As usual the FDA is killing people for frivolous reasons. Existing organ transplants have the same problems of variable inputs and results. To hold mechanical substitutes to a higher standard than existing therapies makes no sense. They are already an improvement due to greater availability (once in production). They don't need to justify their existence by being higher quality too.
Patients who are about to die and know that they are still months away from receiving a donor organ have nothing to lose by taking a chance on artificial replacements.