System for selectively reforming an ICD

• US 5,861,006 A
• Filed: 11/15/1996
• Issued: 01/19/1999
• Est. Priority Date: 11/15/1996
• Status: Expired due to Fees

• Current Assignee: Angeion Corporation (Niterra Co., Ltd.)
• Original Assignee: Angeion Corporation (Niterra Co., Ltd.)
• Inventors: Kroll, Mark W.
• Primary Examiner(s): Jastrzab, Jeffrey R.
• Application Number:
  US08/749,441
• Time in Patent Office: 795 Days
• Field of Search: 607/5, 607/7, 607/27, 607/29, 607/34
• US Class Current: 607/5
• CPC Class Codes: A61N 1/3937 Monitoring output parameters
• CPC Class Codes: A61N 1/3956 Implantable devices for applying electric shocks to the heart, e.g. for cardioversion

Abstract

An implantable cardioverter defibrillator (ICD) in which capacitor systems are automatically reformed using a software-implemented computer system. The charge history and performance of the capacitor system are measured to perform intelligent calculations and to set the automatic capacitor reforming cycle. Individual capacitors among a group of many are isolatively charged as needed. Moreover, a sub optimal charge is used to automatically reform the capacitors to efficiently use battery energy. Further, excess charge is directed from one capacitor to another to thereby conserve energy. Specifically, the disclosure relates to an autonomous capacitor charging system which enhances ICD reliability to sustain real time provision of high current pulses.

Claims

1. An improved implantable cardioverter defibrillator (ICD) system having at least one capacitor system which is charged from a battery system by control circuitry integrated within the ICD to deliver an electrical countershock in response to detection of a cardiac dysrhythmia in which the at least one capacitor system is automatically reformed using a control system to make intelligent calculations of the charge history and performance of the at least one capacitor system, the improverment comprising:

means for measuring the charge history and performance of the at least one capacitor system;

means for automatically calculating charge time based on said charge history and performance of the at least capacitor system; and

means for charging and monitoring the at least one capacitor system based on said charge time;

said means for measuring, said means for automatically calculating charge time and said means for charging and monitoring the at least one capacitor system being in electrical communication with the control circuit in the ICD system.

2. The improved ICD system of claim 1 wherein said means for automatically measuring the charge history and performance of the at least one capacitor system includes a software system directing computer system as part of the control circuitry of the ICD.

3. The improved ICD system of claim 1 wherein said means for automatically calculating said charge time based on said charge history and performance of the at least one capacitor system includes a software system integrated with the control circuit in the ICD system.

4. A software-directed system in cooperation with a control circuit of an implantable cardioverter defibrillator (ICD) device to automatically reform capacitor systems in the ICD device which are charged from a battery system by the control circuit to deliver an electrical countershock in response to detection of a cardiac dysrhythmia, the software-directed system comprising:

means for calculating capacitor performance and charge history based on delay to mandatory reform time (D_M) and most recent charge time (T_L);

means for calculating delay from last shock time (D_S);

means for performing a soft reform;

means for estimating charge time on a preset time interval basis;

means for charging to 100 V to estimate overall charge time as Test (T_TEST); and

means for comparing said charge time as test with said most recent charge time (T_L);

said means for calculating capacitor performance anal charge history, said means for calculating delay from last shock time, said means for performing a soft reform, said means for estimating charge time, said means for charging to 100 volts and said means for comparing having electrical communication therebetween and further being in operative electrical communication with the control circuit of the ICD device.

5. The system according to claim 4 wherein said means for calculating capacitor performance and charge history includes a computer system under the direction of said software and in electrical communication with the control circuit of the ICD device.

6. An implantable cardioverter defibrillator (ICD) device in which capacitor systems charged from a battery system through an invertor by a control circuit to deliver an electrical countershock in response to detection of a cardiac dysrhythmia are automatically reformed using a low frequency charging power through the invertor wherein a software implemented computer system that is part of the control circuit of the ICD provides intelligent calculations to control the automatic reforming, the software-implemented computer system comprising:

means for automatically calculating charge time based on charge history and performance of the capacitor systems;

means for charging and monitoring the capacitor systems based on said charge time; and

circuit means for implementing a soft reform to operate the invertor at said low frequency;

said means for automatically calculating, said means for charging and said circuit means for implementing a soft reform being in electrical communication with each other and integrated with said ICD device.

