Implantable unipolar pacemaker with improved outer electrode plate

Claim 2

In a unipolar implantable living tissue stimulator of the type including pulse generating means, a stimulating electrode electrically connected to said pulse generating means and locatable at the tissue to be stimulated by pulses supplied to said stimulating electrodes by said generating means, and outer electrode means connected to said generating means and in direct electrical contact with body saline solution which extends from said stimulating electrode to said outer electrode means to thereby provide an electrical conductive path therebetween, the improvement comprising: outer electrode means defining an electrically conductive surface of preselected area which is in direct electrical contact with the body saline solution when said stimulator is implanted in a body, said outer electrode means defining a plurality of electrically conductive elements whereby any substantially square area on the surface of any of said elements does not exceed a preselected maximum value which is significantly smaller than the total area of the conductive surface of said outer electrode means.

Claim 3

The improvement as described in claim 1 wherein said outer electrode means is a metal plate, with a plurality of slots defined therein to separate said plate into a plurality of electrically conductive strips, defining said electrically conductive elements, each strip being electrically connected to any other strip only through a single electrically conductive path, the strips having dimensions whereby any substantially square area of the surface of any strip does not exceed said preselected maximum value which is significantly smaller than the total area of the conductive surface of said metal plate.

Claim 4

The improvement as described in claim 1 wherein said outer electrode means is a plate of a biocompatible metal with a plurality of slots extending inwardly from at least one side of said metal plate, to thereby separate said plate into a plurality of electrically conductive elongated substantially rectangular shaped strips, defining said electrically conductive elements, each strip being electrically connected to any other strip through a single conductive path without a return path therebetween, the strips having dimensions whereby the largest substantially square area on the conductive surface of any strip is smaller than the total conductive surface area of said plate by a factor n, where n is not less than 10.

Claim 5

The improvement as described in claim 3 wherein n is not less than 100.

Claim 6

The improvement as described in claim 1 wherein said outer electrode means comprises a plurality of individual electrically conductive metal plates, each of said plates being electrically connected to any other plate through a single electrically conductive path, with any substantially square area on any of said metal plates being significantly smaller than the total surface area of said metal plates, by a factor not less than 10.

Claim 7

The improvement as described in claim 5 wherein the substantially square or circular area on any of said metal plates is smaller than the total area of said metal plates by a factor of not less than 100.

Claim 8

The improvement as described in claim 5 wherein each of said metal plates is in the shape of an elongated rectangle.

Claim 9

The improvement as described in claim 1 wherein said outer electrode means comprises an array of individual electrically conductive wires, each wire being electrically connected to any other wire through a single electrically conductive path, without a current return path therebetween, with the total conductive surface areas of said wires defining the area of the conductive surface of said outer electrode means.

Claim 10

In a unipolar implantable living tissue stimulator of the type including pulse generating means and a stimulating electrode electrically connected to said pulse generating means for stimulating living tissue and outer electrode means connected to said pulse generating means and being in contact with body saline solution, the improvement comprising: said outer electrode means including a sheet of electrically conductive metal of a preselected surface area, and including a layer of electrically conductive matter surrounding and being in direct electrical contact with said sheet of metal and being in direct electrical contact with body saline solution, when said stimulator is implanted in a body, said electrically conductive matter exhibiting heat insulating properties and being characterized by a resistivity which is greater than the resistivity of said sheet of metal by a factor n, where n is on the order of not less than 10, and being further characterized by being resistive to corrosion by body saline solution, said layer of electrically conductive matter providing an electrical current path between said body saline solution and said sheet of metal and distributes heating of said sheet of metal over the entire surface thereof.

Claim 11

In a unipolar implantable living tissue stimulator of the type including pulse generating means and a stimulating electrode electrically connected to said pulse generating means for stimulating living tissue and outer electrode means connected to said pulse generating means and being in contact with body saline solution, the improvement comprising: said outer electrode means including a sheet of electrically conductive metal of a preselected surface area, and including a layer of electrically conductive matter surrounding and being in direct electrical contact with said sheet of metal and being in direct electrical contact with body saline solution, when said stimulator is implanted in a body, said electrically conductive matter exhibiting heat insulating properties and being characterized by a resistivity which is greater than the resistivity of said sheet of metal by a factor n, where n is on the order of not less than 10, and being further characterized by being resistive to corrosion by body saline solution, said layer of electrically conductive matter providing an electrical current path between said body saline solution and said sheet of metal and distributes heating of said sheet of metal over the entire surface thereof.

Claim 12

The improvement as described in claim 9 wherein the resistivity of said sheet of metal is substantially in the range 60 microhm-cm to 200 microhm-cm and n is substantially in the range of 100 to 10,000.

