Method and apparatus for monitoring heart activity, detecting abnormalities, and cardioverting a malfunctioning heart

• US 4,202,340 A
• Filed: 02/15/1978
• Issued: 05/13/1980
• Est. Priority Date: 09/30/1975
• Status: Expired due to Term

• Current Assignee: Mirowski Family Ventures LLC
• Original Assignee: Mieczyslaw Mirowski
• Inventors: Mower, Morton M., Langer, Alois A., Heilman, Marlin S., Mirowski, Mieczyslaw
• Primary Examiner(s): Kamm, William E.
• Application Number:
  US05/878,005
• Time in Patent Office: 818 Days
• Field of Search: 128/2.06 A, 128/2.06 B, 128/2.06 R, 128/2.1 Z, 128/419 D, 128/696, 128/702, 128/708, 128/709, 128/693, 128/901, 128/902
• US Class Current: 607/5
• CPC Class Codes: A61B 5/361 Detecting fibrillation
• CPC Class Codes: A61N 1/3621 for treating or preventing abnormally high heart rate
• 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

Disclosed is a method and an apparatus for monitoring heart activity, for indicating or detecting abnormalities in such activity, and for taking corrective measures to return an arrhythmic heart to normal sinus rhythm. In one embodiment, monitoring and detecting are accomplished by developing a probability density function from ECG signals, or by sampling at least two portions of a probability density function. In another embodiment, a phase lock loop circuit is utilized to indicate fibrillation by the loop'"'"'s inability to lock onto R--R interval signals. And in still another embodiment, cardiac electrodes are used to sense pulsatile impedance changes, absent in the presence of fibrillation. Also disclosed is a two-stage detector whose second stage is brought out of a stand-by state only after an arrhythmic condition is indicated by the first stage.

Claims

1. A method for electronically monitoring the operation of a heart and for enabling the detection of abnormalities in cardiac function, the method comprising the steps of:

sensing at least one cardiac parameter indicative of the operation of the heart being monitored;

operating on the sensed cardiac parameter and generating a probability density function therefrom; and

monitoring said probability density function by comparing the shape thereof with the shape of a probability density function indicative of normal cardiac function;

wherein differences in shape between the normal probability density function and the probability density function generated from the heat being monitored, indicate abnormal cardiac function of the heart being monitored.

2. The method recited in claim 1, and further for reacting to abnormal cardiac functions, the method further comprising the steps of:

cardioverting the heart if it is determined that the heart is in a state requiring cardioversion.

3. An apparatus for electronically monitoring the operation of a heart and for enabling the detection of abnormalities in cardiac function, the apparatus comprising:

sensor means for sensing at least one cardiac parameter indicative of the operation of a heart being monitored;

means for developing electrical signals representative of the sensed cardiac parameter;

means for generating the probability density function of said electrical signals and;

monitoring means for comparing the shape of the generated probability density function with the shape of a probability density function indicative of normal cardiac function;

wherein differences in shape between the normal probability density function and the probability density function generated from the heart being monitored, indicate abnormal function of the heart being monitored.

4. The apparatus recited in claim 3, and having the further capability of cardioverting a heart upon the detection of a cardiac abnormality requiring cardioversion, the apparatus further comprising:

means for issuing first cardioversion signals upon said monitoring means recognizing a condition requiring cardioversion;

second-stage detector means for monitoring a cardiac parameter, for discriminating between normalcy in the monitored parameter and a cardiac state requiring cardioversion; and

means for issuing second cardioversion signals upon said second-stage detector means recognizing a state requiring cardioversion;

energy delivery means for delivering cardioverting energy to a heart; and

means for actuating said energy delivery means only upon the issuance of both said first and said second cardioversion signals.

5. The apparatus recited in claim 4, wherein said second-stage detector means is an impedance detector which senses pulsatile changes of impedance between two cardiac electrodes.

6. The apparatus recited in claim 5, and further comprising:

means for actuating said second-stage detector means only upon said first-stage detector means issuing a cardioversion signal.

