Honestly the last chapters are bullshit.
The plan of getting the heart proposed by Saki made sense and it was perfectly workable. Why? External circulation exists. Ecmo solutions can pump oxigenated blood either substituting or helping heart's functions for weeks. In particular during transplants they use a lung-heart machine bypass.These cannot be used long term, but for 6 hours or even more should be ok. What if the heart stop, you are still maintaining circulation and you are going to replace it the same. But also using a VAD can work, a VAD can replace cardiac functions (there are reports of people with LVADs or BiVADs with sustained (more then 30s without self-recovering) ventricular fibrillation, considered a cardiac arrest, that were not only aware, but some were also asymptomatic ^1).
Also no fucking limb forth and back transplant surgeries, general anesthesia is a bitch to the body, there is a reason why surgeons don't schedule operations close to each other unless it's an emergency.
Not withstading the entire heart transplant surgery recovery period. Or her waking up with not even an ECG monitor attached.
BTW literature doesn't report a maximum limit of transplants and I couldn't find if subsequent transplant operation have stronger or more probable side effect then the first (albeit every surgery have side effect, so the probability is certainly cumulative). It's possible that this was intended misinformation by the others.
1^ For reference:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5731594/