Method of and apparatus for automatically detecting and treating ventricular fibrillation

• US 4,291,699 A
• Filed: 09/21/1978
• Issued: 09/29/1981
• Est. Priority Date: 09/21/1978
• Status: Expired due to Term

• Current Assignee: Purdue Research Foundation (The Trustees of Purdue University (d/b/a Purdue University))
• Original Assignee: Purdue Research Foundation (The Trustees of Purdue University (d/b/a Purdue University))
• Inventors: Geddes, Leslie A., Bourland, Joe D., Terry, Reese S.
• Primary Examiner(s): Kamm, William E.
• Application Number:
  US05/944,369
• Time in Patent Office: 1,104 Days
• Field of Search: 128/419 D, 128/785, 128/723
• US Class Current: 607/6
• CPC Class Codes: A61B 5/0295 using plethysmography, i.e. measuring the variations in the volume of a body part as modified by the circulation of blood therethrough, e.g. impedance plethysmography
• CPC Class Codes: A61B 5/0535 Impedance plethysmography for measuring blood flow A61B5/0295
• CPC Class Codes: A61B 5/0538 invasively, e.g. using a catheter
• CPC Class Codes: A61N 1/36521 the parameter being derived from measurement of an electrical impedance
• 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

Method of and apparatus for automatic defibrillation of the cardiac ventricles of a heart wherein both the mechanical and electrical activities of the ventricles are sensed and used as operating inputs to the controls. Electrical activity is detected and measured with a pair of electrodes, and the waves of an electrocardiogram (ECG) are analyzed. When such electrical analysis indicates that ventricular fibrillation is present and persists, an electrical circuit is actuated for detecting mechanical pumping activity of the heart. Mechanical pumping activity is measured by the change in impedance between the pair of electrodes in one of the ventricles. The change of ventricular impedance is caused by the varying volume of blood contained within the ventricle and depends upon whether the ventricle is in a contracted or a relaxed state. The defibrillator is actuated only when both the mechanical and electrical activity of the ventricle indicates a need for defibrillation. Because some conditions may be encountered which closely resemble ventricular fibrillation, the defibrillator quantitatively preprograms and weighs the relative importance of the electrical and mechanical signals from the heart.

Claims

1. An automatic cardiac ventricular defibrillator comprising:

means for sensing electrical and mechanical activity of a cardiac ventricle in the form of ECG analog signals and the impedance of the ventricle, an ECG analog processor for producing an ECG analog processor signal of a fibrillatory condition, means for communicating the sensed electrical activity to said ECG analog processor, accumulator-control-logic means for counting fibrillatory signals, means for communicating an ECG analog processor signal of a fibrillatory condition from said ECG analog processor to said accumulator-control-logic means, an impedance analog processor operatively connected to said sensing means and responsive to said accumulator-control-logic means and for developing a signal of a non-fibrillatory condition which effects a decrementing count, means for communicating an activation switching action to said impedance analog processor responsively to a predetermined number of counted fibrillatory signals to selectively activate said impedance analog processor, means for communicating impedance measurement of the ventricle to said impedance analog processor, means for communicating an impedance analog processor derived signal of a non-fibrillatory condition to said accumulator-control-logic means while the impedance analog processor is activated, said accumulator-control-logic means being thereafter simultaneously responsive to both ECG analog processor and impedance analog processor signals, and an energy delivery system responsive to said accumulator-control-logic means to effect a defibrillating electrical shock to the heart appropriate to the correction of a fibrillatory heart condition.

2. The automatic cardiac ventricular defibrillator in accordance with claim 1, where the means for sensing electrical and mechanical activity comprises spaced ventricular electrodes for providing a first signal in the form of an ECG analog signal and a second signal in the form of an impedance analog signal whereby both the electrical and the mechanical activities of the ventricle are monitored.

3. The automatic cardiac ventricular defibrillator in accordance with claim 2, including a catheter supporting said electrodes and receivable within the ventricle.

4. The automatic cardiac ventricular defibrillator in accordance with claim 1, wherein said impedance analog processor is effective when said accumulator-control-logic means receives a predetermined number of fibrillatory ECG signals in sufficient predetermined pattern and number.

