at Coronary Computed Tomography Angiography"
It measured nearly 1 in 10 patients with a 0 CAC score as having vulnerable plaque:
https://pmc.ncbi.nlm.nih.gov/articles/PMC5967134/
> "The frequency of atherosclerotic plaque in the coronary arteries in 367 patients with zero CS was 9.3% (34 individuals)"