Method and devices for performing cardiac waveform appraisal

• US 7,248,921 B2
• Filed: 06/01/2004
• Issued: 07/24/2007
• Est. Priority Date: 06/02/2003
• Status: Active Grant

• Current Assignee: Cameron Incorporated (Schlumberger NV)
• Original Assignee: Cameron Incorporated (Schlumberger NV)
• Inventors: Phillips, James William, Palreddy, Surekha, Warren, Jay A.
• Primary Examiner(s): Manuel; George
• Assistant Examiner(s): Flory; Christopher A.
• Application Number:
  US10/858,598
• Publication Number:
  US 20040254611A1
• Time in Patent Office: 1,148 Days
• Field of Search: 607/5, 607/17
• US Class Current: 607/5
• CPC Class Codes: A61B 5/0031 Implanted circuitry
• CPC Class Codes: A61B 5/287 Holders for multiple electrodes, e.g. electrode catheters for electrophysiological study [EPS]
• CPC Class Codes: A61B 5/35 by template matching
• CPC Class Codes: A61B 5/7207 of noise induced by motion artifacts
• CPC Class Codes: A61B 5/7239 using differentiation including higher order derivatives
• CPC Class Codes: A61N 1/3622 comprising two or more electrodes co-operating with different heart regions
• CPC Class Codes: A61N 1/365 controlled by a physiological parameter, e.g. heart potential evoked response A61N1/371
• CPC Class Codes: A61N 1/368 comprising more than one electrode co-operating with different heart regions A61N1/3622, A61N1/3627 take precedence

Abstract

The present invention is directed toward a sensing architecture for use in cardiac rhythm management devices. The sensing architecture of the present invention provides a method and means for certifying detected events by the cardiac rhythm management device. Moreover, by exploiting the enhanced capability to accurately identifying only those sensed events that are desirable, and preventing the use of events marked as suspect, the sensing architecture of the present invention can better discriminate between rhythms appropriate for device therapy and those that are not.

Claims

1. A method of signal detection enhancement for a cardiac rhythm device comprising:

receiving a signal from electrodes implanted for cardiac observation;

observing characteristic features of the signal;

counting the characteristic features;

comparing the number of characteristic features to a threshold to;

certify the signal for use in characterizing a cardiac complex;

or

determine the signal is unsuitable for use in characterizing a cardiac complex;

wherein;

the step of observing characteristic features includes identifying a number of points in the signal where the signal slope reaches a local maximum magnitude;

the step of identifying a number of points in the signal includes identifying zero crossings of the second derivative of the signal;

the step of observing characteristic features includes;

(a) selecting a first zero crossing as a significant maximum slope point;

(b) characterizing subsequent zero crossings as either significant maximum slope points or not significant maximum slope points; and

(c) the significant maximum slope points are observed to be the characteristic features;

the step of characterizing subsequent zero crossings includes application of a rule related to the signal shape between two points in the signal; and

the rule calls for determining whether the path length from a most recent significant maximum slope point to the zero crossing under consideration exceeds the magnitude of the difference in amplitude between;

the signal at the time of the most recent significant maximum slope point; and

the signal at the time of the zero crossing under consideration.

2. A method of signal detection enhancement for a cardiac rhythm device comprising:

receiving a signal from electrodes implanted for cardiac observation;

observing characteristic features of the signal;

counting the characteristic features;

comparing the number of characteristic features to a threshold to;

certify the signal for use in characterizing a cardiac complex;

or

determine the signal is unsuitable for use in characterizing a cardiac complex;

wherein;

the step of observing characteristic features includes identifying a number of points in the signal where the signal slope reaches a local maximum magnitude;

the step of identifying a number of points in the signal includes identifying zero crossings of the second derivative of the signal;

the step of observing characteristic features includes;

(a) selecting a first zero crossing as a significant maximum slope point; and

(b) characterizing subsequent zero crossings as either significant maximum slope points or not significant maximum slope points;

the step of characterizing subsequent zero crossings includes analysis using a first rule and a second rule, the first rule being related to a threshold for consideration of separate points in the signal, the second rule being related to the signal shape between two points in the signal;

wherein the first rule calls for determining whether the path length from a most recent significant maximum slope point to the zero crossing under consideration exceeds a path length threshold;

and the second rule calls for determining whether the path length from a most recent significant maximum slope point to the zero crossing under consideration exceeds the magnitude of the difference in amplitude between;

the signal at the time of the most recent significant maximum slope point; and

the signal at the time of the zero crossing under consideration.

3. An implantable cardioverter/defibrillator comprising:

a lead electrode assembly including a number of electrodes; and

a canister housing operational circuitry;

wherein;

the lead electrode assembly is coupled to the canister; and

the operational circuitry is configured to;

receive a cardiac signal from implanted electrodes;

observe characteristic features of the shape of the signal;

count the characteristic features; and

compare the number of characteristic features to a threshold to;

certify the signal for use in characterizing a cardiac complex;

or

determine the signal is unsuitable for use in characterizing a cardiac complex;

wherein;

the operational circuitry is configured such that the step of observing characteristic features includes identifying a number of points in the signal where the signal slope reaches a local maximum magnitude;

the operational circuitry is configured such that the step of identifying a number of points in the signal includes identifying zero crossings of the second derivative of the signal;

the operational circuitry is configured such that the step of observing characteristic features includes;

selecting a first zero crossing as a significant maximum slope point; and

characterizing subsequent zero crossings as either significant maximum slope points or not significant maximum slope points;

wherein the significant maximum slope points are observed to be the characteristic features;

the operational circuitry is configured such that the step of characterizing subsequent zero crossings includes application of a rule related to the signal shape between two points in the signal; and

the operational circuitry is configured such that the rule calls for determining whether the path length from a most recent significant maximum slope point to the zero crossing under consideration exceeds the magnitude of the difference in amplitude between;

the signal at the time of the most recent significant maximum slope point; and

the signal at the time of the zero crossing under consideration.

4. An implantable cardioverter/defibrillator comprising:

a lead electrode assembly including a number of electrodes; and

a canister housing operational circuitry;

wherein;

the lead electrode assembly is coupled to the canister; and

the operational circuitry is configured to;

receive a cardiac signal from implanted electrodes;

observe characteristic features of the shape of the signal;

count the characteristic features; and

compare the number of characteristic features to a threshold to;

certify the signal for use in characterizing a cardiac complex;

or

determine the signal is unsuitable for use in characterizing a cardiac complex;

wherein;

the operational circuitry is configured such that the step of observing characteristic features includes identifying a number of points in the signal where the signal slope reaches a local maximum magnitude;

the operational circuitry is configured such that the step of identifying a number of points in the signal includes identifying zero crossings of the second derivative of the signal;

the operational circuitry is configured such that the step of observing characteristic features includes;

selecting a first zero crossing as a significant maximum slope point; and

characterizing subsequent zero crossings as either significant maximum slope points or not significant maximum slope points;

wherein the significant maximum slope points are observed to be the characteristic features;

the operational circuitry is configured such that the step of characterizing subsequent zero crossings includes analysis using a first rule and a second rule, the first rule being related to a threshold for consideration of separate points in the signal, the second rule being related to the signal shape between two points in the signal; and

the operational circuitry is configured such that;

the first rule calls for determining whether the path length from a most recent significant maximum slope point to the zero crossing under consideration exceeds a path length threshold; and

the second rule calls for determining whether the path length from a most recent significant maximum slope point to the zero crossing under consideration exceeds the magnitude of the difference in amplitude between;

the signal at the time of the most recent significant maximum slope point; and

the signal at the time of the zero crossing under consideration.