Abstract: In a cardiac pacemaker electrode for transvenous insertion including a lead, a wire spring arrangement in electrical contact with the lead for fastening the electrode in the heart, a hollow cylinder, a piston to which the wire spring arrangement is connected to project from one end of the piston and which is displaceably mounted in the cylinder and an extension position in which at least part of the wire spring arrangement is retracted fully into the cylinder and an extension position in which at least part of the wire spring arrangement projects out of the hollow cylinder for fastening into heart tissue, and a guide wire extending through the lead and movable relative to the lead against the piston for pushing it from its retraction position to its extension position, the interior wall of the cylinder is made of electrically conductive material and is permanently conductively connected, at one end of the cylinder, to the lead, and the electrode is composed of at least one resilient contact element which is e