Implantable cardiac defibrillator employing bipolar sensing and telemetry means

• US 4,614,192 A
• Filed: 03/23/1983
• Issued: 09/30/1986
• Est. Priority Date: 04/21/1982
• Status: Expired due to Term

• Current Assignee: Mirowski Family Ventures LLC
• Original Assignee: Mieczyslaw Mirowski
• Inventors: Imran, Mir, Kolenik, Steve A., Bach, Stanley M. Jr.
• Primary Examiner(s): Kamm, William E.
• Assistant Examiner(s): Shein, Mitchell J.
• Application Number:
  US06/478,038
• Time in Patent Office: 1,287 Days
• Field of Search: 128/419 PG, 128/419 PT, 128/419 D, 128/419 PS, 128/689, 128/705, 128/706, 128/708, 128/903, 128/702-704
• US Class Current: 607/5
• CPC Class Codes: A61B 7/00 Instruments for auscultation
• CPC Class Codes: A61N 1/0563 specially adapted for defibrillation or cardioversion
• CPC Class Codes: A61N 1/37 Monitoring; Protecting
• CPC Class Codes: A61N 1/3925 Monitoring; Protecting
• CPC Class Codes: A61N 1/3931 Protecting, e.g. back-up systems

Abstract

An implantable cardioversion system employing a bipolar electrode for R-wave sensing, the system utilizing heart rate averaging and probability density function techniques in determining whether or not the heart of a patient is to be automatically cardioverted. An improved bipolar electrode facilitates acquisition of a highly accurate R-wave. The implantable system is further provided with the capabilities of (1) providing, upon magnet-type interrogation, an audible indication of proper placement of the bipolar electrode in the body of a patient, (2) providing an audible indication to verify the status of the implanted device (activated or deactivated), (3) the capability of providing, upon request, a transmitted signal modulated with stored information corresponding to the number of times cardioversion of the patient has taken place, (4) the capability of preventing external cardioversion shock from being shunted across the electrodes, and (5) the capability of detecting average heart rate.

Claims

1. An implantable defibrillation system for automatically defibrillating the heart of a patient comprising:

detecting means for detecting fibrillation of the heart;

defibrillation means responsive to said detecting means for generating and applying to said heart at least one high-energy defibrillating pulse, said defibrillating means including a storage capacitor and a high voltage inverter means for charging said storage capacitor, said high voltage inverter means capable of emitting radio frequency (RF) signals during the charging of the storage capacitor, said RF signals capable of being detected externally of the patient;

counting means responsive to said defibrillating means for maintaining defibrillating pulse count information and for providing the pulse count information to a telemetry means;

telemetry means connected to said counting means and said high voltage inverter means for receiving the pulse count information and for transmitting information signals indicative of said pulse count information externally of the patient, wherein said telemetry means includes frequency modulation means for frequency modulating the RF signals emitted by said inverter means during the charging of said storage capacitor in accordance with the pulse count information, said telemetry means being responsive to a telemetry control signal to transmit said information signals;

control means for receiving an activation signal generated externally of the patient and, in response to said activation signal, for providing an inverter start signal to said high voltage inverter means to initiate the running of said inverter means and to discharge said storage capacitor upon completion of the running of the inverter means, and to provide a telemetry control signal to said telemetry means; and

external activation means for generating an activation signal external of the patient.

2. The implantable defibrillation system of claim 1, wherein said counting means comprises a register means for counting the number of defibrillating pulses applied to the heart of a patient and wherein said telemetry means includes serial converting means coupled with said register means for converting the number of pulses maintained in the said register means to a serial stream of pulses, said telemetry means further including pulse width modulation means for pulse width modulating the serial stream of pulses from said serial converting means, said pulse width modulation means coupled with said frequency modulation means wherein said frequency modulation means frequency modulates the RF signals emitted by said high voltage inverter means in accordance with the pulse width modulating signal from said pulse width modulating means.

3. The implantable defibrillation system of claim 2, wherein said serial converting means includes means for receiving said telemetry control signal from said control means.

4. The implantable defibrillation system of claim 1, wherein said control means further includes a test load resistor and means for discharging said storage capacitor across said test resistor upon completion of the running of said inverter means.

5. The implantable defibrillation system of claim 1, wherein said control means includes a reed switch responsive to a magnetic field activation signal and wherein said external activation means includes means for generating a magnetic field activation signal.

6. An implantable defibrillation system, including an electrode positionable in the ventricle of the heart of a patient for detecting R-waves, and a high voltage inverter means for charging a defibrillator storage capacitor, the system comprising,

an implantable audio oscillator means for generating audio tones that are aurally detectable outside the body of a patient;

enabling circuit means having an enable and disable status output coupled with said high voltage inverter means for enabling and disabling the high voltage inverter means;

R-wave detecting means coupled with said electrode for detecting the R-waves of a patient'"'"'s heart;

logic means coupled with said audio oscillator means and each of said enabling circuit means and said R-wave detecting means for providing control signals to said audio oscillator means indicative to the proper positioning of the electrode within the heart of a patient and indicative of the enable/disable status of the inverter means;

switch means responsive to an activation signal generated externally of a patient coupled with said enabling circuit means and said logic means to selectively enable and disable the high voltage inverter means and to enable the control signals from said logic means to control the audio tones emitted by the audio oscillator means.