7. The software implemented computer system of claim 6 wherein said means for charging and monitoring includes FET switches to direct current from one capacitor to another in said capacitor systems.

8. The software-implemented computer system of claim 6 wherein said means for charging and monitoring includes SCR switches which direct excess current from one capacitor to another in said capacitor systems.

9. The software implemented computer system of claim 6 wherein said circuit means for implementing a soft reform includes a battery system connected in series to a resistor having a resistance equal to an equivalent series resistance (ESR) of said battery system.

10. An implantable cardioverter defibrillator (ICD) device having a software implemented computer system wherein capacitor systems charged from a battery system by a control circuit to deliver an electrical countershock in response to detection of a cardiac dysrhythmia are automatically reformed using a limited amount of battery energy to deliver a maximum shock to a patient in whom the ICD device is implanted, the software implemented computer system comprising:

means for monitoring a charge time;

means for estimating reforming needs from said charge time to a sub maximal shock;

means for charging to 100 volts wherein overall charge time is set as test;

means for comparing said charge time as test with a last charge time; and

means for performing a soft reform;

said means for monitoring, said means for estimating, said means for charging, said means for comparing and said means for performing a soft reform being in electrical communication with said ICD device and being directed by said software implemented computer system.

11. The system of claim 10 wherein said means for performing a soft reform includes a circuit having a battery system, a resistor and an invertor.

12. The system of claim 10 wherein said means for charging to 100 volts includes a voltmeter to regulate said charging to 100 volt.

13. An implantable cardioverter defibrillator (ICD) device including at least one capacitor system charged from a battery system by a control circuit to deliver an electrical countershock in response to detection of a cardiac dysrhythmia, the ICD device also including a software system to automatically reform the at least one capacitor system in the ICD wherein delay between consecutive reforms is based on intelligent calculations executed by the software system such that an autonomous reforming cycle is used instead of a fixed time, the device comprising:

a computer directed by said software system to perform an automatic reform of the at least one capacitor system;

circuit means for performing a soft reform directed by said software system;

means for initiating said soft reform; and

means for terminating said soft reform;

said soft reform being autonomously performed based on preset parameters, of performance and charge history of the at least one capacitor system, which said software system utilizes to execute said intelligent calculations to perform said autonomous reforming cycle.

14. The device according to claim 13 wherein said circuit means for performing a soft reform includes a battery system connected in series to a resistor having a resistance equal to an ESR of said battery system.

15. The device according to claim 13 wherein said means for initiating and said means for terminating include a voltmeter to activate said initiating means and said terminating means based on a voltage reading of said capacitor systems.

16. An implantable cardioverter defibrillator (ICD) device including a capacitor system having at least two capacitors charged from a battery system by a control circuit to deliver an electrical countershock in response to detection of a cardiac dysrhythmia is integrated with a circuit isolation device including a software implemented computer system to automatically reform the capacitor system within the ICD device wherein a capacitor, in the capacitor system, is isolatively reformed based on intelligent calculations wherein excess charge from the reformed capacitor is directed to jump start another capacitor such that the amount of energy required to fully charge said another capacitor is reduced by the amount of said excess charge transferred to said another capacitor, the circuit isolation device comprising;

means for performing the automatic reform;

a plurality of FET switches; and

a plurality of SCR switches;

said means for performing the automatic reform, said FET switches and said SCR switches having electrical communications therebetween and being integrated with a control circuit in the ICD device.

17. The device according to claim 16 wherein said FET switches are connected to said capacitor system to direct current to only a selected capacitor in said capacitor system.

18. The device according to claim 16 wherein said SCR switches are connected to said capacitor system to direct excess current from a fully charged capacitor to another capacitor in said capacitor system.

