Arrhythmia detection and defibrillation system and method

• US 4,475,551 A
• Filed: 09/02/1982
• Issued: 10/09/1984
• Est. Priority Date: 08/05/1980
• Status: Expired due to Term

• Current Assignee: Mirowski Family Ventures LLC
• Original Assignee: Mieczyslaw Mirowski
• Inventors: Langer, Alois A., Heilman, Marlin S.
• Primary Examiner(s): Kamm, William E.
• Application Number:
  US06/414,353
• Time in Patent Office: 768 Days
• Field of Search: 126/419 D
• US Class Current: 607/5
• CPC Class Codes: A61N 1/3956 Implantable devices for applying electric shocks to the heart, e.g. for cardioversion
• CPC Class Codes: A61N 1/3987 characterised by the timing or triggering of the shock

Abstract

The invention relates to an arrhythmia detection system and method for defibrillating the heart of a patient experiencing abnormal cardiac rhythm, wherein the abnormal cardiac rhythm (comprising one of fibrillation, high rate tachycardia, and low rate tachycardia) is first detected, the heart rate is sensed so as to distinguish between fibrillation and high rate tachycardia, on the one hand, and low rate tachycardia, on the other hand, and automatic defibrillation of the heart of the patient is implemented when one of fibrillation and high rate tachycardia is determined. In one embodiment, base and apical electrodes are connected to a probability density function (PDF) circuit and a rate circuit. When both abnormal cardiac rhythm and excessively high heart rate are detected, defibrillation of the heart of the patient is implemented. In a second embodiment, a sensing button is also connected to the heart, and a switch is interposed between the electrodes and sensing button, on the one hand, and the interface, on the other hand. During monitoring of cardiac rhythm by the PDF circuit, the switch automatically connects the electrodes to the PDF circuit, while, during sensing of the heart rate, the switch connects the sensing button to the heart rate circuit. Upon detection of the need for defibrillation, the switch automatically connects the defibrillation pulse generator to the electrodes. Further features include a timed reset capability.

Claims

1. A method for delivering defibrillating energy to the heart of a patient experiencing abnormal cardiac rhythm, including ventricular fibrillation, which is characterized by an irregular ECG waveform, and high rate tachycardia and low rate tachycardia, both of which are characterized by regular R-waves occurring at generally stable rates, the deliverance of defibrillating energy taking place irrespective of the regularity of the ECG waveform representing such abnormal cardiac rhythm, said method comprising the steps of:

monitoring an ECG signal from the heart of the patient;

examining said ECG signal to detect said abnormal cardiac rhythm including ventricular fibrillation, high rate tachycardia, and low rate tachycardia;

examining said ECG signal to sense heart rate so as to distinguish between ventricular fibrillation and high rate tachycardia, on the one hand, and low rate tachycardia, on the other hand, said distinguishing being made without regard to the regularity or lack of regularity of the ECG waveform corresponding to said ECG signal;

issuing a defibrillating signal when both examining steps sense ventricular fibrillation or high rate tachycardia;

not issuing a defibrillating signal when both examining steps sense low rate tachycardia or normal sinus rhythm; and

responding to said defibrillating signal by automatically delivering defibrillating energy to the heart of the patient.

2. The method of claim 1, wherein said monitoring step comprises sensing an electrocardiograph (ECG) of the heart to develop ECG data, and said first recited examining step comprises processing said ECG data in accordance with a probability density function.

3. The method of claim 1, comprising the additional step, prior to said monitoring step, of connecting a base electrode and an apical electrode to said heart, said base and apical electrodes being used during said monitoring step.

4. The method of claim 1, comprising the additional step, prior to said monitoring step, of connecting a base electrode, an apical electrode and a sensing button to said heart, said base and apical electrodes being used during said monitoring step, and said sensing button being used during said monitoring step.

5. The method of claim 1, wherein said two examining steps are performed simultaneously.

6. The method of claim 5, wherein said monitoring step comprises sensing an electrocardiograph (ECG) of the heart to develop ECG data, and said first recited examining step comprises processing said ECG data in accordance with a probability density function to produce a detection output when said abnormal cardiac rhythm is detected, said method comprising the additional step of inhibiting said detection output when said sensing step determines the presence of low rate tachycardia.