5. The automatic cardiac ventricular defibrillator in accordance with claim 1, including a preprogrammed means having a quantitative weighting factor assigned to the signals of said ECG analog processor and impedance analog processor whereby the respective signals are made correspondent to said weighting factor before a combination thereof is effective for communicating the energy delivery system to the heart for delivery of the defibrillating electrical shock.

6. The automatic cardiac ventricular defibrillator in accordance with claim 1, in which said accumulator-control-logic means effects a preprogrammed pattern representative of ventricular fibrillation and forming a standard against which the processed signals of the ECG analog processor are compared to identify changes indicative of fibrillation and for additionally detecting changes in impedance as a potential heart fibrillation condition, each of said processed signals to said accumulator-control-logic means providing information potentially confirming a fibrillatory ventricular condition when in accordance with a preprogrammed weighted decision imposed on said signals.

7. The automatic cardiac ventricular defibrillator in accordance with claim 1, wherein the accumulator-control-logic means includes control means and accumulator means for imposing a weighting factor and incrementing or decrementing whereby said accumulator means is effective for operation of said energy delivery system.

8. The automatic cardiac ventricular defibrillator in accordance with claim 1, wherein the accumulator-control-logic means includes a control means responsive independently to said ECG analog and impedance analog processor signals, and accumulator means responsive to said control means to be effective in accordance with fibrillatory activity for said control means and accumulator means to detect and respond to discrete patterns of signals.

9. The automatic cardiac ventricular defibrillator in accordance with claim 1, wherein the accumulator-control-logic means includes an accumulator means and means for effecting decrementing and incrementing of the signal values collected by said accumulator means in accordance with said impedance analog and ECG analog processed signals, and a decoding logic means for activating said impedance analog processor whereby the signals are accumulated in a predetermined weighted relationship to each other and the effecting of said defibrillatory electrical shock is in accordance with the respective signals.

10. The automatic cardiac ventricular defibrillator in accordance with claim 1, further comprising a third electrode for electrical connection to said energy delivery system, and a catheter, said means for sensing electrical and mechanical activity comprising a pair of spaced ventricular electrodes, said catheter supporting said spaced ventricular electrodes whereby said defibrillatory electrical shock is effected between the pair of spaced electrodes and the third electrode.

11. The automatic cardiac ventricular defibrillator in accordance with claim 1, said accumulator-control-logic means including an accumulator, a control member for receiving ECG and impedance related signals, a logic unit operatively connected to said accumulator, and a missing-pulse detector, said control member comprising means for incrementing and decrementing said accumulator in response to said signals, said missing-pulse detector monitoring said ECG analog processor signals to detect a non-fibrillatory condition and responsively acting through said control member to reset said accumulator.

12. The automatic cardiac ventricular defibrillator in accordance with claim 11, wherein said logic unit is responsive to said accumulator for inhibiting the operation of said missing-pulse detector after the accumulator increments to a predetermined level.

13. An apparatus for continuously monitoring heart activity and automatically effecting a defibrillatory shock under heart fibrillating conditions, comprising means for sensing electrical and mechanical activity of the heart and of a predetermined ventricular fibrillation condition, means for measuring the electrical activity of the heart responsively to said sensing means, means for accumulating said measured electrical activity, means for monitoring the mechanical activity of the heart and operatively connected to said accumulating means, said accumulating means responsive to information representing a predetermined ventricular fibrillatory condition communicated from said measuring means and for activating the means for monitoring the mechanical activity, and a delivery means responsive to said accumulator means for correcting ventricular fibrillation when said accumulating means receives mechanical and electrical activity information each independently but conjointly through respective incrementing and decrementing values confirming a ventricular fibrillatory condition.

