Abstract: An apparatus for detecting and treating abnormal electrical conducting tissue of an organ of the body which comprises a catheter insertable within a blood vessel or body cavity into proximity with the organ to be treated. An electrode or other electrical field-producing element is carried within the catheter and is effective to produce an electric field capable of inducing abnormal movement of the organ, e.g., a cardiac arrhythmia, when the electrode is placed at or near the focus of the abnormal electrical conducting tissue of the organ. A relatively undistorted image of such abnormal tissue is obtained using optical phase conjugation of a low energy laser beam which is directed to the focus of the damaged tissue and the along one or more optic fibers carried within the catheter to a viewing apparatus. A laser beam transmitted through another optic fiber carried within the catheter is then employed, if necessary, to destroy the damaged tissue.