There are companies like Revivacor, Thoratec (now part of Abbott), Bivacor, Realheart, etc who all have very active work going on in heart pumps, replacements,

There are companies like Revivacor, Thoratec (now part of Abbott), Bivacor, Realheart, etc who all have very active work going on in heart pumps, replacements, and xenotransplantation and they all need technical folks, yes programmers too. I would caution you to fill up your life outside if that quest, don't trade your personal financial or health security in pursuit of it, and find a way for it to be a "good job", i.e. work for one of the above companies or similar for a handsome living, good work life balance, good health and other benefits, etc. and don't spend your life savings on some startup and then spend the next 10 years doing nothing but that letting that drive your identity.