Yeah, if you were given one operation where the patient has a 100% chance of dying without it, but 80% of you killing them if you operate + 20% chance of them living after, maybe you'd do this once and get lucky. But try doing this twice, you have a a 96% chance of killing a patient, three times makes a 99.2% chance of killing at least a single patient. This probability quickly approaches 100%. If you kill a patient you get dragged into court, branded as a murderer by the opposing lawyer, and your career which you have spent your youth, your 20s and a half a million dollars training for is down the drain. Taking risky cases, if that's not your niche, is is guaranteed to have you out of a job and in debt from legal fees.

To suggest that "bad hearts" are involved in this necessary calculation, is incredibly naive.