14. An automatic heart defibrillator comprising:

sensor means for detecting cardiac electrical and mechanical activity information, means for communicating in the form of electrical signals the cardiac electrical and mechanical activity information from said sensor means, an ECG analog processor for receiving the electrical cardiac activity information from said communicating means, an mechanical-impedance analog processor for receiving the mechanical cardiac activity information from said communicating means, accumulator-control-logic means receiving the output of said ECG analog processor and for counting cardiac signals from said ECG analog processor and for triggering a defibrillatory action at predetermined quantitative threshold values thereof, means for connecting said mechanical-impedance analog processor and said accumulator-control-logic means to furnish an input signal which decrements the counted value derived by said accumulator-control-logic means from the ECG analog processor, the total cardiac information accumulated being the combined independently derived information from said mechanical-impedance and ECG analog processors respectively, said accumulator-control-logic means including logic means for deactivating said mechanical-impedance processor.

15. The defibrillator in accordance with claim 14, in which said mechanical-impedance analog processor is normally deactivated, said logic means responsive to said accumulator-control-logic means at critical heart fibrillatory conditions transmitted by said ECG analog processor and effective to activate said mechanical-impedance analog processor whereby the ECG analog processor and mechanical-impedance processor thereafter perform conjointly and independently to monitor both electrical and mechanical heart activity information and each processor furnishing information to said accumulator-control-logic means which counts the fibrillatory heart activity derived from continuous monitoring by each of said processors.

16. A method for monitoring cardiac ventricular activity for detecting ventricular fibrillation, comprising the steps of continuously sensing the electrical activity of the heart, processing the sensed electrical information by an electrical monitoring means for detection of a predetermined pattern of ventricular fibrillation, operatively activating a mechanical monitoring means upon attainment of the predetermined pattern of ventricular fibrillation, and processing independently and conjointly signals derived from said electrical and mechanical monitoring means whereby upon their conjoint signalling of ventricular fibrillation, through respective incrementing and decrementing values, defibrillatory corrective action is effected.

17. The method in accordance with claim 16, further comprising the steps of weighting the signals respectively generated by the electrical and mechanical monitoring means whereby the weighted signals attain an accumulated value in accordance with the proportions of the respectively weighted signals, and in accordance with said accumulated value thereafter delivering a defibrillating ventricular shock.

18. The method of claim 16, including the step of analyzing the electrical activity of the heart through a missing-pulse detector circuit and suppressing defibrillating operation when the missing-pulse detector circuit detects a non-fibrillating ventricular condition.

19. The method in accordance with claim 16, including the step of positioning ventricular electrode means and thereafter sensing the electrical and mechanical activity of the ventricle.

20. The method in accordance with claim 16, including the steps of incrementing or decrementing an accumulator storage count as derived from the electrical and mechanical monitoring means to detect a pattern of heart activity and to evaluate the predominate presence or predominate absence of ventricular fibrillation, and generating a signal to inhibit decrementing operation at a predetermined accumulated storage count.

21. A method of monitoring cardiac activity and applying a ventricular defibrillation action upon sensing and confirming the existence of a fibrillatory condition, comprising the steps of:

continuously monitoring the electrical activity of the heart for the presence of a predetermined pattern of fibrillatory heart activity, independently activating a second monitoring means which is responsive to the mechanical activity of the heart and which monitors a second and independent set of criteria received from the ventricle and related to the stroke volume of the ventricle, and thereafter independently and conjointly monitoring the heart and delivering a defibrillatory action upon concurrent and jointly verified fibrillatory activity of a predetermined pattern and extent, determined through respective incrementing and decrementing values.

22. A method for monitoring cardiac ventricular activity for detecting ventricular fibrillation, comprising the steps of:

supplying simultaneously to a monitoring means signals of electrical and mechanical activity of the ventricle, and weighting the respective signals by which there is determined a fibrillatory condition and in accordance with a predetermined formula whereby the condition of fibrillation is conjointly verified through respective incrementing and decrementing values by both such signals, and delivering a defibrillating action in response to the conjoint verification by such signals.

23. A method for monitoring cardiac ventricular activity for detecting ventricular fibrillation, comprising the steps of sensing the electrical and mechanical activity of the heart, processing the sensed electrical and mechanical activity for detection of a predetermined pattern of ventricular fibrillation, weighting the signals respectively generated from the electrical and mechanical activity whereby the weighted signals enhance the accuracy in determining the presence of ventricular fibrillation, and conjointly processing through incrementing and decrementing values the weighted signals to determine the presence of ventricular fibrillation, and thereafter delivering a defibrillatory action.