7. The method of claim 1, wherein said first recited examining step and said second recited examining step are performed in sequence, said second recited examining step being performed only when said abnormal cardiac rhythm is detected during said first examining step.

8. The method of claim 7, comprising the additional step, prior to said monitoring step, of connecting a base electrode, an apical electrode and a sensing button to said heart, said base and apical electrodes being used during said detecting step, and said sensing button being used during said sensing step.

9. The method of claim 1, wherein said second recited examining step comprises comparing the heart rate of the heart to a predetermined threshold, said step of automatically delivering defibrillating energy to the heart being executed when said heart rate exceeds said predetermined threshold.

10. The method of claim 9, wherein said second recited examining step further comprises automatically returning to said first recited examining step when said heart rate remains below said predetermined threshold for a predetermined time.

11. A system for delivering defibrillating energy to the heart of a patient experiencing abnormal cardiac rhythm including ventricular fibrillation which is characterized by an irregular ECG waveform, and high rate tachycardia and low rate tachycardia, both of which are characterized by regular R-waves occurring at generally stable rates, the deliverance of defibrillating energy taking place irrespective of the regularity of the ECG waveform representing such abnormal cardiac rhythm, said system comprising:

monitoring means for deriving an ECG signal from the heart of the patient;

detecting means, receiving said ECG signal from said monitoring means for detecting said abnormal cardiac rhythm, said abnormal cardiac rhythm including ventricular fibrillation, high rate tachycardia, and low rate tachycardia, said detecting means normally issuing a defibrillating signal upon detection of said abnormal cardiac rhythm;

automatic defibrillating means responsive to said defibrillating signal for automatically delivering defibrillating energy to the heart of the patient;

sensing means receiving said ECG signal from said monitoring means and simultaneously operative with said detecting means for sensing heart rate so as to distinguish between ventricular fibrillation and high rate tachycardia, on the one hand, and low rate tachycardia, on the other hand, said distinguishing being made without regard to the regularity or lack of regularity of the ECG waveform corresponding to said ECG signal; and

means responsive to said sensing of said ventricular fibrillation and high rate tachycardia by said sensing means for permitting said defibrillating signal to activate said automatic defibrillating means and responsive to said sensing of lowa rate tachycardia by said sensing means for preventing deliverance of said defibrillating signal to said automatic defibrillating means.

12. The system of claim 11, wherein said monitoring means comprises a sensing circuit for sensing an electrocardiograph (ECG) of the heart to develop ECG data, and said detecting means comprises processing means for processing said ECG data in accordance with a probability density function.

13. The system of claim 11, further comprising a base electrode and an apical electrode connected to said heart, and means for connecting said base and apical electrodes to said detecting means and said sensing means.

14. The system of claim 11, wherein said monitoring means comprises a sensing circuit for sensing an electrocardiograph (ECG) of the heart to develop ECG data, and said sensing means comprising a low pass filter circuit connected to said sensing circuit for low pass filtering said ECG data to provide a low pass filter output, said sensing means further comprising a rate circuit connected to said low pass filter circuit for receiving said low pass filter output and responsive thereto for sensing the heart rate.

15. The system of claim 11, wherein said detecting means and said sensing means operate simultaneously, said detecting means including a processing circuit for processing said ECG signal in accordance with a probability density function to develop a detection output, said sensing means comprising a rate circuit responsive to detection of low rate tachycardia for inhibiting said detection output of said processing circuit, whereby to inhibit automatic defibrillation of the heart of the patient upon detection of said low rate tachycardia.

16. The system of claim 11, wherein said monitoring means comprises a base electrode, an apical electrode and a sensing button connected to said heart, and said system further comprises connecting means for connecting said base and apical electrodes to said detecting means, and for connecting said sensing button to said sensing means.

17. The system of claim 16, wherein said connecting means comprises a switch circuit having a first state and a second state, said switch circuit being initially in said first state during operation of said detecting means for detecting said abnormal cardiac rhythm, said switch circuit being responsive to detection of said abnormal cardiac rhythm by said detecting means so as to be actuated to said second state, said switch circuit being responsive to determination of one of said ventricular fibrillation and said high rate tachycardia so as to be actuated to said first state for automatic defibrillation of the heart of the patient by said automatic defibrillating means.

