High impedance, low polarization, low threshold miniature steriod eluting pacing lead electrodes

A lead for body implantation within a patient for stimulation and sensing of a desired cardiac tissue site, said lead having an electrode of differential current density type, comprising:

• a. an electrical conductor having a proximal end and a distal end;
• b. electrical connector means coupled to the proximal end of said conductor for electrically connecting said lead to a cardiac pulse generator;
• c. electrode means coupled to said distal end of said conductor for conducting electrical energy to and from said cardiac tissue site;
• d. insulating sheath means for covering and electrically insulating said electrical conductor from body fluids and tissue extending between said electrode means and said electrical connector means;
• e. insulating body means coupled of the distal end of said insulating sheath means, said insulating body means having a wall spaced apart from and extending around said electrode means to prevent said electrode means from directly contacting said tissue site and thereby defining an electrode chamber, said wall further including an aperture provided therein for allowing body fluid ingress within said chamber and to said electrode means;
• f. wherein said electrode chamber aperture is in the range of 0.1 to 3.0 mm.sup.2 in area;
• and
• g. drug dispensing means carried adjacent the insulating body means for storing a drug to be dispensed while allowing dispensing of said drug within said chamber when wetted by the ingress of body fluids, such that said drug elutes through said chamber aperture, thereby countering undesirable interactions between said lead and said body site.

A body implantable lead, comprising:

• a. an electrical conductor having a proximal end and a distal end;
• b. insulating sheath means for covering said conductor between said proximal and distal ends thereof;
• c. electrical connector means coupled to said proximal end of said conductor for electrically connecting said lead to a pulse generator;
• d. electrode means electrically coupled to said distal end of said electrical conductor for conducting electrical energy to and from said body tissue site desired to be stimulated and sensed, said electrode means comprising a body of a porous metallic or other conductive material with high microscopic surface area in proportion to macroscopic surface area, mounted to a distal end of a conductive pin and extending radially from said conductive pin, a proximal end of said pin being coupled to said distal end of said electrical conductor;
• and
• e. drug dispensing means mounted around said pin, proximal to said porous body, within said insulating sheath, for storing a drug to be dispensed while allowing dispensing of said drug through said porous body to counter undesirable interactions between said lead and said body site.