19. An implantable cardioverter defibrillator (ICD) integrated with an automatic capacitor charging device to form an autonomous capacitor reforming system wherein capacitors in the ICD are reformed based on intelligent calculations, the capacitor reforming system comprising:

the ICD including;

a converter section;

a flyback charging switch;

at least one capacitor; and

a control circuit;

said converter section, said flyback charging switch, said at least one capacitor and said control circuit being in electrical communication and comprising electronic components of said ICD;

the automatic capacitor charging device comprising;

a circuit including;

a plurality of FET switches, a plurality of SCR switches, and connection means for connecting said circuit to said ICD;

a computer system;

a soft reform circuit including;

an invertor, and

a resistor calibrated at an ESR of a battery system in said invertor;

wherein said ICD, said capacitor reforming system, said computer system, and said soft reform circuit being in operative and electrical communication with each other and comprising said autonomous capacitor reforming system.

20. The capacitor reforming system of claim 19 wherein said control circuit includes a voltmeter to monitor voltage readings of the capacitor reforming system.

21. The capacitor reforming system of claim 19 wherein said computer system includes a software directing said computer system to make intelligent calculations and operate the capacitor reforming system.

22. A method to automatically charge a capacitor system in an implantable cardioverter defibrillator (ICD) device wherein a reforming system in cooperation with said ICD device forms an autonomous reforming system based on intelligent calculations performed by a software implemented computer system to reform the capacitor system based on charge and performance history comprising the autonomous reforming system implemented step of:

(a) calculating a mandatory reform time (DM) from a most recent charging time (TL);

(b) comparing said DM with a delay from a last shock (DS);

(c) performing a soft reform if said DS is greater then said DM;

(d) checking if it is time for a weekly charge time estimate;

(e) charging the capacitor system to a minimum voltage if it is time for said weekly charge time estimate;

(f) comparing said weekly charge time estimate with a set time limit;

(g) performing a soft reform if said weekly charge time estimate is greater than said set time limit; and

(h) resetting back to step (a) after one of said step of performing a soft reform, said step of checking if it is time for a weekly charge time estimate and said step of comparing said weekly charge time estimate.

23. The method according to claim 22 wherein said step of performing a soft reform includes running an invertor at a low frequency to conserve batter energy.

24. The method according to claim 22 wherein said step of charging the capacitor system to a minimum voltage includes charging to 100 V to estimate overall charge time as test.

25. An implantable cardioverter defibrillator (ICD) comprising at least one high voltage capacitor system which is charged from a battery system by control circuitry integrated within the ICD to deliver an electrical countershock in response to detection of a cardiac dysrhythmia, the at least one capacitor system being automatically reformed by a system within the ICD that measures the charge history and performance of the at least one capacitor system and automatically calculates an estimated charge time based on said charge history and performance of the at least one capacitor system and initiates charging and monitoring of the at least one capacitor system based on said estimated charge time.

26. The ICD of claim 25 wherein the system for automatically reforming the at least one capacitor system calculates a mandatory reform time based on a most recent charging time and compares the mandatory reform time to a delay measured from a last countershock and initiating a reform of the at least one capacitor system if the delay is greater than the mandatory reform time.

27. The ICD of claim 25 wherein the system for automatically reforming the at least one capacitor system initiates a periodic charging of the at least one capacitor system to a minimum voltage less than a full reform voltage and compares a time period for the periodic charging with a predetermined time limit to determine whether to initiate a full reform cycle of the at least one capacitor system.

28. The ICD of claim 25 wherein the system for automatically reforming the at least one capacitor system selectively performs a soft reform of the capacitor system.

29. An implantable cardioverter defibrillator (ICD) comprising a capacitor system having at least two high voltage capacitors which are charged from a battery system by control circuitry integrated within the ICD to deliver an electrical countershock in response to detection of a cardiac dysrhythmia, the capacitor system being automatically reformed by a system within the ICD that selectively isolates the at least two capacitors during reforming using electronic switches to charge only one capacitor at a time.

30. The ICD of claim 29 wherein the system which automatically reforms the capacitor system also selectively interconnects the at least two capacitors during reforming to transfer residual charge from one capacitor to an other capacitor to decrease an amount of energy otherwise required to charge the other capacitor.