FIXED RATE RECHARGEABLE CARDIAC PACEMAKER

• US 3,867,950 A
• Filed: 06/18/1971
• Issued: 02/25/1975
• Est. Priority Date: 06/18/1971
• Status: Expired due to Term

• Current Assignee: Robert E. Fischell
• Original Assignee: Robert E. Fischell
• Inventors: Fischell, Robert E.
• Primary Examiner(s): Kamm, William E.
• Application Number:
  US05/154,492
• Time in Patent Office: 1,348 Days
• Field of Search: 128/419P,419R,421-423,2.1R,2P,2H
• US Class Current: 607/33
• CPC Class Codes: A61N 1/3655 controlled by body or blood temperature
• CPC Class Codes: A61N 1/3787 from an external energy source

Abstract

An improved fixed-rate cardiac pacer or stimulator adapted for human implantation which utilizes, as its power source, a single, rechargeable cell battery which is recharged through the patient'"'"''"'"'s skin by magnetic induction. The rechargeable battery supplies operating energy to transistorized pulse generating circuitry which is of simplified and fail-safe design effective to produce periodic heart stimulating output pulses at a controlled pulse rate. The electronic pulse generating circuitry is purposely designed such that the output pulse rate varies as a function of the battery voltage and also as a function of body temperature. The mechanical design of the rechargeable pacer or stimulator is compact in order to reduce volume and weight of the device; it is constructed of materials making it more acceptable to human implantation; and, it is hermetically sealed to prevent the infusion of body fluids and at the same time provide shielding against electromagnetic interference.

Claims

1. A cardiac pacer adapted to be implanted in the body of a patient and comprising, in combination a D.C. voltage supply, pulse generating circuit means connected to said voltage supply for generating output heart stimulating pulses at a predetermined rate, catheter means equipped with electrode means for applying said output heart stimulating pulses to the patient'"'"''"'"'s heart, an output transformer having primary and secondary windings which are D.C. isolated from one another, said primary winding being connected to receive the output heart stimulating pulses generated by said pulse generating circuit means, said secondary winding being connected to apply said output heart stimulating pulses to said catheter means, and filter capacitor means connected between the primary and secondary windings of said output transformer for preventing periodic signal noise from appearing at said catheter means.

2. The implantable cardiac pacer specified in claim 1 wherein said D.C. voltage supply is a rechargeable battery and further including, recharging means including means for coupling charging energy through the patient'"'"''"'"'s skin to the rechargeable battery by magnetic induction.

3. The implantable cardiac pacer specified in claim 2 wherein said rechargeable battery is a single nickel-cadmium cell, and said recharging means includes a source of output charging energy operating at a preselected ultrasonic frequency of substantially 25 kilohertz, a magnetic charging head connected to receive the output charging energy of said source and transmit said energy through the patient'"'"''"'"'s skin, a ferrite core input inductive coupling means for receiving said transmitted energy folloWing passage through the patient'"'"''"'"'s skin, and rectifier means connecting electrically said inductive coupling means to said battery.

4. The cardiac pacer specified in claim 1 wherein said pulse generating circuit means includes temperature sensitive circuit means selected to control said output pulse rate to vary in direct proportion with ambient temperture and thereby simulate natural heart beat variation as a function of temperature.

5. The cardiac pacer specified in claim 1 wherein said pulse generating circuit means includes, a timing circuit formed of a resistor and a serially connected capacitor to determine said output pulse rate, said capacitor having a high temperature coefficient effective to cause said output pulse rate to increase with increasing ambient temperature.

6. A cardiac pacer adapted to be implanted in the body of a patient and comprising, in combination, a rechargeable, single cell battery, pulse generating means connected to receive operating voltage from said battery for generating output heart stimulating pulses at a predetermined rate and including a timing circuit which determines said output pulse rate, said timing circuit including a resistance means and a serially connected charging capacitor having a high temperature coefficient effective to cause said output pulse rate to vary directly as a function of the pacer'"'"''"'"'s ambient temperature, said timing circuit being operably connected to said battery to cause the charging rate of said capacitor and the output pulse rate to vary directly as a function of battery voltage, control means for controlling externally of the patient'"'"''"'"'s body the resistance value of said resistance means to selectively vary said output pulse rate, catheter means equipped with electrode means for applying said output heart stimulating pulses to the patient'"'"''"'"'s heart, an output transformer having a primary winding connected to receive the output pulses generated by said pulse generating means and a secondary winding which is D.C. isolated from said primary winding and which is connected to apply said output pulses to said catheter means, a first molded, encapsulating unitary body of epoxy surrounding said battery, said pulse generating circuitry and said output transformer, a metallic housing formed around the exterior surface of said first epoxy body, said first epoxy body being provided with a plurality of electrical connector means mounted thereon and insulated from said metallic housing, certain of said electrical connector means connecting the secondary winding of said output transformer to said catheter means, an input inductive coupling means mounted on said metallically housed first epoxy body external to said metallic housing and being formed of a ferrite core and an energizable coil of insulated wire wound around said core and having its wire ends connected by others of the electrical connector means provided on said epoxy body to supply charging energy to said battery, a second molded, encapsulating body of epoxy surrounding said metallically housed first epoxy body, said input inductive coupling means and said catheter means adjacent the connection of said catheter means to said electrical connector means, and external charging means including a source of charging energy operating at a predetermined ultrasonic frequency of substantially twenty-five kilohertz and a charging head means connected to couple said charging energy to said input inductive coupling means by magnetic induction through the patient'"'"''"'"'s skin.