Claim 13

In a unipolar implantable living tissue stimulator of the type including pulse generating means powered by a source of power rechargeable by an external magnetic field adapted to induce in said stimulator, power on the order of not less than 0.5 watt, the stimulator further including an electrode connected to said pulse generating means and locatable at tissue to be stimulated and outer electrode means connected to said pulse generating means and in direct contact with body saline solution, when the stimulator is implanted in a body, improved outer electrode means to minimize the heating of said outer electrode means due to any portion of said external magnetic field passing therethrough, said improved outer electrode means defining a conductive surface of a preselected area and formed of a plurality of electrically conductive elements having dimensions so that any substantially square area on the surface of any of said elements is smaller than the total area of the conductive surface of said outer electrode means, by a factor n of not less than 5 each of said conductive elements being interconnected to any other element through a singe current path.

Claim 14

In a unipolar implantable living tissue stimulator of the type including pulse generating means powered by a source of power rechargeable by an external magnetic field adapted to induce in said stimulator, power on the order of not less than 0.5 watt, the stimulator further including an electrode connected to said pulse generating means and locatable at tissue to be stimulated and outer electrode means connected to said pulse generating means and in direct contact with body saline solution, when the stimulator is implanted in a body, improved outer electrode means to minimize the heating of said outer electrode means due to any portion of said external magnetic field passing therethrough, said improved outer electrode means defining a conductive surface of a preselected area and formed of a plurality of electrically conductive elements having dimensions so that any substantially square area on the surface of any of said elements is smaller than the total area of the conductive surface of said outer electrode means, by a factor n of not less than 5 each of said conductive elements being interconnected to any other element through a singe current path.

Claim 15

The improvement as described in claim 11 wherein said outer electrode means is a plate of a biocompatible metal with a plurality of slots extending inwardly from at least one side of said metal plate, to thereby separate said plate into a plurality of electrically conductive elongated strips, defining said electrically conductive elements, each strip being electrically connected to any other strip through a single conductive path without a return path therebetween, the strips having dimensions whereby the largest substantially square area on the conductive surface of any strip is smaller than the total conductive surface area of said plate by the factor n where n is not less than 10.

Claim 16

The improvement as described in claim 12 wherein n is not less than 100.

Claim 17

In a unipolar implantable living tissue stimulator of the type including pulse generating means and a stimulating electrode, electrically connected to said pulse generating means for stimulating living tissue and outer electrode means connected to said pulse generating means, and being in contact with body saline solutions, when the stimulator is implanted in a body, said outer electrode means comprising a layer of biocompatible matter which is electrically conductive and electrically coupleable to the body saline solution, said matter being characterized by heat insulating properties and by an electrical resistivity in the range of 20 microhm-cm to 400 ohm-cm.

Claim 18

In a unipolar implantable living tissue stimulator of the type including pulse generating means and a stimulating electrode, electrically connected to said pulse generating means for stimulating living tissue and outer electrode means connected to said pulse generating means, and being in contact with body saline solutions, when the stimulator is implanted in a body, said outer electrode means comprising a layer of biocompatible matter which is electrically conductive and electrically coupleable to the body saline solution, said matter being characterized by heat insulating properties and by an electrical resistivity in the range of 20 microhm-cm to 400 ohm-cm.

Claim 19

The improvement as described in claim 14 wherein the resistivity of said matter is not less than 10 microhm-cm.

Claim 20

The improvement as described in claim 14 wherein the electrical resistivity of said matter is not less than 20 ohm-cm.

Claim 21

In a unipolar implantable living tissue stimulator of the type including pulse generating means with an outer electrically conductive electrode, which is electrically connected to said pulse generating means and is in electrical contact with body saline solution when the stimulator is implanted in a body, an improved outer electrically conductive electrode comprising electrically conductive matter having a preselected surface area with which the body saline solution comes in contact, said matter being dimensioned whereby any continuous substantially square area on the surface thereof does not exceed a preselected value, said substantially square area being smaller than the total surface area of said electrically conductive matter by a factor not less than ten.

Claim 22

In a unipolar implantable living tissue stimulator of the type including pulse generating means with an outer electrically conductive electrode, which is electrically connected to said pulse generating means and is in electrical contact with body saline solution when the stimulator is implanted in a body, an improved outer electrically conductive electrode comprising electrically conductive matter having a preselected surface area with which the body saline solution comes in contact, said matter being dimensioned whereby any continuous substantially square area on the surface thereof does not exceed a preselected value, said substantially square area being smaller than the total surface area of said electrically conductive matter by a factor not less than ten.

Claim 23

The stimulator as described in claim 17 wherein the total surface area of said matter is on the order of not less than 2 square inches and the maximum substantially square area is on the order of not more than 0.02 square inch.

Claim 24

The stimulator as described in claim 17 wherein the stimulator is rechargeable by an external alternating magnetic field of sufficient strength to induce a power on the order of not less than 2 watts in said stimulator and the maximum continuous substantially square area is on the order of not more than 0.02 square inch and the total surface area of said matter is on the order of not less than 2 square inches.