A lead implanted across a heart wall such as an atrial septum includes structure for fixation to the wall. In some embodiments the distal end of the lead includes a sensor for measuring quantities such as pressure at a distal side of the wall. The fixation structures may be positioned on opposite sides of the wall after implant. The fixation structures may be aligned with the lead during delivery of the lead to the implant site and expanded from the lead at the implant site.