7. A cardiac pacer adapted to be implanted in a patient and comprising, in combination, a D.C. voltage supply, pulse generating circuit means connected to said voltage supply for generating output heart stimulating pulses at a predetermined rate, and catheter means equipped with electrode means connected to receive and apply said output heart stimulating pulses to the patient'"'"''"'"'s heart, SAID pulse generating circuit means including a timing circuit to determine said output pulse rate and comprising a resistor and capacitor connected serially with said voltage supply, said capacitor being charged repetitively from said voltage supply at a rate dependent on the existing voltage level of said supply, said pulse generating circuit means including means responsive to the voltage charged on said capacitor and render effective to generate an output pulse each time said capacitor has charged to a preselected threshold voltage, said output pulse rate being dependent upon the time required by said capacitor to charge to said preselected threshold voltage, said capacitor having a high temperature coefficient selected to control the rate at which said capacitor charges to said preselected threshold voltage to also vary in direct proportion with ambient temperature whereby said output pulse rate is dependent upon the existing voltage level of said voltage supply and simulates natural heart beat variation as a function of the patient'"'"''"'"'s internal temperature.

8. An implantable cardiac pacer adapted to be recharged from an external energy source and comprising, in combination, a rechargeable battery, pulse generating circuitry means connected to receive operating voltage from said battery for generating output pulses, pulse applying means equipped with electrode means adapted to apply pulses to the patient'"'"''"'"'s heart, an output transformer having primary and secondary windings connected to receive said output pulses from said pulse generating circuitry and couple them to said pulse applying means, a metallic housing forming a hermetic seal around said battery, said pulse generating circuitry and said output transformer, an inductive coupling means disposed external to said metallic housing for receiving recharging energy from said external source, rectifier means operably connected between said inductive coupling means and said rechargeable battery, and a plurality of electrical connector means mounted in and extending through and insulated from said metallic housing, certain of said plurality of electrical connector means connecting the secondary winding of said output transformer to said pulse applying means, others of said plurality of electrical connector means connecting said inductive coupling means electrically to said rechargeable battery via said rectifier means.

9. The implantable cardiac pacer specified in claim 8 further including a molded, encapsulating body of potting material disposed within said metallic housing and surrounding said battery, said pulse generating circuitry and said output transformer.

10. The implantable cardiac pacer specified in claim 9 wherein said metallic housing is formed by gold plating and said potting material is epoxy.

11. The implantable cardiac pacer specified in claim 9 wherein said inductive coupling means includes a ferrite core and an energizable coil of insulated wire wound around said core and having its ends connected electrically by said others of said plurality of electrical connector means and said rectifier means to said battery, said pulse applying means is a catheter means, the respective configurations of said input inductive coupling means and said metallically housed molded body being substantially similar to permit said input inductive coupling means to be mounted in juxtaposition against said metallically housed body, and further including a second molded, encapsulating body of potting material surrounding said metallically housed body, said input inductive coupling means, and said catheter means adjacent the connection of said catheter means to the electrical connector means provided on said metallically housed body.

12. The implantable cardiac pacer specified in claim 11 further including, an external charger operating at a predetermined ultrasonic frequency for coupling periodic charging enErgy to said input inductive coupling by magnetic induction, and wherein said rectifier means operably connected between said input inductive coupling means and said battery converts said periodic charging energy into direct current charging energy.

13. The implantable pacer specified in claim 11 wherein said metallically housed body has a substantially rectangular configuration with substantially flat top and bottom surfaces and concave side surfaces, said ferrite core is of a flat, substantially rectangular configuration and is mounted flat against the flattened top surface of said metallically housed body, and said catheter means comprises an insulative body containing a pair of wires terminating, at one end, at electrode means and branching out, at the other end, as two individual insulated wires, and a pair of connector assemblies, each adapted to be connected at the branched end of one of said two insulated wires and having a substantially cylindrical shape configured to mate with the concave side surfaces of said metallically housed body, said second body of potting material surrounding at least a portion of said connector assembly pair to anchor said catheter means.

14. The implantable cardiac pacer specified in claim 11 further including a coating of medical Silastic material encapsulating said second body of potting material for making said pacer unit compatible with the patient'"'"''"'"'s body tissue.

15. A cardiac pacer adapted to be implanted in a patient and comprising, in combination, a D.C. voltage supply, transistorized pulse generating circuit means connected to said voltage supply for generating output heart stimulating pulses at a predetermined rate and including a pair of transistors each having collector, emitter and base elements and regenerative feedback circuit means interconnecting the collector, emitter and base elements of said transistor pair, and catheter means equipped with electrode means connected to receive and apply said output heart stimulating pulses to the patient'"'"''"'"'s heart, said pulse generating circuit means including a timing circuit to determine said output pulse rate and comprising a resistor and capacitor connected serially with said voltage supply, said capacitor being charged repetitively from said voltage supply at a rate dependent on the existing voltage level of said supply, one side of said charging capacitor being connected to the base element of one of said transistors to effect conduction in said one transistor and cause said pulse generating circuit means to generate an output pulse each time said capacitor has been charged to a preselected threshold voltage, said output pulse rate being dependent upon the time required by said capacitor to charge to said preselected threshold voltage, said capacitor having a high temperature coefficient selected to control the rate at which said capacitor charges to said preselected threshold voltage to also vary in direct proportion with ambient temperature whereby said output pulse rate is dependent upon the existing voltage level of said voltage supply and simulates natural heart beat variation as a function of the patient'"'"''"'"'s internal temperature.