Devices or methods such as for stimulating excitable tissue or sensing physiologic response or other signals that can use chronic fixation mechanism are described. An implantable apparatus can comprise an electrostimulation electrode assembly that can include a primary fixation member and a secondary fixation member. The primary fixation member can be actively engaged or affixed to a target tissue of a patient, and the second fixation member can be biased against the target tissue, collapsed or compressed against the target tissue when the primary fixation member is affixed to the target tissue. The electrostimulation electrode assembly can also include at least one electrode such as to contact heart or other excitable tissue such as to deliver chronic electrostimulation or sensing physiologic responses.