charlie
The definition of death by chazal doesnt really matter.
The question is indicator. Namely does heartbeat signify life? Yoma 85a can be understood that way. Alternativly even the absence of breathing is only an indicator of death if he “mutal kaeven” (Rashi) i.e. obviously a polio sufferer in an iron lung isnt dead becasue of absence of spontaneus breathing. The question is if a heartbeat in someobody who is not breathing precludes him from being dead(as in a brain-dead patient) since he isnt “mutal kaeven” I beleive this was R’ Elyashiv’s main objection to brain-death.
The Chacham Tzvi has a teshuva that is quite relevent in which he clearly uses the heart as the main indicator of death. However as you point out, he is basing on the mistaken view that the heart is a respiratory organ that pumps air throughout the body. Even if a mistaken assumption however that doesnt neccesary matter (according to brain death opponeents).
what I do fintd surprising about brian -death opponents is how excited they get when somebody reportedly “recovers” from brain-death. As in this thread. Never mind the fact that these reports are never well documented and are allways based on hearsay, usually ciopy/pasted across various media outlets.
Even if it did happen once in a while (it hasnt ever, people survive cardiac-death literally daily. Even wihtough the “lazararus phenomenon” Health mentioned. Every cardiac arrest that survives CPR, every Heart transplant, and Every CABG all had a stopped heart which subsequently restarts.
Is Cardiac death then not death?