An electrode for use in cardiac pacemaking has a conductive tip portion including a substrate composed of a material conventionally employed for pacing electrodes, and a layer of film of iridium oxide overlying the surface of the substrate. The tip portion may be provided with recesses to which the iridium oxide surface layer may be confined. An iridium oxide layer may be formed on both the cathode and the anode for efficient transduction at the electrode-electroyte interface in the environment of the pacemaker patient's body.
A medical electrical lead with an elongated lead body containing an elongated conductor and carrying a tip electrode mounted to and extending the distal tip of the lead body, coupled to the conductor. The distal tip of the lead body includes flange portions extending radially outward from a point immediately adjacent to the electrode and flat portions extending longitudinally and proximally from the electrode. The flange portions and flat portions alternate around the circumference of the lead body tip.
A small diameter, unipolar or bipolar, atrial or ventricular transvenous or epimyocardial pacing lead with a porous, platinized, steroid eluting cathode electrode exhibiting an effective surface area in the range of 0.1 to 4.0 mm.sup.2, preferably 0.6 to 3.0 mm.sup.2, provides low stimulation thresholds in the range of 0.5 volts, 0.5 milliseconds, very high pacing impedance (800 to 2,000 .OMEGA.), relatively low polarization, good to excellent sensing, and adequately low source impedance. The high pacing impedance prolongs the longevity of pacing pulse generators and allows for the miniaturization of their components. The low thresholds allow large safety factors at low applied voltages, which also contribute to increased battery longevity.
An implantable sitmulating lead for a cardiac pacemaker has a distal tip having a surface area adapted to physically contact heart tissue for pacing the heart tissue, sensing heart contractions and promoting tissue ingrowth. The distal tip includes a conductive electrode and a porous non-conductive substrate, which together define the surface area of the distal tip. The conductive electrode and porous substrate are provided as first and second members, although the surface area of each is adaptive to present a singular, smooth distal tip region for the electrode lead.
An implantable stimulation lead is readily adaptable for stylet placement or guidewire lead placement. The implantable lead includes at its distal end an implanting guide structure which includes a rigid member having a through bore. A plug is dimensioned to be received within the through bore and a retaining mechanism releasably retains the plug within the through bore. When the plug is retained within the through bore, the lead is adapted for stylet placement and when the plug is released from the through bore, the lead is adapted for guidewire lead placement. In a preferred embodiment, the distal electrode of the lead provides the rigid member of the implanting guide structure. After the lead is positioned by guidewire lead placement, the proximal end of the lead may be sealed with a plug or the plug of the implanting guide structure or new plug may be replaced or placed in the lead to prevent blood flow through the lead.
