Method and apparatus for detecting a sequence of abnormal events in an electrical signal, particularly in the depolarization signal of a heart

• US 5,058,599 A
• Filed: 06/14/1990
• Issued: 10/22/1991
• Est. Priority Date: 06/15/1989
• Status: Expired due to Term

• Current Assignee: Pacesetter AB
• Original Assignee: Siemens AG
• Inventors: Andersen, Hans
• Primary Examiner(s): Kamm, William E.
• Application Number:
  US07/538,107
• Time in Patent Office: 495 Days
• Field of Search: 128/702-705, 128/419 D
• US Class Current: 600/518
• CPC Class Codes: A61B 5/361 Detecting fibrillation
• CPC Class Codes: A61B 5/7239 using differentiation including higher order derivatives
• 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

A method and apparatus for detecting a sequence of abnormal events in an electrical signal, such as the depolarization signal of the heart, compares a selective signal parameter to a defined threshold, and measures the maximum value of the signal parameter for each event which exceeds the threshold. The characteristic quantity corresponding to the statistical distribution of the respective maximum values for a defined number of most recently, successively occurring events is calculated, with each newly measured maximum value causing the characteristic quality to be updated. The characteristic quality is compared in a comparator to a defined rated value, and a signal indicating the presence of a sequence of abnormal events in the electrical signal is generated if the characteristic quality differs from the rated value by more than a selected amount.

Claims

1. A method for detecting a sequence of events indicating fibrillation among a plurality of normal events in the depolarization signal of a pathologically functioning heart, said method comprising the steps of:

acquiring the depolarization signa from the heart, said depolarization signal including a plurality of events, each event having a duration exceeding a minimum chronological duration and consisting of a plurality of successive instantaneous values, and said depolarization signal having a slope associated with each instantaneous value;

identifying, for each event a beginning time at which the absolute value of said slope of said depolarization signal exceeds the absolute value of a defined slope;

forming, for each event, a product of said defined slope and time elapsed since said beginning time;

measuring, for each event, the overall chronological duration for which the absolute value of said depolarization signal exceeds the absolute value of said product;

calculating a characteristic quantity corresponding to the statistical distribution of the overall chronological durations respectively measured for a most recently occurring event and a for a defined plurality of events appearing in succession immediately preceding said most recently occurring event; and

comparing the calculated characteristic quantity to a defined rated value to obtain a comparison result identifying the presence of a sequence of events indicating fibrillation in said depolarization signal.

2. A method as claimed in claim 1 where the step of calculating a characteristic quantity corresponding to the statistical distribution of the overall chronological durations is further defined by the step of calculating the standard deviation of the overall chronological durations respectively measured for a most recently occurring event and for a defined plurality of events preparing in succession immediately preceding said most recently occurring event.

3. A method as claimed in claim 1 comprising the additional step of:

calculating, for each event, a difference value between the overall chronological duration for an event and said minimum chronological duration,

and wherein the step of calculating a characteristic quantity corresponding to the statistical distribution of the overall chronological durations is further defined as the step of calculating a characteristic quantity corresponding to the statistical distribution of said difference values respectively calculated for a most-recently occurring event and for a defined plurality of events appearing in succession immediately preceding said most recently occurring event.

4. A method for detecting a sequence of events indicating fibrillation among a plurality of normal events in the depolarization signal of a pathologically functioning heart, said method comprising the steps of:

acquiring the depolarization signal from the heart, said depolarization signal including a plurality of events, each event having a duration exceeding a minimum chronological duration and consisting of a plurality of successive instantaneous values, and said depolarization signal having a slope associated with each instantaneous value;

identifying, for each event, a beginning time at which the absolute value of said slope of said depolarization signal exceeds the absolute value of a defined slope;

forming, for each event, a product of said defined slope and time elapsed since said beginning time;

measuring, for each event, the overall chronological duration for which the absolute value of said depolarization signal exceeds the absolute value of said product;

calculating a characteristic quantity corresponding to the statistical distribution of the overall chronological durations respectively measured for a most recently occurring event and for a defined plurality of events appearing in succession immediately preceding said most recently occurring event;

comparing the calculated characteristic quantity to a defined rated value to obtain a comparison result identifying the presence of a sequence of events indicating fibrillation in said depolarization signal;

measuring the heartbeat occurrence rate of said heart;

comparing the measured heartbeat occurrence rate to a defined limit value; and

generating a signal indicating the presence of fibrillation in said depolarization signal when both said characteristic quantity exceeds said defined rated value and said heartbeat occurrence rate exceeds said defined limit value.

