"By your definition the subjective experience says nothing about how a heart actually works."
No, that's a reductionist assumption. When I say "subjective experience" I am explicitly not indicating its quantifiable aspects. I am indicating what Nagel talks about in "What It Is Like to Be a Bat," the what-it-is-likeness, the phenomenological aspect. Not the increased pulse, not the hormones being released, not the neurons firing in the brain that correspond to a feeling of anger--the anger itself. An idealized observer enumerating all of anger's physical correlates does not give that observer the experience of that anger as it is felt by the person experiencing it. There is a difference between understanding something and living something.
Except that not quite true, the subjective experience tells you there are pulses which increase in frequency under stress etc. It’s just the surgeon understands what that means where subjective experience is less useful. Further, the subjective experience fails to separate the causes of a fast heart rate with the response of a fast heart rate.
This should suggest that the experience of consciousness is of minimal value when trying to understand it.