18. The system of claim 17, wherein said detecting means comprises a probability density function circuit for determining when said abnormal cardiac rhythm exists, and a bistable circuit connected to said probability density function circuit and responsive to determination of the existence of said abnormal cardiac rhythm by said probability density function circuit for being actuated to a first state so as to emit a first output indicating existence of said abnormal cardiac rhythm.

19. The system of claim 18, further comprising means for providing said first output of said bistable circuit to said switch circuit, said switch circuit being responsive thereto for being actuated to said second state.

20. The system of claim 19, further comprising timed reset circuit means for automatically resetting said bistable circuit, and means for providing said first output of said bistable circuit to said timed reset circuit means for actuating said timed reset circuit means to start counting to a predetermined final count, said timed reset circuit means resetting said bistable circuit upon reaching of said predetermined final count.

21. The system of claim 18, wherein said sensing means comprises a heart rate circuit responsive to said first output of said bistable circuit for starting a heart rate monitoring operation.

22. The system of claim 21, wherein said heart rate circuit issues a first output when said monitored heart rate of the patient exceeds a predetermined threshold.

23. The system of claim 22, further comprising AND gate means responsive to said first output of said bistable circuit and said first output of said heart rate circuit for actuating said automatic defibrillating means to defibrillate the heart of the patient.

24. The system of claim 23, wherein said AND gate means is responsive to said first output of said bistable circuit and said first output of said heart rate circuit for actuating said switch circuit to said first state.

25. The system of claim 23, wherein said AND gate means is responsive to said first output of said bistable circuit and said first output of said heart rate circuit for automatically resetting said bistable circuit.

26. The system of claim 18, further comprising timed reset circuit means responsive to issuance of said first output by said bistable circuit for starting a counting operation so as to count to a final count value, said timed;

reset circuit means being responsive to reaching of said final count value for resetting said bistable circuit.

27. The system of claim 17, wherein said switch circuit, in said first state, connects said base and apical electrodes to said detecting means, and, in said second state, connects said sensing button to said sensing means,

28. The system of claim 17, further comprising interface means for interfacing said switch circuit to said detecting means and said sensing means, said switch circuit, in said first state, connecting said base and apical electrodes to said interface means, and, in said second state, connecting said sensing button to said interface means.

29. The system of claim 28, further comprising an ECG amplifier for connecting said interface means, on the one hand, to said detecting means and said sensing means, on the other hand.

30. The system of claim 17, further comprising an ECG amplifier for connecting said switch circuit, on the one hand, to said detecting means and said sensing means, on the other hand.

31. The system of claim 11, wherein said monitoring means comprises an ECG input circuit for sensing an ECG of the heart to develop ECG data, and said detecting means comprises a processing circuit for processing said ECG data in accordance with a probability density function, and for issuing a first output when said probability density function is satisfied, said detecting means further comprising a bistable circuit responsive to said first output of said processing circuit for issuing a further output signal indicating detection of said abnormal cardiac rhythm.

32. The system of claim 31, wherein said monitoring means comprises a base electrode, an apical electrode, and a sensing button connected to said heart, and said system further comprises connecting means for initially connecting said base and apical electrodes to said ECG input circuit, said connecting means being responsive to said further output signal from said bistable circuit for connecting said sensing button to said sensing means.

33. The system of claim 31, wherein said sensing means comprises a heart rate circuit for monitoring the heart rate of the patient, said heart rate circuit being responsive to said further output signal from said bistable circuit for beginning its heart rate monitoring operation.

34. The system of claim 33, wherein said heart rate circuit issues an output signal when said heart rate exceeds a predetermined threshold, said system further comprising AND gate means responsive to said further output signal from said bistable circuit and said output signal of said heart rate circuit for issuing an output signal actuating said automatic defibrillating means to defibrillate the heart of the patient.

35. The system of claim 34, further comprising means for providing said output-signal of said AND gate means to said bistable circuit, said bistable circuit being responsive thereto for resetting itself so as to stop issuing said further output signal.

36. The system of claim 34, further comprising a base electrode, an apical electrode, and a sensing button, and connecting means for initially connecting said base and apical electrodes to said ECG input circuit, said connecting means being responsive to said further output signal of said bistable circuit for connecting said sensing button to said heart rate circuit.

37. The system of claim 36, further comprising means for providing said output signal of said AND gate means to said connecting means, said connecting means being responsive to said output signal of said AND gate means for connecting said base and apical cup electrodes to said automatic defibrillating means.