The cardiac vaccines damage seems to work by damaging random heart cells at various percentages to give a varying degrees of general systemic degradation.
This diffuse, non specific individual cell by cell degradation would be difficult to identify and quantify using many diagnostic tools
For some the damage is sub clinical with minimal symptoms, for others it manifests as myocarditis or other heart ailments depending on where the heart is most affected.
It may or may not be reversible.
The thing I wonder about is, does having natural Covid cause the same thing or is it just the vax?