7. The system of claim 6, wherein said logic means includes means for detecting the status output of said enabling circuit means and for receiving the detected R-waves from said R-wave detecting means and for providing,

(1) a continuous control signal to said audio oscillator means when the enabling circuit means is in a disable status,

(2) a periodic control signal to said audio oscillator means synchronized with the R-wave output of the R-wave detecting means when the enabling circuit means is in an enable status and R-waves are received from the R-wave detecting means indicating that the electrode is properly positioned within the heart of a patient, and

(3) the absence of a control signal to said audio oscillator means when the enabling circuit means is in an enable status and no R-waves are received from the R-wave detecting means, indicating that the electrode is not properly positioned within the heart of the patient, whereby the audio oscillator means includes means for generating a continuous tone, a periodic tone, and no tone, in response to control signals (1)-(3), respectively.

8. The system of claim 6, wherein said switch means includes means for changing the status of said enabling circuit means between enable and disable status in response to an activation signal maintained beyond a predetermined time period.

9. The system of claim 6, wherein said audio oscillator means includes a piezoelectric transducer affixed directly to the casing of the implantable defibrillator.

10. An implantable defibrillation system for automatically defibrillating the heart of a patient comprising:

bipolar electrode means implantable in a heart ventricle for sensing ventricular contractions, comprising a pair of electrodes spaced apart between 0.5 cm and 1.5 cm;

detecting means connected with said bipolar electrode means for detecting the sensed ventricular contractions and for providing a heart beat pulse signal proportional to each detected ventricular contraction, and for providing an arrhythmia signal when the detected ventricular contractions exceed a predetermined rate;

defibrillating means connected with said detecting means for providing a defibrillating pulse to the heart of a patient, said defibrillating means including means for charging an internal storage capacitor to a predetermined voltage level upon receipt of said arrhythmia signal, and means for discharging the voltage stored in said storage capacitor across the heart of a patient synchronous with said heart beat pulse signal.

11. An implantable defibrillation system as claimed in claim 10 wherein said detecting means comprises,

processing means for converting the sensed ventricular contractions into a series of uniform heart beat pulse signals proportional to each ventricular contraction, said processing means including an automatic gain control amplifier,

averaging means for averaging the number of heart beat pulse signals per unit of time and providing an analog output signal having a magitude proportional thereto, said averaging means including means for converting the frequency of the uniform pulses to a voltage output signal, and,

threshold means for comparing the voltage output signal with a reference signal and providing an arrhythmia signal when said voltage output signal exceeds the level of said reference signal.

12. An implantable defibrillation system as claimed in claim 11 wherein said pair of electrodes are separated by a distance of one (1) cm.

13. An implantable defibrillation system as claimed in claim 12 wherein said pair of electrodes are mounted on an elongated probe, one electrode mounted at the distal tip of said probe, the other electrode comprising a ring electrode circumferentially surrounding the probe and spaced from said distal tip.

14. An implantable defibrillation system for automatically defibrillating the heart of a patient comprising:

bipolar electrode means implantable in the ventricle of a heart for sensing ventricular contractions;

rate analysis circuit means connected with said bipolar electrode means for detecting the sensed ventricular contractions and for providing, (1) an analog rate output signal having a magnitude proportional to the average number of ventricular contractions per unit of time, and (2) a heart beat pulse signal proportional to each detected ventricular contraction;

threshold means connected with said rate analysis circuit means for receiving said analog rate output signal and for providing a threshold output signal when said analog rate output signal exceeds a predetermined reference level;

high voltage inverter means for receiving said threshold output signal, for charging a storage capacitor to a predetermined voltage level upon receipt of said threshold output signal, and for providing an inverter output signal when the storage capacitor is fully charged;

a storage capacitor connected with said high voltage inverter means for receiving a voltage charge, said storage capacitor coupled with implantable defibrillating electrodes;

logic means connected with said rate analysis circuit means and said high voltage inverter means for receiving said heart beat pulse signal and said inverter output signal and for providing a discharge signal in response to receipt of said heart beat pulse signal and inverter output signal;

discharge means connected with said storage capacitor and said logic means for discharging said storage capacitor across the implantable defibrillating electrodes in response to receipt of said discharge signal.

15. An implantable defibrillation system as claimed in claim 14 further comprising PDF processing means connectable to the heart for receiving EOG waveforms and for processing said EOG waveforms in accordance with a probability density function to provide a probability density function output signal, and wherein said high voltage inverter means includes means for receiving said probability density function output signal and for providing said inverter output signal upon receipt of said probability density function output signal and said threshold output signal.

16. An implantable defibrillation system as claimed in claim 14 wherein said bipolar electrode means comprises a pair of electrodes spaced apart between 0.5 cm and 1.5 cm.