5. A method as claimed in claim 4 where the step of calculating a characteristic quantity corresponding to the statistical distribution of the overall chronological durations is further defined by the step of calculating the standard deviation of the overall chronological durations respectively measured for a most recently occurring event and for a defined plurality of events preparing in succession immediately preceding said most recently occurring event.

6. A method as claimed in claim 4 comprising the additional step of:

calculating, for each event, a difference value between the overall chronological duration for an event and said minimum chronological duration,

and wherein the step of calculating a characteristic quantity corresponding to the statistical distribution of the overall chronological durations is further defined as the step of calculating a characteristic quantity corresponding to the statistical distribution of said difference values respectively calculated for a most recently occurring event and for a defined plurality of events appearing in succession immediately preceding said most recently occurring event.

7. An apparatus for detecting a sequence of events indicating fibrillation among a plurality of normal events in the depolarization signal of a pathologically functioning heart, comprising:

means for acquiring the depolarization signal from the heart, said depolarization signal including a plurality of events, each event having a duration exceeding a minimum chronological duration and consisting of a plurality of successive instantaneous values, and said depolarization signal having a slope associated with each instantaneous value;

means for identifying, for each event, a beginning time at which the absolute value of said slope of said depolarization signal exceeds the absolute value of a defined slope;

means for forming, for each event, a product of said defined slope and time elapsed since said beginning time;

means for measuring, for each event, the overall chronological duration for which the absolute value of said depolarization signal exceeds the absolute value of said product;

means for calculating a characteristic quantity corresponding to the statistical distribution of the overall chronological durations respectively measured for a most recently occurring event and for a defined plurality of events appearing in succession immediately preceding said most recently occurring event; and

means for comparing the calculated characteristic quantity to a defined rated value to obtain a comparison result identifying the presence of a sequence of events indicating fibrillation in said depolarization signal.

8. An apparatus as claimed in claim 7 wherein said means for calculating a characteristic quantity corresponding to the statistical distribution of the overall chronological durations is further defined as means for the step of calculating the standard deviation of the overall chronological durations respectively measured for a most recently occurring event and for a defined plurality of events preparing in succession immediately preceding said most recently occurring event.

9. An apparatus as claimed in claim 7 further comprising:

means fir calculating, for each event, a difference value between the overall chronological duration for an event and said minimum chronological duration,

and wherein said means for calculating a characteristic quantity corresponding to the statistical distribution of the overall chronological durations is further defined as means for calculating a characteristic quantity corresponding to the statistical distribution of said difference values respectively calculated for a most recently occurring event and for a defined plurality of events appearing in succession immediately preceding said most recently occurring event.

10. An apparatus for detecting a sequence of events indicating fibrillation among a plurality of normal events in the depolarization signal of a pathologically functioning heart, comprising:

means for acquiring the depolarization signal from the heart, said depolarization signal including a plurality of events, each event having a duration exceeding a minimum chronological duration and consisting of a plurality of successive instantaneous values, and said depolarization signal having a slope associated with each instantaneous value;

means for identifying, for each event, a beginning time at which the absolute value of said slope of said depolarization signal exceeds the absolute value of a defined slope;

means for forming, for each event, a product of said defined slope and time elapsed since said beginning time;

means for measuring, for each event, the overall chronological duration for which the absolute value of said depolarization signal exceeds the absolute value of said product;

means for calculating a characteristic quantity corresponding to the statistical distribution of the overall chronological durations respectively measured for a most recently occurring event and for a defined plurality of events appearing in succession immediately preceding said most recently occurring event;

means for comparing the calculated characteristic quantity to a defined rated value to obtain a comparison result identifying the presence of a sequence of events indicating fibrillation in said depolarization signal;

means for measuring the heartbeat occurrence rate of said heart;

means for comparing the measured heartbeat occurrence rate to a defined limit value; and

means for generating a signal indicating the presence of fibrillation in said depolarization signal when both said characteristic quantity exceeds said defined rated value and said heartbeat occurrence rate exceeds said defined limit value.

11. An apparatus as claimed in claim 10 wherein said means for calculating a characteristic quantity corresponding to the statistical distribution of the overall chronological durations is further defined as means for calculating the standard deviation of the overall chronological durations respectively measured for a most recently occurring event and for a defined plurality of events preparing in succession immediately preceding said most recently occurring event.

12. An apparatus as claimed in claim 10, further comprising:

means for calculating, for each event, a difference value between the overall chronological duration for an event and said minimum chronological duration,

and wherein the said means for calculating a characteristic quantity corresponding to the statistical distribution of the overall chronological durations is further defined as means for calculating a characteristic quantity corresponding to the statistical distribution of said difference values respectively calculated for a most recently occurring event and for a defined plurality of events appearing in succession immediately preceding said most recently occurring event.