Abstract: An endocardial, implantable lead (1) for connection with an implantable pacemaker comprises an electrical conductor (3) adapted, via at least one electrode (5) connected thereto and in contact with the inner wall of the right auricle (AD), to transfer stimulating pulses to the heart or collect heart pulses from the heart. The lead (1) is spring-biased along a predetermined portion (8, 9) of its length to assume a curved shape (.alpha.), which predetermined portion contains the electrodes (5) and is adapted to be located in the heart auricle and bear against the inner wall thereof. A withdrawable relatively stiff wire (10) is adapted for straightening of the curved shape of the predetermined portion (8, 9) before and during insertion of the electrodes (5) in the auricle.