An implantable active fixation lead system which connects a source of electrical energy, such as a pacemaker, to the cardiac tissue. The lead system includes a lead, an introducer and a guide catheter. The lead has a small diameter lead body, and an active fixation device for engaging the cardiac tissue. The lead body has an overall straight, uncoiled configuration, and an outer diameter of about 13 mils. The lead body includes a plurality of infinitesimal, bio-compatible, bio-stable electrically conductive strands which are tightly bundled together in a cable-like fashion to form a single conductor. A dielectric bio-compatible insulation coating surrounds the conductor to provide an insulation layer between the conductor and the body environment. The fixation device includes a crank portion which engages the introducer.
The introducer is assembled to the lead and includes a coupler which engages the crank portion of the lead fixation device. The coupler includes a closely wound coil, and an elongated generally cylindrical tip engaging member having an aperture which acts as an entranceway for the lead fixation device. The coupler retains and firmly engages the lead crank portion, and controls its engagement to, and disengagement from the cardiac tissue. Furthermore, the coupler prevents the lead active fixation device for over-perforating the cardiac tissue.
A catheter is assembled to the lead and the introducer, for imparting stiffness and improved steerability to the lead.