Bipolar myocardial positive fixation lead with improved sensing

Abstract

A bipolar lead for use in sensing cardiac depolarization signals and for applying electrical stimulation to cardiac tissue comprises a pair of elongated conductors contained within a lead body, the lead body terminating at its distal end in an enlarged head fabricated from an insulating plastic material. The head has a generally planar surface and projecting perpendicularly from that surface is a corkscrew electrode which is adapted to be screwed into myocardial tissue. Also supported on the planar surface of the head so as to surround the corkscrew electrode is a toroidal electrode formed from helically wound conductive wire. One of the conductors passing through the lead body connects at its distal end to the corkscrew electrode which the other conductor attached to the toroidal electrode. The toroidal configuration of the helically wound wire provides substantially increased surface area when compared to a flat disk electrode and, moreover, offers the ability of tissue to grow into the interior regions of the toroidal electrode for improved anchoring, higher amplitude of the sense depolarization signals and a higher slew rate for the signal. Another feature of the invention involves filling the interior of the hollow torus structure with a wool-like material formed from platinum or other inert conductive material for even further increasing the amount of electrode surface in contact with tissue.