You shouldn't be surprised by this. It is impossible to perform a successful organ transplant without suppressing the patient's immune system with anti-rejection drugs. This is the kind of comorbidity that will kill you if you get COVID. And because the supply of hearts is lower than demand, the hospital isn't going to waste one on anyone who second-guesses medical orders. Because again, if you refuse the necessary aftercare because you think you know better than the doctor, you will destroy the heart and you will die anyway.