7. The apparatus recited in claim 4, and further comprising:

a phase lock loop circuit for attempting to lock onto R waves;

wherein irregularity of the R-to-R interval during certain arrhythmias is indicated by the inability of the phase lock loop to lock onto R waves; and

wherein said second cardioversion signals are issued when the phase lock loop is unable to lock onto R waves.

8. An apparatus for sensing the operation of a heart and for cardioverting a heart experiencing certain abnormal cardiac functions, the apparatus comprising:

sensor means for sensing ECG signals of a heart;

operator means for operating on the sensed ECG signals and for developing at least two portions of a probability density function thereof;

discriminator means for comparing the shape of the developed probability density function with the shape of a known probability density function, and for discriminating between normalcy of said developed probability density function and a developed probability density function which is indicative of the need for cardioversion; and

means for discharging cardioverting energy into the heart upon the sensing of a need for cardioversion.

9. The apparatus recited in claim 8, and further comprising means for indicating the need for cardioversion if the detected probability density function fails to correspond with said normal probability density function.

10. The apparatus recited in claim 8, wherein said operator means comprises a window comparator.

11. A two-stage apparatus for cardioverting a malfunctioning heart in such a manner that power is conserved, the apparatus comprising:

first-stage detector means for discriminating between a normal cardiac state and a state requiring cardioversion;

powering means for continually powering said first-stage detector means;

second-stage detector means for further discriminating between a normal cardiac state and a state requiring cardioversion, normally in a stand-by condition and going to an active full power sensing condition upon initiation by said first-stage detector means;

means for enabling said second-stage detector means and for thereby bringing said second-stage detector means from its stand-by condition to its full power active sensing condition;

control means for powering said second-stage detector only upon said first-stage detector means sensing a cardiac state requiring cardioversion;

delivery means for delivering cardioverting energy to the heart; and

means for actuating said delivery means upon said second-stage detector means sensing a cardiac state requiring cardioversion.

12. The apparatus recited in claim 11, wherein said second-stage detector means is an impedance detector which senses the pulsatile changes of impedance between two cardiac electrodes;

and further comprising means for discriminating between normalcy in the pulsatile changes and a cardiac condition requiring cardioversion.

13. The apparatus recited in claim 11, wherein said second-stage detector is normally in a low power stand-by condition.

14. An apparatus for cardioverting a needy heart, the apparatus comprising:

sensor means for sensing the activity of a heart;

means for generating electrical signals indicative of the R-to-R interval of said heart;

phase lock loop circuitry for receiving and locking onto said electrical signals;

sensing means for determining whether or not said phase lock loop circuitry has locked onto said electrical signals;

delivery means for discharging cardioverting energy into said heart;

means for issuing an enabling signal; and

means for utilizing said enabling signal for initiating the discharge of cardioverting energy by said delivery means upon the sensing means determining the inability of said phase lock loop circuitry to lock onto said electrical signals.

15. A method for electronically monitoring and detecting abnormalities in cardiac function, the method comprising the steps of:

sensing the electrical activity of a heart being monitored, and developing a cardiac parameter signal, such as an ECG, therefrom;

operating on the cardiac parameter signal to develop at least two portions of a complete probability density function curve;

deriving a measure of the shape of the probability density function curve by evaluating an indicator function based on measurements made on said portions of a complete probability density function curve; and

monitoring the results of the indicator function by comparing the results to those derived from normal cardiac states to determine if the probability density function has a shape indicative of an abnormal cardiac state.

16. An apparatus for electronically monitoring and detecting abnormalities in cardiac function, the apparatus comprising:

sensing means for sensing the electrical activity of a heart being monitored, and for developing a cardiac parameter signal, such as an ECG, therefrom;

operating means for operating on the cardiac parameter signal to develop at least two portions of a complete probability density function curve;

means for deriving a measure of the shape of the probability density function curve by evaluating an indicator function based on measurements made on said portions of a complete probability density function curve; and

monitoring means for monitoring the results of the indicator function by comparing the results to those derived from normal cardiac states to determine if the probability density function has a shape indicative of an abnormal cardiac state.