Electrode for implantation in the heart

In an electrode arranged to be inserted into the body of a patient and implanted in the patient's heart, which includes an electrode lead, a structure in the form of a helix protruding at the end of the electrode lead which is directed toward the heart for screwing the electrode into cardiac tissue, and a protective device positioned to protrude beyond the front end of the helix during insertion of the electrode to protect against inadvertent hooling of the helix, the improvement wherein said protective device comprises a cylindrical body disposed within said helix to be axially movable relative to said helix between a protective position in which said body is at least flush with the end of said helix, for insertion of said electrode, and a retracted position in which said helix is exposed for screwing into the cardiac tissue, for performing implantation, said cylindrical body being provided at its outer peripheral surface with shaped regions which are adapted to the pitch of said helix in the manner of threads and which are arranged to come into operating engagement with said helix for preventing movement of said cylindrical body toward its retracted position by forces which are effective thereon during insertion of said electrode, and said electrode comprises an actuating element extending between said cylindrical body and a location outside of the patient's body when said electrode lead is at the implantation location, said actuating element comprising means positively engaging said cylindrical body for driving said cylindrical body in a positive manner from its protective position to its retracted position, by transmitting to said body a retracting force applied to said element at the location outside the patient's body.