My husband has suffered a stroke and is now physically disabled. He has made it clear to me that if he has another medical crisis, like a heart attack, I am not to do anything.
Any competent adult has the legal right to accept or reject medical treatment.
Your husband has the legal right to decide what kind of medical care he wants or does not want, even if his death will result. Communicating his decisions in a legally enforceable manner is of the utmost importance. If you haven't already, you and he should talk to his doctor and to a medical social worker about his feelings. When you and he are satisfied that the decision is correct, your husband should sign a proper Natural Death Directive. However, this only applies if two doctors decide that his condition is terminal and irreversible.