20 Pa.C.S. § 5459: Revocation.

(a) When health care power of attorney may be revoked.--While of sound mind, a principal may revoke a health care power of attorney by a writing executed in accordance with the provisions of section 5452 (relating to execution) or by personally informing the attending physician, health care provider or health care agent that the health care power of attorney is revoked.

(b) Reliance on health care power of attorney.--A health care provider may rely on the effectiveness of a health care power of attorney unless notified of its revocation.

(c) Subsequent action by agent.--A health care agent, knowing of the revocation of the health care power of attorney, may not make or attempt to make health care decisions for the principal.