A single-pass endocardial lead electrode adapted for implantation in, on or about the heart and for connection to a system for monitoring or stimulating cardiac activity includes a lead body which is adapted for implantation within a single chamber of the heart, or multiple chambers of the heart. The lead includes a first distal end electrode which has a first electrical conducting surface. The lead body also has a second electrode which has a second electrical conducting surface. The first and second electrodes are either passively or actively attached to the wall of the heart. The lead body also includes a curved portion which facilitates the positioning of the second electrode. The main lead body alternatively includes a recess into which an atrial lead body and an active fixation element attached to one end can travel from a recessed position to a position for fixation to the wall of the heart. The active fixation element can also be moved by turning the terminal pin. The lead body can also include multiple legs, each leg carrying an electrode. The lead is attached to a pulse generator for producing pulses to the multiple sites within the heart. A movement assembly for advancing a helix is also included within the legs and comprises an externally threaded collar which engages with an internally threaded housing or housing insert.
The lead further includes a helical tip which has high impedance. The electrode has at least one features of the group: the helix having a coating of an insulating material on its surface, the helix having its surface beyond the distal end of the electrode and the distal end of the electrode having a porous conductive surface at a base of the helix, a porous conductive element at a base of the helix, and a porous conductive element at the end of the electrode having an insulating coating cover from 5-95% of the surface of the porous conductive element. The porous element may further provide a guiding mechanism for the helix as it travels out of the electrode for securing the electrode to the heart.